Abstract
Avoiding hyperthermia entails considerable metabolic costs for endotherms. Such costs increase in warm conditions, when endotherms may trade food intake for cooler areas to avoid heat stress and maximize their energy balance. The need to reduce heat stress may involve the adoption of tactics affecting space use and foraging behaviour, which are important to understand and predict the effects of climate change and inform conservation. We used resource selection models to examine the behavioural response to heat stress in the Alpine ibex (Capra ibex), a cold-adapted endotherm particularly prone to overheating. Ibex avoided heat stress by selecting the space based on the maximum daily temperature rather than moving hourly to ‘surf the heat wave’, which minimised movement costs but prevented optimal foraging. By integrating these findings with new climate forecasts, we predict that rising temperatures will force mountain ungulates to move upward and overcrowd thermal refugia with reduced carrying capacity. Our approach helps in identifying priority areas for the conservation of mountain species.
Highlights
Global temperatures are increasing at unprecedented rates[1] which may alter selective pressures on animal populations given that thermal balance profoundly affects animal behaviour and population dynamics[2,3]
Ibex resource selection: maximum daily temperature is a better predictor than hourly temperature
The large-scale resource selection model including maximum daily temperature as predictor outperformed the alternative model including hourly temperature (Akaike Information Criterion difference: ΔAIC = 273.76)
Summary
Global temperatures are increasing at unprecedented rates[1] which may alter selective pressures on animal populations given that thermal balance profoundly affects animal behaviour and population dynamics[2,3]. Endotherms may buffer themselves against extreme operative temperatures by actively selecting for thermal refuge areas[11] They can select for woody cover[3,12] and move to shaded areas[13], they can prefer open areas on windy days to increase convective cooling[14,15], or even rest against tree trunks to enhance conductive heat loss[16]. Quantifying the degree to which large herbivores select thermoregulation low-cost areas rather than those where the access to food is higher is a major challenge for ecologists This trade-off may negatively affect individual fitness as the climate progressively warms.
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