Behavioral plasticity mitigates the effects of heat stress in white-tailed deer

Background/Question/Methods

Climate change may affect communities through several mechanisms, including by direct thermal effects on consumers that alter consumption rates, thereby indirectly affecting basal resources. For example, climate warming may cause consumers to reduce activity to avoid thermal stress, which could decrease consumption rates and benefit the resource. However, consumers may evoke a suite of behavioral responses to mitigate heat stress while meeting nutritional demands, including temporal shifts in activity, making use thermal heterogeneity on the landscape, and compensatory feeding during periods that are not thermally stressful. However, few studies consider the role of behavioral plasticity and spatial and temporal heterogeneity in the thermal environment. To evaluate the importance of behavior in mediating the net effects of warming on resource consumption, we conducted two experiments using captive white-tailed deer (Odocoileus virginianus). We first tested the hypothesis that heat stress would cause deer to feed less by presenting individual deer with shaded or unshaded feeders in three day feeding trials. We then presented groups of deer in 0.8 ha enclosures with both shaded and unshaded feeders to test the hypothesis that deer would alter temporal and spatial activity to meet nutritional demands and maintain their functional role as consumers in the community.

Results/Conclusions

Individual deer consumed 17% less food when feeders were unshaded (p = 0.01). In the group-level experiment where both feeder types were available, our data suggest that deer altered their behavior in response to heat stress by altering where and when they fed. Specifically, time budget analysis revealed that deer disproportionately used the shaded feeder during the daytime. Consequently, total daily consumption was greater in shaded feeders (p = 0.049). However, deer used shaded and unshaded feeders at similar rates at night when solar radiation was absent. This supports the conclusion that deer used shade to mitigate heat stress from solar radiation. Our results demonstrate that avoidance of thermal stress could have nutritional consequences. However, by altering their behavior to make use of spatial and temporal heterogeneity in temperature, animals may be able to meet both nutritional and thermal demands. Our results demonstrate the importance of considering behavior to understand the net effects of climate change on consumers and their communities.