Jordi Galbany

Percussive technology in wild chimpanzees ( Pan troglodytes ) shows significant behavioral variation across Africa. An example is baobab ( Adansonia digitata ) fruit pounding, which is only known to occur in the Bandafassi Arrondissement in the Kedougou region (Senegal) and in the Bafing area (Mali). The extent to which this proto-tool use behavior varies between populations is poorly understood. Here, we present a preliminary report of the baobab-pounding behavior of savanna chimpanzees from Dindefelo, Senegal. During the peak baobab fruiting season from November 2021 to January 2022, we obtained evidence of baobab pounding, both primate archaeological evidence (fruit remnants smeared on anvils and cracked, empty baobab shells) and camera trap recordings. We also studied chimpanzee baobab consumption using macroscopical fecal analysis. In addition, in the peak baobab fruiting season from 2019 to 2020, we opportunistically obtained hand-held camera videos of baobab pounding. Dindefelo chimpanzees opened baobab using two pounding and one non-percussive techniques. We recorded all age and sex classes performing baobab pounding, although only adolescents and adults succeeded in opening the fruit. Baobab pounding occurred on the ground (against rocks and baobab roots) and on the trees (against baobab horizontal branches). The apes held the fruit by the stem or the pericarp while cracking it against an anvil. In addition, the fecal analysis data suggest that baobab seed reingestion is common at Dindefelo. These findings expand our knowledge on the diversity of chimpanzee baobab-pounding behavior.

Body size is a fundamental feature of an organism’s biology, and studies of body size growth can yield insights into factors that shape evolutionary change within and between species. However, apart from humans, variability in body size growth within primate species across environments remains poorly known. We used non-invasive parallel-laser photogrammetry to compare body size growth of two ecologically distinct populations of mountain gorillas, from Bwindi Impenetrable National Park, Uganda and Volcanoes National Park, Rwanda, in the Virunga Massif (n = 197, aged 0.3–42.7 years). Bwindi females attained a smaller adult size than Virunga females, despite continuing their growth over a longer duration. Population differences in male adult size were minimal, although Bwindi males continued growth in back breadth over a longer duration. For both sexes, Bwindi gorillas were smaller than Virunga gorillas as young infants, and these size differences decreased over ontogeny. This study provides the first evidence of within-species variation in body size growth among living wild apes between populations that exhibit ecological and life-history differences. This variation could be due to genetic variation, phenotypic plasticity, reproductive trade-offs and/or ecological constraints and have implications for understanding body size growth variation in humans and other species.

Developing comprehensive mammal inventories in protected areas with human presence is essential for effective biodiversity conservation yet remains challenging, particularly for elusive species. Camera trapping has emerged as a valuable tool for documenting mammal diversity, complementary to or as an alternative to traditional direct observation methods. We studied the Dindefelo Community Nature Reserve (Senegal), encompassing a mosaic of vegetation types with a climate characterised by marked seasonality. The local human population depends on its natural resources for subsistence, and livestock roam freely throughout the reserve. Using camera traps, we conducted a 2‐year monitoring program across 29 sampling locations, accumulating 3072 trapping days (approximately 60,000 h of observation). We evaluated how vegetation types, seasonality and anthropogenic factors influenced mammal species richness and vegetation type use. We confirmed the presence of 28 medium‐ and large‐sized mammal species. Mammal species richness varied subtly with vegetation types and seasons but no pronounced differences emerged. Human presence within the reserve had limited negative impacts on mammal species richness. Interestingly, livestock presence, exhibited a positive association with wild mammal diversity, suggesting shared resource use or similar environmental preferences. These results highlight complex interactions between wildlife and human activities. They also emphasise the importance of ongoing monitoring to detect additional rare or elusive species, improving conservation strategies in protected savannahs of western Africa where wildlife and human communities coexist.

Chimpanzees use spatiotemporal cognition for fruit foraging by remembering tree locations and fruiting seasons. However, the spatiotemporal cognition behind exploiting other foods has rarely been studied. Here, we investigate whether chimpanzees use memory to exploit concealed, underground army ant nests. We analyse 679 chimpanzee visits to four nests recorded during five years (2018–2022) using camera traps in a savanna habitat. We explore if chimpanzees intentionally revisit nests, study how they detect ants, and assess ant availability and chimpanzee ant consumption. Nests are concealed, scarce, and intermittently reoccupied, yet chimpanzees eat ants frequently. We find that out of 34 identified chimpanzees who visit the nests, 23 revisit at least one. Chimpanzees visit nest sites significantly more often than similar sites without nests. Individuals revisit significantly sooner and inspect significantly longer nests where they have more recently encountered ants. The apes use sight, smell, taste, touch, and probing tools, to detect ants inside nests. We provide the first evidence suggesting that chimpanzees use spatial and episodic-like memory to exploit concealed social insects throughout multiple years. Our results expand our understanding of the cognitive strategies behind chimpanzee insectivory, suggesting it may have played an important role in the evolution of primate spatiotemporal cognition.

The current distribution of Campbell’s monkeys Cercopithecus campbelli extends from southwestern Gambia to the western Ivory Coast. In Senegal, it has only been confirmed in the western part of the country. Here, we report for the first time its presence in southeastern Senegal. We obtained camera trap footage of a Campbell’s monkey individual in the Dindefelo Community Nature Reserve located in Kedougou region, 174 km away from its known distribution range. In the footage, a single Campbell’s monkey appears alongside a group of at least nine green monkeys Chlorocebus sabaeus. We discuss different hypotheses that could explain the presence of the Campbell’s monkey in Dindefelo, and conclude that this individual may be a single migrant.

Chimpanzees (Pan troglodytes) are categorized as Endangered by the International Union for Conservation of Nature, and habitat loss due to conversion of land for agriculture is one of the major threats to wild populations of this species. This challenging scenario can lead to negative human-chimpanzee interactions, including crop feeding. Chimpanzees consume crops across their geographical range, although little is known about this behavior in savanna habitats. Here we provide new evidence of crop feeding by savanna chimpanzees. We conducted our observations at Dindefelo, a community nature reserve in southeastern Senegal. The chimpanzees were observed to feed on mango (Mangifera indica) and also on baobab (Adansonia digitata), a wild species considered a crop by local people when found in and around villages. Although local people use the fruits of these species for food and income, they tolerated crop-feeding events until recently. In 2023, a case of harassment of a crop-feeding chimpanzee in a mango orchard was witnessed, and four days later a chimpanzee corpse was found at the same place. We conclude that habitat conversion into agricultural fields, uncontrolled bush fires and extraction of wild fruits are the important factors influencing crop-feeding events at Dindefelo. Our findings highlight the need to better understand human-chimpanzee interactions in the anthropogenic landscape of Dindefelo to help mitigate negative attitudes and behaviors towards chimpanzees.

The African brush‐tailed porcupine (Atherurus africanus) is a rodent common from West to East Africa. The last IUCN assessment stated that its presence is uncertain in Senegal. Here, we report the presence of the African brush‐tailed porcupine in the Dindefelo Community Nature Reserve (Dindefelo), in southeastern Senegal, and across the border in northern Guinea. From 2017 to 2022, we obtained 58 camera trap videos from seven different locations in Dindefelo and 86 camera trap videos from Sahoro cave, in Guinea, showing Atherurus africanus. It is likely that this species has always been present in both areas, but it may have gone undetected because it is nocturnal and may be less abundant.

Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from threeGorillasubspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes.

Acoustic signals that reliably indicate body size, which usually determines competitive ability, are of particular interest for understanding how animals assess rivals and choose mates. Whereas body size tends to be negatively associated with formant dispersion in animal vocalizations, non-vocal signals have received little attention. Among the most emblematic sounds in the animal kingdom is the chest beat of gorillas, a non-vocal signal that is thought to be important in intra and inter-sexual competition, yet it is unclear whether it reliably indicates body size. We examined the relationship among body size (back breadth), peak frequency, and three temporal characteristics of the chest beat: duration, number of beats and beat rate from sound recordings of wild adult male mountain gorillas. Using linear mixed models, we found that larger males had significantly lower peak frequencies than smaller ones, but we found no consistent relationship between body size and the temporal characteristics measured. Taken together with earlier findings of positive correlations among male body size, dominance rank and reproductive success, we conclude that the gorilla chest beat is an honest signal of competitive ability. These results emphasize the potential of non-vocal signals to convey important information in mammal communication.