Infanticide attacks and associated epimeletic behaviour in free-ranging common bottlenose dolphins (Tursiops truncatus)

Abstract

Infanticide is considered a conspicuous expression of sexual conflict amongst mammals, including bottlenose dolphins. Although reported previously in this species, confirmed cases of infanticide and associated epimeletic behaviour are very rare and their socio-behavioural context remains poorly understood. Here, we provide evidence of epimeletic and infanticide behaviours in free-ranging bottlenose dolphins in Galicia, NW Spain. After describing the observed events, we include a complete description of the post-mortem examinations (where the carcasses were recovered) in order to confirm the cause of death. With evidences of blunt trauma in two of the presented cases, we confirm that the calves were intentionally killed by adult individuals. The aggressive interaction between adult individuals and the neonates together with the observed ante-mortem injuries bore a strong resemblance to the behaviours and traumatic injuries described in other cases of violent dolphin interactions in other parts of the world. The circumstances under which these infanticides occurred at our site fit the conditions proposed under the sexual selection hypothesis. The difficulties for researchers to observe this type of behaviour in the field and to find carcasses in good enough condition to determine the cause of death, emphasizes the importance of this type of study.