Thomas S. Jung

Climate change drives variable shifts in mammalian body sizes, yet the mechanisms underlying this variation remain unclear. Two explanations prevail: (1) higher temperatures reduce thermal constraints, favouring smaller bodies; or (2) warming enhances primary productivity, supporting larger bodies. We propose that species' overwintering strategies, which mitigate exposure to winter temperatures, determine which mechanism predominates. Using ~50 years of body mass data, we tested these hypotheses in three small mammals with contrasting natural histories in the rapidly warming Yukon, Canada. Snowshoe hares ( Lepus americanus ), exposed to ambient winter conditions, declined in mass over time and responded negatively to temperature and snow. In subnivean species, deer mice ( Peromyscus maniculatus ) showed no long‐term trend but increased body mass with growing degree days, whereas red‐backed voles ( Clethrionomys rutilus ) increased with temperature and snow. The results demonstrate that overwintering ecology mediates climate‐driven body mass change, emphasizing the role of natural history in shaping species' responses to warming.

Habitat selection by reintroduced and remnant populations of wood bison ( Bison bison athabascae ) in the boreal forest are not well understood, especially in landscapes characterized by anthropogenic disturbance. Yet, this information is key for conservation planning for wood bison, a threatened species in Canada. We used data from GPS‐collared bison in northeastern British Columbia to develop seasonal resource selection function models that quantified selection or avoidance of oil and gas infrastructure, as well as natural disturbances and other ecological factors. We predicted that bison would select a range of early seral habitat types including areas associated with linear features and industrial activities. Consistent with our predictions, resource roads were the most influential disturbance features associated with resource selection of GPS‐collared bison during winter and summer. Across both seasons, bison selected for areas close to most linear disturbance features but avoided areas with relatively greater densities of linear disturbances. Bison may use linear disturbances as travel corridors or as foraging habitat, but there appears to be a threshold above which bison avoid these features. Conversely, bison selected areas closer to polygonal disturbances (e.g., well sites) in both seasons and selected areas with greater densities of these features in the winter. Overall, we found that bison selected for anthropogenic features associated with the oil and gas industry. Although these recently disturbed vegetation communities provide foraging habitat, they also lead to conflict with humans that may result in the mortality of bison. Mitigations such as restoring disturbed habitats to a natural state, management actions that discourage or prevent the use of anthropogenic habitats, and fostering a stewardship ethic within industry will improve human‐bison coexistence on landscapes characterized by anthropogenic disturbance.

Some species collect and consume the faeces of other species. However, evidence of such heterospecific coprophagy is rarely documented for wild mammals and has not been reported for Collared Pika (Ochotona collaris). We observed 14 Collared Pika haypiles (food caches) in northwestern Canada that contained faecal pellets of Hoary Marmot (Marmota caligata). Our observations were from two study areas ~700 km apart, suggesting that this behaviour may be widespread. We did not observe Collared Pikas consuming Hoary Marmot pellets, and they may collect them for other, unknown reasons, including as curios. Regardless, our observations are of value because they represent evidence of possible heterospecific coprophagy in Collared Pikas, which can potentially contribute to our understanding of their nutritional strategy.

Small mammals play a central role in northern ecosystems, yet their diversity and habitat associations remain poorly documented in the subarctic mountains of northwestern Canada. I assessed small mammal assemblages across elevational and habitat gradients in Tombstone Territorial Park, located in the Taiga Cordillera Ecozone. My objectives were to document small mammal diversity and habitat associations. In 2005, small mammals were sampled at 27 sites representing seven common habitat types, ranging from lowland boreal forest to subalpine shrublands and alpine tundra. Twelve species of voles, lemmings, mice, and shrews were captured. Species richness and relative abundance were highest in lowland habitats and declined with increasing elevation. Alpine habitats supported fewer, highly specialized species. Several species were restricted to lowland habitats, whereas two species occurred exclusively in alpine tundra. Canonical correspondence analysis revealed a separation of species assemblages based primarily on moisture. These findings demonstrated that moisture, elevation, and habitat type structured small mammal assemblages in this northern mountain landscape. As a first approximation of small mammal assemblages in the Taiga Cordillera Ecozone, I provide a historical baseline for detecting recent and future ecological change. Climate change may facilitate the range expansion of lowland species and alter alpine assemblages, with potential consequences for community composition, trophic interactions, and ecosystem processes, highlighting the importance of small mammal monitoring in a rapidly warming subarctic.

Understanding how crises impact local hunters and wildlife is imperative for developing adaptive strategies to navigate these disruptions. COVID-19 caused widespread disruptions to socioecological systems, yet the response of local hunters to the global pandemic remains understudied. I examined hunting permit sales, harvest records, and hunter effort and motivation data to investigate how the pandemic influenced bison (Bison bison) hunters in the Yukon. Following the onset of COVID-19, the number of permits sold, and bison harvested, increased by 13% and 21%, respectively. Although harvest numbers quickly returned to pre-pandemic levels afterward, the number of permits sold continued to rise, indicating sustained interest. Hunters indicated that increased interest and opportunity during the pandemic were driven by concerns over food security. Less tangible motivations—such as spending time outdoors with family and friends—were also important. My findings reveal how global crises can temporarily increase hunting pressure in some socioecological systems. Wildlife managers should anticipate increased interest and opportunity by local hunters during disruptions to food supply, travel, or social gatherings. These results emphasize the importance of integrating social and ecological data to inform adaptive management strategies that anticipate changes in hunting pressure during societal crises.

Mammalian coat colour is adaptive, conferring benefits that enhance fitness. While most species have converged to an optimal coat colour it remains variable in others. Gloger’s rule predicts darker coats in humid than in arid areas; yet this rule requires further testing. Using coat colour data from 2279 black bears ( Ursus americanus Pallas, 1780) from the Yukon, I examined the spatial prevalence of black and non-black colourmorphs. An information-theoretic approach was used to rank candidate models including age, sex, and ecoregion, as predictors of colourmorph prevalence. Ecoregions differed with respect to humidity, habitat openness, and grizzly bear ( Ursus arctos Linnaeus, 1758) densities, and were used as proxies to test ecogeographical hypotheses. Most black bears were black (64%). Sex and ecoregion were the highest ranked predictors of colourmorph prevalence. Colourmorphs of male black bears—but not females—differed significantly by ecoregion. Males were more apt to be black in humid ecoregions. These results provide partial support for Gloger’s rule operating at ecoregional scales depending on sex. From an evolutionary perspective, the sex-biased conformity to Gloger’s rule suggests that selection for coat colour may operate differently on males and females, providing an intriguing avenue for further research with polychromatic mammals.

Grizzly Bear (Ursus arctos) predation on American Bison (Bison bison)—particularly calves—was likely once common.However, with the range-wide collapse of bison near the close of the 19th century, the two species no longer co-occur across much of their current distributions. Over the past 60 years, efforts to reintroduce bison to their native range have resulted in a few small areas where the two species once again co-occur. Yet, predation of bison by bears is apparently rare and has not been observed outside Yellowstone National Park, where both species have existed for millennia. On 28 June 2023, we observed an adult male Grizzly Bear protecting a buried bison calf that it had apparently killed in Yukon, Canada. This is the first observation of apparent predation of a bison by a Grizzly Bear outside Yellowstone National Park. Our observation further highlights how reintroduced bison are becoming integrated into local food webs, which is a key indicator of ecological restoration.