Temperature-mediated habitat use and selection by a heat-sensitive northern ungulate

Abstract

The behavioural response of animals to unfavourable climatic conditions has received increased attention recently. While many studies have examined the behavioural responses of endotherms to cold temperatures, thermoregulatory behaviour may also occur in response to heat stress. We evaluated whether a heat-sensitive northern ungulate, the moose, Alces alces , showed thermoregulatory behaviour in response to ambient temperature in two populations in southern Norway. We quantified the seasonal habitat use of GPS-collared adult females, as well as fine-scale habitat selection patterns, in relation to time of day and critical temperature thresholds thought to induce heat stress. We also assessed whether temperature-associated changes in spatial behaviour led to a shift in the availability of thermal cover and forage at the chosen location. Frequent exposure to temperatures above critical thresholds occurred in both summer and winter and in both study areas. Moose responded by seeking thermal shelter in mature coniferous forest and avoiding open habitat types, leading to a decrease in local forage availability in summer but not in winter. Differences in habitat choice in response to temperature were most pronounced at twilight. We found that fine-scale habitat selection analyses, using step-selection functions, more effectively revealed thermoregulatory behaviour in both seasons and populations than did habitat use. This is because habitat selection analyses are better able to identify limiting factors operating at different spatiotemporal scales than is habitat use. Our results clearly show that ambient temperature affected fine-scale behavioural decisions of moose with consequences for forage accessibility, especially during summer. As the climate changes, the limiting effect of ambient temperature (cold and high) on animal behaviour is likely to increase, potentially influencing individual fitness and population dynamics. ► Climate is increasingly considered a mediator in animal spatial behaviour. ► We modelled habitat use and selection of a heat-sensitive northern ungulate. ► Thermoregulatory behaviour was stronger in summer than in winter. ► Thermoregulatory behaviour is best modelled using a habitat selection framework. ► Temperature should be considered in habitat–fitness relationships.