2023 journal article

Larger pollen loads increase risk of heat stress in foraging bumblebees

BIOLOGY LETTERS, 19(5).

By: M. Naumchik  n & E. Youngsteadt n

author keywords: Bombus; critical thermal maximum; heat stress; foraging behaviour; thoracic temperature; climate change
MeSH headings : Bees; Animals; Pollen; Feeding Behavior; Temperature; Body Size; Heat-Shock Response
TL;DR: Bumblebees likely adopt behavioural or physiological strategies to counteract the thermal stress induced by pollen transport, and these may limit their foraging opportunities as environmental temperatures continue to increase. (via Semantic Scholar)
UN Sustainable Development Goal Categories
15. Life on Land (Web of Science)
Source: Web Of Science
Added: May 30, 2023

Global declines in bumblebee populations are linked to climate change, but specific mechanisms imposing thermal stress on these species are poorly known. Here we examine the potential for heat stress in workers foraging for pollen, an essential resource for colony development. Laboratory studies have shown that pollen foraging causes increased thoracic temperatures ( T th ) in bees, but this effect has not been examined in bumblebees nor in real-world foraging situations. We examine the effects of increasing pollen load size on T th of Bombus impatiens workers in the field while accounting for body size and microclimate. We found that T th increased by 0.07°C for every milligram of pollen carried ( p = 0.007), resulting in a 2°C increase across the observed range of pollen load sizes. Bees carrying pollen were predicted to have a T th 1.7–2.2°C hotter than those without pollen, suggesting that under certain conditions, pollen loads could cause B. impatiens workers to heat from a safe T th to one within the range of their critical thermal limits that we measured (41.3°C to 48.4°C). Bumblebees likely adopt behavioural or physiological strategies to counteract the thermal stress induced by pollen transport, and these may limit their foraging opportunities as environmental temperatures continue to increase.