Living on the edge: thermophysiology of the southern flying squirrel at its northern range margin
Date of Award
Level of Access Assigned by Author
Master of Science (MS)
Ecology and Environmental Sciences
Danielle L Levesque
Second Committee Member
Third Committee Member
Malcolm L Hunter Jr.
Climate change has the potential to upset entire ecological systems, making predictive models of the utmost importance. The incorporation of physiological parameters into predictive models not only bolsters their accuracy but also provides a mechanistic explanation for ecological changes already observed and those yet to come. North American flying squirrels, for example, have already experienced dramatic range shifts northward over recent decades, with climate change being the suspected driver. While other studies have focused on warming winter temperatures, I explored the hypothesis that rising summer temperatures were driving the observed range shifts. Unable to find a reliable population of the northern species, Glaucomys sabrinus, I focused on southern flying squirrels, Glaucomys volans, to determine the effect of high temperatures on thermoregulation and energy usage. Using flow-through respirometry, I measured the relationship between temperature and metabolic rate/evaporative water loss/body temperature. I used temperature-sensitive data loggers to measure core body temperature in free-ranging flying squirrels to explore an additional thermoregulatory strategy – heterothermy. I discovered no significant increase in metabolic rate in temperatures up to 40°C but did detect an increase in evaporative water loss starting at 36.2°C. Body temperature (Tb) of flying squirrels followed a circadian pattern with ~2°C difference between active and resting phase modal Tb. This daily level of heterothermy is consist with, but slightly higher, than other squirrel species according to the Heterothermy Index. High temperatures are unlikely to cause an energetic strain on southern flying squirrels in Maine as long as water resources remain available. Measurements of microclimate, accounting for group nesting and cavity insulation, are still needed to fully understand the extent of heterothermy and the influence of high ambient temperature on the thermoregulation of G. volans in Maine.
Hensley, Vanessa R., "Living on the edge: thermophysiology of the southern flying squirrel at its northern range margin" (2019). Electronic Theses and Dissertations. 2951.