Chimpanzees (Pan troglodytes verus) and their mammalian sympatriates: Mt. Assirik,Niokolo-Koba National Park,Senegal

In intact, mosaic ecosystems, chimpanzees are sympatric with a wide range of other mammals, which may be predators, prey, or competitors. We delve beyond the nominal data of species lists to interval-level data on 35 medium-bodied and large-bodied mammals encountered at a hot, dry, and open field site in far West Africa. Frequency of encounter, habitat where found, and number of individuals encountered are analysed for species for which enough data were accumulated. Further, we compare findings over three periods (1976–1979, 2000, 2012). Species most often encountered were those normally classed as typical savanna forms. Even a crude classification into forest, woodland, and grassland ecotypes yields differences in species likely to meet apes. Comparison of encounter rates over time was surprisingly congruent, although not all species seen in the 1970s survived to the 2000s. Overall, Assirik’s mammalian fauna is comparable to palaeo-faunal guilds sympatric with various extinct hominins.     

Insectivory of savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal

Little is known about the behavior of chimpanzees living in savanna-woodlands, although they are of particular interest to anthropologists for the insight they can provide regarding the ecological pressures affecting early hominins living in similar habitats. Fongoli, Senegal, is the first site where savanna chimpanzees have been habituated for observational data collection and is the hottest and driest site where such observation of chimpanzees occurs today. Previously, indirect evidence suggested these chimpanzees consumed termites throughout the year, an unusual occurrence for western and eastern chimpanzees. Although meat eating by chimpanzees continues to receive much attention, their use of invertebrate prey has received less emphasis in scenarios of hominin evolution. Here, we further examine the invertebrate diet of Fongoli chimpanzees using direct observational methods and accounting for potential environmental influences. Termite feeding positively correlated with high temperatures. Fongoli chimpanzees spend more time obtaining termites than any other chimpanzee population studied, and this extensive insectivory contributes to the list of distinctive behaviors they display relative to chimpanzees living in more forested habitats. We suggest that savanna chimpanzees at Fongoli differ significantly from chimpanzees elsewhere as a result of the selective pressures characterizing their harsh environment, and this contrast provides an example of a viable referential model for better understanding human evolution. Specifically, our results support the hypotheses that invertebrate prey may have figured more prominently into the diet of early hominins in similar habitats, especially given that invertebrates are an important source of protein and other essential nutrients in a highly seasonal environment.     

Dominance and Immunity in Chimpanzees (Pan troglodytes)

The study reported here examined the effect of dominance status on serum immunoglobulin (IgG and IgM) levels in chimpanzees living in five captive colonies. Blood samples were collected from each individual twice, and agonistic and grooming interactions were observed. After initial group observations, members of four of the five groups were caged singly. Thereafter blood samples were again taken. Both IgG and IgM levels of the animals living in groups were significantly negatively correlated with their dominance status in all five groups. The higher-ranked chimpanzees were likely to show lower levels of IgG and IgM. No such consistent correlation was found between individual Ig levels and frequency of aggressive behaviour or grooming. On transfer to isolated conditions, Ig levels of the chimpanzees did not correlate with their previous dominance status in the groups. Being of high rank is a biological cost for colony-living chimpanzees with regard to immunity levels.     

First GIS Analysis of Modern Stone Tools Used by Wild Chimpanzees (Pan troglodytes verus) in Bossou,Guinea, West Africa

Stone tool use by wild chimpanzees of West Africa offers a unique opportunity to explore the evolutionary roots of technology during human evolution. However, detailed analyses of chimpanzee stone artifacts are still lacking, thus precluding a comparison with the earliest archaeological record. This paper presents the first systematic study of stone tools used by wild chimpanzees to crack open nuts in Bossou (Guinea-Conakry), and applies pioneering analytical techniques to such artifacts. Automatic morphometric GIS classification enabled to create maps of use wear over the stone tools (anvils, hammers, and hammers/ anvils), which were blind tested with GIS spatial analysis of damage patterns identified visually. Our analysis shows that chimpanzee stone tool use wear can be systematized and specific damage patterns discerned, allowing to discriminate between active and passive pounders in lithic assemblages. In summary, our results demonstrate the heuristic potential of combined suites of GIS techniques for the analysis of battered artifacts, and have enabled creating a referential framework of analysis in which wild chimpanzee battered tools can for the first time be directly compared to the early archaeological record.     

Intergroup Competition Enhances Chimpanzee (Pan troglodytes verus) In-group Cohesion

International Journal of Primatology - In-group cohesion is an essential component of successful intergroup competition in both human and nonhuman animals, likely facilitating group members access...     

Ecological context of savanna chimpanzee (Pan troglodytes verus) termite fishing at Fongoli, Senegal

Chimpanzees (Pan troglodytes verus) at Fongoli, Senegal, consume termites year-round. Understanding the ecological context behind this behavior is especially important in light of the environmental conditions at Fongoli. This mosaic savanna habitat is one of the hottest and driest sites where chimpanzees have been studied. Two genera and four species of termites were found in association with tools used by chimpanzees in a sample of 124 termite mounds that were monitored. The chimpanzees of Fongoli termite fish predominantly in woodland and forest habitat types, and, although woodland accounts for the majority of the chimpanzees' home range, forest habitat types comprise only about 4% of their range. Thus, habitat type has an influence on the Fongoli chimpanzees' termite fishing. Termite consumption to the degree seen at Fongoli may have particular significance for hominid evolution, given the expansion of Pliocene hominids into increasingly open, hot, and dry habitats.     

Chimpanzee (Pan troglodytes verus) Density and Environmental Gradients at Their Biogeographical Range Edge

International Journal of Primatology - Identifying ecological gradients at the range edge of a species is an essential step in revealing the underlying mechanisms and constraints that limit the...     

Mandibular Shape, Ontogeny and Dental Development in Bonobos (Pan paniscus) and Chimpanzees (Pan troglodytes)

The postnatal ontogenetic patterns and processes that underlie species differences in African ape adult mandibular morphology are not well understood and there is ongoing debate about whether African ape faces and mandibles develop via divergent or parallel trajectories of shape change. Using three-dimensional (3D) morphometric data, we first tested when in postnatal development differences in mandibular shape are initially evident between sister species Pan troglodytes and P. paniscus. Next, we tested whether each species has a distinct and non-parallel trajectory of mandibular development. Mandibles sampled across a broad developmental range of wildshot bonobos (n = 44) and chimpanzees (n = 59) were radiographed and aged from their dental development. We then collected 3D landmark surface data from all the mandibles. A geometric morphometric analysis of size-corrected 3D data found that bonobos and chimpanzees had parallel and linear ontogenetic trajectories of mandibular shape change. In contrast, mandibular shape was statistically different between P. paniscus and P. troglodytes as early as infancy, suggesting that species shape differences are already established near or before birth. A linear and stable trajectory of shape change suggests that mandibular ontogeny in these apes is unimpacted by non-linear variation in tooth developmental timing.     

Chimpanzees (Pan troglodytes): Problem seeking versus the bird-in-hand,least-effort strategy

Fifteen adult chimpanzees were tested on a series of tasks that differed from standard two-choice object discrimination learning problems in one detail: a third choice was sometimes offered, and it consisted of clearly visible and readily accessible food. Even under conditions where they would have to score 100% on the discrimination learning tasks to get as much food as they could get by taking the “free” food, many of the chimpanzees worked on the problems. Individual differences were large and reliable. Frequency of response to a given problem also varied according to how accurately the animals were performing and increased markedly if the hidden food was made a few grams larger than the free food. The chimpanzees did not rely strictly on a “bird-in-hand” strategy or necessarily always work to get the maximum amount of food with the minimum amount of energy expenditure. Whether this is bad economics or good economics depends on the time scale on which one views adaptation.     

Oil Palm Use by Adjacent Communities of Chimpanzees at Bossou and Nimba Mountains,West Africa

We investigated oil palm (Elaeis guineensis) use for feeding in 3 chimpanzee communities: Bossou and Seringbara in Guinea and Yealé in Côte d'Ivoire. Bossou was used as the benchmark for comparison. Bossou chimpanzees (Pan troglodytes verus) exhibit a wide range of oil palm targeted behaviors. We used direct observations of their two tool use, i.e., nut-cracking and pestle pounding, to establish strict and reliable criteria to ascertain the presence of comparable behaviors at the two adjacent Nimba sites. Based on monthly surveys of oil palms across the three sites, significant differences in patterns of use emerged. Bossou chimpanzees demonstrated the greatest frequency of oil palm use, while Seringbara chimpanzees, 6 km away, failed to exhibit any use and Yealé chimpanzees, 12 km away, showed all uses comparable to Bossou chimpanzees except pestle pounding and mature leaf pith-feeding. We examined the density and distribution of oil palms, tool availability for nut-cracking and pestle pounding, fruit, flower and nut availability, competition with sympatric species for fruit and nuts and the diversity of fruit species in the diet across the 3 sites. We found no clear difference in proximate environmental variables underlying observed variations in oil palm use among the 3 sites, yielding the conclusion that the differences are cultural. Assuming individual interchange between communities and the involvement of social learning in the intracommunity transmission and maintenance of oil palm uses, the result raises interesting questions about diffusion of behavior between neighboring chimpanzee communities.     

Savanna chimpanzees, Pan troglodytes verus, hunt with tools

Although tool use is known to occur in species ranging from naked mole rats [1] to owls [2], chimpanzees are the most accomplished tool users [3-5]. The modification and use of tools during hunting, however, is still considered to be a uniquely human trait among primates. Here, we report the first account of habitual tool use during vertebrate hunting by nonhumans. At the Fongoli site in Senegal, we observed ten different chimpanzees use tools to hunt prosimian prey in 22 bouts. This includes immature chimpanzees and females, members of age-sex classes not normally characterized by extensive hunting behavior. Chimpanzees made 26 different tools, and we were able to recover and analyze 12 of these. Tool construction entailed up to five steps, including trimming the tool tip to a point. Tools were used in the manner of a spear, rather than a probe or rousing tool. This new information on chimpanzee tool use has important implications for the evolution of tool use and construction for hunting in the earliest hominids, especially given our observations that females and immature chimpanzees exhibited this behavior more frequently than adult males.     

Diet of wild chimpanzees (Pan troglodytes verus) at Mt. Assirik,Senegal: I. Composition

The composition of the diet of a savanna-living population of wild chimpanzees (Pan troglodytes verus) at Mt. Assirik in Senegal is presented. The study site had a prolonged dry season, high temperatures, and vegetation dominated by grasses. Data came from direct observation, fecal specimens, and feeding traces; thus, strict criteria for acceptance of the indirect data were specified. Composition of diet was given in terms of species and family of prey, parts eaten, life-form, type of habitat, and criteria for inclusion. Forty-three species of plants with 60 parts were eaten; mostly fruits, from trees, in woodland. Nine species of animal prey were eaten, mostly social insects. An additional 41 species of plants with 53 parts were classed as likely to be eaten by chimpanzees, mostly on the grounds of their being eaten by sympatric anthropoids. Overall, the diet of the apes at Mt. Assirik resembles that of this species elsewhere in Africa, but the size of the dietary repertoire seems small and the proportion of low-quality foodstuffs high. The latter are mostly time-consuming to collect or tedious to obtain or process, and include underground storage organs.     

Task Design Influences Prosociality in Captive Chimpanzees (Pan troglodytes)

Chimpanzees confer benefits on group members, both in the wild and in captive populations. Experimental studies of how animals allocate resources can provide useful insights about the motivations underlying prosocial behavior, and understanding the relationship between task design and prosocial behavior provides an important foundation for future research exploring these animals'' social preferences. A number of studies have been designed to assess chimpanzees'' preferences for outcomes that benefit others (prosocial preferences), but these studies vary greatly in both the results obtained and the methods used, and in most cases employ procedures that reduce critical features of naturalistic social interactions, such as partner choice. The focus of the current study is on understanding the link between experimental methodology and prosocial behavior in captive chimpanzees, rather than on describing these animals'' social motivations themselves. We introduce a task design that avoids isolating subjects and allows them to freely decide whether to participate in the experiment. We explore key elements of the methods utilized in previous experiments in an effort to evaluate two possibilities that have been offered to explain why different experimental designs produce different results: (a) chimpanzees are less likely to deliver food to others when they obtain food for themselves, and (b) evidence of prosociality may be obscured by more “complex” experimental apparatuses (e.g., those including more components or alternative choices). Our results suggest that the complexity of laboratory tasks may generate observed variation in prosocial behavior in laboratory experiments, and highlights the need for more naturalistic research designs while also providing one example of such a paradigm.     

Chronic diseases in captive geriatric female Chimpanzees (Pan troglodytes)

The current aging population of captive chimpanzees is expected to develop age-related diseases and present new challenges to providing their veterinary care. Spontaneous heart disease and sudden cardiac death are the main causes of death in chimpanzees (especially of male animals), but little is known about the relative frequency of other chronic diseases. Furthermore, female chimpanzees appear to outlive the males and scant literature addresses clinical conditions that affect female chimpanzees. Here we characterize the types and prevalence of chronic disease seen in geriatric (older than 35 y) female chimpanzees in the colony at Alamogordo Primate Facility. Of the 16 female chimpanzees that fit the age category, 87.5% had some form of chronic age-related disease. Cardiovascular-related disease was the most common (81.25%) followed by metabolic syndrome (43.75%) and renal disease (31.25%). These data show the incidence of disease in geriatric female chimpanzees and predict likely medical management challenges associated with maintaining an aging chimpanzee population.     

Feeding Behaviour and Diet of Chimpanzees (Pan troglodytes troglodytes) in the Okorobikó Mountains of Rio Muni (West Africa)

Some aspects of the nutritional behaviour of the Okorobikó-Matama (Rio Muni, West Africa) chimpanzees have been studied over two periods — from June 1963 to September 1964 and from July 1966 to February 1969. This research totaled 640 h, 119 of which were in sustained contact with the animals. We have compiled a list of 43 plant and two termite species consumed by the chimpanzees. We studied the relative importance of the plants consumed in terms of the four principal biotopes and seasonal cycles, the feeding behavior, the rhythm of activity and chimpanzees' vertical stratification during feeding. We also took into account group dynamics as a function of feeding, communication and polyspecific associations with other primates. We finally compared some aspects of the nutrition of these chimpanzees with that of gorillas living in nearby zones.     

Hypertension Increases With Aging and Obesity in Chimpanzees (Pan troglodytes)

Cardiovascular disease is a primary cause of morbidity and mortality in captive chimpanzees. Four years of blood pressure (BP) data were analyzed from a captive former laboratory population of 201 healthy adult chimpanzees with assessment of age and obesity on elevated BP. Five different measures of obesity were compared: abdominal girth, basal metabolic rate, body‐mass index (BMI), body weight, and surface area. Systolic BP varied by sex. Obesity did not influence male BP. For females, obesity was a significant determinant of BP. The best measure of female obesity was basal metabolic rate and the worst was BMI. Median systolic BP of healthy weight females (<54.5 kg) was significantly lower (128 mmHg) than overweight or obese females (140 mmHg), but both were lower than all males (147 mmHg). For diastolic BP, neither sex nor any of the five obesity measures was significant. But age was highly significant, with geriatric chimpanzees (>30 years) having higher median diastolic BP (74 mmHg) than young adults of 10–29 years of age (65 mmHg). By these criteria, 80% of this population is normotensive, 7% prehypertensive, and 13% hypertensive. In summary, systolic BP intervals required adjustment for obesity among females but not males. Diastolic BP required adjustment for advanced age (≥30 years). Use of these reference intervals can facilitate timely clinical care of captive chimpanzees. Zoo Biol. 32:79‐87, 2013. © 2012 Wiley Periodicals, Inc.     

Giving the Forest Eyes: The Benefits of Using Camera Traps to Study Unhabituated Chimpanzees (Pan troglodytes verus) in Southeastern Senegal

Habituation has been the standard methodology used to study the natural history of great apes and other primates. Habituation has invaluable strengths, particularly in quantity and diversity of data collected, but along with these come substantial weaknesses, i.e., costs both in time and effort, health risks, and potential exposure of subjects to poaching. With new technologies, we are able to extend our studies beyond the limitations of habituation; camera traps are one technology that can be used to study unhabituated primate groups. In this study we used eight camera traps over the course of 2 yr (1542 camera trap days) to capture thousands of still images of West African savanna chimpanzees (Pan troglodytes verus) in the Falémé region of southeastern Senegal. Images corroborated behavioral observations from habituated chimpanzees at the Fongoli site, where researchers have observed nocturnal activity and cave use. The cameras also captured interspecies interactions at water sources during the dry season and allowed us to determine demographic composition and minimum community size. The photographs provide data on local fauna, including predators (Panthera pardus pardus, Panthera leo senegalesis, and Crocuta crocuta), potential prey, and competitor species (Papio papio, Cercopithecus aethiops, and Erythrocebus patas). As primate habitat across Africa is further threatened and human–wildlife conflict increases, camera trapping could be used as an essential conservation tool, expanding studies of primates without exacerbating potential threats to the species.