The effects of climate and plant phenological changes on herbivorous species are widely recognized, yet less research has focused on omnivorous and carnivorous species, even though they also have vegetative components to their diet. The historical focus on predators regarding simple interactions between obligate carnivores and their prey over-simplifies many species’ roles within ecological communities by casting them purely as predators and minimizes other, equally important roles within the community. We used a long-term, individual-based data set on a polyphagous mammal, the brown bear (Ursus arctos), to estimate diet over 25 years identify long-term patterns and factors contributing to annual variation in diet. We used carbon and nitrogen stable isotope values measured in hair and Bayesian mixing models to determine annual diet among three demographic bear classes, and then used linear regression models to relate diet to indices of food availability. We found that while diet varied among years and demographic classes, variation in both carbon and nitrogen values were explained by bilberry (Vaccinium myrtillus) productivity. Additionally, proportions of animal-derived foods decreased through time, while proportions of bilberry increased, even as the moose population in Sweden increased over this same period. While meat and animal-derived foods are considered higher quality foods for bears, bear diet did not respond to changing moose availability. Our results highlight that even though vegetative diet components in predators are typically considered less important to predator ecology, brown bears in Sweden responded to changes in primary production, regardless of prey availability. It will be crucial to put more emphasis on the vegetative parts of diets as we predict how species and ecological communities respond to climate change because predators serve many more functions within their community besides predation alone.

Comparing life history traits among populations that have been separated genetically for several hundred thousand years, but live in similar habitats on different continents, may help us understand how ecological and anthropomorphic factors shape life histories. We compared patterns of growth in body length and mass, and the influence of population density, habitat quality (NDVI), and reproduction on age-specific length and mass of male and female brown bears between Alberta, Canada, and Sweden. We found that Swedish females were significantly smaller in both length and mass than Alberta females. Swedish females also reached primiparity earlier and at a smaller mass and length. However, there were no continental differences in the patterns of growth in males. We found strong positive effects of NDVI, but only weak negative effects of population density on female mass and length in both areas. Generally, especially mass of Alberta females was more strongly affected by NDVI and density than for Swedish females. Reproduction had stronger negative effects on female mass in Alberta than in Sweden. We found no effects of NDVI and population density on male mass and body length in both areas. The larger variation in female growth and size between the areas, in contrast to males, may be related to differences in female reproductive investment due to differences in population trends, i.e., earlier reproduction in increasing populations or populations below carrying capacity, or to different selection pressures in the past, potentially due to human persecution. Swedish females exhibited characteristics typical of increasing populations, whereas Alberta females exhibited characteristics typical of stable or decreasing populations. The difference in reproduction investment means that Swedish bears can be harvested at higher rates, whereas Alberta bears must be managed more conservatively.