A case of infant swapping by wild northern muriquis (Brachyteles hypoxanthus)

Abstract

Allo-parenting has been observed in a variety of female primates, and typically infants are reunited with their biological mothers assuming that their mothers are alive. We observed an exception to this pattern when two wild northern muriquis (Brachyteles hypoxanthus) exchanged infants of different sexes and then reared their adopted infants through weaning. The process of this exchange began when the infants were 4 and 8 days old, respectively. The mother of a 4-day old female carried and nursed her own daughter and the 8-day old son of a second female. The exchange ended when the second mother was first observed carrying the wrong infant 1.5 days later. This observation raises questions about the age and mechanisms of mother-infant recognition in this species, and about assumptions of mother-infant relatedness based on behavioral observations alone.

Mother–offspring associations in Northern muriquis, Brachyteles hypoxanthus

“…Four of the five mothers with two juvenile offspring spent more time associating with the younger regardless of the offspring's sex. Both of the two mothers that had previously (and atypically) exchanged infants [Martins et al, 2007] spent more time than expected with their adopted juvenile offspring, but only one also spent more time than expected with her biological son.…”

“…c BS also had one infant grandson and one infant granddaughter in the group during the study period. d BS and DD exchanged infants of opposite sexes during their first week of life [Martins et al, 2007], and continued to nurse and carry their adopted infants, which are treated as their offspring except when otherwise noted.…”

Non-kin adoption in the common vampire bat

“…In other cases, individuals adopt familiar nonkin (e.g. chimpanzees: [12]; cercopithecines: [13]; muriquis: [14]; phocid seals: [15]), or unfamiliar or seemingly unfamiliar non-kin (e.g. dolphins: [16]; Barbary macaques: [17]; Rhesus macaques: [18]).…”