Entomological Society of America
On-Demand 10-Minute Session
Available Wednesday, November 11, 2020
Click HERE and search for ‘Waybright’ to access the session on November 11th
Effects of ground temperature on survival and energy usage of overwintering queen bumblebees
Bumble bees are critical pollinators in serious decline, in part due to changing climate. Changes in growing season climate have been the predominant focus of climate change studies in bumble bees and other animals, a focus excluding over half of a temperate bumble bee’s life, which is spent underground in an inactive overwintering state. In the fall, queens burrow into soil and rely on energy stores to survive winter conditions until spring. Body temperatures of diapausing queens therefore track ground temperatures, making winter ground temperatures key determinants of overwintering survival and energy use. However, little is known about the ground temperatures experienced by overwintering bumble bees or how those temperatures determine success during this critical period. We combined measurements of lower lethal temperatures and the temperature dependence of metabolic rates for several species of queens with ground temperatures at different soil depths (0-50 cm) from sites throughout the United States to estimate geographic variation in survival, energy use, and optimal overwintering depth. As deeper depths are generally warmer and shallower depths cooler, overwintering bumble bees face a tradeoff between energy drain at deeper depths and risk of freezing at shallower depths. Analyses suggest that optimal overwintering depth, which balances depletion of energy reserves with freezing risk, varies geographically, and indicate that effects of future changes in winter temperatures on overwintering queen bumble bees will vary strikingly with latitude, altitude, and local conditions.
Presenting Author: Sarah Waybright
Co-Authors: Michael E. Dillon, PhD