The Physiological Challenge of Climate Change for Free-Living Terrestrial Mammals

Most scenarios that seek to predict the responses of terrestrial mammals to climate change focus on the direct thermal effects of higher ambient temperatures. Measurements from free-living mammals reveal that the physiological challenge for many terrestrial mammals facing climate change will arise from the compound effects of higher heat loads, reduced water, and reduced energy intake. Deaths from climate change, particularly for large mammals, are more likely to result from starvation than from heat stroke. The extent of heterothermy exhibited by a mammal, which results from the relaxation of temperature regulation in response to demands from competing homeostatic systems, provides an index of its physiological welfare and, therefore, a tool to assess sensitivity and responses to climate change. Studies of responses to heat in laboratory or captive individuals can identify what mammals can achieve physiologically, but they do not necessarily reveal what an animal will actually do in its natural habitat.