Meeting Abstract

9.6  Saturday, Jan. 4 09:15  Fair-weather Friends: Environmental constraints on ground squirrel activity in the arctic summer WILSTERMAN, K*; WILLIAMS, CT; BUCK, CL; Bucknell University, Department of Biology; University of Alaska Anchorage, Department of Biological Sciences; University of Alaska Anchorage, Department of Biological Sciences kew023@bucknell.edu

Unique among resident arctic vertebrates, the arctic ground squirrel maintains a well-described diel rhythm of activity across the Polar Day despite 24-hour sunlight. We hypothesize that the rhythmic above-ground and below-ground activity patterns within a 24-hour day are driven by environmental factors which influence thermoregulation and energetics. To understand how the physical environment affects rhythms of activity in free-living arctic ground squirrels, we established a local weather station with sensors to measure and record environmental variables (air temperature, precipitation, wind speed and direction, and solar radiation) and outfitted female ground squirrels with collar-mounted light loggers to record above- and below-ground activity patterns. We collected environmental and activity data between 2 June and 2 July 2013 near Toolik Field Station in the northern foothills of the Brooks Range, AK. Individual activity datasets with matching environmental data ranged from 6 to 27 days in length with a median of 21 days. Paradoxically, though daily above-ground activity increased with solar radiation and ambient temperature, squirrels reduced activity levels during peak solar radiation on hot days. Thus, female ground squirrels appear to utilize burrow attendance to buffer exposure to thermal extremes. By going below ground when temperatures are either too high or too low, ground squirrels reduce thermoregulatory costs when ambient temperatures are low and eliminate the risk of overheating when both solar radiation and ambient temperatures are high. These results have implications for how changing weather patterns in the Arctic may constrain ground squirrel foraging opportunities.