Infanticide in ursine colobus monkeys (Colobus vellerosus) in Ghana: new cases and a test of the existing hypotheses

Abstract

Summary During a 13-month study period on four groups of Colobus vellerosus at the Boabeng-Fiema Monkey Sanctuary in Ghana, we recorded all instances of male aggression to infants and mothers with infants using focal-animal and ad libitum sampling. Resident males did not attack infants, whereas new immigrant males who became high-ranking and those that immigrated as part of an all-male band did. During this period, three cases of confirmed infanticide, one case of likely infanticide, and three suspected infanticides were attributed to new males. Not all new alpha males attacked infants; however, after a takeover in Group B2, the new alpha male did not attack an eight- week old infant. Some resident males aided females in infant defence but were not successful. These new cases and previously reported cases of infanticide seem to best-fit predictions of the sexual selection hypothesis. Infant attacks were performed by seemingly unrelated males who gained mating access to mothers after their infants died. Loss of a previous infant shortened the inter-birth intervals of females (N = 6). Male infants may have been targeted preferentially at this site, which would support the * eliminate a future sexual rival' hypothesis, although more cases are needed to reach a firm conclusion.