Behavioral responses around conspecific corpses in adult eastern gorillas (Gorilla beringei spp.)

Abstract

Humans were once considered unique in having a concept of death but a growing number of observations of animal responses to dying and dead conspecifics suggests otherwise. Complex arrays of behaviors have been described ranging from corpse removal and burial among social insects to quiet attendance and caregiving among elephants and primates. Less frequently described, however, are behavioral responses of individuals from different age/sex classes or social position toward the death of conspecifics. We describe behavioral responses of mountain gorillas (Gorilla beringei beringei) to the deaths of a dominant silverback and a dominant adult female from the same social group in Volcanoes National Park in Rwanda and the responses of Grauer’s gorillas (Gorilla b. graueri) to the corpse of an extra-group silverback in Kahuzi-Biega National Park, Democratic Republic of Congo. In gorillas, interactions between groups or with a lone silverback often result in avoidance or aggression. We predicted that: (i) more individuals should interact with the corpses of same-group members than with the corpse of the extra-group silverback; (ii) adult females with infants should avoid the corpse of the extra-group silverback; and (iii) in the mountain gorilla cases, individuals that shared close social relationships with the dead individual should spend more time with the corpse than other individuals in the group. We used a combination of detailed qualitative reports, photos, and videos to describe all occurrences of affiliative/investigative and agonistic behaviors observed at the corpses. We observed similar responses toward the corpses of group and extra-group individuals. Animals in all three cases showed a variety of affiliative/investigative and agonistic behaviors directed to the corpses. Animals of all age/sex classes interacted with the corpses in affiliative/investigative ways but there was a notable absence of all adult females at the corpse of the extra-group silverback. In all three cases, we observed only silverbacks and blackbacks being agonistic around and/or toward the corpses. In the mountain gorilla cases, the individuals who spent the most time with the corpses were animals who shared close social relationships with the deceased. We emphasize the similarity in the behavioral responses around the corpses of group and extra-group individuals, and suggest that the behavioral responses were influenced in part by close social relationships between the deceased and certain group members and by a general curiosity about death. We further discuss the implications close interactions with corpses have for disease transmission within and between gorilla social groups.

Responses to death and dying: primates and other mammals

“…Our paper, along with an accompanying report of unusually prolonged carrying of dead infants by chimpanzee mothers at Bossou (Biro et al 2010) attracted remarkable worldwide media attention, and generated new debates about what other species might know and feel about death. Together these papers probably helped to spark new life into the field of comparative thanatology, evidenced by a surge of publications on death-related reactions in a wide range of species, not only primates (e.g., Cronin et al 2011;Fashing et al 2011;Li et al 2012;Stewart et al 2012;Bezerra et al 2014;Campbell et al 2016;van Leeuwen et al 2016;Yang et al 2016;Porter et al 2019), but also nonprimate mammals (e.g., giraffe: Bercovitch 2012; Strauss and Muller 2012; dingos: Appleby et al 2013, hippopotamus: Inman and Leggett 2019). More detailed analyses are now being published, addressing topics such as physiological and psychological mechanisms underlying behavioral responses to the dead and dying, the extent to which other species might experience grief, how they differentiate between what is alive and what is dead, and what aspects of the "death concept"-which takes years to develop in humans-might be shared with nonhumans (Anderson 2011…”

Why Care: Complex Evolutionary History of Human Healthcare Networks

“…Therefore, I include responses to noncontagious conditions as well. Similarly, I also include responses to dead individuals because (1) care behaviors may start before death and continue afterward (Anderson et al, 2010;Bearzi et al, 2018) and (2) corpses are potential sources of pathogens (Octavio Lopez-Riquelme and Luisa Fanjul-Moles, 2013;Cremer et al, 2018;Porter et al, 2019).…”

Primate thanatology and hominoid mortuary archeology

“…Other examples include displacing and transporting the corpse, and expressions of possible 'compassion,' such as care taking shown towards the corpse. Violent acts toward the corpse also come under corpse interaction, such as hitting, biting, or jumping on it, pulling out fur, nibbling parts of the corpse and other cannibalistic acts (for examples of various expressions of corpse interaction in primates see papers in this special issue, and Anderson et al 2010;Biro et al 2010;Cronin et al 2011;Boesch 2012;Buhl et al 2012;Stewart et al 2012;Campbell et al 2016;van Leeuwen et al 2016;Yang et al 2016;Pruetz et al 2017;Porter et al 2019).…”

“…In the field, a death may rightly be looked upon as providing a source of materials for anatomical, pathological, or biochemical studies, etc., and indeed there exist recommended procedures for burial, excavation, and preparation of nonhuman primate skeletal remains (Garrod et al 2015). Swift removal and disposal of corpses may also be justified in terms of prevention of the spread of disease (in both the field and captivity) (e.g., Porter et al 2019), or in safari parks or zoos, to shield visitors from seeing dead animals, as the latter can give rise to negative reactions (e.g., Benbow 2004), and simply due to concerns about appropriate and ethical treatment of the dead. Such concerns are of course valid, but we call for greater consideration to be given to leaving corpses in situ whenever possible, in order to maximize information return about the responses of the living to the corpse, ideally until the group moves away and finally abandons it.…”