Mating Attempts and Sustained Interest Behaviors of Wild Boars (Sus scrofa) Toward a Dead Conspecific

Responses of animals to dead conspecifics are rarely characterized from ecological or comparative thanatological perspectives. Here, we report the behavioral responses of three wild boars (Sus scrofa) toward the carcass of an adult female conspecific, which was monitored using camera traps throughout the entire decomposition process. These observations were made in Nikko City, Japan, between October 1 and November 11, 2023. One adult male exhibited mounting behavior toward the carcass, providing evidence of necrophilic behavior. This behavior is rarely documented in mammals; according to our literature review, this is the 11th case in mammals and the 4th in terrestrial mammals. Furthermore, the adult male's interest in the carcass persisted for approximately 17 days after the first visit, continuing after mounting events and including behaviors such as stepping on the carcass and resting near the carcass. Documentations of necrophilic behavior are often based on single observations, which may mean that important elements of comparative thanatology, such as behavioral shifts and responses associated with different carcass decomposition stages, are being overlooked. None of the individuals consumed soft tissues, suggesting that visits to the carcass were not motivated by feeding on carrion. These observations highlight sustained interest in a conspecific carcass without feeding and reveal pronounced individual variation in behavioral responses. We suggest that monitoring carcasses can provide valuable insights into comparative thanatology beyond traditional carrion ecology.