@article{twining_sutherland_zalewski_cove_birks_wearn_haysom_wereszczuk_manzo_bartolommei_et al._2024, title={Using global remote camera data of a solitary species complex to evaluate the drivers of group formation}, volume={121}, ISSN={0027-8424 1091-6490}, url={http://dx.doi.org/10.1073/pnas.2312252121}, DOI={10.1073/pnas.2312252121}, abstractNote={The social system of animals involves a complex interplay between physiology, natural history, and the environment. Long relied upon discrete categorizations of “social” and “solitary” inhibit our capacity to understand species and their interactions with the world around them. Here, we use a globally distributed camera trapping dataset to test the drivers of aggregating into groups in a species complex (martens and relatives, family Mustelidae , Order Carnivora ) assumed to be obligately solitary. We use a simple quantification, the probability of being detected in a group, that was applied across our globally derived camera trap dataset. Using a series of binomial generalized mixed-effects models applied to a dataset of 16,483 independent detections across 17 countries on four continents we test explicit hypotheses about potential drivers of group formation. We observe a wide range of probabilities of being detected in groups within the solitary model system, with the probability of aggregating in groups varying by more than an order of magnitude. We demonstrate that a species’ context-dependent proclivity toward aggregating in groups is underpinned by a range of resource-related factors, primarily the distribution of resources, with increasing patchiness of resources facilitating group formation, as well as interactions between environmental conditions (resource constancy/winter severity) and physiology (energy storage capabilities). The wide variation in propensities to aggregate with conspecifics observed here highlights how continued failure to recognize complexities in the social behaviors of apparently solitary species limits our understanding not only of the individual species but also the causes and consequences of group formation.}, number={12}, journal={Proceedings of the National Academy of Sciences}, publisher={Proceedings of the National Academy of Sciences}, author={Twining, Joshua P. and Sutherland, Chris and Zalewski, Andrzej and Cove, Michael V. and Birks, Johnny and Wearn, Oliver R. and Haysom, Jessica and Wereszczuk, Anna and Manzo, Emiliano and Bartolommei, Paola and et al.}, year={2024}, month={Mar} }
 @article{fraik_facka_powell_2023, title={Food and cover resources for small mammals on an industrially logged landscape in the Sierra Nevada of California}, ISSN={["1480-3283"]}, DOI={10.1139/cjz-2022-0154}, abstractNote={ The presence and abundance of organisms within an ecosystem often correlate with habitat variables that may have few, or unknown, functional values. Understanding the functional role of these variables is especially important for organisms occupying landscapes managed for timber production and containing diverse habitat patches of different quantities and structures of vegetation. We investigated the strength of associations reported in the literature between small mammal generalists and vegetation. On an industrially logged landscape in northern CA, we used occupancy and mark-recapture analyses across three years to estimate the presence and total numbers for woodrats ( Neotoma fuscipes Baird, 1858) and deer mice ( Peromyscus maniculatus (Wagner, 1845)) related to vegetative attributes on coniferous and non-coniferous sites. Abundances of the small mammals correlated positively with shrub cover and hardwoods for woodrats and with shrubs and masting species for deer mice. Indices describing the value of vegetation features for both food and cover, but not these resources independently, described both species’ presence and abundances best. We demonstrated that shrubs and non-coniferous trees are particularly important for small mammals and should be of particular focus to forest managers in the Sierras and mountains with similar forest structures. }, journal={CANADIAN JOURNAL OF ZOOLOGY}, author={Fraik, Alexandra K. and Facka, Aaron N. and Powell, Roger A.}, year={2023}, month={Mar} }
 @article{fraik_facka_powell_2023, title={Food and cover resources for small mammals on an industrially logged landscape in the Sierra Nevada of California}, volume={101}, ISSN={["1480-3283"]}, DOI={10.1139/cjz-2022-0154473}, number={6}, journal={CANADIAN JOURNAL OF ZOOLOGY}, author={Fraik, Alexandra K. and Facka, Aaron N. and Powell, Roger A.}, year={2023}, month={Jun}, pages={473–485} }
 @article{powell_mansfield_rogers_2022, title={Comparison of behaviors of black bears with and without habituation to humans and supplemental research feeding}, ISSN={["1545-1542"]}, DOI={10.1093/jmammal/gyac081}, abstractNote={Abstract}, journal={JOURNAL OF MAMMALOGY}, author={Powell, Roger A. and Mansfield, Susan A. and Rogers, Lynn L.}, year={2022}, month={Oct} }
 @article{green_facka_smith_matthews_powell_2022, title={Evaluating the efficacy of reintroducing fishers (Pekania pennanti) to a landscape managed for timber production}, volume={511}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2022.120089}, abstractNote={Understanding the role of landscapes managed for timber production in the conservation of forest-obligate species is a priority for preserving ecological integrity and fostering socioeconomic wellbeing. The forest characteristics generally associated with the survival, reproduction, and persistence of forest-obligate species (e.g., large-diameter trees, standing dead trees, understory vegetation, downed logs) are often believed to be at odds with timber production. One such species is the fisher (Pekania pennanti), a mesocarnivoran (member of the order Carnivora) associated with mature forest characteristics whose range has decreased substantially since the mid-1800s. Fishers exemplify the perceived conflict between forest-obligate species and timber production because they generally require areas exhibiting complex forest structure including multiple canopy layers, old trees and standing dead trees with cavities, logs, and understory vegetation that provide sufficient prey, escape cover, and structures to support reproduction and parturition. Consequently, understanding if fishers can persist in landscapes managed for timber production can provide a critical test of the compatibility among forest-obligate species and forest management. We reintroduced 40 fishers (24 females, 16 males) between November 2009 and December 2011 onto a landscape managed for timber production to establish a new fisher population and to evaluate the viability of fisher populations on a forest managed for timber production. We studied this reintroduced population of fishers for 8 years following the reintroduction using annual live-captures and year-round tracking with radio telemetry. Using population modeling with spatial capture-recapture methods, we estimated this population of fishers to be growing during the 7-year study period. The density of the reintroduced fisher population in 2017 (10.8 fishers/100 km2) was within the reported range of fisher densities across the western United States. The reintroduction of fishers to previously occupied portions of their range is an important component of fisher conservation and will play a role in the recovery of the species in western portions of the fisher's range. Our results suggest that forests managed for timber production with landscape conditions similar to our study area may be important for future fisher reintroductions and species recovery.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Green, David S. and Facka, Aaron N. and Smith, Kevin P. and Matthews, Sean M. and Powell, Roger A.}, year={2022}, month={May} }
 @article{green_martin_powell_mcgregor_gabriel_pilgrim_schwartz_matthews_2022, title={Mixed-severity wildfire and salvage logging affect the populations of a forest-dependent carnivoran and a competitor}, volume={13}, ISSN={["2150-8925"]}, DOI={10.1002/ecs2.3877}, abstractNote={Abstract}, number={1}, journal={ECOSPHERE}, author={Green, David S. and Martin, Marie E. and Powell, Roger A. and McGregor, Eric L. and Gabriel, Mourad W. and Pilgrim, Kristine L. and Schwartz, Michael K. and Matthews, Sean M.}, year={2022}, month={Jan} }
 @article{mansfield_rogers_robison_powell_2021, title={Bed site selection by female North American black bears (Ursus americanus)}, ISSN={["1545-1542"]}, DOI={10.1093/jmammal/gyab148}, abstractNote={Abstract}, journal={JOURNAL OF MAMMALOGY}, author={Mansfield, Susan A. and Rogers, Lynn L. and Robison, Sean and Powell, Roger A.}, year={2021}, month={Dec} }
 @article{gould_powell_olfenbuttel_deperno_2021, title={Growth and reproduction by young urban and rural black bears}, volume={102}, ISSN={0022-2372 1545-1542}, url={http://dx.doi.org/10.1093/jmammal/gyab066}, DOI={10.1093/jmammal/gyab066}, abstractNote={Abstract}, number={4}, journal={Journal of Mammalogy}, publisher={Oxford University Press (OUP)}, author={Gould, Nicholas P and Powell, Roger and Olfenbuttel, Colleen and DePerno, Christopher S}, editor={Hopkins, JackEditor}, year={2021}, month={Jul}, pages={1165–1173} }
 @article{facka_powell_2021, title={Intraspecific Competition, Habitat Quality, Niche Partitioning, and Causes of Intrasexual Territoriality for a Reintroduced Carnivoran}, volume={9}, ISSN={["2296-701X"]}, DOI={10.3389/fevo.2021.734155}, abstractNote={Animals exploring a new environment develop cognitive maps using diverse sensory input and, thereby, gain information needed to establish home ranges. Experiencing, and learning information about, resources should be advantageous to the resident of a home range while lack of such information should put invaders into the home range at a disadvantage. Conspecifics, especially, should avoid the home ranges of one another to ensure that they do not experience reduced resource availability caused by resource depression or depletion. Yet, encountering conspecific competitors of different sexes may elicit responses that can lead to spacing on a landscape that has different costs and benefits on males and females. We tested the hypothesis that female fishers (Pekania pennanti) avoid competition from both males and female conspecifics whereas male fishers avoid competition only from other males. We reintroduced fishers onto our study site in the presence or absence of competitors’ home ranges during late 2009 through 2011. Using satellite transmitters (Argos) and land-based (VHF) telemetry, we monitored fishers and estimated their locations, movements and use of the surrounding landscape during their first 500 days after release. All fishers settled in relatively high-quality habitat but females that encountered the home ranges of conspecifics moved farther, explored larger areas, and settled farther from their release locations than did females that did not encounter a conspecific’s home range. Male fishers exhibited diverse responses upon encountering the home ranges of conspecifics. Thus, female fishers avoid conspecific competition from all fishers, but males tolerate, or impose, competition with females, apparently to increase mating opportunities. These observations are consistent with the movements and strategies of other solitary carnivores.}, journal={FRONTIERS IN ECOLOGY AND EVOLUTION}, author={Facka, Aaron N. and Powell, Roger A.}, year={2021}, month={Nov} }
 @article{berlato_bulman-fleming_clifford_garrett_intile_jones_kamstock_liptak_pavuk_powell_et al._2021, title={Value, Limitations, and Recommendations for Grading of Canine Cutaneous Mast Cell Tumors: A Consensus of the Oncology-Pathology Working Group}, volume={4}, ISSN={["1544-2217"]}, DOI={10.1177/03009858211009785}, abstractNote={ One of the primary objectives of the Oncology Pathology Working Group (OPWG), a joint initiative of the Veterinary Cancer Society and the American College of Veterinary Pathologists, is for oncologists and pathologists to collaboratively generate consensus documents to standardize aspects and provide guidelines for oncologic pathology. Consensus is established through review of relevant peer-reviewed literature relative to a subgroup’s particular focus. In this article, the authors provide a critical review of the current literature for grading of canine cutaneous mast cell tumors, suggest guidelines for reporting, and provide recommendations for its clinical interpretation. The article mainly focuses on histologic grading, but relevant information on mitotic count and cytological grading are also discussed. This document represents the opinions of the working group and the authors but does not constitute a formal endorsement by the American College of Veterinary Pathologists or the Veterinary Cancer Society. }, journal={VETERINARY PATHOLOGY}, author={Berlato, Davide and Bulman-Fleming, Julie and Clifford, Craig A. and Garrett, Laura and Intile, Joanne and Jones, Pamela and Kamstock, Debra A. and Liptak, Julius M. and Pavuk, Alana and Powell, Roger and et al.}, year={2021}, month={Apr} }
 @article{smith_facka_powell_2020, title={Using reintroduction to elucidate breeding system, breeding phenology, and infanticide for a solitary carnivore (fisher, Pekania pennanti)}, volume={98}, ISSN={["1480-3283"]}, DOI={10.1139/cjz-2019-0234}, abstractNote={ Breeding systems affect the timing of reproduction, spacing patterns and social organization, individual fitnesses, and population sizes. For many species, information on breeding systems and mating is limited or untested in wild populations, resulting in management actions that are incompletely informed. We used photographic data collected on a reintroduced fisher (Pekania pennanti (Erxleben, 1777)) population in northern California, USA, to test hypotheses about the breeding system, the timing of breeding, and the potential for male infanticide. We documented fishers of both sexes breeding with multiple partners in the same year, demonstrating polygynandry. We use logistic and linear regression to evaluate the timing and frequency of male visitation at 262 reproductive dens used by 50 individual females. Of 46 documented copulations and 577 male visits, 100% and 95%, respectively, occurred while females had kits in their natal dens. Seventy-five percent of documented male visits occurred before 31 March and 95% occurred before 17 April. Observed breeding occurred within 3.1 ± 1.6 days (mean ± SD) of locating females’ natal dens. We found no evidence for male-directed infanticide. Our results add precision to the timing of the reproductive cycle and provide the first descriptions of male–female interactions for wild fishers. }, number={7}, journal={CANADIAN JOURNAL OF ZOOLOGY}, author={Smith, K. P. and Facka, A. N. and Powell, R. A.}, year={2020}, month={Jul}, pages={433–447} }
 @article{green_matthews_swiers_callas_yaeger_farber_schwartz_powell_2018, title={Dynamic occupancy modelling reveals a hierarchy of competition among fishers, grey foxes and ringtails}, volume={87}, ISSN={["1365-2656"]}, DOI={10.1111/1365-2656.12791}, abstractNote={Abstract}, number={3}, journal={JOURNAL OF ANIMAL ECOLOGY}, author={Green, David S. and Matthews, Sean M. and Swiers, Robert C. and Callas, Richard L. and Yaeger, J. Scott and Farber, Stuart L. and Schwartz, Michael K. and Powell, Roger A.}, year={2018}, month={May}, pages={813–824} }
 @article{rockhill_sollman_powell_deperno_2016, title={A Comparison of Survey Techniques for Medium- to Large-sized Mammals in Forested Wetlands}, volume={15}, ISSN={["1938-5412"]}, DOI={10.1656/058.015.0112}, abstractNote={Abstract 
 Monitoring mammals is becoming increasingly important as state and federal agencies develop wildlife action plans addressing increased urbanization and climatechange impacts on plant and animal populations. We designed and implemented surveys applicable to forested wetlands to assess detection rates, estimate species richness, compare species distributions, and assess relative cost versus success among techniques. The survey techniques implemented included opportunistic observations, predator calling, spotlighting, scent stations, camera survey, and foothold trapping. Opportunistic observations produced the highest species-richness estimate (14), and were the least expensive ($0) because they were conducted while implementing other survey techniques. Trapping was the most expensive technique with a cost of $61 per animal detected but provided age structure and population estimates through mark—recapture analysis. Camera survey was relatively expensive with a cost of $1865 for the entire study period but recorded the most detections (n = 673), which resulted in a low per detection cost ($3). Opportunistic observations and camera surveys documented 2 species not detected by any other method. Our results indicate that, although camera survey was a cost-effective way to detect mammals, richness and distribution estimates could be improved by incorporating a variety of monitoring techniques specific to forested wetlands.}, number={1}, journal={SOUTHEASTERN NATURALIST}, author={Rockhill, Aimee P. and Sollman, Rahel and Powell, Roger A. and DePerno, Christopher S.}, year={2016}, month={Mar}, pages={175–187} }
 @misc{proulx_powell_2016, title={Build habitats, not fences, for caribou}, volume={353}, ISSN={["1095-9203"]}, DOI={10.1126/science.aai9328}, abstractNote={In his News In Depth story “To save caribou, Alberta wants to fence them in” (22 July, p. [333][1]), W. Cornwall reported on a proposed 50-year-long project to create a predator-free, fenced, 100-square-kilometer landscape to farm caribou in the Little Smoky range. The program intends to kill}, number={6307}, journal={SCIENCE}, author={Proulx, Gilbert and Powell, Roger A.}, year={2016}, month={Sep}, pages={1506–1507} }
 @article{stewart_sharma_york_diller_hamey_powell_swiers_2016, title={Forestry}, journal={Ecosystems of California}, author={Stewart, W. and Sharma, B. and York, R. and Diller, L. and Hamey, N. and Powell, R. and Swiers, R.}, year={2016}, pages={817–833} }
 @article{facka_lewis_happe_jenkins_callas_powell_2016, title={Timing of translocation influences birth rate and population dynamics in a forest carnivore}, volume={7}, ISSN={["2150-8925"]}, DOI={10.1002/ecs2.1223}, abstractNote={Abstract}, number={1}, journal={ECOSPHERE}, author={Facka, Aaron N. and Lewis, Jeffrey C. and Happe, Patricia and Jenkins, Kurt and Callas, Richard and Powell, Roger A.}, year={2016}, month={Jan} }
 @article{laver_powell_alexander_2015, title={Screening GPS telemetry data for locations having unacceptable error}, volume={27}, ISSN={["1878-0512"]}, DOI={10.1016/j.ecoinf.2015.02.001}, abstractNote={Technological improvements in battery life and physical dimensions of Global Positioning System (GPS) telemetry have increased the number of locations one can collect, but due to relatively unimproved GPS accuracy this also increases the number of locations with unacceptable measurement error. We propose and show an example of a new method for screening data for locations with unacceptable error. We also propose a new screening metric: estimated elevation error (EEE). EEE identifies unacceptable xy-coordinate error in some cases better than do methods that use horizontal dilution of precision (HDOP) or fix dimension (2-D or 3-D). Our screening method combines test data and a model-averaging information-theoretic framework that uses a priori candidate models of telemetry measurement error. We demonstrate this method using experimental data collected on banded mongooses (Mungos mungo). One can adapt this screening method to any GPS data.}, journal={ECOLOGICAL INFORMATICS}, author={Laver, Peter N. and Powell, Roger A. and Alexander, Kathleen A.}, year={2015}, month={May}, pages={11–20} }
 @article{mcvey_cobb_powell_stoskopf_bobling_waits_moorman_2013, title={Diets of sympatric red wolves and coyotes in northeastern North Carolina}, volume={94}, ISSN={["1545-1542"]}, DOI={10.1644/13-mamm-a-109.1}, abstractNote={Abstract The recent co-occurrence of red wolves (Canis rufus) and coyotes (Canis latrans) in eastern North Carolina provides a unique opportunity to study prey partitioning by sympatric canids. We collected scats from this region and examined them for prey contents. We used fecal DNA analysis to identify which taxa deposited each scat and multinomial modeling designed for mark–recapture data to investigate diets of sympatric red wolves and coyotes. Diets of red wolves and coyotes did not differ, but the proportion of small rodents in the composite scats of both canids was greater in the spring than in the summer. White-tailed deer (Odocoileus virginianus), rabbits (Sylvilagus spp.), and small rodents were the most common diet items in canid scats. The similarity of diet between red wolves and coyotes suggests that these 2 species may be affecting prey populations similarly.}, number={5}, journal={JOURNAL OF MAMMALOGY}, author={McVey, Justin M. and Cobb, David T. and Powell, Roger A. and Stoskopf, Michael K. and Bobling, Justin H. and Waits, Lisette P. and Moorman, Christopher E.}, year={2013}, month={Oct}, pages={1141–1148} }
 @article{scarlata_elias_godwin_powell_shepherdson_shipley_brown_2013, title={Influence of environmental conditions and facility on faecal glucocorticoid concentrations in captive pygmy rabbits (Brachylagus idahoensis)}, volume={22}, ISSN={["0962-7286"]}, DOI={10.7120/09627286.22.3.357}, abstractNote={Abstract}, number={3}, journal={ANIMAL WELFARE}, author={Scarlata, C. D. and Elias, B. A. and Godwin, J. R. and Powell, R. A. and Shepherdson, D. and Shipley, L. A. and Brown, J. L.}, year={2013}, month={Aug}, pages={357–368} }
 @article{rockhill_deperno_powell_2013, title={The Effect of Illumination and Time of Day on Movements of Bobcats (Lynx rufus)}, volume={8}, ISSN={1932-6203}, url={http://dx.doi.org/10.1371/journal.pone.0069213}, DOI={10.1371/journal.pone.0069213}, abstractNote={Understanding behavioral changes of prey and predators based on lunar illumination provides insight into important life history, behavioral ecology, and survival information. The objectives of this research were to determine if bobcat movement rates differed by period of day (dark, moon, crepuscular, day), lunar illumination (<10%, 10 - <50%, 50 - <90%, >90%), and moon phase (new, full). Bobcats had high movement rates during crepuscular and day periods and low movement rates during dark periods with highest nighttime rates at 10-<50% lunar illumination. Bobcats had highest movement rates during daytime when nighttime illumination was low (new moon) and higher movement rates during nighttime when lunar illumination was high (full moon). The behaviors we observed are consistent with prey availability being affected by light level and by limited vision by bobcats during darkness.}, number={7}, journal={PLoS ONE}, publisher={Public Library of Science (PLoS)}, author={Rockhill, Aimee P. and DePerno, Christopher S. and Powell, Roger A.}, editor={Somers, MichaelEditor}, year={2013}, month={Jul}, pages={e69213} }
 @article{lewis_powell_zielinski_2012, title={Carnivore Translocations and Conservation: Insights from Population Models and Field Data for Fishers (Martes pennanti)}, volume={7}, ISSN={["1932-6203"]}, DOI={10.1371/journal.pone.0032726}, abstractNote={Translocations are frequently used to restore extirpated carnivore populations. Understanding the factors that influence translocation success is important because carnivore translocations can be time consuming, expensive, and controversial. Using population viability software, we modeled reintroductions of the fisher, a candidate for endangered or threatened status in the Pacific states of the US. Our model predicts that the most important factor influencing successful re-establishment of a fisher population is the number of adult females reintroduced (provided some males are also released). Data from 38 translocations of fishers in North America, including 30 reintroductions, 5 augmentations and 3 introductions, show that the number of females released was, indeed, a good predictor of success but that the number of males released, geographic region and proximity of the source population to the release site were also important predictors. The contradiction between model and data regarding males may relate to the assumption in the model that all males are equally good breeders. We hypothesize that many males may need to be released to insure a sufficient number of good breeders are included, probably large males. Seventy-seven percent of reintroductions with known outcomes (success or failure) succeeded; all 5 augmentations succeeded; but none of the 3 introductions succeeded. Reintroductions were instrumental in reestablishing fisher populations within their historical range and expanding the range from its most-contracted state (43% of the historical range) to its current state (68% of the historical range). To increase the likelihood of translocation success, we recommend that managers: 1) release as many fishers as possible, 2) release more females than males (55–60% females) when possible, 3) release as many adults as possible, especially large males, 4) release fishers from a nearby source population, 5) conduct a formal feasibility assessment, and 6) develop a comprehensive implementation plan that includes an active monitoring program.}, number={3}, journal={PLOS ONE}, author={Lewis, Jeffrey C. and Powell, Roger A. and Zielinski, William J.}, year={2012}, month={Mar} }
 @article{powell_2012, title={Diverse perspectives on mammal home ranges or a home range is more than location densities}, volume={93}, ISSN={["0022-2372"]}, DOI={10.1644/12-mamm-5-060.1}, abstractNote={Abstract Home ranges relate to all aspects of a mammal's biology. The 5 papers in this Special Feature provide statistical, economic, game theoretic, mechanistic, information dependent, and conceptual approaches to understanding home ranges and why animals have them. All the papers emphasize the importance of testing a priori hypotheses, especially hypotheses that elucidate why animals behave as they do. All the papers relate resources and habitat quality to home ranges. Finally, the authors oppose viewing home ranges as the product of measurements and suggest viewing home ranges as the cognitive maps that animals maintain and update.}, number={4}, journal={JOURNAL OF MAMMALOGY}, author={Powell, Roger A.}, year={2012}, month={Aug}, pages={887–889} }
 @article{mitchell_powell_2012, title={Foraging optimally for home ranges}, volume={93}, ISSN={["1545-1542"]}, DOI={10.1644/11-mamm-s-157.1}, abstractNote={Abstract Economic models predict behavior of animals based on the presumption that natural selection has shaped behaviors important to an animal's fitness to maximize benefits over costs. Economic analyses have shown that territories of animals are structured by trade-offs between benefits gained from resources and costs of defending them. Intuitively, home ranges should be similarly structured, but trade-offs are difficult to assess because there are no costs of defense, thus economic models of home-range behavior are rare. We present economic models that predict how home ranges can be efficient with respect to spatially distributed resources, discounted for travel costs, under 2 strategies of optimization, resource maximization and area minimization. We show how constraints such as competitors can influence structure of homes ranges through resource depression, ultimately structuring density of animals within a population and their distribution on a landscape. We present simulations based on these models to show how they can be generally predictive of home-range behavior and the mechanisms that structure the spatial distribution of animals. We also show how contiguous home ranges estimated statistically from location data can be misleading for animals that optimize home ranges on landscapes with patchily distributed resources. We conclude with a summary of how we applied our models to nonterritorial black bears (Ursus americanus) living in the mountains of North Carolina, where we found their home ranges were best predicted by an area-minimization strategy constrained by intraspecific competition within a social hierarchy. Economic models can provide strong inference about home-range behavior and the resources that structure home ranges by offering falsifiable, a priori hypotheses that can be tested with field observations.}, number={4}, journal={JOURNAL OF MAMMALOGY}, author={Mitchell, Michael S. and Powell, Roger A.}, year={2012}, month={Aug}, pages={917–928} }
 @article{scarlata_elias_godwin_powell_shepherdson_shipley_brown_2012, title={Relationship between fecal hormone concentrations and reproductive success in captive pygmy rabbits (Brachylagus idahoensis)}, volume={93}, ISSN={["1545-1542"]}, DOI={10.1644/11-mamm-a-223.1}, abstractNote={Abstract The Columbia Basin pygmy rabbit (Brachylagus idahoensis) is critically endangered and the focus of a captive-breeding program. However, reproductive success in captivity to date has not been sufficient to sustain reintroduction efforts. The goal of this study was to investigate patterns of fecal progestagen and glucocorticoid excretion in females during mating, gestation, and lactation and identify hormonal relationships to reproductive success. Fresh fecal samples were collected from 48 adult, female rabbits over 3 breeding seasons at a frequency of 4–7 samples per week. Results showed that a large (17-fold) increase in progestagen concentrations 1 day after mating provides a reliable means of determining if a successful mating occurred. In general, higher glucocorticoid concentrations during the breeding season, specifically during mating and gestation, were associated with lower reproductive success. Females that failed to conceive during the breeding season had higher glucocorticoid and lower progestagen baseline concentrations than females that did conceive. Glucocorticoid excretion during late gestation, but not lactation, was negatively associated with litter success, suggesting it affects offspring survival more during the prenatal than the postnatal period. Progestagen and glucocorticoid concentrations at the end of gestation were positively related to litter size, which may be an important factor in juvenile survival. In summary, higher concentrations of fecal glucocorticoids during the breeding season were associated with reduced conception rates and survival of subsequent litters. Ultimately, identifying what factors cause elevated glucocorticoids in pygmy rabbits could provide opportunities to alleviate negative stressors and increase the reproductive output of the captive population.}, number={3}, journal={JOURNAL OF MAMMALOGY}, author={Scarlata, Candace D. and Elias, Becky A. and Godwin, John R. and Powell, Roger A. and Shepherdson, David and Shipley, Lisa A. and Brown, Janine L.}, year={2012}, month={Jun}, pages={759–770} }
 @misc{powell_2012, title={Those puppy-dog eyes}, volume={100}, DOI={10.1511/2012.98.355}, number={5}, journal={American Scientist}, author={Powell, R. A.}, year={2012}, pages={356–356} }
 @article{powell_mitchell_2012, title={What is a home range?}, volume={93}, ISSN={["1545-1542"]}, DOI={10.1644/11-mamm-s-177.1}, abstractNote={Abstract “Home range” is a standard concept in animal ecology and behavior but few people try to understand what home ranges mean to the animals that have them and often assume that a home-range estimate, quantified using some method, is the home range. This leads to 2 problems. First, researchers put much energy into discerning and using the “best” methods for estimating home ranges while no one understands, really, what a home range is. Second, maps delineating home-range estimates may have little connection with what home ranges are and what they mean to the animals that have them. To gain insight into these problems, Roger Powell (hereafter, Roger) documented his own use of space for 65 days, obtaining complete data on where he went, what he did, and how much energy and money he expended and gained in each place. Roger's use of space is consistent with how other mammals use space and, therefore, examination of his data provides insight into what a home range is and how ecologists should approach quantifying other animals' home ranges. We present estimates of Roger's home range in 5 different metrics, or currencies, that provide important and different insights. Home-range estimators that combine different types of information to estimate the spatial distribution and qualities of resources that structure animal behavior (i.e., fitness surfaces) will probably provide the most insight into animals' home ranges. To make reasonable estimates of home ranges, researchers must collect data on habitat, resources, and other attributes of the landscape, so that they can understand basic behaviors of animals and understand how animals may view their environment. We propose that the best concept of a home range is that part of an animal's cognitive map of its environment that it chooses to keep updated.}, number={4}, journal={JOURNAL OF MAMMALOGY}, author={Powell, Roger A. and Mitchell, Michael S.}, year={2012}, month={Aug}, pages={948–958} }
 @article{rockhill_chinnadurai_powell_deperno_2011, title={A COMPARISON OF TWO FIELD CHEMICAL IMMOBILIZATION TECHNIQUES FOR BOBCATS (LYNX RUFUS)}, volume={42}, ISSN={["1937-2825"]}, DOI={10.1638/2010-0152.1}, abstractNote={Abstract: Anesthetic protocols that allow quick induction, short processing time, and rapid reversal are necessary for researchers performing minimally invasive procedures (including morphometric measurements or attachment of radiocollars). The objective of this study was to evaluate the effectiveness of medetomidine and butorphanol as a substitute for xylazine in ketamine-based field immobilization protocols for bobcats (Lynx rufus) to reduce recovery and total field times. During 2008 and 2009, 11 bobcats were immobilized with an intramuscular combination of ketamine (10 mg/kg)-xylazine (0.75 mg/kg) (KX) or ketamine (4 mg/kg)-medetomidine (40 mcg/kg)-butorphanol (0.4 mg/kg) (KMB). Time to initial sedation, recumbency, and full anesthesia were recorded postinjection. Time to head up, sternal, standing, full recovery, and total processing times were recorded post-reversal. Throughout anesthesia, heart rate (HR), respiratory rate (RR), rectal temperature (RT), and noninvasive hemoglobin-oxygen saturation (SpO2) were recorded at 5-min intervals. The KX combination had a median time to full anesthesia of 10 min, a median recovery time of 46 min, and a median total processing time of 83 min. Alternatively, the KMB combination had a median time to full anesthesia of 21 min, a median recovery time of 18 min, and a median total processing time of 64 min. The KX protocol produced a median HR of 129 beats/min, RR of 25 breaths/min, RT of 38.3°C, and SpO2 of 93%. The KMB protocol produced a median HR of 97 beats/min, RR of 33 breaths/min, RT of 38.4°C, and SpO2 of 92%. Though both protocols provided safe and reliable sedation, the benefits of using medetomidine and butorphanol to lower ketamine doses and decrease processing time for brief nonsurgical sedation of bobcats in the field are presented.}, number={4}, journal={JOURNAL OF ZOO AND WILDLIFE MEDICINE}, author={Rockhill, Aimee P. and Chinnadurai, Sathya K. and Powell, Roger A. and DePerno, Christopher S.}, year={2011}, month={Dec}, pages={580–585} }
 @article{biggins_hanebury_miller_powell_2011, title={Black-footed ferrets and Siberian polecats as ecological surrogates and ecological equivalents}, volume={92}, ISSN={["0022-2372"]}, DOI={10.1644/10-mamm-s-110.1}, abstractNote={Ecologically equivalent species serve similar functions in different communities, and an ecological surrogate species can be used as a substitute for an equivalent species in a community. Siberian polecats (Mustela eversmanii) and black-footed ferrets (M. nigripes) have long been considered ecological equivalents. Polecats also have been used as investigational surrogates for black-footed ferrets, yet the similarities and differences between the 2 species are poorly understood. We contrasted activity patterns of radiotagged polecats and ferrets released onto ferret habitat. Ferrets tended to be nocturnal and most active after midnight. Polecats were not highly selective for any period of the day or night. Ferrets and polecats moved most during brightly moonlit nights. The diel activity pattern of ferrets was consistent with avoidance of coyotes (Canis latrans) and diurnal birds of prey. Similarly, polecat activity was consistent with avoidance of red foxes (Vulpes vulpes) in their natural range. Intraguild predation (including interference competition) is inferred as a selective force influencing behaviors of these mustelines. Examination of our data suggests that black-footed ferrets and Siberian polecats might be ecological equivalents but are not perfect surrogates. Nonetheless, polecats as surrogates for black-footed ferrets have provided critical insight needed, especially related to predation, to improve the success of ferret reintroductions.}, number={4}, journal={JOURNAL OF MAMMALOGY}, author={Biggins, Dean E. and Hanebury, Louis R. and Miller, Brian J. and Powell, Roger A.}, year={2011}, month={Aug}, pages={710–720} }
 @article{scarlata_elias_godwin_powell_shepherdson_shipley_brown_2011, title={Characterizing gonadal and adrenal activity by fecal steroid analyses in pygmy rabbits (Brachylagus idahoensis)}, volume={171}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2011.03.002}, abstractNote={In 2001, the sudden collapse of the Columbia Basin population of pygmy rabbits prompted the initiation of a captive breeding program to facilitate reintroduction, but reproductive success in captivity has not met expectations. Therefore, the objective of this study was to characterize the reproductive and adrenal endocrinology of this endangered rabbit species so that appropriate management strategies could be developed to monitor animal welfare and increase reproduction. Fecal samples were collected from 27 female pygmy rabbits over three breeding and non-breeding seasons. HPLC analyses verified the presence of progesterone in the excreta of pygmy rabbits, but the majority of progestagen metabolites were unidentified polar compounds. By contrast, >70% of glucocorticoid immunoactivity was associated with cortisol. Longitudinal fecal hormone profiles during pregnancy were characterized by a large spike in progestagens shortly after mating, a gradual increase in progestagen and glucocorticoid concentrations throughout gestation and a return of hormones to baseline soon after birth (Day 24). The spike in progestagens 1 day after mating was a significant discovery for this species and appears to provide a reliable means of determining if a successful mating has occurred. Seasonal analyses of hormone excretion found that progestagen baselines did not vary between the breeding and non-breeding seasons, but, as expected, were highest during the breeding season in association with pregnancy. Across seasons, the lowest concentrations of glucocorticoids were associated with the highest rates of offspring production and survival, suggesting a possible link between heightened adrenal activity and lowered reproductive fitness in pygmy rabbits.}, number={3}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Scarlata, Candace D. and Elias, Becky A. and Godwin, John R. and Powell, Roger A. and Shepherdson, David and Shipley, Lisa A. and Brown, Janine L.}, year={2011}, month={May}, pages={373–380} }
 @article{king_powell_2011, title={Managing an invasive predator pre-adapted to a pulsed resource: a model of stoat (Mustela erminea) irruptions in New Zealand beech forests}, volume={13}, ISSN={["1573-1464"]}, DOI={10.1007/s10530-011-9993-y}, number={12}, journal={BIOLOGICAL INVASIONS}, author={King, Carolyn M. and Powell, Roger A.}, year={2011}, month={Dec}, pages={3039–3055} }
 @misc{morales_moorcroft_matthiopoulos_frair_kie_powell_merrill_haydon_2010, title={Building the bridge between animal movement and population dynamics}, volume={365}, ISSN={["1471-2970"]}, DOI={10.1098/rstb.2010.0082}, abstractNote={While the mechanistic links between animal movement and population dynamics are ecologically obvious, it is much less clear when knowledge of animal movement is a prerequisite for understanding and predicting population dynamics. GPS and other technologies enable detailed tracking of animal location concurrently with acquisition of landscape data and information on individual physiology. These tools can be used to refine our understanding of the mechanistic links between behaviour and individual condition through ‘spatially informed’ movement models where time allocation to different behaviours affects individual survival and reproduction. For some species, socially informed models that address the movements and average fitness of differently sized groups and how they are affected by fission–fusion processes at relevant temporal scales are required. Furthermore, as most animals revisit some places and avoid others based on their previous experiences, we foresee the incorporation of long-term memory and intention in movement models. The way animals move has important consequences for the degree of mixing that we expect to find both within a population and between individuals of different species. The mixing rate dictates the level of detail required by models to capture the influence of heterogeneity and the dynamics of intra- and interspecific interaction.}, number={1550}, journal={PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={Morales, Juan M. and Moorcroft, Paul R. and Matthiopoulos, Jason and Frair, Jacqueline L. and Kie, John G. and Powell, Roger A. and Merrill, Evelyn H. and Haydon, Daniel T.}, year={2010}, month={Jul}, pages={2289–2301} }
 @misc{gaillard_hebblewhite_loison_fuller_powell_basille_van moorter_2010, title={Habitat-performance relationships: finding the right metric at a given spatial scale}, volume={365}, ISSN={["1471-2970"]}, DOI={10.1098/rstb.2010.0085}, abstractNote={The field of habitat ecology has been muddled by imprecise terminology regarding what constitutes habitat, and how importance is measured through use, selection, avoidance and other bio-statistical terminology. Added to the confusion is the idea that habitat is scale-specific. Despite these conceptual difficulties, ecologists have made advances in understanding ‘how habitats are important to animals’, and data from animal-borne global positioning system (GPS) units have the potential to help this clarification. Here, we propose a new conceptual framework to connect habitats with measures of animal performance itself—towards assessing habitat–performance relationship (HPR). Long-term studies will be needed to estimate consequences of habitat selection for animal performance. GPS data from wildlife can provide new approaches for studying useful correlates of performance that we review. Recent examples include merging traditional resource selection studies with information about resources used at different critical life-history events (e.g. nesting, calving, migration), uncovering habitats that facilitate movement or foraging and, ultimately, comparing resources used through different life-history strategies with those resulting in death. By integrating data from GPS receivers with other animal-borne technologies and combining those data with additional life-history information, we believe understanding the drivers of HPRs will inform animal ecology and improve conservation.}, number={1550}, journal={PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={Gaillard, Jean-Michel and Hebblewhite, Mark and Loison, Anne and Fuller, Mark and Powell, Roger and Basille, Mathieu and Van Moorter, Bram}, year={2010}, month={Jul}, pages={2255–2265} }
 @article{kie_matthiopoulos_fieberg_powell_cagnacci_mitchell_gaillard_moorcroft_2010, title={The home-range concept: are traditional estimators still relevant with modern telemetry technology?}, volume={365}, ISSN={["1471-2970"]}, DOI={10.1098/rstb.2010.0093}, abstractNote={Recent advances in animal tracking and telemetry technology have allowed the collection of location data at an ever-increasing rate and accuracy, and these advances have been accompanied by the development of new methods of data analysis for portraying space use, home ranges and utilization distributions. New statistical approaches include data-intensive techniques such as kriging and nonlinear generalized regression models for habitat use. In addition, mechanistic home-range models, derived from models of animal movement behaviour, promise to offer new insights into how home ranges emerge as the result of specific patterns of movements by individuals in response to their environment. Traditional methods such as kernel density estimators are likely to remain popular because of their ease of use. Large datasets make it possible to apply these methods over relatively short periods of time such as weeks or months, and these estimates may be analysed using mixed effects models, offering another approach to studying temporal variation in space-use patterns. Although new technologies open new avenues in ecological research, our knowledge of why animals use space in the ways we observe will only advance by researchers using these new technologies and asking new and innovative questions about the empirical patterns they observe.}, number={1550}, journal={PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={Kie, John G. and Matthiopoulos, Jason and Fieberg, John and Powell, Roger A. and Cagnacci, Francesca and Mitchell, Michael S. and Gaillard, Jean-Michel and Moorcroft, Paul R.}, year={2010}, month={Jul}, pages={2221–2231} }
 @article{cagnacci_boitani_powell_boyce_2010, title={Theme issue 'Challenges and opportunities of using GPS-based location data in animal ecology' introduction}, volume={365}, number={1550}, journal={Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences}, author={Cagnacci, F. and Boitani, L. and Powell, R. A. and Boyce, M. S.}, year={2010}, pages={2157–2162} }
 @article{cattet_boulanger_stenhouse_powell_reynolds-hogland_2008, title={An evaluation of long-term capture effects in ursids: Implications for wildlife welfare and research}, volume={89}, ISSN={["1545-1542"]}, DOI={10.1644/08-MAMM-A-095.1}, abstractNote={Abstract The need to capture wild animals for conservation, research, and management is well justified, but long-term effects of capture and handling remain unclear. We analyzed standard types of data collected from 127 grizzly bears (Ursus arctos) captured 239 times in western Alberta, Canada, 1999–2005, and 213 American black bears (U. americanus) captured 363 times in southwestern North Carolina, 1981–2002, to determine if we could detect long-term effects of capture and handling, that is, effects persisting ≥1 month. We measured blood serum levels of aspartate aminotransferase (AST), creatine kinase (CK), and myoglobin to assess muscle injury in association with different methods of capture. Serum concentrations of AST and CK were above normal in a higher proportion of captures by leghold snare (64% of 119 grizzly bear captures and 66% of 165 black bear captures) than capture by helicopter darting (18% of 87 grizzly bear captures) or by barrel trap (14% of 7 grizzly bear captures and 29% of 7 black bear captures). Extreme AST values (>5 times upper reference limit) in 7 (6%) grizzly bears and 29 (18%) black bears captured by leghold snare were consistent with the occurrence of exertional (capture) myopathy. We calculated daily movement rates for 91 radiocollared grizzly bears and 128 radiocollared black bears to determine if our activities affected their mobility during a 100-day period after capture. In both species, movement rates decreased below mean normal rate immediately after capture (grizzly bears: X̄ = 57% of normal, 95% confidence interval = 45–74%; black bears: 77%, 64–88%) and then returned to normal in 3–6 weeks (grizzly bears: 28 days, 20–37 days; black bears: 36 days, 19–53 days). We examined the effect of repeated captures on age-related changes in body condition of 127 grizzly bears and 207 black bears and found in both species that age-specific body condition of bears captured ≥2 times (42 grizzly bears and 98 black bears) tended to be poorer than that of bears captured once only (85 grizzly bears and 109 black bears), with the magnitude of effect directly proportional to number of times captured and the effect more evident with age. Importantly, the condition of bears did not affect their probability of capture or recapture. These findings challenge persons engaged in wildlife capture to examine their capture procedures and research results carefully. Significant capture-related effects may go undetected, providing a false sense of the welfare of released animals. Further, failure to recognize and account for long-term effects of capture and handling on research results can potentially lead to erroneous interpretations.}, number={4}, journal={JOURNAL OF MAMMALOGY}, author={Cattet, Marc and Boulanger, John and Stenhouse, Gordon and Powell, Roger A. and Reynolds-Hogland, Melissa. L.}, year={2008}, month={Aug}, pages={973–990} }
 @article{mitchell_powell_2008, title={Estimated home ranges can misrepresent habitat relationships on patchy landscapes}, volume={216}, ISSN={["1872-7026"]}, DOI={10.1016/j.ecolmodel.2008.05.001}, abstractNote={Home ranges of animals are generally structured by the selective use of resource-bearing patches that comprise habitat. Based on this concept, home ranges of animals estimated from location data are commonly used to infer habitat relationships. Because home ranges estimated from animal locations are largely continuous in space, the resource-bearing patches selected by an animal from a fragmented distribution of patches would be difficult to discern; unselected patches included in the home range estimate would bias an understanding of important habitat relationships. To evaluate potential for this bias, we generated simulated home ranges based on optimal selection of resource-bearing patches across a series of simulated resource distributions that varied in the spatial continuity of resources. For simulated home ranges where selected patches were spatially disjunct, we included interstitial, unselected cells most likely to be traveled by an animal moving among selected patches. We compared characteristics of the simulated home ranges with and without interstitial patches to evaluate how insights derived from field estimates can differ from actual characteristics of home ranges, depending on patchiness of landscapes. Our results showed that contiguous home range estimates could lead to misleading insights on the quality, size, resource content, and efficiency of home ranges, proportional to the spatial discontinuity of resource-bearing patches. We conclude the potential bias of including unselected, largely irrelevant patches in the field estimates of home ranges of animals can be high, particularly for home range estimators that assume uniform use of space within home range boundaries. Thus, inferences about the habitat relationships that ultimately define an animal's home range can be misleading where animals occupy landscapes with patchily distributed resources.}, number={3-4}, journal={ECOLOGICAL MODELLING}, author={Mitchell, Michael S. and Powell, Roger A.}, year={2008}, month={Sep}, pages={409–414} }
 @article{mitchell_powell_2007, title={Optimal use of resources structures home ranges and spatial distribution of black bears}, volume={74}, ISSN={["1095-8282"]}, DOI={10.1016/j.anbehav.2006.11.017}, abstractNote={Research has shown that territories of animals are economical. Home ranges should be similarly efficient with respect to spatially distributed resources and this should structure their distribution on a landscape, although neither has been demonstrated empirically. To test these hypotheses, we used home range models that optimize resource use according to resource-maximizing and area-minimizing strategies to evaluate the home ranges of female black bears, Ursus americanus, living in the southern Appalachian Mountains. We tested general predictions of our models using 104 home ranges of adult female bears studied in the Pisgah Bear Sanctuary, North Carolina, U.S.A., from 1981 to 2001. We also used our models to estimate home ranges for each real home range under a variety of strategies and constraints and compared similarity of simulated to real home ranges. We found that home ranges of female bears were efficient with respect to the spatial distribution of resources and were best explained by an area-minimizing strategy with moderate resource thresholds and low levels of resource depression. Although resource depression probably influenced the spatial distribution of home ranges on the landscape, levels of resource depression were too low to quantify accurately. Home ranges of lactating females had higher resource thresholds and were more susceptible to resource depression than those of breeding females. We conclude that home ranges of animals, like territories, are economical with respect to resources, and that resource depression may be the mechanism behind ideal free or ideal preemptive distributions on complex, heterogeneous landscapes.}, journal={ANIMAL BEHAVIOUR}, author={Mitchell, Michael S. and Powell, Roger A.}, year={2007}, month={Aug}, pages={219–230} }
 @article{reynolds-hogland_mitchell_powell_brown_2007, title={Selection of den sites by black bears in the southern Appalachians}, volume={88}, ISSN={["1545-1542"]}, DOI={10.1644/06-MAMM-A-329R1.1}, abstractNote={Abstract We evaluated selection of den sites by American black bears (Ursus americanus) in the Pisgah Bear Sanctuary, western North Carolina, by comparing characteristics of dens at 53 den sites with availability of habitat characteristics in annual home ranges of bears and in the study area. We also tested whether den-site selection differed by sex, age, and reproductive status of bears. In addition, we evaluated whether the den component of an existing habitat model for black bears predicted where bears would select den sites. We found bears selected den sites far from gravel roads, on steep slopes, and at high elevations relative to what was available in both annual home ranges and in the study area. Den-site selection did not differ by sex or age, but it differed by reproductive status. Adult females with cubs preferred to den in areas that were relatively far from gravel roads, but adult females without cubs did not. The habitat model overestimated the value of areas near gravel roads, underestimated the value of moderately steep areas, and did not include elevation as a predictor variable. Our results highlight the importance of evaluating den selection in terms of both use and availability of den characteristics.}, number={4}, journal={JOURNAL OF MAMMALOGY}, author={Reynolds-Hogland, Melissa J. and Mitchell, Michael S. and Powell, Roger A. and Brown, Dottie C.}, year={2007}, month={Aug}, pages={1062–1073} }
 @book{king_powell_2007, title={The natural history of weasels and stoats: Ecology, behavior, and management}, ISBN={0195300564}, publisher={Oxford; New York: Oxford University Press}, author={King, C. M. and Powell, R. A.}, year={2007} }
 @article{wittmer_powell_king_2007, title={Understanding contributions of cohort effects to growth rates of fluctuating populations}, volume={76}, ISSN={["0021-8790"]}, DOI={10.1111/j.1365-2656.2007.01274.x}, abstractNote={1. Understanding contributions of cohort effects to variation in population growth of fluctuating populations is of great interest in evolutionary biology and may be critical in contributing towards wildlife and conservation management. Cohort-specific contributions to population growth can be evaluated using age-specific matrix models and associated elasticity analyses. 2. We developed age-specific matrix models for naturally fluctuating populations of stoats Mustela erminea in New Zealand beech forests. Dynamics and productivity of stoat populations in this environment are related to the 3-5 year masting cycle of beech trees and consequent effects on the abundance of rodents. 3. The finite rate of increase (lambda) of stoat populations in New Zealand beech forests varied substantially, from 1.98 during seedfall years to 0.58 during post-seedfall years. Predicted mean growth rates for stoat populations in continuous 3-, 4- or 5-year cycles are 0.85, 1.00 and 1.13. The variation in population growth was a consequence of high reproductive success of females during seedfall years combined with low survival and fertility of females of the post-seedfall cohort. 4. Variation in population growth was consistently more sensitive to changes in survival rates both when each matrix was evaluated in isolation and when matrices were linked into cycles. Relative contributions to variation in population growth from survival and fertility, especially in 0-1-year-old stoats, also depend on the year of the cycle and the number of transitional years before a new cycle is initiated. 5. Consequently, management strategies aimed at reducing stoat populations that may be best during one phase of the beech seedfall cycle may not be the most efficient during other phases of the cycle. We suggest that management strategies based on elasticities of vital rates need to consider how population growth rates vary so as to meet appropriate economic and conservation targets.}, number={5}, journal={JOURNAL OF ANIMAL ECOLOGY}, author={Wittmer, Heiko U. and Powell, Roger A. and King, Carolyn M.}, year={2007}, month={Sep}, pages={946–956} }
 @article{reynolds-hogland_mitchell_powell_2006, title={Spatio-temporal availability of soft mast in clearcuts in the Southern Appalachians}, volume={237}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2006.09.035}, abstractNote={Soft mast is an important resource for many wild populations in the Southern Appalachians, yet the way clear-cutting affects availability of soft mast though time is not fully understood. We tested a theoretical model of temporal availability of soft mast in clearcuts using empirical data on percent cover and berry production of Gaylussacia, Vaccinium, and Rubus spp. plants in 100 stands that were clearcut (0–122 years old) in the Southern Appalachian Mountains. We modeled the relationship between soft mast availability and stand age, evaluated the effects of topography and forest type on soft mast, developed statistical models for predicting the spatio-temporal distribution of soft mast, and tested the hypothesis that percent cover of berry plants and berry production provided similar information about soft mast availability. We found temporal dynamics explained berry production better than it predicted percent plant cover, whereas topographic variables influenced percent plant cover more than they influenced berry production. Berry production and percent plant cover were highest in ∼2–9-year-old stands. Percent plant cover was lowest in 10–69-year-old stands and intermediate in 70+-year-old stands. Three of our spatio-temporal models performed well during model testing and they were not biased by the training data, indicating the inferences about spatio-temporal availability of soft mast extended beyond our sample data. The methods we used to estimate the distribution of soft mast may be useful for modeling distributions of other resources.}, number={1-3}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Reynolds-Hogland, Melissa J. and Mitchell, Michael S. and Powell, Roger A.}, year={2006}, month={Dec}, pages={103–114} }
 @article{powell_2005, title={Evaluating welfare of American black bears (Ursus americanus) captured in foot snares and in winter dens}, volume={86}, ISSN={["1545-1542"]}, DOI={10.1644/05-MAMM-A-014R2.1}, abstractNote={Abstract Much research on wild mammals requires trapping, especially livetrapping, yet few methods used to capture wild mammals have been tested against an accepted standard for animal welfare and few data exist regarding physiological responses to capture. My coworkers and I livetrapped 208 American black bears (Ursus americanus) 356 times between May 1981 and August 2001 in the Pisgah National Forest in the Southern Appalachian Mountains by using Aldrich-type foot snares modified for bear safety with automobile hood springs and swivels spliced into cables. We outfitted most bears with transmitter collars and followed 18 bears to their winter dens. We outfitted 8 bears with transponder collars mounted with remotely dischargable darts loaded with anesthesia. We recorded the physical injuries of all bears handled and obtained 186 standard blood chemistry profiles from 112 bears. I compared the blood chemistry profiles of snared bears to profiles of bears in dens, to profiles for healthy, captive bears, and to profiles for wild bears that were collar-darted. Aldrich-type foot snares modified for bear safety, as we used them, and den handling met the accepted standard for trap injuries. Blood chemistry profiles indicated that bears captured in snares experienced high levels of physical exertion and were dehydrated. Blood chemistry parameters responsive to exertion increased with increasing injury scores.}, number={6}, journal={JOURNAL OF MAMMALOGY}, author={Powell, RA}, year={2005}, month={Dec}, pages={1171–1177} }
 @article{mitchell_powell_2004, title={A mechanistic home range model for optimal use of spatially distributed resources}, volume={177}, ISSN={["1872-7026"]}, DOI={10.1016/j.ecolmodel.2004.01.015}, abstractNote={Home ranges of animals are associated with the spatial distribution of limiting resources on a landscape, yet no mechanistic models representing this relationship exist. We present models of how animals might choose patches for their home ranges in ways that are optimal with respect to spatially distributed resources. The models assume that animals choose patches for their home ranges based on resource benefits discounted for travel costs. Animals might select patches to maximize resources within their home ranges over random use of the landscape (resource maximization), or to satisfy a minimum resource threshold needed for survival or reproduction (area minimization). We evaluated how landscape configuration structures home ranges of animals by performing individual-based, spatially explicit computer simulations using each model on simulated landscapes that differed only in the spatial continuity of resources among patches (from over-dispersed to clumped). The most important factor determining quality, efficiency, resource content, and spatial distribution of home ranges was the extent to which resources were clumped on a landscape. Characteristics of resource-maximizing home ranges were determined only by the distribution of resources, and differed from those of area-minimizing home ranges depending upon the magnitude of the resource threshold required. An increase in resource threshold increased area and total resource content for area-minimizing home ranges, but did not change their quality or efficiency. Because animals can consume or protect resources within their home ranges, they can depress the value of resources available to other animals and hence how those animals will choose their home ranges. Depression of resource values on a landscape by animals should result in different configuration and spatial distribution of home ranges on a landscape than would be predicted in its absence. We modified the two home range models to depress the value of resources available to other animals within patches selected for each home range. We generated home ranges with the new models on the simulated landscapes and evaluated how home ranges with resource depression varied with landscape configuration and with the number of home ranges on the landscape. We compared characteristics and spatial distribution of home ranges with resource depression to those of home ranges that do not. For the number of simulations we performed, resource depression resulted in home ranges that differed little in configuration and landscape interactions from those without, except that they were distributed more evenly on the landscapes and overlapped each other less. As the number of home ranges on a landscape increased, resource distributions declined in quality and heterogeneity, and home ranges became larger, less efficient, and of lower quality. Our results suggest that, in addition to landscape configuration, the extent to which animals depress resources included in their home ranges should determine the evenness of spatial dispersion, overlap, and home range structure, especially where animals select home ranges to satisfy a specific resource threshold and the density of animals is high. Because resource depression sets a limit on the number of home ranges a landscape with fixed resource levels can support, our models provide a means of assessing carrying capacity of a landscape.}, number={1-2}, journal={ECOLOGICAL MODELLING}, author={Mitchell, MS and Powell, RA}, year={2004}, month={Sep}, pages={209–232} }
 @inbook{powell_2004, title={Home ranges, cognitive maps, habitat models and fitness landscapes for Martes}, ISBN={0387226915}, DOI={10.1007/0-387-22691-5_6}, booktitle={Martens and fishers (Martes) in human-altered environments: An international perspective}, publisher={New York: Springer Science}, author={Powell, R. A.}, editor={D. J. Harrison, A. K. Fuller and Proulx, G.Editors}, year={2004}, pages={135–146} }
 @article{nasution_brownie_pollock_powell_2004, title={The effect on model identifiability of allowing different relocation rates for live and dead animals in the combined analysis of telemetry and recapture data}, volume={9}, ISSN={["1085-7117"]}, DOI={10.1198/1085711043181}, abstractNote={Models are described for the joint analysis of live-trapping and radio telemetry data from a study on black bears (Ursus americanus) in which all animals received ear tags and a subset also received radio tags. Concerns about bias in survival estimates led to investigation of identifiability and estimator precision for a series of models that allowed differenttelemetry relocation rates for living and dead animals, in addition to emigration and seasonal variation in survival. Identifiability was determined by showing that the expected information matrix was nonsingular. Models with fidelity constant across time, and with the same degree of time specificity for survival rates and relocation rates for dead animals, were determined to be nonidentifiable. More general models, with a greater degree of time specificity for survival rates, were near-singular, and estimators under these near-singular models had poor precision. Analysis of data from the study on black bears illustrated that estimates of survival have poor precision when relocation rates are estimated separately for live and dead animals. It is recommended that the effort expended to relocate both living and dead animals be consistently high in each telemetry survey, so that relocation rates will be high and constant across time and mortality status.}, number={1}, journal={JOURNAL OF AGRICULTURAL BIOLOGICAL AND ENVIRONMENTAL STATISTICS}, author={Nasution, MD and Brownie, C and Pollock, KH and Powell, RA}, year={2004}, month={Mar}, pages={27–41} }
 @article{kovach_powell_2003, title={Effects of body size on male mating tactics and paternity in black bears, Ursus americanus}, volume={81}, ISSN={["1480-3283"]}, DOI={10.1139/Z03-111}, abstractNote={The reproductive behaviour of large, solitary mammals is difficult to study. Owing to their secretive nature and wide-ranging habits, aspects of male mating behaviour are poorly documented in solitary than in social species. We used radiotelemetry and microsatellite DNA analysis to investigate the influence of body size on male mating tactics and short-term reproductive success in the black bear, Ursus americanus, a solitary carnivore. We investigated male ranging behaviour and documented male encounters with breeding females to determine whether males employed conditional mating tactics according to their body sizes. We found that male home-range sizes were not positively associated with body size, but encounter rates with breeding females were. Although all males searched widely for females, mating access appeared to be largely determined by fighting ability. Large males encountered more breeding females and had more frequent encounters during the females' estimated receptive periods than did small- and medium-sized males. Paternity was highly skewed toward the three dominant males who fathered 91% of the cubs sampled during the 3-year study. Paternity was correlated with the frequency of male encounters during female receptive periods. Male encounters, however, overestimated the success of medium-sized males and underestimated the overall variance in male reproductive success. Multiple paternity occurred in two of seven litters, indicating that sperm competition is important in black bear mating behaviour. Implications for male lifetime reproductive success are discussed.}, number={7}, journal={CANADIAN JOURNAL OF ZOOLOGY}, author={Kovach, AI and Powell, RA}, year={2003}, month={Jul}, pages={1257–1268} }
 @inbook{powell_buskirk_zielinski_2003, title={Fishers and martens}, ISBN={0801874165}, DOI={10.4098/at.arch.94-47}, abstractNote={Digital Repository of Scientific Institutes (RCIN) was established and is being developed mainly as an outcome of two projects acquired and jointly accomplished by a group of Polish scientific institutes.}, booktitle={Wild mammals of North America: Biology, management, and conservation (2nd ed.)}, publisher={Baltimore: Johns Hopkins University Press}, author={Powell, R. A. and Buskirk, S. W. and Zielinski, W. J.}, year={2003}, pages={635–649} }
 @inbook{powell_2003, title={Linking fitness landscapes with the behavior and distribution of animals}, ISBN={1559639725}, booktitle={Landscape ecology and resource management: Linking theory with practice}, publisher={Washington, DC: Island Press}, author={Powell, R. A.}, editor={Bissonette, J. A. and Storch, I.Editors}, year={2003}, pages={93–123} }
 @article{mitchell_powell_2003, title={Response of black bears to forest management in the southern Appalachian mountains}, volume={67}, ISSN={["1937-2817"]}, DOI={10.2307/3802676}, abstractNote={We evaluated responses of black bears ( Ursus americanus) to changes in habitat in the Pisgah National For- est in North Carolina, USA. Changes in habitat were due to forest management, which affected bear habitat in complex ways. Harvested stands provided plentiful food resources that decreased with regeneration of the canopy. However, their value was offset by a lack of resources associated with mature overstory. Following canopy closure, early-successional food resources in harvested stands tended to decrease, although some soft mast remained more abundant than in unharvested stands. We used a tested Habitat Suitability Index (HSI) to evaluate effects of har- vest management on bear habitat. Values of HSI for harvested stands tended to differ little among young stands and older stands regenerating in pine (Pinus spp.) or hardwood, and all had lower HSI values than unharvested stands. Although effects of roads are modeled negatively in the HSI, proximity of harvested stands to logging roads did not bias comparisons to harvested stands. We used time-series analysis to characterize year-to-year changes on HSI maps for our study area from 1981 through 1994, and designated the results as an index of habitat change. We used this index to evaluate use of changed areas by black bears, estimated from 127 home ranges. Adult females used changed areas inversely proportional to the index of change, whereas adult and juvenile males showed no preferences. With respect to year-to-year variation at the peripheries of their home ranges, adult males and adult females selected habitat patches where suitability had increased and rejected patches where suitability had declined. Home ranges of adult males contained proportionally fewer areas of habitat decline than those of females or juvenile males. Adult females used areas where habitat suitability decreased, proportional to the decrease, but did not prefer them to areas of stable or improved suitability. Adult males appeared to avoid areas of decreased suitability altogether. Forest management positively affected some aspects of bear habitat but had an overall negative effect on habitat suitability in the southern Appalachians. Forest management will not improve bear habitat overall in areas where resources are abundant. Where soft mast is limiting, however, trade-offs between overall habitat suitability and improved productivity of soft mast may be warranted.}, number={4}, journal={JOURNAL OF WILDLIFE MANAGEMENT}, author={Mitchell, MS and Powell, RA}, year={2003}, month={Oct}, pages={692–705} }
 @misc{powell_proulx_2003, title={Trapping and marking terrestrial mammals for research: Integrating ethics, performance criteria, techniques, and common sense}, volume={44}, ISSN={["1930-6180"]}, DOI={10.1093/ilar.44.4.259}, abstractNote={We propose that researchers integrate ethics, performance criteria, techniques, and common sense when developing research trapping programs and in which members of institutional animal care and use committees address these topics when evaluating research protocols. To ask questions about ethics is in the best tradition of science, and researchers must be familiar with codes of ethics and guidelines for research published by professional societies. Researchers should always work to improve research methods and to decrease the effects on research animals, if for no other reason than to minimize the chances that the methods influence the animals' behavior in ways that affect research results. Traps used in research should meet performance criteria that address state-of-the-art trapping technology and that optimize animal welfare conditions within the context of the research. The proposal includes the following criteria for traps used in research: As Criterion I, killing-traps should render >/= 70% of animals caught irreversibly unconscious in </= 3 min (calculated with 95% confidence). As Criterion II, live-traps should trap >/= 70% of animals with </= 50 points scored for physical injury (calculated with 95% confidence). The types of traps described include killing-traps (snap traps, rotating jaw traps, snares, pitfalls, and drowning sets), common sets, and the common types of live-traps (box and cage traps, pitfalls, foothold traps. snares, corrals and nets, and dart collars). Also described are trapping methods for specific mammals, according to which traps fulfill Criteria I and II for which species, and techniques for short-term, long-term, and permanent marking of mammals.}, number={4}, journal={ILAR JOURNAL}, author={Powell, RA and Proulx, G}, year={2003}, pages={259–276} }
 @article{mitchell_zimmerman_powell_2002, title={Test of a habitat suitability index for black bears in the southern Appalachians}, volume={30}, number={3}, journal={Wildlife Society Bulletin}, author={Mitchell, M. S. and Zimmerman, J. W. and Powell, R. A.}, year={2002}, pages={794–808} }
 @inbook{powell_2001, title={Martens and tayra}, booktitle={The mammal encyclopedia (2nd ed.)}, publisher={Oxford: Equinox}, author={Powell, R. A.}, year={2001} }
 @article{powell_2001, title={Who limits whom: Predators or prey?}, volume={18}, journal={Endangered Species Update}, author={Powell, R. A.}, year={2001}, pages={98–102} }
 @inbook{powell_2000, title={Animal home ranges and territories and home range estimators}, ISBN={0231113404}, DOI={10.2307/3803113}, abstractNote={1. Hypothesis Testing in Ecology, by Charles J. Krebs2: A Critical Review of the Effects of Marking on the Biology of Vertebrates, by Dennis L. Murray and Mark R. Fuller3. Animal Home Ranges and Territories and Home Range Estimators, by Roger A. Powell4. Delusions in Habitat Evaluation: Measuring Use, Selection, and Importance, by David L. Garshelis5. Investigating Food Habits of Terrestrial Vertebrates, by John A. Litvaitis6. Detecting Stability and Causes of Change in Population Density, by Joseph S. Elkinton7. Monitoring Populations, by James P. Gibbs8. Modeling Predator--Prey Dynamics, by Mark S. Boyce9. Population Viability Analysis: Data Requirements and Essential Analyses, by Gary C. White10. Measuring the Dynamics of Mammalian Societies: An Ecologist's Guide to Ethological Methods, by David W. Macdonald, Paul D. Stewart, Pavel Stopka, and Nobuyuki Yamaguchi11. Modeling Species Distribution with GIS, by Fabio Corsi, Jan de Leeuw, and Andrew K. Skidmore}, booktitle={Research techniques in animal ecology: Controversies and consequences}, publisher={New York: Columbia University Press}, author={Powell, R. A.}, editor={Boitani, L. and Fuller, T.Editors}, year={2000}, pages={65–110} }
 @inproceedings{steele_powell_1999, title={Biogeography of small mammals in the Southern Appalachians: Patterns of local and regional abundance}, booktitle={Proceedings of the Appalachian Biogeography Symposium : held June 25-29, 1995 at the Donaldson Brown Center, Virginia Polytechnic Institute and State University, Blacksburg, VA}, publisher={Martinsville, Va.: Virginia Museum of Natural History}, author={Steele, M. A. and Powell, R. A.}, year={1999}, pages={155–165} }
 @inbook{powell_1999, title={Fisher/Martes pennanti}, ISBN={1560988452}, booktitle={The Smithsonian book of North American mammals}, publisher={Washington, DC: Smithsonian Institution Press}, author={Powell, R. A.}, editor={Wilson, D. E. and Ruff, S.Editors}, year={1999}, pages={167–168} }
 @article{sorensen_powell_1998, title={Estimating survival rates of black bears}, volume={76}, ISSN={["1480-3283"]}, DOI={10.1139/cjz-76-7-1335}, abstractNote={Capture-recapture, radiotelemetry (on a monthly and a yearly basis), and age-distribution methods were used to estimate annual survival rates for black bears (Ursus americanus) in the southern Appalachians from 1981 to 1996. Using capture-recapture data, the Jolly-Seber estimator calculated the annual survival rate for all bears over all years to be 0.64 ± 0.04 (mean ± SE). Because of small sample sizes, this method did not produce yearly estimates or allow separation of the data into age or sex classes. Both the Kaplan-Meier estimator (using monthly telemetry data) and the percent survival estimator (using yearly telemetry data) computed an overall annual survival rate of 0.76 ± 0.04. Survival rates for the early years of the study (1981-1987) were significantly lower than in the late years (1988-1996). No significant difference in survival rate was detected between the sexes or among age-classes. Because it is difficult to capture and recapture large numbers of animals, radiotelemetry methods are preferable for large mammals such as black bears. If bears wear their collars for at least a year, calculating survival from yearly telemetry data provides a good estimate of bear survival. Using monthly telemetry data, however, provided the most detailed understanding of bear survival. Survival estimates produced by the age-distribution method were unreliable.}, number={7}, journal={CANADIAN JOURNAL OF ZOOLOGY}, author={Sorensen, VA and Powell, RA}, year={1998}, month={Jul}, pages={1335–1343} }
 @article{seaman_griffith_powell_1998, title={KERNELHR: a program for estimating animal home ranges}, volume={26}, number={1}, journal={Wildlife Society Bulletin}, author={Seaman, D. E. and Griffith, B. and Powell, R. A.}, year={1998}, pages={95–100} }
 @article{powell_mitchell_1998, title={Topographical constraints and home range quality}, volume={21}, ISSN={["1600-0587"]}, DOI={10.1111/j.1600-0587.1998.tb00398.x}, abstractNote={The topography of an area affects the animals that live in at. Using digitized topographic maps of our mountainous study area in North Carolina. USA, and using radio telemetry data for locations of black bears Ursus americanus, we tested the hypotheses that topography influences home ranges of black bears and that topography affects access to resources by black bears. Use of space by bears correlated positively with steepness of slope but negatively with relative elevation. The perimeters of bears” home ranges aligned with ridges and valleys more than expected by chance and home ranges were oriented on major topographic features, such as watersheds and basins. Bears’ homo ranges had lower resource values than was optimal for their home range locations and access to resources was limited by topography'. Ignoring topography may lead researchers to misunderstand the ecology and behavior of animals that live in mountainous areas.}, number={4}, journal={ECOGRAPHY}, author={Powell, RA and Mitchell, MS}, year={1998}, month={Aug}, pages={337–341} }
 @book{powell_zimmermann_seaman_1997, title={Ecology and behaviour of North American black bears: Home ranges, habitat and social organization}, ISBN={0412579901}, publisher={London; New York: Chapman & Hall}, author={Powell, R. A. and Zimmermann, J. W. and Seaman, D. E.}, year={1997} }
 @article{powell_king_1997, title={Variation in body size, sexual dimorphism and age-specific survival in stoats, Mustela erminea (Mammalia: Carnivora), with fluctuating food supplies}, volume={62}, ISSN={["0024-4066"]}, DOI={10.1006/bijl.1996.0154}, abstractNote={Most hypotheses attempting to explain the evolution of pronounced sexual dimorphism in body size in the three species of weasels (Mustela erminea,M. frenata,M. nivalis) assume that sexual dimorphism is a long-term adaptation, associated with the different reproductive strategies of the two sexes. We here examine an auxiliary hypothesis which predicts that the degree of sexual dimorphism may also vary over the short-term, because when food is temporarily abundant, sexual selection should favour a greater growth rate of males than of females. This hypothesis concerns a phenotypic response which could introduce temporarily increased variation into an existing genotypic trait. We document the present size and sexual dimorphism of stoats introduced last century to New Zealand from Britain in relation to between-year variation in food supply in a single habitat (forests of southern beech,Nothofagussp.). Southern beech trees produce heavy crops of flowers and seed at 3–5 year intervals, which are associated with very variable supplies of important prey of stoats, including several species of seed-eating birds, litter-feeding insects, and feral house mice (Mus musculus). Alternative prey are scarce. Regressions of condylobasal length and head-body length on mouse population indices were significant in both sexes. Mean condylobasal length was larger in both male and female stoats born after a heavy seedfall compared with those born in non-seedfall years. However, the largest males born in years of heavy seedfall were removed by selective mortality before the age of 3 years, so the condylobasal lengths for old (≥3.0 yr) males converged on a common mean regardless of food supply in their birth year. Sexual dimorphism did not vary with food supplies (as reflected in seedfall records or mouse population indices) at any age. First-year survivorship, at least from the age of independence, was significantly negatively correlated with density of stoats in the summer of their birth year.}, number={2}, journal={BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY}, author={Powell, RA and King, CM}, year={1997}, month={Oct}, pages={165–194} }
 @article{seaman_powell_1996, title={Accuracy of kernel estimators for animal home range analysis}, volume={77}, journal={Ecology (Brooklyn, New York, N.Y.)}, author={Seaman, D. E. and Powell, R. A.}, year={1996}, pages={2075–2085} }
 @article{seaman_powell_1996, title={An evaluation of the accuracy of kernel density estimators for home range analysis}, volume={77}, ISSN={["0012-9658"]}, DOI={10.2307/2265701}, abstractNote={Kernel density estimators are becoming more widely used, particularly as home range estimators. Despite extensive interest in their theoretical properties, little empirical research has been done to investigate their performance as home range estimators. We used computer simulations to compare the area and shape of kernel density estimates to the true area and shape of multimodal two—dimensional distributions. The fixed kernel gave area estimates with very little bias when least squares cross validation was used to select the smoothing parameter. The cross—validated fixed kernel also gave surface estimates with the lowest error. The adaptive kernel overestimated the area of the distribution and had higher error associated with its surface estimate.}, number={7}, journal={ECOLOGY}, author={Seaman, DE and Powell, RA}, year={1996}, month={Oct}, pages={2075–2085} }
 @article{powell_zimmerman_seaman_gilliam_1996, title={Demographic analyses of a hunted black bear population with access to a refuge}, volume={10}, ISSN={["1523-1739"]}, DOI={10.1046/j.1523-1739.1996.10010224.x}, abstractNote={Studying one of two bear species not experiencing widespread population decline, provides insight into the population responses of the six bear species that are in decline and into responses of other long‐lived species for which data are difficult to collect. Black bear (Ursus americanus) sanctuaries were established in North Carolina (U.S.) in 1971 to protect core populations of bears and to provide dispersing bears for hunting. Population index values, derived from counts of bears visiting bait stations, were significantly greater inside the Pisgah Bear Sanctuary than outside and were greater along trails than along roads. Survivorship of bears outfitted with transmitter collars was greater for sanctuary bears alone than for sanctuary plus non‐sanctuary bears. Monte Carlo analyses of Leslie matrices showed that the bear population in the sanctuary would be stable if cub survivorship, p0, was about O.7, and the population in the sanctuary plus the surrounding area would be stable if p0 was about 0.83. Estimates of litter survivorship in North Carolina indicate, however, that p0 can not exceed O.71. Overall, the matrix analyses indicated an ultimate population decline in the total bear population (sanctuary plus surrounding area). The population index of the bait station did not show a discernible decline. The Pisgah Bear Sanctuary provides dispersing bears for hunters and provides some protection for the resident bears. The sanctuary may not, however, provide resident bears with enough protection to maintain a viable breeding population within its boundaries. Reducing human access to bears and their habitat appears crucial, either by making large sanctuaries or by eliminating roads.}, number={1}, journal={CONSERVATION BIOLOGY}, author={Powell, RA and Zimmerman, JW and Seaman, DE and Gilliam, JF}, year={1996}, month={Feb}, pages={224–234} }
 @article{zimmerman_powell_1995, title={RADIOTELEMETRY ERROR - LOCATION ERROR METHOD COMPARED WITH ERROR POLYGONS AND CONFIDENCE ELLIPSES}, volume={73}, ISSN={["0008-4301"]}, DOI={10.1139/z95-134}, abstractNote={ We assert that researchers should use statistics derived from the linear distances between actual and estimated locations of test transmitters to estimate location error in radiotelemetry data. We call this approach the location error method. We used the distribution of such linear distances from a test data set from a study on black bears (Ursus americanus) in the mountains of North Carolina to predict error statistics for another test data set. We then compared the predicted with the actual error statistics. We also predicted error statistics for the second test data set using the error polygon method and Lenth's maximum likelihood estimator method. Linear and areal predictions of error using the location error method closely matched actual error in the second data set. The 90% confidence area calculated from test data contained 90% of the actual locations. The linear error measures taken from the error polygon method averaged twice the length of the 90% confidence distances generated from test data, and the 90% error polygons actually contained 95% of the true locations. The 95% confidence ellipse of Lenth's maximum likelihood estimator method [Formula: see text] was also a poor indicator of the precision of the actual location errors (95th percentile = 187 ha). Investigators should use bearing analysis on known locations only to find and correct biases in the bearing data prior to triangulation. }, number={6}, journal={CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE}, author={ZIMMERMAN, JW and POWELL, RA}, year={1995}, month={Jun}, pages={1123–1133} }
 @article{powell_1994, title={EFFECTS OF SCALE ON HABITAT SELECTION AND FORAGING BEHAVIOR OF FISHERS IN WINTER}, volume={75}, ISSN={["0022-2372"]}, DOI={10.2307/1382553}, abstractNote={Several researchers reported that fishers ( Martes pennanti ) select lowland-conifer habitats, where snowshoe hares ( Lepus americanus ) are abundant, for foraging and resting and therefore, avoid open, upland-hardwood habitats. In the Ottawa National Forest, Upper Peninsula, Michigan, in the 1970s, porcupines ( Erethizon dorsatum ) occurred in open, upland-hardwood habitat that provided fishers with more than on-half of their energy requirements. If fishers select habitat on the basis of location of important prey, they should hunt disproportionately in hardwood habitat. Fishers, however, appeared to recall locations of porcupine dens in winter and traveled directly to dens, thereby minimizing distance traveled in habitat of porcupines. I hypothesized that fishers would avoid upland-hardwood habitat, despite availability of porcupines, because foraging for porcupines is efficient. Tracks of fishers were followed and mapped. Distribution of habitats available near tracks and available in the study area were quantified using random transects on maps of habitat types. Fishers selected habitats on at least two different scales. On the coarser scale, fishers foraged in areas with greater availability of pine habitat and lowland conifers and less upland hardwoods than was available over the entire study area. On a finer scale, within the vicinity where fishers foraged, they selected lowland-conifer forest and avoided open areas, northern-hardwood, aspen-birch and hemlock forests. Fishers selected dense, lowland forests and avoided northern hardwoods for rest sites; selection of habitats for rest sites was stronger than for travel, making this a possible third scale of selection.}, number={2}, journal={JOURNAL OF MAMMALOGY}, author={POWELL, RA}, year={1994}, month={May}, pages={349–356} }
 @inbook{powell_1994, title={Evolution and biogeography}, ISBN={0801428947}, booktitle={Martens, sables and fishers: Biology and conservation}, publisher={Ithaca, NY: Comstock Pub. Associates}, author={Powell, R. A.}, editor={S. W. Buskirk, A. S. Harestad and M. G. Raphael and Powell, R. A.Editors}, year={1994}, pages={11–12} }
 @inbook{powell_zielinski_1994, title={Fisher}, booktitle={The scientific basis for conserving forest carnivores: American marten, fisher, lynx, and wolverine in the western United States}, publisher={Fort Collins, CO: U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station}, author={Powell, R. A. and Zielinski, W. J.}, editor={L. F. Ruggiero, K. Aubry and S. W. Buskirk and Zielinski, W. J.Editors}, year={1994}, pages={38–73} }
 @inbook{buskirk_powell_1994, title={Habitat ecology of American martens and fishers}, ISBN={0801428947}, booktitle={Martens, sables, and fishers: Biology and conservation}, publisher={Ithaca, NY: Comstock Pub. Associates}, author={Buskirk, S. W. and Powell, R. A.}, editor={S. W. Buskirk, A. S. Harestad and M. G. Raphael and Powell, R. A.Editors}, year={1994}, pages={283–296} }
 @book{martens, sables and fishers: biology and conservation_1994, ISBN={0801428947}, publisher={Ithaca, NY: Cornell University Press}, year={1994} }
 @inbook{holmes_powell_1994, title={Morphology, ecology and the evolution of sexual dimorphism in North American Martes}, ISBN={0801428947}, booktitle={Martens, sables, and fishers: Biology and conservation}, publisher={Ithaca, NY: Comstock Pub. Associates}, author={Holmes, T. and Powell, R. A.}, editor={S. W. Buskirk, A. S. Harestad and M. G. Raphael and Powell, R. A.Editors}, year={1994}, pages={72–84} }
 @article{lapasha_powell_1994, title={PINE VOLE (MICROTUS-PINETORUM) MOVEMENT TOWARD AREAS IN APPLE ORCHARDS WITH REDUCED-POPULATIONS}, volume={69}, ISSN={["0022-1589"]}, DOI={10.1080/00221589.1994.11516547}, abstractNote={Using radiotelemetry, the movements and activity of 24 adult pine voles (Microtus pine- toruni) were examined before and during removal of neighbouring voles in three North Carolina orchards. Each site had control and treatment plots that were monitored concurrently for 28 d, the first 7 d defining normal behaviour patterns. For the following 21 d, animals were removed from half of each treatment plot while baited, inoperable traps were tended in half of each control plot. Relative to controls, treatment animals moved significantly toward removal areas and significantly increased activity. Although both sexes responded to removal of neighbours, males tended to move further than females. Pine voles actively invade areas in which populations have been reduced, therefore control measures in orchards cannot be limited to one-time removal of problem animals.}, number={6}, journal={JOURNAL OF HORTICULTURAL SCIENCE}, author={LAPASHA, DG and POWELL, RA}, year={1994}, month={Nov}, pages={1077–1082} }
 @inbook{powell_1994, title={Population ecology}, ISBN={0801428947}, booktitle={Martens, sables and fishers: Biology and conservation}, publisher={Ithaca, NY: Comstock Pub. Associates}, author={Powell, R. A.}, editor={S. W. Buskirk, A. S. Harestad and M. G. Raphael and Powell, R. A.Editors}, year={1994}, pages={99–100} }
 @inbook{powell_1994, title={Structure and spacing of Martes populations}, ISBN={0801428947}, booktitle={Martens, sables, and fishers: Biology and conservation}, publisher={Ithaca, NY: Comstock Pub. Associates}, author={Powell, R. A.}, editor={S. W. Buskirk, A. S. Harestad and M. G. Raphael and Powell, R. A.Editors}, year={1994}, pages={101–121} }
 @book{powell_1993, title={The fisher: Life history, ecology and behavior. (2nd ed.)}, ISBN={0816622655}, publisher={Minneapolis: University of Minnesota Press}, author={Powell, R. A.}, year={1993} }
 @inproceedings{powell_1993, title={Why do some forest carnivores exhibit intrasexual territoriality and what are the consequences for management?}, volume={21}, ISBN={0662226593}, booktitle={Proceedings of the International Union of Game Biologists XXI Congress : forests and wildlife ... towards the 21st century}, publisher={Chalk River, Ont.: Canadian Forest Service}, author={Powell, R. A.}, year={1993}, pages={268–273} }
 @book{powell_1992, title={An analysis and evaluation of a black bear sanctuary in western North Carolina: Final report for Study B2, Project W-57, Federal Aid in Wildlife Restoration Act}, publisher={Raleigh, NC: Dept. of Zoology, North Carolina State University}, author={Powell, R. A.}, year={1992} }
 @article{steele_powell_1992, title={Biogeography of small mammals in the Southern Appalachians: Patterns of local and regional abundance}, volume={64}, number={suppl.}, journal={Journal of the Pennsylvania Academy of Science}, author={Steele, M. A. and Powell, R. A.}, year={1992}, pages={207} }
 @article{powell_fried_1992, title={HELPING BY JUVENILE PINE VOLES (MICROTUS-PINETORUM), GROWTH AND SURVIVAL OF YOUNGER SIBLINGS, AND THE EVOLUTION OF PINE VOLE SOCIALITY}, volume={3}, ISSN={["1045-2249"]}, DOI={10.1093/beheco/3.4.325}, abstractNote={We quantified the behavior of juvenile pine voles (Microtus pinetorum) in families maintained in outdoor enclosures protected from rain and predators and determined the effects of number of juveniles present (0–3) on their younger siblings and their parents. Juveniles exhibited behaviors characteristic of helpers in cooperative breeding species: brooding, grooming, and retrieving younger siblings, and maintaining nests, runways, and food caches. The number of juveniles had no effect on weights, growth rates, or survival of younger siblings or on survival of parents, but families with three juveniles had shorter interlitter intervals than other families. There was a trend toward lower weights for younger siblings when juveniles continued to nurse from their mothers. Juveniles brooded and groomed younger siblings more when their mothers were absent than when mothers were present. In families with juveniles, younger siblings were alone significandy less often than in families without juveniles, but number of juveniles in the family had little effect on duration or frequency with which juveniles brooded or groomed younger siblings. These data are consistent with cooperative breeding having evolved via individual selection for delayed dispersal. We argue that the limited availability of vacant tunnel systems and the high cost of digging new tunnel systems constrains dispersal in pine voles and has led to the evolution of cooperative breeding.}, number={4}, journal={BEHAVIORAL ECOLOGY}, author={POWELL, RA and FRIED, JJ}, year={1992}, pages={325–333} }
 @book{powell_buskirk_jones_1991, title={Symposium on the Biology and Management of Martens and Fishers: Abstracts of presentations}, publisher={Laramie, WY: University of Wyoming}, author={Powell, R. A. and Buskirk, S. W. and Jones, J.}, year={1991} }
 @article{miller_biggins_wemmer_powell_hanebury_horn_vargas_1990, title={DEVELOPMENT OF SURVIVAL SKILLS IN CAPTIVE-RAISED SIBERIAN POLECATS (MUSTELA-EVERSMANNI) .1. LOCATING PREY}, volume={8}, ISSN={["0289-0771"]}, DOI={10.1007/BF02350279}, number={2}, journal={JOURNAL OF ETHOLOGY}, author={MILLER, B and BIGGINS, D and WEMMER, C and POWELL, R and HANEBURY, L and HORN, D and VARGAS, A}, year={1990}, month={Dec}, pages={89–94} }
 @article{miller_biggins_wemmer_powell_calvo_hanebury_wharton_1990, title={DEVELOPMENT OF SURVIVAL SKILLS IN CAPTIVE-RAISED SIBERIAN POLECATS (MUSTELA-EVERSMANNI) .2. PREDATOR AVOIDANCE}, volume={8}, ISSN={["0289-0771"]}, DOI={10.1007/BF02350280}, number={2}, journal={JOURNAL OF ETHOLOGY}, author={MILLER, B and BIGGINS, D and WEMMER, C and POWELL, R and CALVO, L and HANEBURY, L and WHARTON, T}, year={1990}, month={Dec}, pages={95–104} }
 @article{horner_powell_1990, title={INTERNAL STRUCTURE OF HOME RANGES OF BLACK BEARS AND ANALYSES OF HOME-RANGE OVERLAP}, volume={71}, ISSN={["0022-2372"]}, DOI={10.2307/1381953}, abstractNote={Eight black bears ( Ursus americanus ) outfitted with motion-sensitive transmitter collars were radiotracked from May through December 1984 in the Pisgah Bear Sanctuary in the mountains of western North Carolina. Activities and movement patterns within areas of overlap among neighboring bears were analyzed to determine whether neighbors exhibited spatial or temporal avoidance. The distributions of locations within home ranges were clumped but bears did not use specific areas for specific activities. Home ranges overlapped extensively, and even core areas (areas of high-intensity use) overlapped. Neighboring bears often used areas of overlap for the same activities and at the same time. The clumped or patchy use of areas within home ranges requires analyses that emphasize internal structure of home ranges and not merely outlines or total-area measures.}, number={3}, journal={JOURNAL OF MAMMALOGY}, author={HORNER, MA and POWELL, RA}, year={1990}, month={Aug}, pages={402–410} }
 @inproceedings{seaman_powell_1990, title={Identifying patterns and intensity of home range use}, volume={8}, ISBN={0944740030}, DOI={10.2307/3872925}, abstractNote={Assessing patterns of concentrated and diffuse use of an animal's home range is an important component of understanding ecological and behavioral processes. We present the Area Independent Method (AIM), a graphical and quantitative technique for identifying the pattern of home range use (i.e., clumped or even) and for distinguishing between heavily and lightly used parts of an individual's home range when clumping is present. This technique does not require that the data have any specified statistical distribution. The results of the AIM are compared with those from Samuel et al. (1985) when both methods are applied to radio-telemetry locations of 18 black bears (Ursus americanus). Total home range size has a lesser effect on the size of the core area identified by the AIM than by Samuel et al.'s (1985) method. Both methods result in core area usage that is little affected by total home range size. This technique provides an objective method for comparing areas of concentrated and peripheral use among individuals. Int. Conf. Bear Res. and Manage. 8:243-249 Home ranges reveal the ecological requirements of animals since they include all of the resources that are used by a resident. Home ranges and the movements within them are the behavioral manifestations of basic biological requirements such as finding sufficient food, shelter, and mates. Knowledge about home ranges contributes to both management and ecological theory. Direct management applications include assessing how much space and what kind of habitat are necessary (e.g., Poelker and Hartwell 1973). Our theoretical understanding may benefit from learning the effect of various factors (e.g., food supply and breeding requirements) on spacing behavior and movements (Simon 1975, Carpenter and MacMillan 1976, Gass et al. 1976). Management efforts may suffer if their data lack detail; simple outlines of home ranges may include unused habitat and resources, and thus give distorted pictures of what animals use (Dixon and Chapman 1980). Of course, concentration of use by an animal does not imply that heavily used areas or resources are more important than others. The importance of different areas must be decided by studies of the activities associated with the areas of different levels of use (e.g., Belovsky 1978). From a theoretical standpoint, an ecological factor that changes the pattern of concentrated use (but does not change the perimeter of the range) may have a real and important effect. Realizing this can help us progress to a more thorough understanding of behavioral ecology. To perform detailed studies of home range we need a technique for identifying the core of a home range. The core is the area of most concentrated use, and the technique for identifying the core must reflect our understanding of the biological meaning of a core. Two factors are of primary importance in this concept. First, the core area is used much more heavily than other areas of the home range (this will be defined explicitly in the methods to follow). This is important because an area that is used only slightly more than average could result from random use. The requirement that the core be used much more than other areas may be considered vaguely analogous to the statistical requirement for a number to be far above (or below) the mean before we say that it is significantly different from the mean. Second, the core size must not be strictly determined by total home range size. The result of this condition is that animals with equal sized home ranges but different use patterns (e.g., central place foragers, strongly territorial animals, and extensive wanderers) can have different core sizes. Several methods exist for identifying core areas (e.g., Ford and Krumme 1979, Dixon and Chapman 1980, Samuel et al. 1985). Dixon and Chapman (1980) outline a subjective procedure in which the core is delineated by eye, which cannot form a legitimate basis for studies that involve statistical testing of hypotheses concerning core size, so we will only discuss objective procedures. Ford and Krumme (1979) developed a method called MAP (minimum area vs. probability) that designated any arbitrary constant amount of use as the core. In other words, the researcher is free to decide that the highest x percent of use represents the core of the home range for all individuals in the study. A crucial drawback to such a method is that the core is not strictly tied to intensity of use, and will almost certainly include areas of low use or exclude areas of high use. Samuel et al. (1985) presented a method for objectively identifying the maximum possible core area. This method defined the core as being all areas used more heavily than would result from the even distribution of use by the resident. The core area defined in this way is responsive to the patterns of use of different individuals, and cannot include areas used with frequency lower than the mean. This paper will present the Area Independent Method (AIM) for identifying areas of concentrated use, compare 244 BEARS-THEIR BIOLOGY AND MANAGEMENT it with the method of Samuel et al. (1985), and show the results of applying the 2 techniques to radio-location data from 18 black bears. We would like to thank M.D. Samuel, J.M. Reed and 3 anonymous reviewers for many helpful suggestions on the manuscript, and C. Brownie for statistical assistance. M.A. Fritz, M.A. Homer, T.H. May, C.B. Cooper, and numerous Earthwatch volunteers helped collect the data. The research was made possible by funding and cooperation from R. Bacon, Citibank Corp., Earthwatch/The Center for Field Research, G. and R. King, National Geographic Society, the U.S. National Park Service, North Carolina Agricultural Research Service, North Carolina Wildlife Resources Commission, and the Port Clyde and Stinson Canning Companies (who donated hundreds of cases of canned sardines for bait).}, booktitle={Bears--their biology and management : eighth International Conference on Bear Research and Management : a selection of papers from the Conference held at Victoria, British Columbia, Canada, February 1989}, publisher={International Association for Bear Research and Management}, author={Seaman, D. E. and Powell, R. A.}, editor={L. M. Darling, W. R. Archibald and Dean, F. C.Editors}, year={1990}, pages={243–249} }
 @inproceedings{powell_seaman_1990, title={Production of important black bear foods in the Southern Appalachians}, volume={8}, ISBN={0944740030}, DOI={10.2307/3872918}, booktitle={Bears--their biology and management : eighth International Conference on Bear Research and Management : a selection of papers from the Conference held at Victoria, British Columbia, Canada, February 1989}, publisher={International Association for Bear Research and Management}, author={Powell, R. A. and Seaman, D. E.}, editor={L. M. Darling, W. R. Archibald and Dean, F. C.Editors}, year={1990}, pages={183–187} }
 @inbook{powell_1989, title={Effects of resource productivity, patchiness and predictability on mating and dispersal strategies}, ISBN={0632023619}, booktitle={Comparative socioecology : the behavioural ecology of humans and other mammals}, publisher={Oxford; Boston: Blackwell Scientific Publications}, author={Powell, R. A.}, editor={Standen, V. and Foley, R. A.Editors}, year={1989}, pages={101–123} }
 @article{powell_zielinski_1989, title={MINK RESPONSE TO ULTRASOUND IN THE RANGE EMITTED BY PREY}, volume={70}, ISSN={["0022-2372"]}, DOI={10.2307/1381439}, abstractNote={Grâce a un labyrinthe en Y, les reponses de Mustela vison aux ultra-sons sont examinees. La gamme d'emission d'ultra-sons testes correspond a celle emise par les proies potentielles de ces animaux}, number={3}, journal={JOURNAL OF MAMMALOGY}, author={POWELL, RA and ZIELINSKI, WJ}, year={1989}, month={Aug}, pages={637–638} }
 @article{durda_powell_barthalmus_1989, title={PHYSIOLOGICAL AND BEHAVIORAL-EFFECTS OF GUTHION ON PINE VOLES, MICROTUS-PINETORUM}, volume={43}, ISSN={["0007-4861"]}, DOI={10.1007/bf01702241}, number={1}, journal={BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY}, author={DURDA, JL and POWELL, RA and BARTHALMUS, GT}, year={1989}, month={Jul}, pages={80–86} }
 @inproceedings{powell_1987, title={Black bear home range overlap in North Carolina and the concept of home range applied to black bears}, volume={7}, ISBN={0944740014}, DOI={10.2307/3872630}, booktitle={Bears--their biology and management : seventh International Conference on Bear Research and Management : a selection of papers from the Conference held at Williamsburg, Virginia, USA and Plitvice Lakes, Yugoslavia, February and March 1986}, publisher={International Association for Bear Research and Management}, author={Powell, R. A.}, editor={al., P. E. ZagerEditor}, year={1987}, pages={235–242} }
 @inbook{powell_1987, title={Ursus americanus Pallas, black bear}, ISBN={0917134141}, booktitle={Endangered, threatened, and rare fauna of North Carolina}, publisher={Raleigh, NC: North Carolina State Museum of Natural Sciences}, author={Powell, R. A.}, year={1987}, pages={33–36} }
 @article{powell_clark_richardson_forrest_1985, title={BLACK-FOOTED FERRET MUSTELA-NIGRIPES ENERGY-EXPENDITURE AND PREY REQUIREMENTS}, volume={34}, ISSN={["0006-3207"]}, DOI={10.1016/0006-3207(85)90054-0}, abstractNote={Black-footed ferrets Mustela nigripes are exceedingly rare and only a single extant population in Wyoming is known. Tracks in the snow and direct observations have provided data on activity and show that a ferret can travel from 0 to 7 km and may move up to 50 litres of soil from prairie dog Cynomys spp. burrows in a night. We constructed an additive model to estimate ferret energy expenditure, including energy for running, digging, investigating burrows, and thermoregulation. From field data, we estimate that ferrets expended an average of 130 kcal day−1 during winter. We used the Siberian polecat M. eversmanni as a biological model for the endangered ferret to estimate energy and nutrient aquisition from two ferret prey species. Gross energy content, proximate analyses and utilisation by the polecats of the two prey did not differ and were comparable to results for other carnivores. The polecats consumed an average of 125 kcal day−1 during trials, which is equivalent to 104 metabolisable kcal day−1. At least 20 prairie dogs must be eaten by a ferret during the four winter months (December–March) to meet these requirements. During summer months lactating female ferrets might need to eat prairie dogs at up six times this rate. Our results have conservation implications, including expected ferret densities in prairie dog towns.}, number={1}, journal={BIOLOGICAL CONSERVATION}, author={POWELL, RA and CLARK, TW and RICHARDSON, L and FORREST, SC}, year={1985}, pages={1–15} }
 @article{powell_1985, title={Fisher pelt primeness}, volume={13}, journal={Wildlife Society Bulletin}, author={Powell, R. A.}, year={1985}, pages={67–70} }
 @inproceedings{warburton_powell_1985, title={Movements of black bears on the Pisgah National Forest}, volume={39}, booktitle={Proceedings of the ... Annual Conference, Southeastern Association of Fish and Wildlife Agencies}, author={Warburton, G. S. and Powell, R. A.}, year={1985}, pages={351–361} }
 @inbook{fox_powell_1985, title={Niche spaces and small mammal communities}, booktitle={Form-function analyses: The teeth and skulls of carnivores: Special issue of Australian mammalogy}, publisher={Bedford Park, Australia: Australian Mammal Society}, author={Fox, B. and Powell, R. A.}, editor={Powell, R. A. and Archer, M.Editors}, year={1985} }
 @article{powell_1985, title={POSSIBLE PATHWAYS FOR THE EVOLUTION OF REPRODUCTIVE STRATEGIES IN WEASELS AND STOATS}, volume={44}, ISSN={["0030-1299"]}, DOI={10.2307/3565792}, number={3}, journal={OIKOS}, author={POWELL, RA}, year={1985}, pages={506–508} }
 @inbook{powell_1984, title={Martens and tayra}, booktitle={Encyclopedia of mammals}, publisher={London: Allen & Unwin}, author={Powell, R. A.}, year={1984}, pages={118–119} }
 @article{powell_zielinski_1983, title={Competition and coexistence in mustelid communities}, volume={174}, journal={Acta Zoologica Fennica}, author={Powell, R. A. and Zielinski, W. J.}, year={1983}, pages={223–227} }
 @article{powell_leonard_1983, title={SEXUAL DIMORPHISM AND ENERGY-EXPENDITURE FOR REPRODUCTION IN FEMALE FISHER MARTES-PENNANTI}, volume={40}, ISSN={["0030-1299"]}, DOI={10.2307/3544579}, abstractNote={We develop a model for the energy expenditure of a lactating female fisher. The model includes energy expenditure for maintenance, hunting, prey capture, lactation, climbing, and thermoregulation. Using radio telemetry, we followed the activities of a female fisher with kits in Manitoba, Canada and applied our model to this animal. These are the first estimates of energy expenditure and energy requirements of a free-living female mustelid during lactation. When the kits were small, the female spent as much as 21 h per d away from them hunting, travelling over 13 km, and expended as much as 2285 kJ. Our estimates of energy expenditure for a female fisher during lactation support the hypothesis that sexual dimorphism in body size is related to energy budgets in the Mustelidae.}, number={2}, journal={OIKOS}, author={POWELL, RA and LEONARD, RD}, year={1983}, pages={166–174} }
 @article{powell_1982, title={EVOLUTION OF BLACK-TIPPED TAILS IN WEASELS - PREDATOR CONFUSION}, volume={119}, ISSN={["0003-0147"]}, DOI={10.1086/283897}, abstractNote={Contrasting coloration is widespread in the animal kingdom (Rothschild 1975). For many years, authors have suggested that contrasting coloration is often used to confuse predators (Hailman 1977; Mortensen 1918; Wickler 1968). Many insects, especially lepidopterans, and fishes have contrasting spots (deflection marks) which are believed to deflect a predator's attack away from vital body parts (Blest 1957; Hailman 1977; Robbins 1980; Wickler 1968). Use of contrasting coloration is common among mammals but use of such coloration to confuse predators has been the subject of controversy (Coblentz 1980; Hirth and McCullough 1977; Pitcher 1979; Smythe 1970, 1977). Long-tailed weasels (Mustela frenata) and short-tailed weasels (M. erminea) have black-tipped tails that contrast with the rest of their coloration. The contrast is especially sharp during winter when individuals in northern populations are white except for their black tail tips. Both of these species are small (weights range from ca. 100 g to ca. 300 g; Hall 1951). A third species, the least weasel (M. nivalis), considerably smaller (ca. 40 to 60 g in North America; Hall 1951), also changes color during winter but does not have the black tail tip. Its tail is relatively much shorter than the tails of the other two species. Except for early speculations (Seton 1929; Stone and Cram 1902), there are no explanations in the literature for the black tail tips on weasels. Weasels are subject to predation by many other predators (see review in Powell 1973) and occasionally predation may be a major factor in population regulation (Powell 1973). It has been suggested that at least during winter the black tail tip may enhance the cryptic nature of the white coloration and reduce predation on weasels by other predators (Powell 1978b; Stone and Cram 1902). Though in winter both weasels and snow are white, they are seldom the same shade. Snow color is affected by shadows, thaws, ice crystalline structure, and debris. As winter progresses, weasels often become stained yellow on their hips. Color differences, movement, and shadows make a moving weasel easy to see against the snow. The black tail tip, however, is more conspicuous than is the body of the weasel. This draws the attention of an observer toward the tail and thus makes the weasel's body considerably more difficult o see. Stone and Cram and I have hypothesized that the black tail tip will draw the attention of a potential predator, especially a diurnal avian predator that hunts primarily by sight, away from the weasel's body to its tail. An attacking predator may thus be more likely to miss the weasel and strike at the tail. I have also hypothesized that because least weasels are smaller and have such short tails, a black tail tip would be too close to the weasel and would not misdirect an attacking hawk (Powell 1978b). Because the grasping ability of hawks is not good enough to hold something as fine as the tail of a weasel, looking in museum collections for weasels missing parts of their tails does not give further insight into these hypotheses.}, number={1}, journal={AMERICAN NATURALIST}, author={POWELL, RA}, year={1982}, pages={126–131} }
 @article{powell_1982, title={Ecological 'nonarguments' and human value judgements}, volume={10}, journal={Wildlife Society Bulletin}, author={Powell, R. A.}, year={1982}, pages={141} }
 @article{powell_1982, title={PRAIRIE DOG COLONIALITY AND BLACK-FOOTED FERRETS}, volume={63}, ISSN={["0012-9658"]}, DOI={10.2307/1940133}, number={6}, journal={ECOLOGY}, author={POWELL, RA}, year={1982}, pages={1967–1968} }
 @book{powell_1982, title={The fisher: Life history, ecology and behavior}, ISBN={0816610533}, DOI={10.5962/bhl.title.42020}, publisher={Minneapolis: University of Minnesota Press}, author={Powell, R. A.}, year={1982} }
 @article{powell_powell_1982, title={The predator-prey concept in elementary education}, volume={10}, journal={Wildlife Society Bulletin}, author={Powell, C. B. and Powell, R. A.}, year={1982}, pages={238–244} }
 @inproceedings{powell_1981, title={Fisher food requirements and hunting behavior}, booktitle={Worldwide Furbearer Conference proceedings, Aug. 3-11, 1980, Frostburg, Maryland}, publisher={Baltimore, MD: Worldwide Furbearer Conference}, author={Powell, R. A.}, editor={Chapman, J. A. and Pursley, D.Editors}, year={1981}, pages={883–917} }
 @article{powell_1981, title={Martes pennanti}, volume={156}, DOI={10.2307/3504050}, journal={Mammalian Species}, author={Powell, R. A.}, year={1981}, pages={1–6} }
 @article{powell_brooks_1981, title={SMALL MAMMAL CHANGES IN POPULATIONS FOLLOWING TORNADO BLOWDOWN IN NORTHERN MIXED FOREST}, volume={62}, ISSN={["0022-2372"]}, DOI={10.2307/1380723}, abstractNote={Journal Article Small Mammal Changes in Populations Following Tornado Blowdown in Northern Mixed Forest Get access Roger A. Powell, Roger A. Powell Department of Zoology, North Carolina State University, Raleigh, NC 27650Department of Biology, Ripon College, Ripon, WI 54971 Search for other works by this author on: Oxford Academic Google Scholar William S. Brooks William S. Brooks Department of Zoology, North Carolina State University, Raleigh, NC 27650Department of Biology, Ripon College, Ripon, WI 54971 Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 62, Issue 2, 21 May 1981, Pages 397–400, https://doi.org/10.2307/1380723 Published: 21 May 1981 Article history Received: 21 November 1979 Accepted: 20 August 1980 Published: 21 May 1981}, number={2}, journal={JOURNAL OF MAMMALOGY}, author={POWELL, RA and BROOKS, WS}, year={1981}, pages={397–400} }
 @article{powell_1980, title={Fisher arboreal activity}, volume={94}, journal={Canadian Field-Naturalist}, author={Powell, R. A.}, year={1980}, pages={90–91} }
 @article{powell_1980, title={STABILITY IN A ONE-PREDATOR-3-PREY COMMUNITY}, volume={115}, ISSN={["1537-5323"]}, DOI={10.1086/283580}, abstractNote={May (1973) showed that complex model communities tend to be less stable than simple model communities, but noted that complex real communities do appear to be stable. Therefore research should seek to elucidate what kinds of complexities are stabilizing. Five model predator-prey communities, developed from the literature and based on the fisher-porcupine-snowshoe hare-deer carrion predator-prey community in Upper Peninsula Michigan, show stability in both one-predator-one-prey and one-predator-three-prey forms. In addition, most of the one-predator-three-prey communities are more stable than one-predator-one-prey communities. One major reason for this stability of the more complex communities is believed to be lack of competition between the prey. Lack of competition between prey is believed to be reasonably widespread in predator-prey communities.}, number={4}, journal={AMERICAN NATURALIST}, author={POWELL, RA}, year={1980}, pages={567–579} }
 @article{powell_1980, title={The value of wildlife and wilderness}, volume={8}, journal={Wildlife Society Bulletin}, author={Powell, R. A.}, year={1980}, pages={79} }
 @article{powell_1979, title={ECOLOGICAL ENERGETICS AND FORAGING STRATEGIES OF THE FISHER (MARTES-PENNANTI)}, volume={48}, ISSN={["1365-2656"]}, DOI={10.2307/4109}, abstractNote={SUMMARY (1) This paper presents a model for the daily energy budget of free-living solitary mammals and applies the model to the fisher. Energy expenditure of mammals is the sum of the energies expended in different activities, the most important of which for carnivores are sleeping, running (hunting) and prey capturing. Energy expenditure for a carnivore in each of these activities is a linear function of the mammal's weight to a specified power and its running speed. Two fishers were trained to run on a treadmill to determine the values of the equation parameters for this species. The energy available to a fisher from common prey items is presented. (2) Wild fishers were tracked in the snow and were live-trapped, outfitted with radio transmitters and monitored for activity. Inserting time active and inactive and distance run into the energy budget model yields estimates of energy expended during periods of radio contact and estimates of daily energy expenditure. Daily energy expenditure is estimated to be of the same order of magnitude as, but less than, daily energy acquired from kills and scavenges. (3) The energy budget model and field data are used to develop a simple optimal foraging strategy model for the fisher. A fisher's optimal foraging strategy depends on estimated search times for each prey relative to estimated energy obtained from each prey but does not depend on handling times and handling energy expenditures.}, number={1}, journal={JOURNAL OF ANIMAL ECOLOGY}, author={POWELL, RA}, year={1979}, pages={195–212} }
 @article{powell_1979, title={Fishers, population models and trapping}, volume={7}, journal={Wildlife Society Bulletin}, author={Powell, R. A.}, year={1979}, pages={149–154} }
 @article{powell_1979, title={Mustelid spacing: Variations on a theme by Mustela}, volume={50}, journal={Zeitschrift fur Tierpsychologie}, author={Powell, R. A.}, year={1979}, pages={153–165} }
 @article{powell_1978, title={A comparison of fisher and weasel hunting behavior}, volume={1}, number={1}, journal={Carnivore}, author={Powell, R. A.}, year={1978}, pages={28–34} }
 @inproceedings{powell_brander_1977, title={Adaptations of fishers and porcupines to their predator-prey system}, booktitle={Proceedings of the 1975 Predator Symposium, held in conjunction with the American Society of Mammalogists 55th annual meeting, June 16-19, 1975, University of Montana, Missoula}, publisher={Missoula, MT: Montana Forest & Conservation Experiment Station, University of Montana}, author={Powell, R. A. and Brander, R. B.}, editor={Phillips, R. L. and Jonkel, C.Editors}, year={1977}, pages={45–53} }
 @article{powell_1973, title={A model for raptor predation on weasels}, volume={54}, DOI={10.2307/1378888}, abstractNote={Journal Article A Model for Raptor Predation on Weasels Get access Roger A. Powell Roger A. Powell Department of Biology, The University of Chicago, Chicago, Illinois 60637 Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 54, Issue 1, 26 April 1973, Pages 259–263, https://doi.org/10.2307/1378888 Published: 26 April 1973 Article history Accepted: 01 September 1972 Published: 26 April 1973}, journal={Journal of Mammalogy}, author={Powell, R. A.}, year={1973}, pages={259–263} }
 @article{powell_1972, title={A comparison of populations of boreal red-backed vole (Clethrionomys gapperi) in tornado blowdown and standing forest}, volume={86}, journal={Canadian Field-Naturalist}, author={Powell, R. A.}, year={1972}, pages={377–379} }