Death among geladas (Theropithecus gelada): a broader perspective on mummified infants and primate thanatology

Abstract

Despite intensive study in humans, responses to dying and death have been a neglected area of research in other social mammals, including nonhuman primates. Two recent reports [Anderson JR, Gillies A, Lock LC. 2010. Pan thanatology. Current Biology 20:R349-R351; Biro D, Humle T, Koops K, Souse C, Hayashi M, Matsuzawa T. 2010. Chimpanzee mothers at Bossou, Guinea carry the mummified remains of their dead infants. Current Biology 20:R351-R352] offered exciting new insights into behavior toward dying and dead conspecifics in our closest living relatives-chimpanzees. Here, we provide a comparative perspective on primate thanatology using observations from a more distant human relative-gelada monkeys (Theropithecus gelada)-and discuss how gelada reactions to dead and dying groupmates differ from those recently reported for chimpanzees. Over a 3.75-year study period, we observed 14 female geladas at Guassa, Ethiopia carrying dead infants from 1 hr to ≥48 days after death. Dead infants were carried by their mothers, other females in their group, and even by females belonging to other groups. Like other primate populations in which extended (>10 days) infant carrying after death has been reported, geladas at Guassa experience an extreme climate for primates, creating conditions which may favor slower rates of decomposition of dead individuals. We also witnessed the events leading up to the deaths of two individuals and the responses by groupmates to these dying individuals. Our results suggest that while chimpanzee mothers are not unique among primates in carrying their dead infants for long periods, seemingly "compassionate" caretaking behavior toward dying groupmates may be unique to chimpanzees among nonhuman primates (though it remains unknown whether such "compassionate" behavior occurs outside captivity).

Maternal responses to dead infants in Yunnan snub-nosed monkey (Rhinopithecus bieti) in the Baimaxueshan Nature Reserve, Yunnan, China

“…Recently, several papers have been published detailing maternal and individual responses in primates to the death of group members. In primate species such as Japanese macaques (Macaca fuscata), gelada baboons (Theropithecus gelada), and chimpanzees (Pan troglodytes), mothers have been observed to carry the bodies of their dead offspring for several days (Sugiyama et al 2009;Cronin et al 2011;Fashing et al 2011). In other species such as mountain gorillas (Gorilla beringei), group members are reported to exhibit allomaternal behavior toward another's dead infant (Warren and Williamson 2004).…”

“…2. The slow decomposition hypothesis (Fashing et al 2011) suggests that under conditions in which a hot, dry (or cold, dry) climate slows down the decomposition process, primate mothers may continue to carry dead infants until clear signals of decomposition (possibly particular odor cues) indicate death. 3.…”

Evidence of Placentophagia and Mother-Infant Cannibalism in Free-Ranging Macaca mulatta tcheliensis in Mount Taihangshan, Jiyuan, China

“…Although relatively rare in primates, infant cannibalism has been associated with infanticide, principally in the context of an unrelated extragroup male attempting to take over a group and, on a few occasions, by related individuals, usually the mother of the infant or, in the case of common marmosets, the grandmother of the infant ( Table 2 ) [Bezerra et al, 2007]. In the majority of the documented cases in which an infant was killed, however, it was not eaten [Hrdy, 1974;Dellatore et al, 2009;Fashing et al, 2011].…”

Observations on the response of a pod of hippos to a dead juvenile hippo (Hippopotamus amphibius, Linnaeus 1758)

“…Bearzi, Eddy, Piwetz, Reggente, & Cozzi, ; Reggente et al, ). Species displaying these behaviours include giraffes (Bercovitch, ; Strauss & Muller, ), elephants (Douglas‐Hamilton, Bhalla, Wittemyer, & Vollrath, ), nonhuman primates (Cronin, Leeuwen, Mulenga, & Bodamer, ; Fashing et al, ; Yang, Anderson, & Li, ), and cetaceans (close relatives to hippos, Reggente et al, ), and reports commonly relate to a female interacting with the carcass of a juvenile. There are photographs/videos showing hippos interacting with hippo carcasses (Breen, ; Harris, ; Hippo keeps crocs from dead juvenile, ; Hippopotamus (Hippopotamus amphibius), ; ViralHog, ) and defending carcasses from other animals (Csaba, ; Harris, ; Hippo keeps crocs from dead juvenile, ); providing anecdotal evidence that hippos may also display epimeletic behaviour towards dead conspecifics.…”