Primates

Responses to dead and dying conspecifics and heterospecifics by wild mountain gorillas ( Gorilla beringei beringei ) and chimpanzees ( Pan troglodytes schweinfurthii ) Abstract Comparative [“evolutionary”)] thanatology is devoted to investigating how animals respond to signs of death and dying, in conspecifics and other species. Responses to corpses often involve fear and confusion, and “deceased infant carrying” by females is widespread in nonhuman primates. Such behavior could result from “animacy detection malfunctions” (Gonçalves and Biro in Philos Trans R Soc (B) 373:20170263, 2018): corpses have attributes of animate agents, but—like objects—they do not act, but instead are acted upon by outside forces. Many or most nonhuman primates have core cognitive mechanisms for detecting animacy, but these might not resolve this paradox. Skeletons of conspecifics, seriously injured or ill individuals behaving oddly and not responding as expected to social acts and signals, and corpses, skeletons, and sick or injured individuals belonging to other species could trigger milder animacy detection malfunctions. A central question is whether any nonhuman primates learn from experience that death involves permanent loss of biological functionality and is universal. The relevant literature is mostly anecdotal or devoted to case studies, and this question is open. In response to calls for more information, I describe 25 cases of responses to corpses, skeletons, and mortally injured or ill individuals, both conspecifics and heterospecifics, seen during fieldwork on mountain gorillas (Gorilla beringei beringei) and chimpanzees (Pan troglodytes schweinfurthii). Observations were generally consistent with the animacy detection malfunction hypothesis, although cases of prolonged deceased infant carrying are problematic. Also, one case in gorillas apparently involved sympathetic concern for a dying individual, and sympathetic concern might have occurred in a chimpanzee case.

Corpse-directed play parenting by a sterile adult female chimpanzee Abstract The study of representational play in nonhuman primates, including chimpanzees (Pan troglodytes), provides interspecific perspectives on human cognitive development and evolution. A notable form of representational play in chimpanzees is play parenting, wherein parental behavior is directed at inanimate objects. Though observed in captivity, unambiguous examples of play parenting by wild chimpanzees are rare. Here, we report two cases from Ngogo in Kibale National Park, Uganda, in which a wild adult female chimpanzee (P. t. schweinfurthii) directed parental behaviors at corpses. Both cases involved the same adult female chimpanzee, aged 20–21 years. The first case was observed on 5 March 2016, and the play object was the corpse of a bushbaby (Galago thomasi); in the second case, observed on 6 May 2017, the play object was a recently deceased chimpanzee infant postmortally stolen from the mother. The chimpanzee possessed the first and second play objects for approximately 5.5 h and 1.8 h, respectively. In both cases, she performed a variety of maternal behaviors, including co-nesting, grooming, and dorsally carrying the play objects. In contrast to previous observations of play parenting in captivity, the play parent was a presumably sterile adult female, well beyond the average age of first birth. These observations contribute to the expanding literature on chimpanzee interactions with the corpses of both conspecifics and heterospecifics.

Chimpanzees foraging on aquatic foods: algae scooping in Bossou

Nesting, sleeping, and nighttime behaviors in wild and captive great apes Abstract The past few decades have seen a burgeoning of scientific studies on great apes’ use of nests for sleeping in the wild, as well as their nesting behavior and sleep in captivity. We review recent advances in knowledge of these topics, with the aim of promoting information exchange between people working in the field and with captive great apes. We trace developments in research into nest-building techniques in adults and immatures, factors that influence selection of general sleeping sites and specific locations, social aspects of sleep, postures, and nighttime activities. We argue that exchanges of information deriving from studies of captive and wild apes are valuable for obtaining a better understanding of sleep-related adaptations in our nearest evolutionary neighbors, and conclude by making some recommendations regarding sleeping arrangements in captivity from a welfare perspective.

Infant carrying by a wild chimpanzee father at Bulindi, Uganda Abstract Although infanticide by wild adult male chimpanzees has been reported from multiple sites, affiliative infant carrying by males is rare. We observed infant carrying by an alpha male chimpanzee at Bulindi (Uganda) on two consecutive mornings and collected faecal samples from the newborn infant female, her mother and all candidate fathers to determine whether the alpha male was the infant’s father using a likelihood-based method of paternity assignment. In contrast to previous observations of male care of orphans, in this case the mother was present during observations. Further, unlike reports of male aggression towards infants, the infant was reunited with her mother on the third morning, and survived. Neither mother nor infant presented visible injuries. The alpha male never directed aggression towards the infant. Rather, he displayed attentive behaviours, for example by holding the infant to his chest, supporting her while moving, grooming her, and ‘cuddling’ and ‘rocking’ her. Paternity results revealed with a high degree of certainty that the alpha male was the infant’s father. There are several alternative explanations for the male’s behaviour, but this unusual case also highlights the need for further studies to determine under what circumstances adult male chimpanzees can recognise their own offspring.

A comparison of methods to determine chimpanzee home-range size in a forest–farm mosaic at Madina in Cantanhez National Park, Guinea-Bissau Abstract Human activities impact the distribution of numerous species. Anthropogenic habitats are often fragmented, and wildlife must navigate through human-influenced and ‘natural’ parts of the landscape to access resources. Different methods to determine the home-range areas of nonhuman primates have not considered the additional complexities of ranging in anthropogenic areas. Here, using 6 months of spatial data on the distribution of chimpanzee presence (feces, feeding traces, nests, opportunistic encounters; n = 833) collected across the wet and dry seasons, we examine different analytical techniques to calculate the home-range size of an unhabituated chimpanzee (Pan troglodytes verus) community inhabiting a forest–farm mosaic at Madina, Cantanhez National Park in Guinea-Bissau. The minimum convex polygon method and the grid cell (500 m × 500 m cell size) method estimated the chimpanzees home-range size at 19.02 and 15.50 km2, respectively with kernel analysis calculating a lower value of 8.52 km2. For the grid cell method, home-range estimates varied with cell size, with larger cells producing larger estimates. We compare our home-range estimates with other chimpanzee research sites across Africa. We recommend the use of kernel analysis for determining primate home ranges, especially for those groups exploiting fragmented habitats including forest–farm mosaics, as this method takes account of inaccessible or infrequently used anthropogenic areas across the complete home range of the primate group. However, care must be taken when using this method, since it is sensitive to small sample sizes that can occur when studying unhabituated communities, resulting in underestimated home ranges.

Fostering of a wild, injured, juvenile by a neighbouring group: implications for rehabilitation and release of Barbary macaques confiscated from illegal trade Abstract Illegal live trade is one of the greatest threats to endangered Barbary macaques. Since trade focuses on young and Barbary macaques show extensive alloparental care, rehabilitation and release into wild foster groups is a promising strategy to free space in sanctuaries to allow continued confiscations, improve individual welfare, minimize captive care costs, and reinforce wild populations. However, little documentation exists on Barbary macaque releases and the age at which released macaques would be accepted by foster groups is unknown. Here, I report on a wild, nearly 3-year-old Barbary macaque male that was separated from his group after serious injury from a car collision. A neighbouring group found the distressed juvenile 2 days later, approached, groomed, and affiliated with him, and accepted him into the group. He remained with the foster group for 4 months until returning to his natal group. This observation challenges concerns that only infants and young juveniles may be accepted into non-natal groups, suggesting that even older confiscated juveniles could be candidates for release. This also adds to the literature on behavioural responses to distressed and injured individuals, demonstrating the capacity of wild monkeys to exhibit affiliative behaviours even towards unfamiliar distressed conspecifics, providing a rare example of potential consolation of an unknown individual. As so little documentation currently exists on the acceptance of Barbary macaques into wild foster groups, this observation provides valuable information for developing rehabilitation and release strategies for confiscated individuals, which can be critical for continuing to fight illegal trade of this endangered species.

Reactions to novel objects in monkeys: what does it mean to be neophobic? Abstract Animals’ reactions to novel objects vary not only with zoological taxa and their ecology but also in the types of presented stimuli, the context, and individual characteristics. Behavioral reactions can vary from extremely neophobic (avoiding novel objects) to extremely neophilic (intense exploration of novel objects); most often, a mixture of these behavioral patterns appears. In primates, reactions toward novel objects vary according to species, age, sex, population, and the types of objects. Most experiments in this field have used a free exploration design with food or non-food objects. Here, we tested the reactions of captive male rhesus macaques using various stimuli, motivation levels, rewards, and time limits. We found that the monkeys explored and manipulated novel objects in various contexts, with little evidence of a neophobic response; however, environment, types of stimuli, and other parameters of the test can significantly affect monkeys’ reactions.

Preferential hand use by captive chimpanzees ( Pan troglodytes ) in manual and tool digging Abstract Digging for underground storage organs of plants has been reported in various populations of wild chimpanzees (Pan troglodytes). However, it is unknown so far whether chimpanzees display lateral biases in manual digging as direct observations of this behavior are still lacking. It was therefore the aim of the present study to assess, for the first time, hand preferences for digging in a group of nine captive chimpanzees. We found that with only one exception, all individuals engaged in manual digging for buried food. Five individuals displayed a significant right-hand preference, two a significant left-hand preference, and one was ambidextrous. No apparent differences between males and females were found with regard to the direction or strength of hand preferences for manual digging. Only one out of four parent–offspring pairs was congruent in their preferred hand for manual digging. Three of the eight chimpanzees who dug manually also used tools in order to excavate buried food. Among those three individuals, one displayed a significant right-, one a significant left-hand preference, and one was ambidextrous. Only one of these three chimpanzees was consistent in preferring the same hand for manual and tool digging. The present findings are in line with the notion that chimpanzees display significant hand preferences at the individual level for haptic-guided behaviors, with a tendency for the right hand.

Urbanisation as an important driver of nocturnal primate sociality Abstract Urbanisation is an important factor driving species and biodiversity decline. Although habitat alterations can be detrimental for species, studies have shown that many diurnal primates are able to adapt to novel environments. Little is known about the ability of nocturnal primates to survive within an urban environment. To increase our understanding on this topic, we present ad libitum observations on group movement and sociality from urban and rural populations of the African lesser bushbaby (Galago moholi) in South Africa from 2014–2018. Our data show considerable changes in the social dynamics within urban bushbaby populations. In contrast to rural individuals, which spent the majority of their activity period solitarily or in pairs, urban individuals displayed a larger degree of sociality throughout their active period, forming groups of up to ten individuals. Furthermore, urban individuals spent less time moving around, while increasing social (communication/pair-grooming), foraging and feeding behaviour. Urban individuals fed on a range of different anthropogenic and natural food sources (insects/tree gum/nectar) compared to their rural counterparts. In summary, urban bushbabies showed a large degree of behavioural plasticity, with changes in social dynamics and structure frequently observed. Such alterations in sociality, along with the ability to utilise different feeding resources, may explain the ability of the species to survive within a highly altered environment.