Maternal caretaking behavior towards a dead juvenile in a wild, multi-level primate society

Abstract

Maternal caretaking and transport of dead infants are widespread among nonhuman primates, having been reported in numerous species of monkeys and apes. By contrast, accounts of such behaviors toward dead juveniles are scarce. Here, we describe responses by the mother and other group members to the death of a juvenile in a wild, multi-level group of Sichuan snub-nosed monkeys (Rhinopithecus roxellana). Following the juvenile's fatal accident, his mother transported and cared for the corpse for four days. Immature monkeys belonging to the same one-male unit, and some individuals from other social units also showed interest in and tended the corpse. Comparisons of this case with those involving the deaths of infants and an adult female in the same population highlight possible effects of physiological, psychological and emotional factors in primate thanatological responses, and provide an additional perspective on the origin and evolution of compassionate acts.

Figure 1

Responses of group members in Rhinopithecus roxellana. (A) The mother (red arrow) holds the dead juvenile (yellow arrow), and juvenile J3 (blue arrow) touches it. The OMU adult male (white arrow) remains nearby in a tree. (B) The mother holds the head of the corpse against her chest. (C) The mother struggles to walk with the corpse. (D) The mother, sitting alone beside the dead juvenile, emits calls. (E) The mother carries the corpse as she moves towards her OMU. (F) After the mother laid some leaves on the corpse a juvenile (teal arrow) approached, looked and left. (G) The mother (red arrow) draped the corpse (yellow arrow) over a branch, and moved to sit near the adult male (white arrow). (H) The mother put the head of the dead juvenile against her left breast, as if breastfeeding. (I) The mother had difficulty carrying the now-clearly decomposing corpse. (J) The decomposing body of the dead juvenile. (K) The mother looks toward where she abandoned the corpse and emits contact vocalizations. (L) The mother (red arrow) grooms the adult male (white arrow).

Figure 2

The average distances covered by the group and mother before, the juvenile's death, after death, and after corpse abandonment by the mother.