Desforges Jean-Pierre, van Beest Floris M, Marques Gonçalo M, Pedersen Stine H, Beumer Larissa T, Chimienti Marianna, Schmidt Niels Martin
Bioscience Department Aarhus University Roskilde Denmark.
Arctic Research Centre Aarhus University Aarhus Denmark.
Ecol Evol. 2020 Nov 22;11(1):338-351. doi: 10.1002/ece3.7049. eCollection 2021 Jan.
Animals have adapted behavioral and physiological strategies to conserve energy during periods of adverse conditions. Heterothermy is one such adaptation used by endotherms. While heterothermy-fluctuations in body temperature and metabolic rate-has been shown in large vertebrates, little is known of the costs and benefits of this strategy, both in terms of energy and in terms of fitness. Hence, our objective was to model the energetics of seasonal heterothermy in the largest Arctic ungulate, the muskox (), using an individual-based energy budget model of metabolic physiology. We found that the empirically based drop in body temperature (winter max ~-0.8°C) overwinter in adult females resulted in substantial fitness benefits in terms of reduced daily energy expenditure and body mass loss. Body mass and energy reserves were 8.98% and 14.46% greater in modeled heterotherms compared to normotherms by end of winter. Based on environmental simulations, we show that seasonal heterothermy can, to some extent, buffer the negative consequences of poor prewinter body condition or reduced winter food accessibility, leading to greater winter survival (+20%-30%) and spring energy reserves (+10%-30%), and thus increased probability of future reproductive success. These results indicate substantial adaptive short-term benefits of seasonal heterothermy at the individual level, with potential implications for long-term population dynamics in highly seasonal environments.
动物已经进化出行为和生理策略，以便在不利条件下保存能量。异温性就是恒温动物所采用的一种此类适应性策略。虽然大型脊椎动物已表现出异温性——体温和代谢率的波动，但对于这种策略在能量和适应性方面的成本与收益却知之甚少。因此，我们的目标是使用基于个体的代谢生理能量预算模型，来模拟最大的北极有蹄类动物麝牛季节性异温性的能量学特征。我们发现，成年雌性麝牛在冬季基于经验的体温下降（冬季最高体温约为 -0.8°C），在减少每日能量消耗和体重减轻方面带来了显著的适应性益处。到冬季结束时，与正常体温的麝牛相比，模拟的异温性麝牛的体重和能量储备分别高出8.98%和14.46%。基于环境模拟，我们表明季节性异温性在一定程度上可以缓冲冬季前身体状况不佳或冬季食物可获取性降低的负面影响，从而提高冬季存活率（提高20%-30%）和春季能量储备（提高10%-30%），进而增加未来繁殖成功的概率。这些结果表明季节性异温性在个体层面具有显著的适应性短期益处，对高度季节性环境中的长期种群动态可能具有潜在影响。
