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Adult Male Wild Boar Mounted a Dead Female and Revisited the Carcass 12 Times

Wild boar standing on a riverbank in Gunma Prefecture, Japan
Research · Behaviour

Camera traps in Nikko City, Japan, recorded an adult male wild boar (Sus scrofa) repeatedly returning to the carcass of an adult female, with mounting attempts during his first two visits. The male visited the carcass 12 times between 6 and 18 October 2023 and continued interacting with it as decomposition progressed.

The carcass was monitored from 1 October to 11 November with motion-triggered video and daily interval images. Three wild boar approached it during the study, but their responses differed strongly. Three independent observers identified the repeated visitor as the same adult male from body size, body shape, external genitalia and snout length. He made 12 visits from 6 to 18 October. A juvenile female accompanied him during three visits and appeared alone once without clear carcass-directed behaviour; a third, subadult animal of unknown sex visited twice later during skeletonisation and showed only exploratory movement.

Mounting occurred only during the first two visits

The adult male was filmed mounting the carcass for a total of 719 seconds — about 12 minutes — during his first two visits on 6 October. Nosing and chin-resting, behaviours associated with wild-boar courtship, were also recorded. These observations led the authors to classify the mounting as necrophilic behaviour: attempted copulation directed toward a dead conspecific or closely related species.

The trigger for the mounting remains unknown

Sniffing was especially frequent during the two visits in which mounting occurred, so the authors consider olfactory or other chemical cues a possible proximate trigger. One possibility is that cues linked to the female’s reproductive state remained detectable, but her oestrous status was unknown and the male first reached the carcass 4.6 days after it was placed. The authors therefore could not determine what triggered the necrophilic behaviour.

Interest continued after the mating attempts

Later visits included stepping on the carcass, sniffing it and resting nearby, even as the body reached advanced decomposition and skeletonisation. None of the three wild boars consumed soft tissue, although the adult male later chewed a rib bone. The researchers interpret the prolonged pattern as sustained interest rather than scavenging.

The literature review identified ten previous mammalian reports, making this the 11th documented case in mammals and the fourth in terrestrial mammals. The authors emphasise that one case does not show that such behaviour is typical of wild boar. They place the observations within comparative thanatology — the study of how animals respond to death and dead conspecifics — because the three individuals reacted very differently and the adult male’s behaviour changed as decomposition progressed. The authors also note that repeated physical contact with conspecific carcasses could increase transmission risk for infections such as African and classical swine fever even when animals do not scavenge soft tissue.

Sources and image credit

  1. Inagaki, A., Okuda, K., Allen, M. L., & Koike, S. (2026). Mating attempts and sustained interest behaviors of wild boars (Sus scrofa) toward a dead conspecific. Ecology and Evolution, 16(6), e73848. https://doi.org/10.1002/ece3.73848Primary open-access research article first published 16 June 2026 under CC BY 4.0. A camera trap monitored an adult female wild boar carcass in Nikko City from 1 October to 11 November 2023. Three wild boar visited; one adult male returned 12 times from 6–18 October, mounted the carcass for a total of about 12 minutes during the first two visits and continued non-feeding interactions as decomposition progressed. The authors describe this as a single documented case and do not infer that the behaviour is typical of the species.
  2. Tokyo University of Agriculture and Technology. (2026, June 26). Press release on wild boar responses to a dead conspecific.Institutional press release from the research team summarising the observations and reproducing camera-trap frames from the published study.

Image: Yasuo Hamashima / Wikimedia Commons — wild boar (Sus scrofa) photographed on a riverbank in Gunma Prefecture, Japan, 4 March 2012; representative living animal, not one of the study individuals; cropped to 16:9 from the original · CC BY-SA 4.0 · Source

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