Maternal caretaking behavior towards a dead juvenile in a wild, multi-level primate society

Abstract

Maternal caretaking and transport of dead infants are widespread among nonhuman primates, having been reported in numerous species of monkeys and apes. By contrast, accounts of such behaviors toward dead juveniles are scarce. Here, we describe responses by the mother and other group members to the death of a juvenile in a wild, multi-level group of Sichuan snub-nosed monkeys (Rhinopithecus roxellana). Following the juvenile’s fatal accident, his mother transported and cared for the corpse for four days. Immature monkeys belonging to the same one-male unit, and some individuals from other social units also showed interest in and tended the corpse. Comparisons of this case with those involving the deaths of infants and an adult female in the same population highlight possible effects of physiological, psychological and emotional factors in primate thanatological responses, and provide an additional perspective on the origin and evolution of compassionate acts.

Mother-infant relationships in wild Guinea baboons (Papio papio)

“…The duration of interactions towards the infants in this study (<1 to 5 days) was in line with the reports in other species (e.g., Northern muriquis: 1-3 days [Freire Filho et al, 2022], chacma baboons: 2-10 days [Carter et al, 2020], Japanese macaques: mean 3.3 days (range, 1-17; SD, 2.7) [Sugiyama et al, 2009], Sichuan snub-nosed monkeys: 5 days [Yang et al, 2022]), but relatively short compared to the maximum registered in other primate species (e.g., Tonquean macaques: 25 days [De Marco et al, 2018], Hanuman langurs: 27 days [Sharma et al, 2011], geladas: 48 days [Fashing et al, 2011], chimpanzees: 68 days [Biro et al, 2010] and 89 days [Soldati et al, 2022]). In a similar study with chacma baboons, Carter and colleagues (2020) proposed that the cost derived from carrying a dead infant in species that travel long daily distances leads to short durations.…”

“…In all cases, the deceased individuals were infants, and only in one instance was the infant older than six months. Consistent with reports from other nonhuman primate species, dead infant carry was the most observed post-mortem behaviour (see Introduction), and protection and grooming were observed occasionally (Biro et al, 2010;Carter et al, 2020;Cronin et al, 2011;Fashing et al, 2011;Yang et al, 2022).…”

“…The mother-infant bond hypothesis holds that the post-mortem behaviours depend on the formation of the mother-infant bond prior to the infant's death and predicts that these behaviours will last longer in older infants, as they are more strongly bonded with their mothers. This hypothesis is by far the most cited in the literature, repeatedly stating that because the mother-infant bond is the strongest social bond in primates, such attachment elicits maternal behaviours even after the death of the infant (e.g., Biro et al, 2010;De Marco et al, 2018;Matsuzawa, 1997;Yang et al, 2022).…”

“…or "do animals grieve?" are central to the discipline of comparative thanatology (Anderson, 2011(Anderson, , 2016Anderson et al, 2018;Bearzi et al, 2018;Carter et al, 2020;Fashing et al, 2011;Fernández-Fueyo et al, 2021;Gonçalves & Biro, 2018;Gonçalves & Carvalho, 2019;Soldati et al, 2022;Watson & Matsuzawa, 2018;Yang et al, 2022).…”

“…The most extensive array of post-mortem behaviours has been described in the primate order; these include observations from captivity and the wild. In Old World monkeys, such observations include yellow baboons (Papio cynocephalus [Altmann, 1980]), chacma baboons (Papio ursinus [Carter et al, 2020]), Japanese macaques (Macaca fuscata [Sugiyama et al, 2009;Takeshita et al, 2020]), Sichuan snub-nosed monkeys (Rhinopithecus roxellana [Yang et al, 2022]), Indian langurs (Presbytis entellus [Jay, 1962]), Hanuman langurs (Semnopithecus entellus [Sharma et al, 2011]), Geladas (Theropithecus gelada [Fashing et al, 2011]), Zanzibar red colobus (Piliocolobus kirkii [Georgiev et al, 2019]), bonnet macaques (Macaca radiata [Das et al, 2019]), and lion-tailed macaques (Macaca silenus [Das et al, 2019]); in New World monkeys, these species include blonde capuchins (Sapajus flavius [Andrade et al, 2020]), brown capuchins (Sapajus apella [Trapanese et al, 2020]), and northern muriquis (Brachyteles hypoxanthus [Freire Filho et al, 2022]). Post-mortem behaviours have also been observed in several ape species: chimpanzees (Pan troglodytes [Biro et al, 2010;Cronin et al, 2011;Matsuzawa, 1997;Soldati et al, 2022;Van Lawick-Goodall, 1968]), Sumatran orang-utans (Pongo abelii [Dellatore et al, 2009]) and gorillas (Gorilla beringei [Warren & Williamson, 2004]).…”