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 be..., Capture and Handling
We used a helicopter to chemically immobilize adult moose (≥ 1 year) each year in March (2020–2023; Levine et al. 2022a). For the duration of the study, we aimed to maintain a sample size of 15 collared animals per sex. Males were captured once, and females were recaptured annually. We removed the right, incisiform canine (Swift et al. 2002) and determined age via cementum annuli (Matson’s Laboratory, Milltown, MT). We estimated body mass using morphometrics (Hundertmark and Schwartz 1998). To assess nutritional condition, we measured the maximum depth of rump fat using a portable ultrasound device (Ibex Pro, E.I. Medical Imaging, Loveland, Colorado) with a 5-MHz linear-array transducer (Stephenson et al. 1998) and accompanied ultrasound with palpation to determine a body condition score (Levine et al. 2022b). We derived percent ingesta-free body fat (hereafter nutritional condition) from scaled rump fat (Cook et al. 2010; Stephenson et al. 1998) and body condition ..., , # Data from: Sex-specific tradeoffs influence thermoregulation under climate change

During the summers of 2021 and 2022, we identified bed sites used by collared moose between parturition (mid-May) and growth of winter pelage (September) using mean location of clustered (≤15 m apart) GPS-collar fixes (Verzuh et al. 2021). We censored GPS data to 3-D or 2-D fixes and dilution of precision <2 (D’Eon and Delparte 2005; Moen et al. 1997). Sites were limited to beds used for 1+ h during daylight hours (i.e., sunrise to sunset at the site). We visited bed sites within 2 weeks of use. We confirmed bed sites by searching a 15m radius for signs of use: matted vegetation, muddy depressions, faecal matter, or moose hair. For each confirmed bed site (i.e., used site), we assessed three available sites at a randomly generated azimuth (0° to 359°) and distance (15 to 330m; Verzuh et al. 2021) from the used site. To collect microclimate data at used and available sites, we placed weather stations at ...,