Too hot to handle: summer space use shift in a cold-adapted ungulate at the edge of its range

Global warming has been exerting an increasing stress on mammal populations occurring at the bioclimatic edges of their ranges. Moose, as heat-sensitive ungulates, are expected to be increasingly susceptible to thermal stress; however, the behavioral responses of animals could mitigate unfavorable weather conditions. We aimed to evaluate the temperature-mediated behavioral changes in moose occurring at the southwestern edge of the species’ range in Europe. We predicted that increasing temperature in summer would modify the daily activity pattern of animal and fine-scale utilization of thermal cover. We analysed data from 36 moose, who were fitted with GPS collars from two study sites located in Eastern Poland. The distance between moose locations served for assessing moose activity. We applied additive modelling to test the effect of the daily temperature on daily activity patterns and landscape use of moose. Moose, when exposed to temperatures exceeding thermal comfort, increased their activity during cooler twilight hours. On the hottest days, moose were more likely to use tree canopy cover, especially during midday hours. Finally, with increased temperatures and the risk of thermal stress, at that part of the day, moose utilized denser forest stands which could have provided extra protection against solar radiation. Our observations suggested that under a scenario of further climate warming, moose at the southwestern periphery of their range will be forced to make further behavioral alterations. However, it is not clear whether they will be able to compensate for the negative effects of on-going climate change.