Male weasels decrease activity and energy expenditure in response to high ambient temperatures.

Karol Zub,Marek Konarzewski,Paulina A Szafrańska,Quinn E Fletcher,Adam J Munn

doi:10.1371/journal.pone.0072646

Karol Zub, Marek Konarzewski + Show 3 more

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https://doi.org/10.1371/journal.pone.0072646

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Abstract

The heat dissipation limit (HDL) hypothesis suggests that the capacity of endotherms to dissipate body heat may impose constraints on their energy expenditure. Specifically, this hypothesis predicts that endotherms should avoid the detrimental consequences of hyperthermia by lowering their energy expenditure and reducing their activity in response to high ambient temperatures (Ta). We used an extensive data set on the daily energy expenditure (DEE, n = 27) and the daily activity time (AT, n = 48) of male weasels (Mustela nivalis) during the spring and summer breeding season to test these predictions. We found that Ta was related in a “hump-shaped” (i.e. convex) manner to AT, DEE, resting metabolic rate (RMR) and metabolic scope (the ratio of DEE to RMR). These results support the HDL hypothesis because in response to warm Tas male weasels reduced their AT, DEE, and RMR. Although the activity and energy expenditure of large endotherms are most likely to be constrained in response to warm Tas because they are less able to dissipate heat, our results suggest that small endotherms may also experience constraints consistent with the HDL hypothesis.

Highlights

The thermal neutral zone of birds and mammals describes the range of ambient temperatures (Ta) over which they do not have to expend additional energy to maintain their body temperature [1]
We provided evidence that male weasels are able to avoid high daily energy expenditure (DEE) by reducing their activity time in response to cold Tas
While our previous work focused on the influence of cold Tas on the activity time (AT) and DEE of male weasels, the present work addresses the effect of high temperatures on the AT and DEE of male weasels during the breeding season

Summary

Introduction

The thermal neutral zone of birds and mammals describes the range of ambient temperatures (Ta) over which they do not have to expend additional energy to maintain their body temperature [1]. Studies on racing horses and dogs, as well as on exercising humans, have demonstrated that challenges associated with dissipating heat in response to hot and humid conditions reduces locomotor performance, but may cause animals to die as a result of hyperthermia [2,3]. The recently formulated heat dissipation limit (HDL) hypothesis proposes that maximal energy expenditure is not constrained by the availability of energy in the environment, but instead by the capacity of animals to dissipate body heat [4]. The HDL hypothesis was formulated to explain the ability of lactating laboratory mice to increase milk energy output when their capacity to dissipate body was experimentally increased [5,6]. Excessive heat production during lactation is attributed to the high energetic costs of energy processing and milk production. The HDL hypothesis may be relevant for explaining patterns in other life-stages (e.g. migration [7]), in addition to explaining broader ecological (e.g. Bergmann’s rule [4]), evolutionary (e.g. senescence [8]), and inter-specific patterns (e.g. avian plumage differences [9])

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