Two cases of mother-infant cannibalism in orangutans.

Observations of ape cannibalism have to this point been limited to chimpanzees (Pan troglodytes) where it is associated with infanticide and consumption by unrelated individuals (Watts and Mitani, Primates 41(4):357-365, 2000). Here we report for the first time observations of two unrelated female Sumatran orangutans (Pongo abelii) cannibalizing the remains of their infants on different occasion, a behavior never before reported in any ape species. The two orangutans were wild-born rehabilitated individuals, and had been reintroduced to an area hosting a largely unregulated primate tourism industry and experienced restricted ranging conditions. Though it is possible that this is a strategy to regain energy and nutrients or a result of individual history, comparative data suggest that this is an aberrant behavior which may be linked to environmental stressors within the area.