Data from: Sex-specific tradeoffs influence thermoregulation under climate change

Increasingly, climate change is pushing species to the limits of their
thermal tolerance, with cascading effects across ecosystems. Animals use
behavior to prevent these harmful physiological states, but their need and
ability to do so varies with their traits. Within species, traits like sex
and reproductive status affect heat sensitivity, perhaps eliciting
differences in behavioral responses to thermal extremes. We evaluated
whether sex and reproductive status affected thermoregulatory behavior and
its efficacy in moose (Alces alces), a heat-sensitive endotherm that
relies on thermal refuge. We expected traits associated with elevated heat
load would be linked to heightened selection for thermal refuge and that
differences in selection would successfully alleviate differing risks of
overheating. Thus, reproductive females and males, who are more
heat-sensitive, would have stronger selection for thermal refuge than
non-reproductive females. We assessed selection of thermal refuge at bed
sites and generated biophysical models to evaluate if selection mitigated
risk of overheating. Reproductive status did not elicit differences in
selection by females. The sexes, however, differed in selection of the
tradeoff between solar cover and cooling from wind. Females selected
refuge with canopy cover and avoided wind. Males did not select cover and
had weaker avoidance of wind than females. Yet, both sexes were more
likely to overheat in areas of low cover, even if wind speeds were high.
Hence, males had weaker selection of refuge than females despite being
more likely to overheat, and life history tradeoffs failed to explain the
sub-optimal thermoregulatory behavior. We identify sex-specific
thermoregulatory tradeoffs, highlighting the disproportionate effects of
climate change on certain demographic groups. Moreover, we emphasize the
relevance of trait-based approaches for studying changing ecosystems.

气候变化正日益将物种推至其热耐受极限，并对整个生态系统产生级联效应。动物可通过行为策略规避此类有害生理状态，但其规避需求与实施能力因自身性状而异。在同一物种内，性别与繁殖状态等性状会影响个体的热敏感性，进而可能引发其对极端高温事件的行为响应差异。本研究以依赖热庇护所（thermal refuge）的热敏性内温动物（endotherm）驼鹿（*Alces alces*）为研究对象，探究性别与繁殖状态是否会影响其体温调节行为（thermoregulatory behavior）及其实施效果。我们推测，与更高热负荷相关的性状，会与个体对热庇护所的更强选择偏好相关联，且这种选择偏好差异可有效缓解个体面临的不同过热风险。据此推测，相较于非繁殖期雌性，繁殖期雌性与雄性这类热敏性更强的个体，对热庇护所的选择偏好会更强。我们通过评估驼鹿卧息地的热庇护所选择情况，并构建生物物理模型（biophysical models），以此判断其庇护所选择是否能缓解过热风险。繁殖状态并未引发雌性个体在庇护所选择上的差异。但不同性别个体在权衡太阳遮蔽与风力降温的选择策略上存在显著差异。雌性个体倾向于选择具有林冠遮蔽的庇护所，并主动避开多风区域；而雄性个体则不会主动选择遮蔽区域，且相较于雌性，其对多风区域的回避程度更低。不过，即便风速较高，当遮蔽程度较低时，雌雄个体均更易出现过热情况。因此，尽管雄性个体更易过热，但其对庇护所的选择偏好却弱于雌性，而生活史权衡（life history tradeoffs）理论无法解释这种次优的体温调节行为。本研究揭示了性别特异性的体温调节权衡机制，凸显了气候变化对特定种群类群的不成比例影响。此外，本研究强调了基于性状的研究方法在气候变化下的生态系统研究中的重要价值。