Interspecies sexual behaviour between a male Japanese macaque and female sika deer


Interspecies sexual behaviour or ‘reproductive interference’ has been reported across a wide range of animal taxa. However, most of these occurrences were observed in phylogenetically close species and were mainly discussed in terms of their effect on fitness, hybridization and species survival. The few cases of heterospecific mating in distant species occurred between animals that were bred and maintained in captivity. Only one scientific study has reported this phenomenon, describing sexual harassment of king penguins by an Antarctic fur seal. This is the first article to report mating behaviour between a male Japanese macaque (Macaca fuscata yakui) and female sika deer (Cervus nippon yakushimae) on Yakushima Island, Japan. Although Japanese macaques are known to ride deer, this individual showed clearly sexual behaviour towards several female deer, some of which tried to escape whilst others accepted the mount. This male seems to belong to a group of peripheral males. Although this phenomenon may be explained as copulation learning, this is highly unlikely. The most realistic hypothesis would be that of mate deprivation, which states that males with limited access to females are more likely to display this behaviour. Whatever the cause for this event may be, the observation of highly unusual animal behaviour may be a key to understanding the evolution of heterospecific mating behaviour in the animal kingdom.

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This article and this observation were made possible by funds donated to the “Saru: Singes du Japon” Grant Initiative d’Excellence W15RJSHO project by the University of Strasbourg and the French Ministry for Higher Education. We also thank Hiroyuki Miyamoto from JSPS Strasbourg office and Hideki Sugiura from Kyoto University Wildlife Research Center for their help on Yakushima Island. We thank Munro Language Services for English language editing.

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Correspondence to Cédric Sueur.

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Ethics statement

Authors declare no competing interests and no conflicts of interests. Our approach solely involved observations of non-human animals. Animals were not handled, and no invasive experiments were carried out. This study was conducted with the approval of the Prefecture of Kagoshima (with the help of the Wildlife Research Centre and the Japanese Society for the Promotion of Science) to be in the Yakushima Forest and with the authorisation of our institute (IPHC, CNRS). Animals were already used to human presence on Yakushima.

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Supplementary video file: Movie of sexual mounts of a Japanese macaque male on two different deer: (MP4 87498 kb)

Supplementary video file: Movie of sexual mounts of a Japanese macaque male on two different deer: (MP4 87498 kb)

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Pelé, M., Bonnefoy, A., Shimada, M. et al. Interspecies sexual behaviour between a male Japanese macaque and female sika deer. Primates 58, 275–278 (2017).

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  • Heterospecific mating
  • Sexual harassment
  • Primate
  • Macaca fuscata yakui
  • Reproductive interference