Maternal cannibalism in two populations of wild chimpanzees

Abstract

Maternal cannibalism has been reported in several animal taxa, prompting speculations that the behavior may be part of an evolved strategy. In chimpanzees, however, maternal cannibalism has been conspicuously absent, despite high levels of infant mortality and reports of non-maternal cannibalism. The typical response of chimpanzee mothers is to abandon their deceased infant, sometimes after prolonged periods of carrying and grooming the corpse. Here, we report two anomalous observations of maternal cannibalism in communities of wild chimpanzees in Uganda and Ivory Coast and discuss the evolutionary implications. Both infants likely died under different circumstances; one apparently as a result of premature birth, the other possibly as a result of infanticide. In both cases, the mothers consumed parts of the corpse and participated in meat sharing with other group members. Neither female presented any apparent signs of ill health before or after the events. We concluded that, in both cases, cannibalizing the infant was unlikely due to health-related issues by the mothers. We discuss these observations against a background of chimpanzee mothers consistently refraining from maternal cannibalism, despite ample opportunities and nutritional advantages. We conclude that maternal cannibalism is extremely rare in this primate, likely due to early and strong mother-offspring bond formation, which may have been profoundly disrupted in the current cases.

Coping with mortality: responses of monkeys and great apes to collapsed, inanimate and dead conspecifics

“…A striking feature of filial cannibalism in both monkeys and great apes is that mothers continue to protect, carry and care for the remains of the infant's body when they have already begun to cannibalize it, and they display no signs of distress during this period. Several authors note that maternal consumption of the corpse remains partial and provides little nutritional benefit (Fowler & Hohmann 2010;Anderson 2018;De Marco et al 2018;Fedurek et al 2020;Watts 2020). As Watson and Matsuzawa (2018) point out, if there is a gradual weakening of the mother-infant bond from treating the infant body as if it was alive to treating it as food, cannibalism should represent the end of the process; quite to the contrary, there is an overlap between cannibalism and care, which may reflect contradictory motives that produce confusion in females.…”

“…Two cases of partial cannibalism by group members have been recorded in chimpanzees (Lonsdorf et al 2020). In other cases, partial cannibalism by the mother was followed by the ingestion of pieces of skin or flesh by a group member in brown capuchins (Trapanese et al 2020) and mountain gorillas (Watts 2020), while several individuals consumed the carcass with the mother in groups of chimpanzees (Fedurek et al 2020) and bonobos (Pan paniscus) (Fowler & Hohmann 2010;Tokuyama et al 2017). It may be worth adding that although infanticide, sometimes including cannibalism, has been documented in many primate species (Hiraiwa-Hasegawa 1992; van Schaik & Janson 2000), we will not consider it here, as hostile motivations of infanticidal individuals may continue to affect their behaviour after killing (see Das et al 2019;Gonçalves & Carvalho 2019;Lowe et al 2020;Thompson et al 2020).…”

Dead infant carrying by chimpanzee mothers in the Budongo Forest

“…Both mothers were forced to use atypical modes of infant carrying, including mouth carrying, more typically used for objects (Lonsdorf et al 2020), as live infants cling to the back or belly of their mothers during travel. Also relevant is that, unlike other groups of animals, chimpanzees do not often cannibalise their own dead infants (but see Fedurek et al 2020 for two exceptions). Overall, these data suggest that the ‘unawareness hypothesis’ is an unlikely explanation of chimpanzee behaviour towards dead conspecifics.…”

Reactions to infant death by wild vervet monkeys (Chlorocebus pygerythrus) in KwaZulu-Natal, South Africa: prolonged carrying, non-mother carrying, and partial maternal cannibalism

“…This cannibalistic act might suggest awareness that her infant was dead, but then why would Nessie go on to perform care-taking behaviours? Seemingly rare instances of maternal cannibalism have been reported in other primate species including Tonkean macaques (de Marco et al 2018 ), chimpanzees (Fedurek et al 2020 ), and, at two different sites, bonobos (Tokuyama et al 2017 ). To our knowledge, maternal cannibalism has never previously been reported in vervet monkeys, and this is the only case recorded in 10 years of observations at our field site.…”