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Primates; Journal of Primatology Jan 2023After stone tools, bone tools are the most abundant artefact type in the Early Pleistocene archaeological record. That said, they are still relatively scarce, which...
After stone tools, bone tools are the most abundant artefact type in the Early Pleistocene archaeological record. That said, they are still relatively scarce, which limits our understanding of the behaviours that led to their production and use. Observations of extant primates constitute a unique source of behavioural data with which to construct hypotheses about the technological forms and repertoires exhibited by our hominin ancestors. We conducted two different experiments to investigate the behavioural responses of two groups of captive chimpanzees (Pan troglodytes; n = 33 and n = 9) to disarticulated, defleshed, ungulate bones while participating in a foraging task aimed at eliciting excavating behaviour. Each chimpanzee group was provided with bone specimens with different characteristics, and the two groups differed in their respective experience levels with excavating plant tools. We found that several individuals from the inexperienced group used the provided bones as tools during the task. In contrast, none of the individuals from the experienced group used bones as excavating tools, but instead continued using plant tools. These chimpanzees also performed non-excavating bone behaviours such as percussion and tool-assisted extraction of organic material from the medullary cavity. Our findings serve as a proof-of-concept that chimpanzees can be used to investigate spontaneous bone tool behaviours such as bone-assisted excavation. Furthermore, our results raise interesting questions regarding the role that bone characteristics, as well as previous tool-assisted excavating experience with other raw materials, might have in the expression of bone tool-assisted excavation.
Topics: Animals; Pan troglodytes; Hominidae; Feeding Behavior; Tool Use Behavior; Archaeology
PubMed: 36401675
DOI: 10.1007/s10329-022-01033-w -
Current Biology : CB Jan 2020Between-group competition in social animals appears to be a prominent selective pressure shaping the evolution of territoriality and cooperation [1-4]. Evidence for an...
Between-group competition in social animals appears to be a prominent selective pressure shaping the evolution of territoriality and cooperation [1-4]. Evidence for an effect of between-group competition on fitness in territorial species, however, is mostly lacking because of difficulty in measuring between-group competition and its long-term impact [5]. Between-group competition corresponds to a complex set of interactions between neighboring groups, and its intensity seems to depend on the competitive abilities of each interacting group [6, 7]. We tested whether the competitive ability of groups and the pressure exerted by neighboring groups affected the reproductive success of wild female chimpanzees (Pan troglodytes verus). Using long-term data on four neighboring groups in the Taï National Park, Côte d'Ivoire, collected over the course of 54 observation years, we measured the competitive ability of habituated groups using the number of mature males and the pressure exerted by non-habituated neighbors with an index of neighbor pressure that combined the frequency of neighboring encounters and related spatial information. Importantly, we found that experiencing low neighbor pressure provides fitness benefits through increased offspring survival and shorter inter-birth intervals. Also, many males in a group are associated with shorter inter-birth intervals. We conclude that high between-group competition hampers fast reproduction and offspring survival when exposure is during the prenatal period. Our findings suggest that having many males in a group results in fitness benefits and that between-group competition should be considered as a potential selective pressure that shaped key social adaptations in the hominoid lineage.
Topics: Animals; Competitive Behavior; Cote d'Ivoire; Female; Male; Pan troglodytes; Reproduction
PubMed: 31902731
DOI: 10.1016/j.cub.2019.11.039 -
Philosophical Transactions of the Royal... Sep 2022Gestures play an essential role in primate communication. However, little is known about how complexity of gestural use (in terms of repertoire size, intentional use,...
Gestures play an essential role in primate communication. However, little is known about how complexity of gestural use (in terms of repertoire size, intentional use, flexibility and use of gestural sequences) relates to individual and dyadic measures of sociality and whether more complex gestural use is more effective in eliciting a response. We observed 19 captive chimpanzees (), 16 Sumatran orangutans () and 18 siamangs () to assess the complexity and effectiveness of their gestural use. We found that, beyond interspecies variation, the number of gesture types used in a dyad was higher when individuals had stronger social bonds; the probability of accounting for others' attention increased with age, especially for visual gestures; and sequences were more likely used by younger or socially less integrated individuals. In terms of effectiveness, older individuals and those using fewer sequences were more likely to be responded to, while across dyads, the probability of obtaining a response was higher when both individuals accounted for the other's attention and when they used fewer sequences. Overall, this confirms the link between sociality and complex gestural use and suggests that more complex forms of communication, at least in terms of intentional use, may be more effective at achieving communicative goals. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.
Topics: Animal Communication; Animals; Gestures; Hylobatidae; Pan troglodytes; Pongo abelii; Primates
PubMed: 35934967
DOI: 10.1098/rstb.2021.0299 -
Psychological Science Jan 2019Social risk is a domain of risk in which the costs, benefits, and uncertainty of an action depend on the behavior of another individual. Humans overvalue the costs of a...
Social risk is a domain of risk in which the costs, benefits, and uncertainty of an action depend on the behavior of another individual. Humans overvalue the costs of a socially risky decision when compared with that of purely economic risk. Here, we played a trust game with 8 female captive chimpanzees ( Pan troglodytes) to determine whether this bias exists in one of our closest living relatives. A correlation between an individual's social- and nonsocial-risk attitudes indicated stable individual variation, yet the chimpanzees were more averse to social than nonsocial risk. This indicates differences between social and economic decision making and emotional factors in social risk taking. In another experiment using the same paradigm, subjects played with several partners with whom they had varying relationships. Preexisting relationships did not impact the subjects' choices. Instead, the apes used a tit-for-tat strategy and were influenced by the outcome of early interactions with a partner.
Topics: Animals; Behavior, Animal; Decision Making; Female; Humans; Pan troglodytes; Risk-Taking; Social Behavior; Trust
PubMed: 30511893
DOI: 10.1177/0956797618811877 -
Current Biology : CB Jul 2017The two closest living relatives of humans, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes), share many traits that are common in humans but rare in other... (Comparative Study)
Comparative Study
The two closest living relatives of humans, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes), share many traits that are common in humans but rare in other mammals, including societies with high fission-fusion dynamics, male philopatry, female dispersal and extensive social bonding among unrelated individuals [1]. The major difference between these two species is that male aggression is more frequent and intense in male-dominated chimpanzees than in bonobos, where the highest-ranking individuals are female [1]. One potential explanation is that because periods of female sexual receptivity and attractiveness are more extended in bonobos [2], males compete less intensely for each mating opportunity. This would reduce the strength of selection for traits that lead to success in direct contest competition between males and in sexual coercion of females, thus increasing the potential for female choice [3]. Accordingly, it has been predicted that the influence of male dominance rank on reproductive success and the extent of male reproductive skew should be lower in bonobos than in chimpanzees [1]. Although relevant for understanding the evolution of the unusual levels of egalitarianism and cooperation found in human hunter-gatherers [4], comparative analyses in the genus Pan have been limited by the scanty paternity data available for wild bonobos [5]. Here, we show using the largest sample of paternity data available that, contrary to expectation, male bonobos have a higher reproductive skew and a stronger relationship between dominance rank and reproductive success than chimpanzees.
Topics: Animals; Democratic Republic of the Congo; Male; Pan paniscus; Pan troglodytes; Reproduction; Sexual Behavior, Animal
PubMed: 28697359
DOI: 10.1016/j.cub.2017.05.039 -
PloS One 2017Many facilities that house captive primates play music for animal enrichment or for caregiver enjoyment. However, the impact on primates is unknown as previous studies...
Many facilities that house captive primates play music for animal enrichment or for caregiver enjoyment. However, the impact on primates is unknown as previous studies have been inconclusive. We conducted three studies with zoo-housed chimpanzees (Pan troglodytes) and one with group-housed chimpanzees at the National Centre for Chimpanzee Care to investigate the effects of classical and pop/rock music on various variables that may be indicative of increased welfare. Study one compared the behaviour and use of space of 18 animals when silence, classical or pop/rock music was played into one of several indoor areas. Overall, chimpanzees did not actively avoid the area when music was playing but were more likely to exit the area when songs with higher beats per minute were broadcast. Chimpanzees showed significantly fewer active social behaviours when music, rather than silence, was playing. They also tended to be more active and engage in less abnormal behaviour during the music but there was no change to either self-grooming or aggression between music and silent conditions. The genre of music had no differential effects on the chimpanzees' use of space and behaviour. In the second study, continuous focal observations were carried out on three individuals with relatively high levels of abnormal behaviour. No differences in behaviour between music and silence periods were found in any of the individuals. The final two studies used devices that allowed chimpanzees to choose if they wanted to listen to music of various types or silence. Both studies showed that there were no persistent preferences for any type of music or silence. When taken together, our results do not suggest music is enriching for group-housed captive chimpanzees, but they also do not suggest that music has a negative effect on welfare.
Topics: Aggression; Animal Welfare; Animals; Animals, Zoo; Eating; Female; Grooming; Locomotion; Male; Music; Pan troglodytes
PubMed: 28355212
DOI: 10.1371/journal.pone.0172672 -
Animal Cognition Mar 2014Prospective memory (PM) involves remembering to do something at a specific time in the future. Here, we investigate the beginnings of this ability in young children...
Prospective memory (PM) involves remembering to do something at a specific time in the future. Here, we investigate the beginnings of this ability in young children (3-year-olds; Homo sapiens) and chimpanzees (Pan troglodytes) using an analogous task. Subjects were given a choice between two toys (children) or two food items (chimpanzees). The selected item was delivered immediately, whereas the unselected item was hidden in an opaque container. After completing an ongoing quantity discrimination task, subjects could request the hidden item by asking for it (children) or by pointing to the container and identifying the item on a symbol board (chimpanzees). Children and chimpanzees showed evidence of prospective-like memory in this task, as evidenced by successful retrieval of the item at the end of the task, sometimes spontaneously with no prompting from the experimenter. These findings contribute to our understanding of PM from an ontogenetic and comparative perspective.
Topics: Animals; Child, Preschool; Choice Behavior; Female; Humans; Judgment; Male; Memory, Episodic; Pan troglodytes; Reward
PubMed: 23884791
DOI: 10.1007/s10071-013-0661-8 -
Proceedings. Biological Sciences Dec 2016Human brains are markedly asymmetric in structure and lateralized in function, which suggests a relationship between these two properties. The brains of other closely...
Human brains are markedly asymmetric in structure and lateralized in function, which suggests a relationship between these two properties. The brains of other closely related primates, such as chimpanzees, show similar patterns of asymmetry, but to a lesser degree, indicating an increase in anatomical and functional asymmetry during hominin evolution. We analysed the heritability of cerebral asymmetry in chimpanzees and humans using classic morphometrics, geometric morphometrics, and quantitative genetic techniques. In our analyses, we separated directional asymmetry and fluctuating asymmetry (FA), which is indicative of environmental influences during development. We show that directional patterns of asymmetry, those that are consistently present in most individuals in a population, do not have significant heritability when measured through simple linear metrics, but they have marginally significant heritability in humans when assessed through three-dimensional configurations of landmarks that reflect variation in the size, position, and orientation of different cortical regions with respect to each other. Furthermore, genetic correlations between left and right hemispheres are substantially lower in humans than in chimpanzees, which points to a relatively stronger environmental influence on left-right differences in humans. We also show that the level of FA has significant heritability in both species in some regions of the cerebral cortex. This suggests that brain responsiveness to environmental influences, which may reflect neural plasticity, has genetic bases in both species. These results have implications for the evolvability of brain asymmetry and plasticity among humans and our close relatives.
Topics: Animals; Brain; Cerebral Cortex; Dominance, Cerebral; Environment; Humans; Pan troglodytes
PubMed: 28003442
DOI: 10.1098/rspb.2016.1319 -
PLoS Biology 2012A recent report by the Institute of Medicine leaves few urgent reasons standing for the continued use of chimpanzees in biomedical research. It is high time to think...
A recent report by the Institute of Medicine leaves few urgent reasons standing for the continued use of chimpanzees in biomedical research. It is high time to think about their retirement, Frans de Waal argues, without neglecting prospects for non-invasive research on behavior, cognition, and genetics.
Topics: Animal Care Committees; Animal Experimentation; Animals; Behavior, Animal; Biomedical Research; Cognition; Morals; National Academies of Science, Engineering, and Medicine, U.S., Health and Medicine Division; National Institutes of Health (U.S.); Pan troglodytes; United States
PubMed: 22479150
DOI: 10.1371/journal.pbio.1001291 -
Anatomical Record (Hoboken, N.J. : 2007) Aug 2010Research has shown that Pan and Homo have similar ectocranial suture synostosis patterns possibly because of their phylogenetic relationship. However, unlike human data,...
Research has shown that Pan and Homo have similar ectocranial suture synostosis patterns possibly because of their phylogenetic relationship. However, unlike human data, it is unclear if the ontogeny of suture activity for Pan exhibits a relationship with the expanding neurocranium or the masticatory apparatus. These relationships were assessed by examining the associations between ectocranial suture status and morphology and cranial volume (as a proxy for neurocranial expansion) and dental development (as an indicator of adulthood and proxy for masticatory influence) in a large sample of Pan troglodytes skulls. One hundred and fifty-five P. troglodytes dry skulls were examined, and data were collected on ectocranial suture closure status, cranial volume, and dental eruption status. Regression models were calculated for suture status by cranial volumes, and Kendall's tau (a nonparametric measure of association) was calculated for suture status by dental eruption status. Results suggest that suture synostosis activity in P. troglodytes exhibits a period of stasis after neurocranial expansion cessation and does not have a strong relationship with brain development (r(2) ranged from 0.09 to 0.28), as similarly seen in Homo. Instead, suture synostosis has a stronger relationship with dental development (tau ranged from 0.59 to 0.72), where most osseous activity occurs after full adult dental eruption. This suggests that masticatory forces may influence both ectocranial suture morphology and synostosis more than brain expansion does in Pan, as also similarly noted in Homo.
Topics: Animals; Brain; Cranial Sutures; Female; Male; Pan troglodytes; Skull; Tooth Eruption
PubMed: 20665807
DOI: 10.1002/ar.21167