Torpor is a reversible reduction in endotherm body temperature and metabolic rate. Because torpid endotherms can attain lower body temperatures in colder environments, minimum torpor metabolism generally increases with rising air temperature whereas euthermic metabolism generally declines with rising air temperature. As a result, the fundamental metabolic niche of endotherms that express torpor should be driven by climate and should be broadest in colder environments. On the other hand, if torpor serves primarily as an energy conservation strategy and its expression is influenced by energy availability, then the realized metabolic niche should be defined by resources. To evaluate the influence of resource and climate on torpor use and metabolism of hibernating mammals, we monitored the torpor expression of free-ranging eastern chipmunks (Tamias striatus) over two winters of varying resource abundance. In the low-food year, soil temperature constrained maximum torpor expression but was too invariant across small spatial scales to explain individual variation in torpor expression. In the high-food year, torpor was drastically reduced, and local density of seed-producing trees predicted fine-scale spatial variation in torpor expression. Thus, the fundamental metabolic niche of hibernating chipmunks in cold environments is broad and constrained by climate, whereas the realized metabolic niche is highly variable among individuals and years and is determined primarily by local resource abundance.

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The miniaturization and affordability of new technology is driving a biologging revolution in wildlife ecology with use of animal‐borne data logging devices. Among many new biologging technologies, accelerometers are emerging as key tools for continuously recording animal behavior. Yet a critical, but under‐acknowledged consideration in biologging is the trade‐off between sampling rate and sampling duration, created by battery‐ (or memory‐) related sampling constraints. This is especially acute among small animals, causing most researchers to sample at high rates for very limited durations. Here, we show that high accuracy in behavioral classification is achievable when pairing low‐frequency acceleration recordings with temperature. We conducted 84 hr of direct behavioral observations on 67 free‐ranging red squirrels (200–300 g) that were fitted with accelerometers (2 g) recording tri‐axial acceleration and temperature at 1 Hz. We then used a random forest algorithm and a manually created decision tree, with variable sampling window lengths, to associate observed behavior with logger recorded acceleration and temperature. Finally, we assessed the accuracy of these different classifications using an additional 60 hr of behavioral observations, not used in the initial classification. The accuracy of the manually created decision tree classification using observational data varied from 70.6% to 91.6% depending on the complexity of the tree, with increasing accuracy as complexity decreased. Short duration behavior like running had lower accuracy than long‐duration behavior like feeding. The random forest algorithm offered similarly high overall accuracy, but the manual decision tree afforded the flexibility to create a hierarchical tree, and to adjust sampling window length for behavioral states with varying durations. Low frequency biologging of acceleration and temperature allows accurate behavioral classification of small animals over multi‐month sampling durations. Nevertheless, low sampling rates impose several important limitations, especially related to assessing the classification accuracy of short duration behavior.

Summary Given fundamental energetic trade‐offs among growth, maintenance and reproduction, individual differences in energy saving should have consequences for survival and reproductive success. Many endotherms use periodic heterothermy to reduce energy and water requirements and individual variation in heterothermy should have fitness consequences. However, attempts to disentangle individual‐ and population‐level variation in heterothermy are scarce. Here, we quantified patterns of heterothermy of 55 free‐ranging eastern chipmunks (Tamias striatus), food‐hoarding hibernators. Over five hibernation periods, we obtained a total of 7108 daily individual heterothermy indices (median: 118 per individual). Based on an individual reaction norm approach, we found that the use of heterothermy was repeatable and varied among individuals of the same population under similar environmental conditions. This among‐individual variation had consequences for winter survival and reproductive success. Individuals using less heterothermy at the beginning of the winter had decreased survival in resource‐rich but not in resource‐poor years and higher reproductive success in the subsequent breeding season. These results support the hypothesis that fluctuating selection maintains heterothermic diversity and suggest that individualized ecophysiology can contribute to a more thorough understanding of the evolution of energy‐saving strategies in endotherms. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12797/suppinfo is available for this article.

Social-ecological and biocultural systems connect people to their environment at the intersection of nature and culture. The harvest of local wildlife for human consumption is critically important to the food security of the world's Indigenous peoples and to the conservation of biodiversity, either as a driver of biodiversity loss or of biodiversity protection, depending on system properties. By their nature, local food systems are assumed to be both ecologically determined and culturally defined. Here, we analyze standardized local food consumption surveys conducted in 21 Indigenous communities across northern North America. Using measures of dietary similarity from the ecological sciences and a variance partitioning statistical approach, we reveal a profound and prevailing importance of culture in defining the types and amounts of animal species consumed as food, operating within the environmental constraint of local availability. This quantitative, multicommunity analysis reveals the sustainability and cultural agency inherent in local food systems and the importance of cultural-ecological coupling in an era of accelerating social and environmental change.

Recent research is revealing incredible diversity in the thermoregulatory patterns of wild and captive endotherms. As a result of these findings, classic thermoregulatory categories of 'homeothermy', 'daily heterothermy', and 'hibernation' are becoming harder to delineate, impeding our understanding of the physiological and evolutionary significance of variation within and around these categories. However, we lack a generalized analytical approach for evaluating and comparing the complex and diversified nature of the full breadth of heterothermy expressed by individuals, populations, and species. Here we propose a new approach that decomposes body temperature time series into three inherent properties-waveform, amplitude, and period-using a non-stationary technique that accommodates the temporal variability of body temperature patterns. This approach quantifies circadian and seasonal variation in thermoregulatory patterns, and uses the distribution of observed thermoregulatory patterns as a basis for intra- and inter-specific comparisons. We analyse body temperature time series from multiple species, including classical hibernators, tropical heterotherms, and homeotherms, to highlight the approach's general usefulness and the major axes of thermoregulatory variation that it reveals.

Identification of critical habitat is central to major conservation laws protecting endangered species in North America and around the world. Yet the actual ecological research that is required to identify which habitats are critical to the survival or recovery of species is rarely discussed and poorly documented. Here we quantitatively assess the information and methods used to identify critical habitat in the recovery strategies of 53 vertebrates at risk in Canada. Of the CH identifications assessed, 17% were based habitat occupancy information, 28% on habitat characteristics and/or functions and 40% assessed habitat suitability by linking functional use and biophysical characteristics. However, only 15% of the recovery strategies we evaluated examined relationships between habitat and population viability, abundance, individual fitness, or survival. Furthermore, the breadth of evidence used to assess critical habitats was weaker among long-lived taxa and did not improve over time. Hence, although any approach used to identify CH is likely to be a step in the right direction in minimally protecting and maintaining habitats supporting critical life-cycle processes, there is a persistent gap between the widely recognized importance of critical habitat and our ability to quantitatively link habitats to population trends and individual fitness.

Hibernators suppress physiological processes when expressing torpor, yet little is known about the effects of torpor on male reproductive physiology. Studies of hibernating mammals suggest that deep torpor negatively impacts spermatogenesis and that transitions between torpor and euthermic arousals increase cellular oxidative stress, with potentially damaging effects on sperm. Here, we hypothesize that variation in torpor expression affects the reproductive readiness of hibernators by impacting their sperm production. To test this, we examined the relationship between torpor expression and spermatogenesis in captive eastern chipmunks (Tamias striatus). We determined torpor depth with temperature data loggers and assessed its relationship with spermatogenesis by examining spermatogenic progression, cell division, sperm counts, sperm maturity, and DNA damage. We show that deep hibernators (high levels of torpor) largely halted spermatogenesis in late hibernation in comparison to shallow hibernators (low levels of torpor), where ongoing spermatogenesis was observed. Despite these differences in spermatogenic state during hibernation, spermatogenic progression, sperm numbers, and maturity did not differ in spring, potentially reflecting similar degrees of reproductive readiness. Interestingly, shallow hibernators exhibited higher rates of DNA damage in spermatogenic cells during hibernation, with this trend reversing in spring. Our results thus indicate that, once heterothermy is terminated, deep hibernators resume spermatogenesis, but are characterized by higher rates of DNA damage in spermatogenic cells at the seasonal stage when spring mating commences. Therefore, our study confirmed post-hibernation recovery of sperm production but also a potential impact of deep torpor expression during winter on DNA damage in spring.