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Le chimpanzé d'Afrique de l'Ouest (Pan troglodytes verus) est inscrit sur la liste des espèces « en danger critique d'extinction » de l’Union Internationale pour la Conservation de la Nature depuis 2016, suite au déclin de ses effectifs. Ce travail se focalise sur la nidification du chimpanzé dans la savane boisée, chaude et sèche de Bantankiline. Son objectif est d’améliorer l’état des connaissances sur la nidification du chimpanzé au Sénégal par : 1) l’identification des dortoirs du chimpanzé à Bantankiline ; 2) l’identification des espèces végétales les plus utilisées pour construire les nids de repos ; 3) la détermination de la hauteur des nids par rapport au sol et 4) l’identification des menaces sur la survie du chimpanzé dans ce site. Pour cela, nous avons recensé au total 809 nids de chimpanzé et parcouru 155,1 kilomètres répartis entre 37 transects, soit une moyenne de 4,19 kilomètres par transect. Les nids ont été recensés au cours des années 2018, 2020 et 2021. Les résultats montrent que la majorité des nids (environ 655 nids, soit 80,96 % des observations) est portée principalement par 6 espèces végétales : Pterocarpus erinaceus, Parkia biglobosa, Anogeissus leiocarpus, Diospyros mespiliformis, Cola cordifolia, Hexalobus monopetalus. Khaya senegalensis, Piliostigma thonningii et Adansonia digitata sont faiblement utilisés par les chimpanzés pour la nidification à Bantankiline. L’inventaire quantitatif des espèces végétales par la méthode des plots nous a permis de recenser au total 3582 pieds d’arbres répartis entre 50 espèces le long des transects. Nous avons noté la prédominance de 4 espèces végétales lors du recensement : Hexalobus monopetalus, Pterocarpus erinaceus, Combretum glutinosum et Combretum micranthum. Parkia biglobosa est peu abondante dans le site d’étude mais elle est la deuxième espèce végétale la plus utilisée par les chimpanzés pour la nidification après P. erinaceus. La hauteur moyenne des arbres utilisés comme supports de nids est de 13 m et la hauteur moyenne des nids se situe à 9,91 m. Ces informations scientifiques sont d’une importance capitale pour l’élaboration des documents de gouvernance de ces sites par les services techniques et la prise de décisions pour la conservation du chimpanzé et de ses espèces sympatriques au Sénégal.

Chimpanzees use tools extensively, but tool-assisted hunting has been reported at only two sites thus far. Systematic tool-assisted hunting has only been recorded at the Fongoli site in Senegal, where hundreds of cases have been recorded of chimpanzees using tools to hunt bushbaby (Galago senegalensis) prey. Here, we report a putative case of tool-assisted hunting at the Bantan study site in southeastern Senegal, based on indirect evidence of tools and tool-making traces in a context similar to that observed at neighboring Fongoli chimpanzee community. If our interpretations are correct, the simplest explanation is that Fongoli females have dispersed to this neighboring community, bringing with them the behavior of tool-assisted hunting. However, the persistence and frequency of tool-assisted hunting at other sites in Senegal is still unknown. Tool-assisted hunting in the Bantan chimpanzee community would present only the third such known site for such behavior among wild chimpanzees thus far.

The hypothesis that dangerous snakes served as evolutionary selective pressures on traits characterizing the Order Primates (Snake Detection Hypothesis, SDH), specifically vision and aspects of the brain, has received recent attention. We provide data on 52 encounters between chimpanzees (Pan troglodytes verus) in a savanna landscape and snakes and other large reptiles at the Fongoli site in Senegal, over the course of eight years. These encounters yielded data on 178 interactions between identified individual chimpanzees and reptiles. The majority of encounters with identified reptiles (62%) involved potentially deadly snakes. Constrictors of the family Pythonidae were encountered more frequently than any other reptile. Chimpanzees exhibited a variety of reactions to reptiles, ranging from attacking with objects to ignoring them. Even reptiles other than snakes were met with some degree of alarm when they were in water or moving quickly. We assessed variables that may affect apes’ reactions, as well as the age-sex class of chimpanzees. As a test of Isbell’s snake detection hypothesis, we examined chimpanzees’ reaction intensity to venomous versus constricting snakes but found no difference. We did find significant age-sex differences in chimpanzees’ reactions to snakes, with adolescent males exhibiting higher-intensity reactions than adult males and females and adolescent female chimpanzees. Chimpanzees reacted at significantly higher intensities when snakes were arboreal in location, but reptile species, size, and activity did not significantly influence individuals’ reactions to snakes. We also report one inferred encounter between an adult female chimpanzee and a venomous snake, which led to her death. Our data suggest that snakes are significant threats to chimpanzees in savanna environments and support the hypothesis that danger from snakes could have exerted significant evolutionary pressure on the Order Primates.

Identifying ecological gradients at the range edge of a species is an essential step in revealing the underlying mechanisms and constraints that limit the species’ geographic range. We aimed to describe the patterns of variation in chimpanzee (Pan troglodytes verus) density and habitat characteristics perpendicular to the northern edge of their range and to investigate potential environmental mechanisms underlying chimpanzee distribution in a savanna–mosaic habitat. We estimated chimpanzee densities at six sites forming a 126-km latitudinal gradient at the biogeographical range edge of the western chimpanzee in the savanna–mosaic habitats of southeastern Senegal. To accompany these data, we used systematically placed vegetation plots to characterize the habitats at each site for habitat heterogeneity, tree density and size, and floral assemblages, among other variables. We found that both biotic and abiotic factors are potential determinants of the chimpanzee range limit in this ecoregion. Specifically, chimpanzee-occupied landscapes at the limit had smaller available floral assemblages less habitat heterogeneity, and contained fewer closed canopy habitats in which chimpanzees could seek refuge from high temperatures than in landscapes farther from the range limit. This pattern was accompanied by a decline in chimpanzee density with increasing proximity to the range limit. Our results provide several indications of the potential limits of food species diversity, thermal refuge, and water availability to the chimpanzee niche and the implications of these limits for chimpanzee biogeography, especially in the face of climate change predictions, as well as for species distributional modeling more generally.

Caves play an important ecological role for nonhuman primates in Africa and Asia. Savanna chimpanzees (Pan troglodytes verus) living in the Mandingue plateau of Senegal and Mali use caves for thermoregulation, where these refugia provide a cool microclimate during the hot, dry season. In this study, we examined cave use frequency for a chimpanzee community in southeastern Senegal. We used images from a camera trap placed at the mouth of a large laterite cave to investigate the hypotheses that sex, reproductive state, and seasonality influence the frequency of cave use. The camera collected 14,053 still images of chimpanzees between 2011 and 2013 over 325 camera trap days. Our results indicate no difference in cave use frequency between males and females overall. However, female reproductive state did significantly influence cave use, with lactating mothers using the cave more frequently than both males and nonlactating females. Chimpanzees used the cave during the hottest times of the day and were more likely to visit the cave during periods of low water availability and high maximum temperatures associated with the dry season. These results suggest the importance of thermoregulation in extreme heat for all individuals, and specifically for lactating females with nursing infants that likely experience higher metabolic and hydration stress. This study provides insight into the dynamics of primate cave use by contributing evidence that chimpanzee cave use may be influenced by reproductive states in addition to thermoregulatory needs.

Water conservation played a role in the evolutionary adaptation of humans to hot, dry environments, but until now the extent of such biological adaptability was unknown. A new study compares great apes and humans to illuminate the complexities of water balance in humans and the factors that influence it.

Intrinsic to several hypotheses explaining the evolution of foraging behavior complexity, such as proto-tool use, is the assumption that more complex ingestive behaviors are adaptations allowing individuals to access difficult to procure but nutritionally or energetically rewarding foods. However, nutritional approaches to understanding this complexity have been underutilized. The goal of this study was to evaluate potential nutritional determinants of two unusual foraging behaviors, fruit cracking with anvils and seed reingestion, by adult male western chimpanzees (Pan troglodytes verus) at Fongoli, Senegal during the baobab (Adansonia digitata) fruit season. We examined these behaviors in relation to nutrient and energy intake, and compared macronutrient and energy concentrations found in baobab fruits to other plant foods. Adult males ingested at least 31 distinct foods from 23 plant species. Baobab fruit comprised the majority of daily energy intake (68 ± 34%, range: 0%-98%). The energetic concentration of baobab fruit varied by phenophase and part ingested, with ripe and semi-ripe fruit ranking high in energy return rate. Males preferred ripe and semi-ripe baobab fruit but unripe fruit intake was higher overall. The seed kernels were high in protein and fat relative to fruit pulp, and these kernels were easier to access during the unripe stage. During the ripe stage, seed kernels were accessible by reingestion, after the seed coat was softened during gut passage. In addition to providing macronutrients and energy, baobab fruit was a relatively abundant food source. We conclude that baobab pulp and seed are high quality foods at Fongoli during the baobab season because they are nutritionally balanced, high in energy, and relatively abundant in the environment. These nutritional and abundance characteristics may explain, in part, why these chimpanzees use anvils and reingestion to access a mechanically challenging food.

Identifying ecological gradients at the range edge of a species is an essential step in revealing the underlying mechanisms and constraints that limit the species’ geographic range. We aimed to describe the patterns of variation in chimpanzee (Pan troglodytes verus) density and habitat characteristics perpendicular to the northern edge of their range and to investigate potential environmental mechanisms underlying chimpanzee distribution in a savanna-mosaic habitat. We estimated chimpanzee densities at six sites forming a 126 km latitudinal gradient at the biogeographical range edge of the western chimpanzee in the savanna-mosaic habitats of southeastern Senegal. To accompany these data, we used systematically placed vegetation plots to characterize the habitats at each site for habitat heterogeneity, tree density and size, floral assemblages, among other variables. We found that both biotic and abiotic factors are potential determinants of the chimpanzee range limit in this ecoregion. Specifically, chimpanzee-occupied landscapes at the limit had smaller available floral assemblages, less habitat heterogeneity, and contained fewer closed canopy habitats in which chimpanzees could seek refuge from high temperatures than landscapes farther from the range limit. This pattern was accompanied by a decline in chimpanzee density with increasing proximity to the range limit. Our results provide several indications of the potential limits of food species diversity, thermal refuge, and water availability to the chimpanzee niche and the implications of these limits for chimpanzee biogeography, especially in the face of climate change predictions, as well as to species distributional modeling more generally.

Updated information on Critically Endangered western chimpanzees (Pan troglodytes verus) in Senegal is urgently needed, given that gold mining is rapidly transforming landscapes and livelihoods. Specifically, biodiversity assessments will better elucidate the chimpanzee extinction risk here and yield baselines for monitoring. We compared mammal species richness between Fongoli (unprotected) and Assirik in Niokolo-Koba National Park to assess the efficacy of the only nationally protected area where chimpanzees range in this country. The primary habitat difference between these sites was the degree of human activity. Although Assirik and Fongoli had similar mammal assemblages and were equivalent in primate species richness, the protected area was higher in species richness overall, particularly for ungulates and carnivores. The protected status and management plan of Niokolo-Koba almost certainly resulted in fewer mammal extinctions. In unprotected areas, the flexible behavioural responses of chimpanzees to human-driven landscape dynamics is likely essential to their long-term survival. Furthermore, the near absence of chimpanzee killings in this country greatly facilitates conservation efforts. Given that mineral extraction is a key development strategy in Senegal, we encourage primatologists to collaborate with mining stakeholders to ensure that sustainability programming includes contributions from experts in savannah chimpanzee behavior and ecology.

Humans' extensive use of fire is one behavior that sets us apart from all other animals. However, our ancestors' reliance on controlled forms of fire-i.e., for cooking-was likely preceded by a long familiarity with fire beginning with passive exploitation of naturally burned landscapes and followed by intermediate steps including active ecological modification via intentional burning. Here we explore our pyrophilic beginnings using observational data from savanna-dwelling chimpanzees. These data highlight the extent to which anthropogenic burning impacts the behavior and ecology of sympatric primates and provides an opportunity to study the ways in which apes living in a fire-altered world exploit opportunities presented by burning. Using monthly burn scar data and daily range use data we quantify the impact of burning episodes on chimpanzee habitat. Over the course of one dry season, approximately 74% of the total estimated range of the Fongoli community of savanna-dwelling chimpanzees (Pan troglodytes verus) was impacted by fire. We combine fire occurrences with behavioral data to test for relationships between burning and rate of encounter with food items and duration of subsequent patch residence time. Results show more frequent encounters and shorter patch residence times in burned areas. These data can be leveraged as a frame of reference for conceptualizing our extinct relatives' behavior around fire.

Adaptations associated with shifting from a predominately forested habitat to a more open environment are considered a crucial step in hominin evolution. Understanding how chimpanzees, one of our closest-living relatives, are exposed to the selection pressures associated with living in a relatively sparse, hot, and dry environment can inform us about the relative importance of potential environmental stressors involved in adaptations to drier environments. We investigated the extent to which chimpanzees living in an extreme savanna habitat experience seasonal variability in either energy balance or thermoregulation (dehydration and heat exposure), as well as whether these potential environmental constraints are taxing to chimpanzee individuals. Specifically, we tested the hypothesis that savanna environments impose seasonally-relevant costs to chimpanzees. To this end, we collected 368 urine samples from one community of chimpanzees at Fongoli, Senegal, and measured c-peptide, creatinine, and cortisol as measures of physiological responses to environmental food, water, and heat constraints, respectively. We then evaluated the influence of climatic and phenological factors on these indicators. Results illustrated significant seasonal variation in all biomarkers, which corresponded to relevant ecological correlates. Furthermore, creatinine but not c-peptide correlated with cortisol levels, suggesting that chimpanzees in this environment endure periods of heat and dehydration stress, but are able to avoid stressful levels of negative energy balance. Using savanna chimpanzees as a referential model, our research lends support to the notion that thermoregulatory challenges were a significant factor in hominin evolution, and suggests these challenges may have overshadowed the challenges of maintaining adequate energetic balance during the expansion of the hominin range from wetter to drier environments.

Objectives Great ape nests are hypothesized to aid safe, secure sleep via providing thermoregulation or protection from predators and vectors. We aimed to describe and investigate variation in chimpanzee nest architecture across two populations in response to local weather conditions. Materials and methods We experimentally tested whether nests provide insulation by measuring heat loss within and outside nests, and took detailed measurements of the number, size, and type of materials used in nest building across two dry-habitat research sites (Fongoli, Senegal, and Issa, Tanzania). We tested application of principal components analysis (PCA) to extract composite quantitative measures of the key components of shape and architecture, before testing how PCs vary across populations with overnight weather conditions that reflect hypothesized thermoregulatory function. Results Heat loss is greater and occurs faster outside of nests. PCA allowed meaningful comparison of nests within and between sites. Nest variation at both sites revealed chimpanzees built thicker nests in cooler conditions and used more broken branches and support in moister conditions. Chimpanzees in Fongoli used more lining and mattress material in colder conditions, whilst in Issa nest depth and support branch size were larger in windier conditions. Discussion Shape and architectural measures reflected insulation and stability of nest structure. Chimpanzees in Fongoli and Issa may achieve the same functional goals by adjusting nest shape and architecture in different ways. These results suggest that wild chimpanzees show flexible building techniques in response to local, overnight weather conditions in making an insulating and stable, supportive platform for sleep.

Diaguiri is a non-protected area situated in south-eastern Senegal. Chimpanzees (Pan troglodytes verus) have been living here since 1999 but information on the characteristics of their nest sites have been lacking until now. Furthermore, we implemented nest survey methods recently standardised to arid landscapes during a national chimpanzee survey. Variations in nest decay rates are poorly understood in savanna-woodland mosaic habitats. This study aims to describe in Diaguiri: (1) the distribution of chimpanzee nests and the location of their core sleeping area, (2) the tree species used for nest building, (3) the association between nests and nesting tree heights, and (4) differences in nest decay rates between habitats. We surveyed 43 km of chimpanzee nesting habitats and recorded 871 nests in gallery forest and woodland habitats between March 2015 and June 2016. Diaguiri chimpanzees used at least 17 tree species for nest building, and 58.8% of nests were in only 3 tree species: Pterocarpus erinaceus, Anogeissus leiocarpus and Diospyros mespiliformis. Nest decay rate was faster in gallery forests than in woodlands. These data are of great value for understanding habitat use by a Critically Endangered subspecies of savanna chimpanzee, for population density estimates of the species and for conservation programmes in this region and in savanna biomes.

Objectives I report on the nocturnal behavior of Fongoli chimpanzees in a savanna mosaic during different seasons and lunar phases and test the hypothesis that hot daytime temperatures influence activity at night. I predicted that apes would be more active at night during periods of greater lunar illuminosity given diurnal primates' lack of visual specializations for low-light conditions and in dry season months when water scarcity exacerbated heat stress. Materials and methods I observed chimpanzees for 403 hrs on 40 nights between 2007 and 2013 and categorized their activity as social, movement, or vocalization. I scored their activity as occurring after moonrise or before moonset and considered the influence of moon phase (fuller versus darker phases) as well as season on chimpanzee nocturnal behavior in the analyses. Results Results indicate that apes were more active after moonrise or before moonset during fuller moon phases in the dry season but not the wet season. Most night-time activity involved movement (travel or forage), followed by social behavior, and long-distance vocal communication. Discussion Animals in highly seasonal habitats often exhibit thermoregulatory adaptations but, like other primates, chimpanzees lack physiological mechanisms to combat thermal stress. This study provides evidence that they may exhibit behaviors that allow them to avoid high temperatures in a savanna environment, such as feeding and socializing at night during the hottest time of year and in the brightest moon phases. The results support theories invoking thermal stress as a selective pressure for hominins in open environments where heat would constrain temporal foraging niches, and suggest an adaptability of sleeping patterns in response to external factors.

Savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal, appear to be able to predict the “behavior” of wildfires of various intensities. Although most wildfires are avoided, even the most intense fires are met with relative calm and seemingly calculated movement by apes in this arid, hot, and open environment. In addition to reviewing instances of such behavior collected during the course of the Fongoli study, we also report chimpanzees’ use of burned landscapes during the dry season, when more than 75% of these apes’ home range may be burned annually. In burned areas, chimpanzees spent more time foraging and traveling than in unburned areas. Chimpanzees’ behavior in a fire context can help inform paleoanthropological hypotheses regarding early members of our own lineage and can provide insight into the ability of early hominins to conceptualize the behavior of fire and thus set the stage for our lineage’s use of fire.

Lethal coalitionary aggression is of significant interest to primatologists and anthropologists given its pervasiveness in human, but not nonhuman, animal societies. Chimpanzees (Pan troglodytes) provide the largest sample of recorded lethal coalitionary aggression in nonhuman primates, and most long-term chimpanzee study sites have recorded coalitionary killing of conspecifics. We report an inferred lethal attack by resident males on a former alpha male chimpanzee (P. t. verus) at Fongoli in Senegal. We describe the male’s presence in the community, his overthrow, social peripheralization for >5 yr, and his attempt to rejoin the group as well as circumstances surrounding his death. We report attacks by multiple chimpanzees on his dead body, most frequently by a young adult male and an older female. The latter also cannibalized the body. Coalitionary killing is rare among West African chimpanzees compared to the East African chimpanzee (P. t. schweinfurthii). This pattern may relate to differences in population densities, research effort, and subspecies differences in biology and behavior.

OBJECTIVES Food scarcity is proposed to be a limitation to chimpanzees at the limits of their range; however, such a constraint has never been investigated in this context. We investigated patterns of δ13 C and δ15 N variation along a latitudinal gradient at the northwestern West African chimpanzee (Pan troglodytes verus) range limit with the expectation that isotope ratios of chimpanzees at the range limit will indicate different dietary strategies or higher physiological constraints than chimpanzees further from the edge. MATERIALS AND METHODS We measured δ13 C and δ15 N values in hair (n = 81) and plant food (n = 342) samples from five chimpanzee communities located along a latitudinal gradient in Southeastern Senegal. RESULTS We found clear grouping patterns in hair δ13 C and δ15 N in the four southern sites compared to the northernmost site. Environmental baseline samples collected from these sites revealed overall higher plant δ15 N values at the northernmost site, but similar δ13 C values across sites. By accounting for environmental baseline, Δ13 C and Δ15 N values were clustered for all five sites relative to total Pan variation, but indicated a 13 C-enriched diet at the range limit. DISCUSSION Clustering in Δ13 C and Δ15 N values supports that strategic shifting between preferred and fallback foods is a likely ubiquitous but necessary strategy employed by these chimpanzees to cope with their environment, potentially allowing chimpanzees at their limits to avoid periods of starvation. These results also underline the necessity of accounting for local isotopic baseline differences during inter-site comparison.

Updated information on Critically Endangered western chimpanzees (Pan troglodytes verus) in Senegal is urgently needed, given that gold mining is rapidly transforming landscapes and livelihoods. Specifically, biodiversity assessments will better elucidate the chimpanzee extinction risk here and yield baselines for monitoring. We compared mammal species richness between Fongoli (unprotected) and Assirik in Niokolo-Koba National Park to assess the efficacy of the only nationally protected area where chimpanzees range in this country. The primary habitat difference between these sites was the degree of human activity. Although Assirik and Fongoli had similar mammal assemblages and were equivalent in primate species richness, the protected area was higher in species richness overall, particularly for ungulates and carnivores. The protected status and management plan of Niokolo-Koba almost certainly resulted in fewer mammal extinctions. In unprotected areas, the flexible behavioural responses of chimpanzees to human-driven landscape dynamics is likely essential to their long-term survival. Furthermore, the near absence of chimpanzee killings in this country greatly facilitates conservation efforts. Given that mineral extraction is a key development strategy in Senegal, we encourage primatologists to collaborate with mining stakeholders to ensure that sustainability programming includes contributions from experts in savannah chimpanzee behavior and ecology.

Since its inception, archaeology has traditionally focused exclusively on humans and our direct ancestors. However, recent years have seen archaeological techniques applied to material evidence left behind by non-human animals. Here, we review advances made by the most prominent field investigating past non-human tool use: primate archaeology. This field combines survey of wild primate activity areas with ethological observations, excavations and analyses that allow the reconstruction of past primate behaviour. Because the order Primates includes humans, new insights into the behavioural evolution of apes and monkeys also can be used to better interrogate the record of early tool use in our own, hominin, lineage. This work has recently doubled the set of primate lineages with an excavated archaeological record, adding Old World macaques and New World capuchin monkeys to chimpanzees and humans, and it has shown that tool selection and transport, and discrete site formation, are universal among wild stone-tool-using primates. It has also revealed that wild capuchins regularly break stone tools in a way that can make them difficult to distinguish from simple early hominin tools. Ultimately, this research opens up opportunities for the development of a broader animal archaeology, marking the end of archaeology's anthropocentric era.

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 Faleme 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.

We studied the nesting behavior of the critically endangered West African chimpanzee (Pan troglodytes verus). We assumed that the nesting data stemmed from a single, unhabituated community at the Bagnomba hill site in the savanna-woodlands of southeastern Senegal. The aim of this study was to examine chimpanzees’ nesting habits in terms of the tree species utilized and sleeping nest heights. We recorded a total of 550 chimpanzee nests at Bagnomba between January 2015 and December 2015. The chimpanzees here made nests in particular tree species more often than others. The majority of nests (63%) were in two tree species: Diospyros mespiliformis and Pterocarpus erinaceus. The average height of nesting trees was 10.54 m (SD 3.91, range, 0.0–29.0 m) and average nest height was 7.90 m (SD 3.62, range, 0.0–25.0 m). The result of a linear regression analysis (r = 0.7874; n = 550; p

Sleep is a vulnerable state for animals as it compromises the ability to detect predators. The evolution of shelter construction in the great apes may have been a solution to the trade-off between restorative sleep and predation-risk, which allowed a large bodied ape to sleep recumbent in a safe, comfortable spot. In this article we review the evidence of predator pressure on great apes and specifically investigate the potential influence of predation-risk on chimpanzee nesting behavior by comparing nests between chimpanzees living in a habitat of several potential predators (Issa, Ugalla, Tanzania) and a habitat relatively devoid of predators (Fongoli, Senegal). Chimpanzees in Issa did not nest more frequently in forest vegetation than chimpanzees in Fongoli although forest vegetation is expected to provide greater opportunity for escape from terrestrial predators. Nor do chimpanzees in Issa nest in larger groups or aggregate together more than Fongoli chimpanzees, as would be expected if larger groups provide protection from or greater detection of predators. Nests in Issa also did not appear to provide greater opportunities for escape than nests in Fongoli. Chimpanzees in Issa nested more frequently within the same tree as other community members, which may indicate that these chimpanzees nest in greater proximity than chimpanzees in Fongoli. Finally, Issa chimpanzees built their nests proportionately higher and more peripherally within trees. The selection of high and peripheral nesting locations within trees may make Issa chimpanzees inaccessible to potential predators. Many factors influence nest site selection in chimpanzees, of which danger from terrestrial predators is likely to be one. Am. J. Primatol. 75:593-604, 2013. © 2013 Wiley Periodicals, Inc.

Objectives We evaluated risk-sensitive foraging in adult male western chimpanzees (Pan troglodytes verus) occupying a savanna environment at Fongoli, Senegal. The aim of this study was to determine how the risks of predation and heat stress influenced their behavior while feeding on a key food, fruit of the baobab tree (Adansonia digitata). Materials and methods Proximity of fruiting baobab trees to anthropogenic landmarks were compared to food intake, feeding rate, and behavioral indicators of fear in adult males (N = 11) at Fongoli. Additionally, we compared foraging to vegetative habitats, baobab ripe fruit nutritive quality, surface water availability, and foraging party composition. Results Fruit abundance increased with proximity to anthropogenic landmarks, and chimpanzees exhibited higher frequencies of antipredator behaviors as they approached these risky areas. However, predation risk did not deter adult males from visiting these fruiting trees; instead, risky foraging bouts were associated with higher food intakes and longer feeding times. Additionally, higher feeding rates were observed in open-canopy habitats, and this behavior may have minimized their risk of heat stress. Conclusions Adaptations that minimize predation risk are widespread in mammalian prey species, but these traits are poorly understood in chimpanzees. Great apes encounter few nonhuman predators capable of successfully capturing and killing them; thus, such events are rarely observed. Although people rarely hunt chimpanzees in Senegal, we found that adult males perceived humans as predators and adjusted their behavior while foraging in risky habitats. From an applied perspective, risk-taking behavior is important for understanding and mitigating the problem of crop-feeding in locations where chimpanzees and humans live in sympatry.

Whether nonhuman primates show population-level handedness is a topic of much scientific debate. A previous study of handedness for termite fishing reported population-level left handedness in the chimpanzees from Gombe National Park, Tanzania. In the current study, we examined whether similar hand preferences were evident in a savanna-dwelling chimpanzee population with regards to termite fishing. Hand preference data were collected for 27 chimpanzees from February 2007 through July 2008 and November 2011 through January 2012 in southeastern Senegal. Overall, the Fongoli chimpanzees demonstrate a trend toward population-level handedness, though the results did not reach conventional levels of statistical significance likely due to the limited sample size. Fongoli chimpanzees showed the same pattern of left hand preference as reported at Gombe and the two populations did not differ significantly. When the data were combined across all studies, wild chimpanzees showed a population-level left hand preference for termite fishing.

Transferring food is considered a defining characteristic of humans, as such behavior is relatively uncommon in other animal species save for kin-based transfer. Chimpanzees (Pan troglodytes) are one exception, as they commonly transfer meat among nonrelatives but rarely transfer other resources. New observations at Fongoli, Senegal, show habitual transfer of wild-plant foods and other non-meat resources among community members beyond transfers from mother to offspring. We explore various explanations for these behaviors with a focus on age- and sex-class patterns in transfer events. In a total of 27 of 41 cases, male chimpanzees at Fongoli transferred wild-plant foods or tools to females. Most other cases involved transfer among males or males taking food from females. In light of male-female transfer patterns at Fongoli, we examine four hypotheses that have been applied to food transfer in apes: (1) testing for male-coercive tendency (van Noordwijk and van Schaik, Behav Ecol Sociobiol 63:883-890, 2009), (2) costly signaling (Hockings et al. PLoS ONE 2:e886, 2007), (3) food-for-sex (Gomes and Boesch, PLoS ONE 4:5116, 2009), and (4) sharing-under-pressure (Gilby, Anim Behav 71:953-963, 2006). We also consider hypotheses posed to explain transfer among callitrichids, where such behavior is more common (Ruiz-Miranda et al. Am J Primatol 48:305-320, 1999). Finally, we examine variables such as patch and food size and food transport. We discuss our findings relative to general patterns of non-meat transfer in Pan and examine them in the context of chimpanzee sociality in particular. We then contrast chimpanzee species and subspecies in terms of non-meat food and tool transfer and address the possibility that a savanna environment contributes to the unusual pattern observed at Fongoli.

Ecology and Evolutionary Biology Interdepartmental Program, Iowa State University, Ames, IA 50011KEY WORDS chimpanzee; insectivory; termite fishing; ecology; evolutionABSTRACT Little is known about the behavior ofchimpanzees living in savanna-woodlands, although theyare of particular interest to anthropologists for theinsight they can provide regarding the ecological pres-sures affecting early hominins living in similar habitats.Fongoli, Senegal, is the first site where savanna chim-panzees have been habituated for observational datacollection and is the hottest and driest site where suchobservation of chimpanzees occurs today. Previously,indirect evidence suggested these chimpanzees consumedtermites throughout the year, an unusual occurrence forwestern and eastern chimpanzees. Although meat eatingby chimpanzees continues to receive much attention,their use of invertebrate prey has received less emphasisin scenarios of hominin evolution. Here, we furtherexamine the invertebrate diet of Fongoli chimpanzeesusing direct observational methods and accounting forpotential environmental influences. Termite feedingpositively correlated with high temperatures. Fongolichimpanzees spend more time obtaining termites thanany other chimpanzee population studied, and thisextensive insectivory contributes to the list of distinctivebehaviors they display relative to chimpanzees livingin more forested habitats. We suggest that savannachimpanzees at Fongoli differ significantly from chim-panzees elsewhere as a result of the selective pressurescharacterizing their harsh environment, and this con-trast provides an example of a viable referential modelfor better understanding human evolution. Specifically,our results support the hypotheses that invertebrateprey may have figured more prominently into the diet ofearly hominins in similar habitats, especially given thatinvertebrates are an important source of protein andother essential nutrients in a highly seasonal environ-ment. Am J Phys Anthropol 000:000–000, 2010.

In a unique case where a chimpanzee infant captured by human poachers was returned by researchers to her natal group, an adolescent male helped the injured mother carry her infant on each of 2 days following the return. I explore various hypotheses to explain this behavior and suggest that the apparent recognition of both the infant’s and mother’s needs by the male supports the consideration of empathy in this case. As data accumulate, questions regarding empathy in non-humans should focus on more intricate levels as suggested by DeWaal (Annu Rev Psych 59: 279–300, 2008), rather than adhering to the assertion that empathy is uniquely human.

Chimpanzees (Pan troglodytes) make nests for resting and sleeping, which is unusual for anthropoid primates but common to all great apes. Arboreal nesting has been linked to predation pressure, but few studies have tested the adaptive nature of this behavior. We collected data at two chimpanzee study sites in southeastern Senegal that differed in predator presence to test the hypothesis that elevated sleeping platforms are adaptations for predator defense. At Assirik in the Parc National du Niokolo-Koba, chimpanzees face four species of large carnivore, whereas at Fongoli, outside national park boundaries, humans have exterminated almost all natural predators. We quantified the availability of vegetation at the two sites to test the alternative hypothesis that differences in nesting reflect differences in habitat structure. We also examined possible sex differences in nesting behavior, community demographic differences, seasonality and nest age differences as variables also potentially affecting nest characteristics and nesting behavior between the two sites. Chimpanzees at Fongoli nested at lower heights and farther apart than did chimpanzees at Assirik and sometimes made nests on the ground. The absence of predators outside of the national park may account for the differences in nest characteristics at the two sites, given the similarities in habitat structure between Fongoli and Assirik. However, Fongoli chimpanzees regularly build arboreal nests for sleeping, even under minimal predation pressure, and this requires explanation. Am. J. Primatol. 70:393–401, 2008. © 2007 Wiley-Liss, Inc.

Le Sénégal est situé sur la limite nord-ouest de l’aire de répartition du Chimpanzé. On y trouve la sous-espèce de l’Afrique de l’Ouest, Pan troglodytes verus, qui est inscrite dans la catégorie des espèces en danger d’extinction sur la liste rouge de l’Union Mondiale pour la Nature. Elle est la plus menacée des trois sous-espèces de chimpanzés. Dans cette région, il vit dans des conditions climatiques de savane très dures en plus de la forte pression anthropique exercée sur l’habitat. Le dernier recensement effectué dans cette région estime une population d’environ 400 à 500 individus. Plusieurs études ont été effectuées sur le chimpanzé dans cette région, mais peu ont porté sur son comportement alimentaire. Sur le site de Fongoli (12°41N, 12°30W), nous avons effectué un suivi de l’écologie nutritionnelle de ce primate non humain. Pour cela, nous avons d’abord procédé par observation directe afin d’établir une liste des espèces consommées et la manière dont elles sont consommées. Ensuite, ces aliments sont échantillonnés pour des analyses au laboratoire. Les analyses nous ont permis de mettre en évidence et de quantifier les sucres, la matière grasse, les fibres solubles dans les détergents (neutres, acides et lignines) et la présence ou non de tannin. Nos résultats ont montré que ces chimpanzés ont un régime principalement frugivore, mais consomment également des feuilles, des fleurs, des graines. Ils sont aussi insectivores et consomment des protéines d’origine animale. L’analyse nutritive des aliments montre un régime riche en sucre provenant essentiellement des fruits, une quantité importante de fibres et de matière grasse. Cependant, l’accès à cette nourriture devient de plus en plus difficile à cause du facteur anthropique. Nous pensons que la maîtrise du comportement alimentaire du chimpanzé dans cette région est d’une importance capitale pour une meilleure conservation de cette ressource.Je tiens à exprimer toute ma reconnaissance à mes encadreurs, les Prs Cheikh Tidiane Ba et Jill D. Pruetz, les Drs Papa Ibnou Ndiaye et Stacy Marie Lindshield. Je les remercie de m’avoir encadré, orienté, aidé et conseillé. J’adresse mes sincères remerciements à tous les professeurs, intervenants, et à toutes les personnes qui par leurs paroles, leurs écrits, leurs conseils et leurs critiques ont guidé mes réflexions et ont accepté de me rencontrer et de répondre à mes questions durant mes recherches. Je remercie vivement la société Mako Exploration Company pour l’ouverture d’esprit de son Administrateur Général Adjoint M. Fally Diop et du Manager du Bureau Environnement et Social Paul Cannon ainsi que pour leur soutien moral et financier. J’ai aimablement été accueilli par cette société. J’ai aussi pu bénéficier de l’aide précieuse du Capitaine Cheikh Sylla responsable du bureau Environnement. Je souhaite enfin remercier Dondo Kante, Michel Sadiakho et tout le village de Fongoli qui ont facilité mon intégration et mes travaux de terrain.

La limite nord de l’aire de répartition du chimpanzé se trouve dans la partie sud-Est du Sénégal, précisément dans la région de Kédougou caractérisée par des conditions climatiques inhabituelles pour ce primate. Le dernier recensement du Chimpanzé dans ce pays, effectué entre 1998 et 1999 avait permis d’estimer l’effectif de la population à environ 500 individus dont 80 % évoluent en dehors des aires protégées. Actuellement, la dégradation des habitats du chimpanzé au Sénégal ne cesse de progresser en raison d’effets anthropiques et de changements climatiques. D’où le besoin de réactualiser les données concernant ce primate au niveau national. C’est ainsi qu’un suivi hors parc basé particulièrement sur la collecte d’indices de présence du chimpanzé par la méthode de reconnaissance a été proposé par Jill Pruetz au courant de l’année 2014. C’est dans ce contexte que nous avons effectué des prospections dans plusieurs sites dont Bagnomba pour répertorier les principaux habitats des chimpanzés. A Bagnomba (786221 W, 1407110 N), situé sur la partie sud-Est du Parc National du Niokolo Koba en dehors des limites de l’aire protégée, nous avons observé un groupe de chimpanzés constitué de 8 individus, dont 5 adultes et 3 juvéniles, et recensé plus de 400 nids de chimpanzé. Les particularités écologiques des habitats du chimpanzé dans cette zone (relief, végétation, disponibilité d’aliments, entre autres) associées à leur caractère sacré par les populations locales constituent des atouts qui favoriseraient la conservation des chimpanzés dans cette zone si des mesures idoines de protection étaient prises. Actuellement, un suivi rapproché de la population de chimpanzé à Bagnomba dont le principal objectif est de déterminer la structure des groupes, le comportement et les couloirs de migration entre les habitats. Nous avons par ailleurs répertorié des facteurs anthropiques tels que le déboisement et l’orpaillage qui constituent des menaces réelles pour la conservation du chimpanzé dans cette localité. Pour cette raison, nous pensons que l’acquisition de données scientifiques fiables aidera les décideurs à prendre les dispositions nécessaires pour garantir la survie de ce primate non humain dans cette région.Nous tenons à remercier vivement les personnes et institutions sans qui ce travail ne pourrait aboutir. Il s’agit entre autres de USFWS, African Wildlife Foundation, la direction des Eaux et Forêts et Chasse et de la Conservation des Sols, la Direction des Parcs Nationaux, les populations locales, les agents du projet Fongoli Savana Chimpanzees et l’Institut Jane Goodall Espagne basé au Sénégal.

The direct effects of competition between humans and nonhuman animals over non-timber forest products (NTFPs) are not well understood. In some cases, a type of sustainability appears. In other cases, there is overharvesting by humans, which can negatively affect biodiversity directly and human economics indirectly. The purpose of this chapter is to highlight the economic, cultural, ecologic, and conservation complexities entwined in the human collection of NTFPs. To do this, we will examine competition between western chimpanzees (Pan troglodytes verus) and humans for the wild fruit species Saba senegalensis at the Fongoli research site in southeastern Senegal. Interviews conducted with local people focused on the type, use, and economic importance of wild growing plants. For humans living there, the Saba fruit represents a much-needed source of sustenance and income at a time when crop stores are depleted and new crops have yet to produce. Ecologic studies were also conducted. For chimpanzees, Saba is a vital food source at a time when most other foods are scarce. If the rate of Saba removal from the area is not controlled, however, chimpanzees and humans may both be forced to face a future without this important fruit.

Much attention has been paid to how humans both adapt and acclimate to heat stress, primarily due to the relevance of these issues to hominid evolution in open Plio-Pleistocene environments. However, little is known about the responses of human's closest living relative, the chimpanzee (Pan troglodytes), to similar environmental stressors. In southeastern Senegal, one of the hottest and driest habitats that chimpanzees (P. t. verus) live in today, apes rely on behavioral mechanisms of dealing with ther- mal stress. Chimpanzees' use of caves was based primarily on indirect evidence (feeding traces, feces, and hairs) gathered from one cave from January to December 2004, but data from observational records collected from May 2001 through March 2006 supplement these data. The hypothesis that chimpanzees' use of caves is a response to heat was tested by collecting data on temperatures within the largest cave and in different habitats used by chim- panzees, such as gallery forest and woodland. Results indicate that chimpanzees primarily use caves as shelters during the hottest times of year and that caves are consis- tently and significantly cooler than open habitats. Insight into the way that chimpanzees in Senegal cope with ex- treme temperatures may help us to better understand the behavior of early hominids in such an environment.

SummaryAlthough 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.

Nests built by wild chimpanzees (Pan troglodytes verus) were studied at the Fongoli research site in southeastern Senegal from January 2004–May 2004 to investigate the role of comfort in nest building behavior by relating measures of nest comfort and building effort. Nest comfort across zones of the nest surface were compared with construction effort for 25 nests. Several variables of nest comfort were assessed: (1) physical discomfort, (2) visible discomfort, and (3) softness. Physical discomfort was used as a representative measure of nest discomfort. Building effort was measured by (1) construction force, (2) complexity, and (3) added material. Spearman rank correlations compared Effort and Comfort measures for both whole nests and central versus edge zones. The results show that construction force and complexity do not influence comfort of the nest as a whole. Greater Construction force correlates with more nest edge discomfort, yet the central area shows no difference. More complex nests do result in a more comfortable central area in the nest. Nests built with greater force may result in more discomfort, whereas complexity may allow chimpanzees to maintain comfort in a central area for sleep. Chimpanzees may place additional leaves or twigs over hard branches, protruding from the nest surface after construction, to increase comfort of the central nest area. Functions of chimpanzee nest building are likely to be several, but these results suggest comfort is a factor in nest building behavior. Am. J. Primatol. 69:930–939, 2007. © 2007 Wiley-Liss, Inc.

For anthropologists, meat eating by primates like chimpanzees ( Pan troglodytes ) warrants examination given the emphasis on hunting in human evolutionary history. As referential models, apes provide insight into the evolution of hominin hunting, given their phylogenetic relatedness and challenges reconstructing extinct hominin behaviour from palaeoanthropological evidence. Among chimpanzees, adult males are usually the main hunters, capturing vertebrate prey by hand. Savannah chimpanzees ( P. t. verus ) at Fongoli, Sénégal are the only known non-human population that systematically hunts vertebrate prey with tools, making them an important source for hypotheses of early hominin behaviour based on analogy. Here, we test the hypothesis that sex and age patterns in tool-assisted hunting ( n =308 cases) at Fongoli occur and differ from chimpanzees elsewhere, and we compare tool-assisted hunting to the overall hunting pattern. Males accounted for 70% of all captures but hunted with tools less than expected based on their representation on hunting days. Females accounted for most tool-assisted hunting. We propose that social tolerance at Fongoli, along with the tool-assisted hunting method, permits individuals other than adult males to capture and retain control of prey, which is uncommon for chimpanzees. We assert that tool-assisted hunting could have similarly been important for early hominins.

Use of flexible probes to fish for macrotermitine termites and manufactured wands to dip for doriline ants is reported for a new site of chimpanzee field study. The flexible probes of vegetation used in termite fishing and ant dipping by the chimpanzees of Fongoli, in southeastern Senegal, are similar to those used at Assirik (Senegal) and Gombe (Tanzania). Based on the principle that form reflects function, we predict that ant dipping when seen will prove to be the two-handed technique.