A case of male infanticide in captive sika deer (Cervus nippon)

Male infanticide has been reported in wide range of mammalian taxa however it remains very rare in even-toed ungulates where it was documented in two species only. Among six hypotheses explaining this phenomenon, the sexual selection hypothesis is supported by the largest evidence in mammals. Here, we report the first case of male infanticide in sika deer (Cervus nippon) which occurred at Ostrava Zoo. At the end of rutting season, new male had been joined with two pregnant females that successfully gave birth and reared offspring in his presence then. However, in the next season, the same male attacked and killed his own newborn female offspring. Since this male was separated from the herd for most of the time in the rut, we argue that he could be confused about paternity. Therefore, this case of infanticide might be driven by the same mechanism as that which is in line with the sexual selection hypothesis. In addition, based on our evidence we cannot reject the social pathology hypothesis as an alternative explanation.

An observation of intergroup infanticide in grey-cheeked mangabeys (Lophocebus albigena)

In primates, infanticide is occasionally observed during intergroup conflicts but does not fit the predictions of the sexual selection hypothesis. I report an observation of an intergroup infanticide during a sub-group foray in grey-cheeked mangabeys (Lophocebus albigena) at the Ngogo site in Kibale National Park, Uganda. Intergroup infanticide appears to be a form of extreme and long-term food defence across primate species, and occurs in conjunction with other forms of food defence.

Sexual selection and the evolution of altruism: males are more altruistic and cooperative towards attractive females

Explaining altruism through an evolutionary lens has been a challenge for evolutionary theorists. Where altruism towards kin is well understood through kin selection, altruism towards non-kin is an evolutionary puzzle. Contemporary research has found that, through a game-theoretic framework, sexual selection could be an explanation for the evolution of altruism. Research suggests that males are more altruistic towards females they are interested in engaging with, sexually or romantically when distributing stakes in economic games. This study, adopting a between-groups design, tested the sexual selection explanation for altruism by asking participants to self-report altruistic and cooperative intention when reading moral scenarios accompanied by attractive or unattractive images. We find that participants, particularly males, report being more altruistic and cooperative when viewing an attractive image of a female. This study replicates the sexual selection hypothesis in explaining altruism through an alternative experimental framework to game theory.