rstb.royalsocietypublishing.org Opinion piece Cite this article: Anderson JR. 2018 Chimpanzees and death. Phil. Trans. R. Soc. B 373: 20170257. http://dx.doi.org/10.1098/rstb.2017.0257 Accepted: 20 May 2018 One contribution of 18 to a theme issue ‘Evolutionary thanatology: impacts of the dead on the living in humans and other animals’. Subject Areas: behaviour, cognition Keywords: chimpanzees, dying, death, predation, aggression, suicide, culture Author for correspondence: James R. Anderson e-mail: j.r.anderson@psy.bun.kyoto-u.ac.jp Chimpanzees and death James R. Anderson Department of Psychology, Graduate School of Letters, Kyoto University, Kyoto 606-8501, Japan JRA, 0000-0003-2441-0728 Information about responses to death in nonhuman primates is important for evolutionary thanatology. This paper reviews the major causes of death in chimpanzees, and how these apes respond to cues related to dying and death. Topics covered include disease, human activities, preda- tion, accidents and intra-species aggression and cannibalism. Chimpanzees also kill and sometimes eat other species. It is argued that, given their cog- nitive abilities, their experiences of death in conspecifics and other species are likely to equip chimpanzees with an understanding of death as cessation of function and irreversible. Whether they might understand that death is inevitable—including their own death, and biological causes of death is also discussed. As well as gathering more fundamental information about responses to dying and death, researchers should pay attention to possible cultural variations in how great apes deal with death. This article is part of the theme issue ‘Evolutionary thanatology: impacts of the dead on the living in humans and other animals’. 1. Introduction Given favourable social and environmental conditions—such as abundant food, few predators, absence of epidemics and little disturbance from humans— chimpanzees might live until at least 50 years of age. However, as a result of various challenges to their survival at different stages of life most chimpanzees do not live as long, and males generally die earlier than females [1–4]. At Mahale (Tanzania), around half of all infant chimpanzees die before they are weaned [5]. Deaths have been witnessed or inferred by researchers at all long-term chimpanzee study sites. Because female chimpanzees tend to emigrate from their natal communities, unexplained disappearances are conservatively assumed to reflect possible transfer. By contrast, if infants, juveniles or adult males disappear researchers often consider them to have died, although this often goes unverified. Even when dead chimpanzees are found it is not always possible to establish the precise cause of death [6–9]. Known and inferred mortality factors in wild chimpanzees include disease, hunting by humans, nonhuman predators, general senescence, accidents and intra- and inter-group aggression [3,4]; some factors reported in captivity [10] are also likely to apply to wild populations. The aims of this paper are to (1) review causes of death in chimpanzees, (2) consider how chimpanzees respond to death and death-related cues and (3) address the question how chimpanzees’ ‘psychology of death’ compares with that of their nearest evolutionary neighbours, namely humans. The broader, overall aim is to stimulate primatol- ogists to gather and present further information to help progress in the field of comparative evolutionary thanatology. 2. Causes of death (a) Disease Chimpanzees in the wild are susceptible to a range of potentially fatal diseases such as pneumonia, human respiratory viruses, simian immunodeficiency viruses, Ebola and anthrax [11 –16]. Diseases accounted for most deaths of & 2018 The Author(s) Published by the Royal Society. All rights reserved.