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The energetic consequences of body size, behaviour, and fine-scale environmental variation remain understudied, particularly among free-ranging carnivores, due to logistical and methodological challenges of studying them in the field. Here, we present novel activity, heart rate, and metabolic data on free-ranging Canada lynx (Lynx canadensis Kerr, 1792) to (i) investigate intraspecific patterns of energy expenditure, particularly how they relate to body size, environmental conditions, and activity variation, and (ii) position lynx - a cold-climate, mesocarnivore - within interspecific allometries of carnivore energetics. Lynx demonstrated limited behavioural and metabolic responses to environmental conditions, despite extreme cold and moderate snow depths during our study, but marked body size patterns with larger lynx having higher activity and lower resting heart rate than smaller lynx. Compared with similar-sized carnivores, lynx were less active and had lower heart rate, likely due to their ambush hunting style, but higher energy expenditure, likely due to their coldclimate existence and access to abundant prey. Overall, lynx were more similar to other ambush hunters than to sympatric cold-climate species and mesocarnivores. Our data provide insight into the relative importance of abiotic and biotic drivers of carnivore energetics and the ways in which predators maintain energy balance in variable environments. Key words: activity, allometry, biologger, boreal ecology, energy expenditure, heart rate, Canada lynx, Lynx canadensis, mesocarnivore, winter. Les consequences energetiques de la taille du corps, du comportement et de variations environnementales a petite echelle demeurent sous-etudiees, particulierement chez les carnivores en liberte en raison de defis logistiques et methodologiques associes a leur etude sur le terrain. Nous presentons de nouvelles donnees sur l'activite, le rythme cardiaque et le metabolisme pour des lynx du Canada (Lynx canadensis Kerr, 1792) en liberte afin (i) d'examiner les motifs intraspecifiques de depense d'energie, plus particulierement leurs relations a la taille du corps, aux conditions ambiantes et aux variations de l'activite, et (ii) de positionner le lynx, un mesocarnivore de climat froid, au sein d'allometries interspecifiques d'energetique des carnivores. Les lynx presentent des reactions comportementales et metaboliques limitees aux conditions ambiantes, malgre des froids extremes et des epaisseurs de neige moderees durant l'etude, mais des motifs de taille du corps marques, les plus grands lynx presentant une plus grande activite et un rythme cardiaque au repos plus faible que les lynx plus petits. Comparativement a d'autres carnivores de taille semblable, les lynx etaient moins actifs et leur rythme cardiaque etait plus faible, probablement en raison de leur mode de chasse par embuscade, mais de plus grandes depenses energetiques, vraisemblablement en raison de leur vie en climat froid et leur acces a une abondance de proies. Globalement, les lynx sont plus semblables a d'autres chasseurs par embuscade qu'a des especes sympatriques et des mesocarnivores de climat froid. Nos donnees permettent de mieux comprendre l'importance relative de facteurs abiotiques et biotiques qui influencent l'energetique des carnivores et les moyens qu'emploient les predateurs pour maintenir leur equilibre energetique dans des milieux variables. [Traduit par la Redaction] Mots-cles : activite, allometrie, capteur de parametres biologiques, ecologie boreale, depense energetique, rythme cardiaque, lynx du Canada, Lynx canadensis, mesocarnivore, hiver., Introduction Predators occupying high trophic positions tend to have high energy requirements due to their large body size (Kleiber 1932; Schmidt-Nielsen 1984; Peters 1986; White et al. 2019); elevated resting [...]

Perceived predation risk alters prey behaviour and physiology, but few studies have examined downstream consequences on prey demography in wild populations. Perceived predation risk could alter adult reproductive performance via reduced investment in offspring quality and post-birth care. We manipulated perceived predation risk in snowshoe hare (Lepus americanus Erxleben, 1777) by exposing pregnant mothers to chases by a domestic dog (Canis familiaris Linnaeus, 1758). Litter size was comparable between risk-augmented and control groups, but treated females had more stillbirths and gave birth to leverets of lower body condition. Leverets from risk-augmented females had 88% higher 40-day mortality rate. Maternally preventable causes of death like starvation or predation by red squirrel (Tamiasciurus hudsonicus (Erxleben, 1777)) caused this difference, particularly during the nursing period. Risk-augmented mothers were always more active than controls, but the difference was greatest during the nursing period. We found that perceived predation risk reduces maternal productivity pre- and post-partum, implying downstream consequences to populations. Because our treatment ended before parturition, we can link offspring performance such as survival and behaviour specifically to maternal life-history trade-offs, which has not been shown in a wild mammal. [ABSTRACT FROM AUTHOR]