A Case of Male Adoption in a Troop of Japanese Monkeys (Macaca fuscata fuscata)

Abstract

During the past few years interest among primatologists in male parental care has increased. In this paper I will describe a series of events which occurred in the Arashiyama B troop of Japanese macaques in the spring of 1978 that resulted in the third highest ranking male, Ran63, becoming the primary caretaker of two sisters— one 10 months of age and the other 22 months of age at the time of the adoption — and another unrelated male infant also 10 months of age at the time of the adoption. The term primary caretaker is being used here to define a situation in which (1) the mother is no longer available to be the caretaker, (2) the adoptee(s) maintain close proximity to the male while traveling, foraging or eating provisioned food and may even be carried by the male (although Ran63 did not in this case carry any of his adoptees), (3) the male protects the adoptee(s) from the aggression of other troop members, and (4) the male and the adoptee(s engage in grooming and huddling while resting and sleeping. Following the description of the adoptions, a series of questions involving altruism, kin selection, and reproductive strategies will be explored. It is hoped that by exploring these questions the behavior of Japanese macaque males toward motherless infants and juveniles will be better understood. Because of the rarity of such adoptions, the data are necessarily anecdotal. As an aside, adult Arachiyama females have not been observed adopting motherless infants.