As part of our research in modules on (1) stress level and (2) foraging strategies and nutritional status in the studied brown bear populations, we attempted to explain the relationship between estimates of dietary quality (% faecal nitrogen and faecal carbon) and stress level (measured as faecal cortisol metabolites concentration). These indicators should show seasonal changes, in line with the seasonal availability of particular types of food and their predominance in a given season, as well as bear physiology (periods of hypophagia and hyperphagia).
In this study, we investigated seasonal differences in food quality of two brown bear subpopulations in the Polish Carpathians using diet quality estimates. Studied subpopulations inhabit areas that differ in artificial feeding practices: the western subpopulation (Tatra Mountains) is not artificially fed, while the eastern subpopulation (Bieszczady Mountains) uses artificial food targeted to ungulates year-round.
We found that bears in Tatras fed on significantly higher quality diet, as shown by FN and FC values, and had significantly higher FC levels in hyperphagia, when they accumulate fat reserves for wintering. Also, the pattern in FCM levels for this subpopulation followed the changes in energy intake during the seasons of hypo- and hyperphagia. No seasonal patterns could be observed in Bieszczady. Artificial feeding practices may disrupt nutrient phenology and seasonality, relative to subpopulations with natural diets. We showed that the availability of human-provided foods may alter not only the overall dietary quality, but also hormonal patterns linked to seasonal nutritional requirements.
Our publication is available here https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0242341&type=printable