Marco Salvatori, Natalia Bragalanti, Andrea Corradini, Luca Pedrotti, Luca Corlatti, Valentina La Morgia, Vincenzo Gervasi, Chiara Rossi, Heidi Hauffe, Barbara Crestanello, Davide Righetti, Giulia Bombieri

Large carnivores have been extirpated from much of their historical range, but targeted conservation actions have supported their recovery. The reintroduction of the brown bear in the central Alps represents a notable example, yet long-term viability of this population remains uncertain due to its small size, isolation, and increasing conflicts with humans. Using spatial capture-recapture and survival models based on genetic data and known bear deaths collected on 222 individuals over 21 years (2003− 2023), we assessed spatio-temporal trends in bear density, abundance, survival, and range expansion, accounting for sex and age-specific differences. Population size in 2023 was estimated between 92 and 122 individuals (mean = 106). Density increased at an annual rate of 8 %, with a mean in 2023 of 1.6 bears/100 km2 in the whole study area, and 2.5 within the area permanently occupied by females. Bear density was higher in proximity to the release site and on steeper slopes. Survival probability varied by sex and age, and was lower for males and younger individuals. Site fidelity was highest for females, with no permanent emigration recorded. Despite the high site fidelity, the area occupied by females expanded substantially, increasing by 140% over two decades. However, this expansion remains confined to the western side of the Adige Valley, which represents a major ecological barrier in the central Alps, hindering connectivity with the nearest Dinaric-Pindos bear population. Despite growth, the population remains small and vulnerable to stochastic events. Observed spatial patterns and dynamics seem to reflect the interplay between intrinsic biological traits, like female philopatry, and anthropogenic factors, including artificial barriers. Sustained genetic monitoring, improved connectivity, and science-based management will be crucial to ensure the long-term persistence of this population in a human-dominated landscape and increasingly hostile social context.

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