Investigating Intraspecific Attacks in Brown Bears (Ursus arctos) Using a Forensic Approach: Evidence from Northern Italy

Fatal intraspecific aggression in brown bears (Ursus arctos) remains poorly documented, yet elucidating its dynamics is critical in order to understand species’ physiology, informing management strategies, and advancing wildlife forensic science applications, which are useful in cases where a natural or illegal cause of death needs to be discerned. In this study, we reported four confirmed cases of lethal aggression (two yearlings and two adults) in the Italian Alps. Comprehensive autopsies were performed to characterize lesion patterns and infer the aggressor identity. Claw-induced lacerations, bite marks and the aspect of hemorrhages suggested the attack sequence. Aggressor identity was investigated by using forensic odontology through inter-canine distance (I-CD) and genetic analysis of peri-lesional saliva. I-CD allowed us to plausibly hypothesize the aggressor’s species and, in the cases where it was possible, to classify the sex and/or age group of the aggressors. While genetic analysis allowed the identification of the four brown bear victims, it did not provide informative results on the aggressors. The cause and manner of death were coded according to international criteria (International Classification of Diseases 11th Revision ICD-11, WHO). Adult fatalities, supported by gastric content analysis, reflect trophic competition regardless of the mating context and highlight the role of anthropogenic food sources in conflict emergence. These findings underscore the value of integrated approaches in wildlife investigations and provide new insights into ecophysiological factors driving lethal intraspecific aggression.