Behavior Of Chimpanzees Research Articles

The influence of oestrous swellings on the grooming behaviour of chimpanzees of the Budongo Forest, Uganda

Allogrooming among primates has been suggested as a strategy for enhancing reproductive success, by allowing males to enhance their proximity to oestrous females, or by influencing female choice through the development of affiliative relationships with males. Female chimpanzees have swollen anogenital regions signalling receptivity and by adapting their grooming investment accordingly, males could increase their copulatory success whilst females may increase chances of copulations with preferred males. Five and a half years of data from chimpanzees in the Budongo Forest, Uganda, were examined to investigate how sexual swellings influence grooming behaviour between males and females of different age classes. Based on the availability of oestrous females, significantly less grooming than expected occurred between anoestrous females and adult males, as well as between adult (anoestrous and oestrous) females and subadult males, but significantly more grooming than expected occurred between oestrous females and adult males or subadult males. Both oestrous adult and subadult females devoted more time to grooming interactions with adult males than did anoestrous females. Grooming interactions between adult males and oestrous adult females were initiated and terminated significantly more often by males, but those between anoestrous subadult females and adult males were initiated significantly more frequently by females.

Savanna chimpanzees dig for food

Professor Toshisada Nishida wrote “chimpanzees are always new to me” (1) almost 15 years ago, but his statement still holds. Far from exhausting the breadth and depth of chimpanzee behavior, even when there are more long-term field studies than ever before, field primatologists studying Pan troglodytes continue to report new discoveries. Moreover, some of these findings, such as that of the spear-hunting chimpanzees of Fongoli, Senegal (2), are so unexpected that they make popular as well as scientific news. Likely to make similar waves is the report by Hernandez-Aguilar et al. (3) in this issue of PNAS that wild chimpanzees use digging tools to harvest plant underground storage organs.

Towing the party line: territoriality, risky boundaries and male group size in spider monkey fission–fusion societies

Spider monkey communities are classic fission-fusion primate societies. I present data suggesting that spider monkeys (Ateles chamek) at Lago Caiman are territorial; adult males traveled further and faster than adult females and subgroup size was significantly higher in boundary areas of the spider monkey territory where intercommunity disputes were observed than in non-boundary areas. I then go on to examine data from 20 Ateles communities distributed across 14 study sites and five species to investigate how a series of demographic, ecological and geographical parameters influence the number of males in a given spider monkey community. Analyses suggest that the number of males is not significantly related to the number of females in a community, the area of the community home range, or the total perimeter length of the community boundary. However, risky boundary perimeter length, or the length of perimeter that directly borders another spider monkey community, explains 88% of observed variations in the number of males in each community. I discuss the results in relation to spider monkey ecology and territoriality, as well as the potential of this relationship for explaining chimpanzee (Pan) behavior given their extremely similar fruit specialist, male philopatry, territoriality and fission-fusion social system.

Conspecific Influences on Vigilance Behavior in Wild Chimpanzees

Diurnal primates rely on visual monitoring behavior to collect various kinds of ecological and social information. Vigilance behavior is monitoring specifically to detect external threats. Previous studies of vigilance behavior were focused mainly on the influence of predation threats, whereas the influences of conspecific factors, such as intragroup threats, have been relatively unstudied. Individual vigilance is predicted to be inversely related to the group size or the number of individuals nearby if the main target of the vigilance is a predation threat and positively related if the main target of the vigilance is a conspecific threat. I studied wild chimpanzees (Pan troglodytes schweinfurthii) in Mahale Mountains National Park, Tanzania, and measured the vigilance duration when they are resting on the ground via 2-min focal observation. In both males and females, vigilance duration increased as the number of individuals nearby increased. This result agrees with the idea that the chimpanzees are vigilant toward other group members. In addition, maternal vigilance monitors and protects the safety of dependent offspring as the duration of maternal vigilance was longer when a dependent infant was separated from its mother than when the offspring was in contact with its mother. The results indicate that the vigilance behavior in wild chimpanzees was affected by conspecific factors.

Innovative social behavior in chimpanzees (Pan troglodytes)

We present evidence of agonistic buffering in captive chimpanzees, recorded from 1993 until 2005, mainly from ad libitum sampling in over 2000 hr of observation. A total of 33 agonistic buffering episodes were analyzed for context and effects of this complex social behavior. Agonistic buffering was directed at the whole chimpanzee colony as they supported an individual who initially received aggression from the alpha male, independently of the victim's age, sex or social rank. Chimpanzee agonistic buffering behavior is compared with that in other nonhuman primate species, and we describe some particularities of chimpanzee agonistic buffering: the status of the buffers used-socially important offspring such as those from the alpha female-and the social rank of the adult male responsible for the buffering episode-alpha male. Possible functions for this behavior in chimpanzees are suggested as appeasement of group members in a particularly crowded captive setting, and/or as a "forced reconciliation" mechanism. Chimpanzees exhibit behavioral flexibility by adapting themselves to new social and physical situations and use novel behavior to achieve social benefits.

The limited impact of kinship on cooperation in wild chimpanzees

The complex cooperative behavior exhibited by wild chimpanzees generates considerable theoretical and empirical interest, yet we know very little about the mechanisms responsible for its evolution. Here, we investigate the influence of kinship on the cooperative behavior of male chimpanzees living in an unusually large community at Ngogo in Kibale National Park, Uganda. Using long-term field observations and molecular genetic techniques to identify kin relations between individuals, we show that male chimpanzees clearly prefer to affiliate and cooperate with their maternal brothers in several behavioral contexts. Despite these results, additional analyses reveal that the impact of kinship is limited; paternal brothers do not selectively affiliate and cooperate, probably because they cannot be reliably recognized, and the majority of highly affiliative and cooperative dyads are actually unrelated or distantly related. These findings add to a growing body of research that indicates that animals cooperate with each other to obtain both direct and indirect fitness benefits and that complex cooperation can occur between kin and nonkin alike.

Hunting and Occasional Consumption of Prey Items by Chimpanzees at the Primate Foundation of Arizona

Researchers have documented hunting by wild chimpanzees (Pan troglodytes) for >30 yr. However, no one had reported the behavior in captive chimpanzees. The Primate Foundation of Arizona (PFA) is a biomedical research facility, and though every effort is made to ensure that rodents and other indigenous animals do not enter cages, an occasional small mammal or bird enters the outside cage area. We document 18 known successful hunts over 2.5 yr by ≥8 captive chimpanzees housed at PFA. The most common prey were rock squirrels (Cittallus variegatus; n = 8) and birds (n = 7). The most common killing method was a bite to the head (n = 9), indicating that the deaths were deliberate and not accidental. Two adult males, 1 wild- and 1 captive-born, together accounted for 11 of the 18 hunting episodes. The chimpanzees generally captured and killed the prey in their outdoor enclosures. The results have implications for the surveillance of outdoor areas in other facilities and the potential for disease or introduction of parasitic vectors, and are also an interesting comparison to wild chimpanzee behavior.

Attempting to reduce regurgitation and reingestion in a captive chimpanzee through increased feeding opportunities: a case study

Persistent regurgitation and reingestion is an abnormal behavior seen in many captive NHPs, particularly gorillas and chimpanzees. Successful reduction of regurgitation in captive gorillas has been achieved by providing browse, such as branches and leaves, and feeding continuously throughout the day. However, this modality has not been tested in chimpanzees. The authors tested these methods in a 15-year-old male chimpanzee (Pan troglodytes) with a seven-year history of regurgitation and reingestion by alternately providing additional opportunities to forage or giving daily browse. The results show that providing browse on a daily basis models the feeding behavior of wild chimpanzees and is a successful way to reduce regurgitation and reingestion in a chimpanzee unresponsive to previous dietary changes.

Competitive and cooperative aspects of social intelligence in chimpanzees

Many primate species live in groups with specific social structures. Much attention has been given to the social intelligence hypothesis, which claims that higher cognitive ability is required to survive in a complex than in a simple social world. Here, I describe four sets of studies that investigated social intelligence in captive chimpanzees, including tactical interactions in competition for food, the learning of tool use in a social situation, assisting of infants by mothers, and cooperative problem-solving behavior in an experimental situation. The results illustrate similarities and differences between humans and chimpanzees. Experimental studies using food as a reward tend to emphasize the competitive and selfish nature of chimpanzee behavior, whereas mother-offspring relationships in a non-food context may be a basis for the cooperative aspect of social intelligence.

Vernon Reynolds. The Chimpanzees of the Budongo Forest: Ecology, Behaviour and Conservation

Vernon Reynolds first studied the chimpanzees of theBudongo Forest, Uganda, in 1962. His study wasinterrupted because of his university teaching positionand the unsafe situation in Uganda. His return to thefield was triggered by a newspaper article about twoinfant chimpanzees that had been smuggled fromUganda to Dubai. These two infants had almost cer-tainly been captured in the Budongo Forest. Reynoldsacquired sufficient funds to return to Uganda andrevisited Budongo in 1990, 27 years after leaving. In1991, he resumed a long-term study of the chimpanzeesliving in the Sonso area, located in the middle of theBudongo Forest, in collaboration with Andy Plumptre,a research director of the Budongo Forest Project.Reynolds and his colleagues have studied the Sonsochimpanzees intensively for 15 years.In his book, Reynolds recounts the history of theBudongo Forest and the work of a large numberof students and senior researchers studying the wildchimpanzees that live there. In five of the twelvechapters of the book he describes the life of the localpeople who live near the Budongo Forest and thehistory of activity to conserve the chimpanzees and theforest; this demonstrates the author’s enthusiasm forchimpanzee conservation and great insight into thecomplex issues concerning wildlife conservation.In Chapter 1 Reynolds outlines the history of theBudongo Forest. Except for forests that are nationalparks, for example Kibale Forest, all forests in Ugandaare ‘‘forest reserves’’ managed by the Ugandan gov-ernment. In these reserves the forest is managed forthe maintenance and use of forest resources, and aneffort has been made to increase the crop of mahoganytrees, which produce valuable timber. In the 1920s, theCynometra trees that dominated the Budongo Forestwere felled because they had no value as timber, andmahogany trees were planted, although without suc-cess. In the 1960s, trees with no commercial value,including Cynometra trees, were treated with a potentarboricide, and the number of Cynometra trees de-creased. Nevertheless, mahogany trees did not increaseas intended, and the treatment resulted in the estab-lishment of more species of non-timber fruiting tress,for example figs. Today, Budongo Forest has a greaterdensities of trees producing fleshy fruits, and of fruit-eating primates, in the logged and arboricide-treatedforest areas than it does in the unlogged, untreatedNature Reserves.The Budongo Forest is a relatively young forest,possibly 300–500-years old, and has changed as a resultof human activity. In this book, Reynolds emphasizesthe importance of practising chimpanzee conservationin such habitats, where most chimpanzees now live.In Chapters 2–8 Reynolds describes the ecology andsocial behavior of the Sonso chimpanzees. He presentsthe results of studies in Budongo and in other chim-panzee study sites, including several sites in Uganda,for example Kibale National Park and Kalinzu Forest.This book provides valuable information on chimpan-zee ecology and behavior, which differ among studysites and communities.In Chapter 2 Reynolds describes demographic andbasic data of the Sonso community, the process ofhabituation of Sonso chimpanzees, and associatedrisks, for example disease transmission and increased

Shared intentionality

We argue for the importance of processes of shared intentionality in children's early cognitive development. We look briefly at four important social-cognitive skills and how they are transformed by shared intentionality. In each case, we look first at a kind of individualistic version of the skill -- as exemplified most clearly in the behavior of chimpanzees -- and then at a version based on shared intentionality -- as exemplified most clearly in the behavior of human 1- and 2-year-olds. We thus see the following transformations: gaze following into joint attention, social manipulation into cooperative communication, group activity into collaboration, and social learning into instructed learning. We conclude by highlighting the role that shared intentionality may play in integrating more biologically based and more culturally based theories of human development.

A MAJOR TRIO

A MAJOR TRIO

Stacking of blocks by chimpanzees: developmental processes and physical understanding

The stacking-block task has been used to assess cognitive development in both humans and chimpanzees. The present study reports three aspects of stacking behavior in chimpanzees: spontaneous development, acquisition process following training, and physical understanding assessed through a cylindrical-block task. Over 3 years of longitudinal observation of block manipulation, one of three infant chimpanzees spontaneously started to stack up cubic blocks at the age of 2 years and 7 months. The other two infants began stacking up blocks at 3 years and 1 month, although only after the introduction of training by a human tester who rewarded stacking behavior. Cylindrical blocks were then introduced to assess physical understanding in object-object combinations in three infant (aged 3-4) and three adult chimpanzees. The flat surfaces of cylinders are suitable for stacking, while the rounded surface is not. Block manipulation was described using sequential codes and analyzed focusing on failure, cause, and solution in the task. Three of the six subjects (one infant and two adults) stacked up cylindrical blocks efficiently: frequently changing the cylinders' orientation without contacting the round side to other blocks. Rich experience in stacking cubes may facilitate subjects' stacking of novel, cylindrical shapes from the beginning. The other three subjects were less efficient in stacking cylinders and used variable strategies to achieve the goal. Nevertheless, they began to learn the effective way of stacking over the course of testing, after about 15 sessions (75 trials).

Sniffing behaviors in Mahale chimpanzees

Although it is difficult for observers to determine how non-human primates use olfaction in a natural environment, sniffing is one clue. In this study, the sniffing behaviors of wild chimpanzees were divided into six categories, and sex differences were found in most categories. Males sniffed more frequently than females in sexual and social situations, while females sniffed more often during feeding and self-checking. Chimpanzees sniffed more frequently during the dry season than during the wet season, presumably due to the low humidity. This suggests that the environment affects olfactory use by chimpanzees and that chimpanzees easily gather new information from the ground via sniffing.

Lacan’s Misuse of Psychology

This article critically examines the relations between Lacan’s psychoanalytic theory and more conventional psychological ideas. It does so by concentrating on Lacan’s notion of the ‘mirror stage’. Lacan and some of his followers have suggested that psychoanalytic theory is ‘beyond psychology’. It is argued that Freud believed that psychoanalytic theory was beyond conventional psychology in a synthetic rather than rejectionist way. Lacan cited the work of orthodox psychologists such as Wolfgang Köhler, James Mark Baldwin and Charlotte Bühler as providing evidential basis for his ideas about the mirror stage. The rhetoric of these citations is examined in detail. It is suggested that Lacan makes a distinction between the ‘facts’ of psychology and the interpretation of the facts. However, close rhetorical examination shows inaccuracies in his citations about the behaviour of children and chimpanzees in reaction to mirror images. Moreover, the evidential basis that he cites is neither supported by contemporary psychology, nor, more seriously, did it suggest what Lacan was claiming at the time of his writing.

Ecological and social influences on the hunting behaviour of wild chimpanzees, Pan troglodytes schweinfurthii

There has been considerable discussion of the factors that influence the hunting behaviour of male chimpanzees. Explanations invoking social benefits hinge upon the potential for males to share meat with sexually receptive females in exchange for mating (‘meat for sex’), or to share meat with other males in exchange for social support (‘male social bonding’). Ecological factors may also affect hunting: chimpanzees may hunt more frequently (1) in response to food shortages (‘nutrient shortfall’); (2) when energy reserves are high (‘nutrient surplus’); (3) in habitat types with good visibility and increased prey vulnerability; and/or (4) when ecological factors favour cooperative hunting. We used 25 years of data on chimpanzees in Gombe National Park, Tanzania, to examine the relative importance of social and ecological factors in the decision to hunt red colobus monkeys, Colobus badius. The presence of sexually receptive females was associated with a significant decrease in hunting probability, suggesting that males face a trade-off between hunting and mating (‘meat or sex’ rather than ‘meat for sex’). Hunting by specific males did not vary with adult male party size, providing evidence against the male social-bonding hypothesis. After controlling for the effects of party size, diet quality was not associated with the probability of hunting or hunting successfully. Hunts were more likely to occur and to succeed in woodland and semideciduous forest than in evergreen forest, emphasizing the importance of visibility and prey mobility. Finally, per capita meat availability decreased with adult male party size, suggesting that hunting was not cooperative. These results provide evidence against social explanations for hunting in favour of more simple ecological alternatives.

Diversity of items of low nutritional value ingested by chimpanzees from Kanyawara, Kibale National Park, Uganda: an example of the etho-ethnology of chimpanzees

English For more than 30 years, field studies have shown that chimpanzees ingest items of low nutritional value such as rough leaves, bitter stems and clay, apparently thereby protecting themselves against parasites and modulating their health. The authors describe the diversity and the biological activities of items of low nutritional value used by Kanyawara chimpanzees in Uganda, according to scientific observations enriched by the viewpoints of local field assistants and a traditional healer. Their perception of chimpanzees' behaviour and the overlap with human medicinal uses led the authors to explore chimpanzee behaviour in a comparative cultural perspective. In spite of the rarity of such observations on wild individuals, study of self-medicative practices offers the opportunity to suggest an epistemology of the chimpanzee so as to better understand the acquisition and transmission of behaviours linked to diseases. French Depuis une trentaine d'années, des études de terrain ont montré que les chimpanzés ingèrent régulièrement des matériels de faible valeur nutritive comme des feuilles rugueuses, des tiges amères ou encore des argiles qui peuvent influer sur leur santé. Les données scientifiques décrites ici soulignent la diversité et les activités biologiques des items non-nutritifs utilisés par les chimpanzés de Kanyawara en Ouganda et s'enrichissent des témoignages des assistants et du médecin traditionnel local. Leur perception de ces comportements et les recouvrements avec les usages ethnomédicinaux permettent d'explorer le comportement des chimpanzés dans une perspective de comparaison culturelle. Cette étude est aussi l'occasion de souligner l'intérêt - malgré la difficulté inhérente à des observations rares portant sur des individus sauvages - d'une épistémologie du chimpanzé qui doit permettre de mieux appréhender l'acquisition et la transmission des comportements en lien avec la maladie.

Comparing infant and juvenile behavior in bonobos (Pan paniscus) and chimpanzees (Pan troglodytes): a preliminary study

The dichotomy between the two Pan species, the bonobo (Pan paniscus) and chimpanzee (Pan troglodytes) has been strongly emphasized until very recently. Given that most studies were primarily based on adult individuals, we shifted the "continuity versus discontinuity" discussion to the infant and juvenile stage. Our aim was to test quantitatively, some conflicting statements made in literature considering species differences between immature bonobos and chimpanzees. On one hand it is suggested that infant bonobos show retardation in motor and social development when compared with chimpanzees. Additionally it is expected that the weaning process is more traumatic to chimpanzee than bonobo infants. But on the other hand the development of behaviors is expected to be very similar in both species. We observed eight mother-infant pairs of each species in several European zoos. Our preliminary research partially confirms that immature chimpanzees seem spatially more independent, spending more time at a larger distance from their mother than immature bonobos. However, the other data do not seem to support the hypothesis that bonobo infants show retardation of motor or social development. The development of solitary play, environmental exploration, social play, non-copulatory mounts and aggressive interactions do not differ between the species. Bonobo infants in general even groom other group members more than chimpanzee infants. We also found that older bonobo infants have more nipple contact than same aged chimpanzees and that the weaning process seems to end later for bonobos than for immature chimpanzee. Additionally, although immature bonobos show in general more signs of distress, our data suggest that the weaning period itself is more traumatic for chimpanzees.

Effects of short- and long-term changes in spatial density on the social behavior of captive chimpanzees (Pan troglodytes)

The constraints of captivity may often require non-human primates to experience restrictions in space for both long- and short-term periods of time. The tension-reduction model predicts that great apes should increase affiliative behaviors and decrease aggressive behaviors as a coping strategy. The conflict avoidance model, however, predicts that great apes should decrease all social interactions (affiliative and aggressive) as a coping strategy. The purpose of this study was to test the conflict-avoidance and tension-reduction models by examining the effects of both short-term (1–2 days) and long-term (6 months) changes in spatial density on social behavior in 23 adult captive chimpanzees (6 males, 17 females) housed at the Primate Foundation of Arizona. Affiliative (i.e., social groom, social play) and agonistic (i.e., charging display, attack) were assessed using scan-sampling techniques while subjects were rotated from high-density to low-density conditions for varying lengths of time. Results of short-term increases in spatial density (crowding) supported the conflict-avoidance strategy for females, through reduced levels of aggressive (F1,16=17.11, p=0.001) and affiliative (F1,16=21.13, p<0.001) behaviors. Males, however, supported the tension-reduction model during short-term high-density by decreasing aggression (F1,5=10.53, p=0.02) while increasing affiliation (F1,5=9.10, p=0.03). Females partially supported the tension-reduction model during long-term high-density by increasing affiliative behaviors (F1,16=14.19, p=0.002) compared to short-term high-density levels, while rates of aggression remained low. Finally, males supported the tension-reduction by reducing aggression (F1,5=7.668, p=0.04) and increasing affiliation (F1,5=6.08, p=0.05) during long-term high-density. Results confirm that chimpanzees use different strategies during short-term versus long-term increases in spatial density and that these strategies may be influenced by individual sex. However, sample sizes are small and additional research on male chimpanzees is needed.

The Context and Quality of Social Relationships Affect Vigilance Behaviour in Wild Chimpanzees

AbstractPrevious studies of vigilance behaviour have focused mainly on the influence of predation threat, whereas the influences of conspecific factors, such as within‐group threats, are relatively unstudied. To elucidate the influences of conspecific factors, this study examined vigilance behaviour in wild chimpanzees (Pan troglodytes schweinfurthii) in Mahale Mountains National Park, Tanzania. Vigilance level was lower during foraging than during resting, which indicated a conflict between vigilance and foraging activity. In addition, vigilance level was higher when chimpanzees were on the ground where an encounter with leopards (Panthera pardus) is likely than when the chimpanzees were in trees. Males, but not females, increased their level of vigilance as the number of individuals within 3 m increased. In both males and females, daily party size – an index of group cohesion – did not affect the vigilance level. The level of maternal vigilance was higher when a dependent infant was separated from its mother than when the offspring was in contact with its mother. Both males and females increased their vigilance when a less‐associated group member was nearby, when compared with when there was no less‐associated group member nearby. This finding suggests that variation in relationship quality influences the vigilance level and that individuals need to increase their level of vigilance when the level of within‐group threats is high. This study indicated that variation in vigilance cannot be understood unless conspecific factors, such as variation in the relationship quality with associates, are considered.