New records of within-group infanticide and cannibalism in wild chimpanzees

Abstract

ABSTRACT. Two cases of within-group infanticide and cannibalism were observed among the M Group chimpanzees of the Mahale Mountains, Tanzania. In both cases, victimized infants were male, 5 -6 months of age, and in good health when killed. Four to five years have passed since the mothers of the victims immigrated into M Group as nulliparous immigrants. In one case the 2nd-ranking male was observed to detach the infant from the mother's belly. Both infants were finally killed by the alpha male after several adult males scrambled for the bodies. There was no evidence that the mothers had mated with males other than those of M Group. Nor was there evidence that the mothers had restrictive mating relationships with some of the M Group adult males. What little evidence is available shows that the mothers had mated mostly with adolescent and other immature males during their conception cycles. However, at least in one case, the mother began to mate more with adult males rather than with immature males after the infanticide. It is proposed that the function of withingroup male infanticide can be explained by the male-male competition hypothesis developed for hanuman langurs and other nonhuman primates.

Causes of death in the Kasekela chimpanzees of Gombe National Park, Tanzania

“…This is in contrast to Mahale, where within-community infanticide by males has been a significant cause of death [Nishida et al, 2003]. Many of the infanticide victims at Mahale were offspring of females who joined M-group after the K-group community disappeared [Hamai et al, 1992].…”

Morphological Identification of Hair Recovered from Feces for Detection of Cannibalism in Eastern Chimpanzees

“…Cannibalism by chimpanzees has only been observed in the aftermath of lethal attacks [e.g., Bygott, 1972;Goodall, 1986;Hamai et al, 1992;Watts and Mitani, DOI: 10.1159/000488509 2000]. Chimpanzees rarely scavenge [Gilby et al, 2017] and have never been observed to scavenge conspecifics who have died of natural or accidental causes [Goodall, 1986].…”

“…In contrast, infanticide by females is usually restricted to the first 2 months after an infant's birth and is likely driven by long-term resource competition, whereby females eliminate a future competitor and gain access to resources that would otherwise be used by the victim [Goodall, 1977;Townsend et al, 2007;Pusey et al, 2008]. Victims of infanticide are frequently cannibalized to some degree and may be shared with family members or group mates [e.g., Bygott, 1972;Goodall, 1977;Nishida et al, 1979;Takahata, 1985;Hamai et al, 1992;Watts and Mitani, 2000]. In contrast, adult victims are only occasionally (and partially) consumed [Goodall, 1986;Pruetz et al, 2017].…”

“…Intragroup lethal aggression, usually against males, also occasionally occurs [Kaburu et al, 2013;Wilson et al, 2014;Pruetz et al, 2017], though is less understood. Finally, both males and females commit intracommunity infanticide [e.g., Goodall, 1977;Takahata, 1985;Hamai et al, 1992;Arcadi and Wrangham, 1999;Watts and Mitani, 2000;Townsend et al, 2007;Pusey et al, 2008;Wilson et al, 2014;Nishie and Nakamura, 2017] though the proposed motivation and victim selection differ markedly between the sexes. Males target infants that they suspect are not their own in a sexually selected strategy that hastens the onset of female receptivity [Hrdy, 1979].…”

Landscapes of the dead: the evolution of human mortuary activity frombody to place in Palaeolithic Europe

“…We should not allow these to hold us back from identifying general patterns in the archaeological record that can, if nothing else, be read to imply the existence of superstitious belief and its origins. Goodall 1977;Norikoshi 1982;Takahata 1985;Hamai et al 1992), the curation of dead infants by their mothers for up to 68 days after death (Biro et al 2010;Matsuzawa 2003), the intellectual and physical investigation of corpses (morbidity) and various examples of social theatre in close proximity to corpses which appears to be occasioned by them (e.g. Bygott 1972;Teleki 1973;Goodall 1977;Boesch and Boesch-Achermann 2000;Anderson et al 2010;Cronin et al 2011).…”