First Case of Spinner Dolphin (Stenella longirostris) Infanticide off Reunion Island: Necropsy’s Findings and Post Mortem Inter-Species Interactions

This paper reports the first case of delphinid infanticide off Reunion Island (Indian Ocean). This event provided a rare opportunity to record almost immediate visual and acoustic behaviour in an infanticidal context. The necropsy demonstrated that calf’s death was caused by traumatical injuries, most probably inflicted through purposeful violent interactions. Teeth marks found on the calf’s skin would incriminate conspecifics. However, epimeletic and in particular nurturant behaviour from a mother towards her dying calf could induce superficial tooth marks as those observed here. Post mortem acoustic and behavioural observations displayed agonistic and sexual interactions from three Indo-Pacific bottlenose dolphin males towards the mother-calf pair spinner dolphin. The nature of the inter-species interaction strongly suggests that Indo-Pacific bottlenose dolphins could have caused traumatic lethal lesions on the calf to gain sexual access to a female from a smaller species.