Characteristics of the thermal landscape for moose at Voyageurs National Park

Background/Question/Methods

Recent scientific and anecdotal evidence suggests that warming temperatures may play a role in the decline of moose (Alces alces) populations in Minnesota.  Moose may respond to warm temperatures by physiological and behavioral mechanisms (e.g., panting or selection of cool habitats).  The ability of habitat selection to reduce heat load requires variation in the thermal environment.  The thermal environment of moose can be described with operative temperature, which combines convective and radiant heat fluxes into a single metric, and is most easily measured using black globe thermometers.  We recorded black globe temperatures (BGT) across a range of cover types and landscape positions in Voyageurs National Park (VNP) to describe the thermal environment of moose.  We also developed spatially and temporally-explicit models of operative temperature for the period July 1-14, 2010 using landscape and vegetation characteristics along with meteorological data. 

Results/Conclusions

Significant predictors of black globe temperatures varied by season and time of day, and included vegetation cover type, canopy cover, and slope/aspect.  Vegetation cover type and canopy cover were the strongest influence on BGT during summer, while slope/aspect was most significant during winter.  During summer, open canopy cover and non-forested cover types were the warmest habitat type during the day, yet shifted to be coolest at night compared to other habitat types. Regression models of operative temperature predicted a range of greater than 10°C across the landscape during this time period, demonstrating fine-scale patterns of operative temperature that may influence habitat selection and behavior of moose during extreme temperature events.