Do sex, age or ecological needs shape an endangered brown bear population diet? New insights from faecal metabarcoding.

Conservation strategies usually focus on megafauna and keystone species to protect habitats. In temperate ecosystems, brown bear appears as one of the potential megafauna keystone species thanks to its omnivorous diet. However, most of the trophic interactions’ studies used coproscopic analyses that generally miss highly digested items and rarely investigated the effect of sex, age and individual. In addition, the diet was frequently investigated according to climatic seasons, while Bear Ecological Periods - BEP - (e.g. mating, hyperphagia) really drive individual movement and foraging. In this study, we collected brown bear faeces of different age class and sex across BEP from a critically endangered population. We used metabarcoding and four markers specific to plants, fungi, arthropods and vertebrates to investigate the brown bear diet in the Pyrénées mountains. The diet was mainly composed of plants but also of arthropods, vertebrates and fungi. Pyrenean brown bear consumed significantly fewer arthropods during hyperphagia than other BEP, and exhibited preferences for different plant life forms during mating (diversified herbs), pre-hyperphagia (fleshy-fruits) and hyperphagia (dry-fruits). Females consumed plants more often than males, which in turn consumed more wild vertebrates. We highlighted the most diverse level of mycophagy (21 genera) of an omnivore Ursid thanks to metabarcoding. We showed the high variability of this brown bear population diet among BEP and sexes, but not among age-classes. This detailed diet study provides new insights for brown bear conservation, and invites similar approaches on other animals.