Effect of Temperature on Habitat Use by Moose in Voyageurs National Park in the Summer

Abstract

Moose (Alces alces) are an integral part of biological processes and a favorite sight of visitors to Voyageurs National Park (VNP). In the face of global climate change moose may also become a bellwether species for the persistence of northern species in VNP and the surrounding area. Climate change will affect national parks like VNP in many ways, ranging from changes in vegetation and possible loss of wildlife species to altered visitation rates by people. Minnesota is at the southern edge of moose distribution. Climate change predictions are for a 3o to 4o C increase in average summer temperatures by 2100, which would result in an increased number of summer days during which moose would be heat stressed. We deployed GPS collars on moose in VNP to evaluate changes in habitat use and activity as related to fine-scale changes in ambient temperature. We captured and radiocollared 21 moose by aerial darting or net-gunning. We measured black globe temperatures in habitats across VNP. The annual Minimum Convex Polygon home range area was about 15 km2, while seasonal home ranges were about 10 km2. Home range size was slightly less than in adjoining areas of northeast Minnesota. There was no difference in proportional cover type in the home range among annual, winter, and summer home ranges, and cover type use was similar to cover type use by moose in northeast Minnesota. Wet bog and wet marsh/fen cover types were preferred in hot summer temperatures, while open water was not used very much, with less than 1% of locations in water when temperatures were above 30 C. Use of almost all cover types was similar whether temperature, dew point, or heat index were used as the metric. For future analysis of cover type use ambient or black globe temperature should be an adequate metric. Habitats that are of most use to moose in hot temperatures have a wet substrate and some canopy cover during the day. At night moose seemed to be less limited by heat dissipation because of colder temperatures and the lack of solar radiation. Monitoring the population status of moose at Voyageurs National Park is of critical importance in order to make contrasts with the declining moose populations in other regions of Minnesota.