Wild chimpanzees on the edge: nocturnal activities in croplands

Changes in movement patterns in relation to sun conditions and spatial scales in wild western gorillas

For most primates living in tropical forests, food resources occur in patchworks of different habitats that vary seasonally in quality and quantity. Efficient navigation (i.e., spatial memory-based orientation) towards profitable food patches should enhance their foraging success. The mechanisms underpinning primate navigating ability remain nonetheless mostly unknown. Using GPS long-term tracking (596 days) of one group of wild western lowland gorillas (Gorilla gorilla gorilla), we investigated their ability to navigate at long distances, and tested for how the sun was used to navigate at any scale by improving landmark visibility and/or by acting as a compass. Long episodic movements ending at a distant swamp, a unique place in the home range where gorillas could find mineral-rich aquatic plants, were straighter and faster than their everyday foraging movements relying on spatial memory. This suggests intentional targeting of the swamp based on long-distance navigation skills, which can thus be efficient over a couple of kilometres. Interestingly, for both long-distance movements towards the swamp and everyday foraging movements, gorillas moved straighter under sunlight conditions even under a dense vegetation cover. By contrast, movement straightness was not markedly different when the sun elevation was low (the sun azimuth then being potentially usable as a compass) or high (so providing no directional information) and the sky was clear or overcast. This suggests that gorillas navigate their home range by relying on visual place recognition but do not use the sun azimuth as a compass. Like humans, who rely heavily on vision to navigate, gorillas should benefit from better lighting to help them identify landmarks as they move through shady forests. This study uncovers a neglected aspect of primate navigation. Spatial memory and vision might have played an important role in the evolutionary success of diurnal primate lineages.

High urinary oxidative DNA damage in wild chimpanzees ranging in proximity of agricultural fields in Sebitoli area, Uganda

Agriculture expansion is a major cause of habitat loss and exposure to phytochemical pollution for non-human primates. In addition to endocrine disruption, exposure to pesticides may have other sublethal physiological consequences for animals, such as generation of oxidative damage to macromolecules. In this study, we analyzed the pesticides contained in the river water across the home range of wild chimpanzees (Pan troglodytes) in Sebitoli area located on the Northern part of Kibale National Park (Uganda). We tested whether levels of three urinary markers of oxidative damage vary among individuals in relation to their ranging patterns, as a proxy for pesticide exposure intensity. To better characterize the foraging habitat use, the trophic level, and the energetic status of study individuals, we also quantified urinary levels of carbon and nitrogen stable isotope signatures and of C-peptide. Among the 511 pesticides screened, 18 compounds including herbicides, insecticides, and fungicides were found in the water sampled in the Western part of the home range of chimpanzees. In this area, chimpanzees used to feed on maize crops. By contrast, in the Eastern part where crop feeding was never observed, we found only seven pesticides. According to their ranging patterns and thus crop feeding frequency, the 139 urine samples collected from 43 Sebitoli chimpanzees were categorized as belonging to low, medium, and high exposure level. Chimpanzees from the high exposure zone had higher oxidative DNA damage (8-OHdG) than chimpanzees from both the low and medium exposure groups, who had similar levels of oxidative DNA damage. In addition, individuals with higher C-peptide tended to have significantly higher oxidative DNA damage and lipid peroxides. The three exposure groups had similar levels of urinary 8-isoprostanes and of urinary lipid peroxides. These results were robust for any potential confounding effect of other variables because neither age category nor sex or isotope levels were significantly associated with markers of oxidative damage. Our study points to genotoxic effects as one potential sublethal consequence of ranging in proximity of agricultural fields owing to exposure to pesticides or other unidentified sources of stress. Given our phylogenetic proximity, this information is relevant for the conservation of this species which is endangered and also sentinel for human health.

Lunar Cycle, Climate, and Onset of Parturition in Domestic Dromedary Camels: Implications of Species-Specific Metabolic Economy and Social Ecology

Given energy costs for gestating and caring for male offspring are higher than those of female newborns, external environmental conditions might be regarded as likely to affect the timing of delivery processes differentially depending on the sex of the newborn calf to be delivered. The aim of the present paper is to evaluate the association between environmental stressors such as the moon phase and weather-related factors and the onset of labor in female dromedaries. A binary logistic regression model was developed to find the most parsimonious set of variables that are most effective in predicting the probability for a gravid female dromedary to give birth to a male or a female calf, assuming that higher gestational costs and longer labor times are ascribed to the production of a male offspring. Although the differences in the quantitative distribution of spontaneous onset of labor across lunar phases and the mean climate per onset event along the whole study period were deemed nonsignificant (p > 0.05), a non-negligible prediction effect of a new moon, mean wind speed and maximum wind gust was present. At slightly brighter nights and lower mean wind speeds, a calf is more likely to be male. This microevolutionary response to the external environment may have been driven by physiological and behavioral adaptation of metabolic economy and social ecology to give birth to cooperative groups with the best possible reduction of thermoregulatory demands. Model performance indexes then highlighted the heterothermic character of camels to greatly minimize the impact of the external environment. The overall results will also enrich the general knowledge of the interplay between homeostasis and arid and semi-arid environments.

Anti-predator strategies of adult male Central Himalayan Langurs (Semnopithecus schistaceus) in response to domestic dogs in a human-dominated landscape

The evolution of predator-prey relationships is an important topic in primatology. Many aspects of primate society have been explained as a response to predation pressure. While predation has been discussed in broad theoretical terms, few systematically collected data exist on the subject. Furthermore, little information exists regarding the inter-male variation in responses to predators. To address this data gap, predatory dog-primate interactions were studied in a 78-member group of habituated, individually recognized Central Himalayan Langurs (CHL) (Semnopithecus schistaceus) living in a high-altitude subsistence agricultural landscape of northern India. We recorded 312 langur-dog interactions over 2 years. These predation events resulted in 15 serious attacks on adult females, infants, juveniles and sub-adults, in eight of which the prey was killed and consumed on the spot. In response to dog predation, adult males performed three types of anti-predator response behaviors: direct fighting with a predator, emitting alarm calls, fleeing and/or freezing. Differences were noted in each male's response to village dogs. The results showed that the likelihood of CHL adult males engaging in more costly counterattacks or attention getting alarm calls were better predicted by the level of investment in the group (genetic relatedness, duration of residency, social relationships), but not rank and mating rate. Long-duration resident adult males performed high and/or intermediate cost behaviors to protect vulnerable members of the group; their potential offspring, maternal siblings or cousins, and adult female social partners. Short-term residents or recent immigrant males exhibited two less energetically costly, more self-preserving behaviors, depending on their rank: (1) high-ranking short-tenure duration males, with high mating frequencies, performed flee and freeze responses; (2) low-ranking, low-mating-frequency males performed more alarm calls. Counterattacks and alarm calls were performed by adult males with relatively more experience with village dogs and were directed towards dogs with predatory histories significantly more often than dogs with non-predatory histories. Natural selection and kin selection have both contributed to the evolution of CHL anti-predator tactics.

Listening to Their Nights: Sleep Disruptions in Captive Housed Chimpanzees Affect Their Daytime Behavior

Chimpanzee's nocturnal sleep is a dynamic and complex process, still not fully understood. As in humans, not getting enough quality sleep due to frequent or lasting disruptions may affect their physical and mental health, hence wellbeing, which may be reflected in their daytime behavior. This study aims to understand the impact of abiotic factors, such as temperature and humidity on the nocturnal activity as well as the impact of nocturnal awakening events on daytime behavior in sanctuary-housed chimpanzees. We monitored noisy nocturnal activity through audio recordings for one year, documenting the number and duration of sound events produced by chimpanzees to indicate sleep fragmentation and disruption intensity, respectively. Our results indicate that indoor temperature and humidity indeed influence the chimpanzee's nocturnal activity. Furthermore, sleep fragmentation and intensity of nocturnal events significantly influenced the following day's behavior. After nights marked by frequent and/or intense sleep disruptions, higher levels of inactivity, and abnormal and self-directed behaviors were observed, and chimpanzees spent more time on affiliative interactions and in social proximity. These findings highlight the importance of controlling factors influencing nocturnal sleep quality. Furthermore, we demonstrated that economic audio recordings used to monitor nocturnal activity, provide insights into the chimpanzee's behavior and wellbeing.

Interindividual differences in crop foraging behavior of chimpanzees (Pan troglodytes schweinfurthii) at a forest–agriculture interface

The expansion of agriculture in equatorial areas is fragmenting and reducing wildlife habitats. For primates, it also increases opportunities to consume crops as high-energy resources, exacerbates conflicts with farmers, and increases exposure to diseases and agrochemicals at the edge of protected areas. In species with sex differences in ranging behavior, individual exposure to such opportunities and threats may vary by sex. Chimpanzees show a great feeding flexibility and are territorial species with varied ranging patterns according to site, sex, or individuals. Within a community whose territory is crossed by a high-traffic road and partially bordered by maize gardens, we tested hypotheses of interindividual differences in access to crops based on age, sex, ranging behavior, and kinship. By analyzing the presence of Sebitoli chimpanzees (Pan troglodytes schweinfurthii, Kibale National Park, Uganda) on video clips from 16 camera traps, we estimated the individual dispersion range across the community’s territory and the crop foraging frequency along maize gardens over 16 months. While all age and sex classes were represented at the forest–garden interface, large intrasex differences were observed: some mature males and females were not observed to participate. The crop foraging frequency of adult females in maize gardens was significantly correlated with the location of their ranging areas. Related individuals revealed similar range patterns within the forest territory without sharing crop foraging habits. However, social learning and energy and risks–benefits trade-offs as potential drivers of crop consumption are not excluded.

Can urbanization accentuate hand use in the foraging activities of primates?

OBJECTIVES

How a species uses its anatomical manipulators is determined by its anatomy, physiology, and ecology. While ecology explains interspecific variation in gripping, grasping, and manipulating objects, its role in intraspecific variation in mouth- and hand-use by animals is less explored. Primates are distinguished by their prehensile capabilities and manual dexterity. In context to the adaptive pressures of urbanization on primates, we examined if mouth and hand use differed across the forest-urban gradient in food retrieval and processing under experimental and naturalistic conditions in cercopithecids, a family comprising several urbanizing primates.

MATERIALS AND METHODS

We recorded the acquisition and processing of peanuts under experimental conditions in three groups of bonnet macaques (BM, Macaca radiata) differing in their dietary dependence on packaged food items along a rural-urban gradient. To affirm the pattern obtained in the experiment, we coded food acquisition of three cercopithecid species in similar habitats from video sources.

RESULTS

Urban macaques had a disproportionately higher hand use to acquire and process peanuts while rural macaques had higher mouth use. Based on analyses of videos, urban populations of BM, Japanese macaque (M. fuscata) and vervet monkey (Chlorocebus pygerythrus) showed a bias toward hand use during food acquisition.

DISCUSSION

The adaptive pressures of urbanization, like the manual constraints of extracting packaged foods and perhaps, the need for visual-haptic exploration of novel objects seem to accentuate hand use in synanthropic groups of primates. Additional research should ascertain similar patterns in other primates and determine specific aspects of urbanization that modulate the observed trend.

Between forest and croplands: Nocturnal behavior in wild chimpanzees of Sebitoli, Kibale National Park, Uganda

Some animal species have been presumed to be purely diurnal. Yet, they show flexibility in their activity rhythm, and can occasionally be active at night. Recently, it has been suggested that chimpanzees may rarely engage in nocturnal activities in savannah forests, in contrast to the frequent nocturnal feeding of crops observed at Sebitoli, Kibale National Park, Uganda. Here we thus aimed to explore the factors that might trigger such intense nocturnal activity (e.g. harsher weather conditions during daytime, low wild food availability or higher diurnal foraging risk) in this area. We used camera-traps set over 18 km² operating for 15 months. We report activities and group composition from records obtained either within the forest or at the forest interface with maize fields, the unique crop consumed. Maize is an attractive and accessible food source, although actively guarded by farmers, particularly during daytime. Out of the 19 156 clips collected, 1808 recorded chimpanzees. Of these, night recordings accounted for 3.3% of forest location clips, compared to 41.8% in the maize fields. Most nocturnal clips were obtained after hot days, and most often during maize season for field clips. At night within the forest, chimpanzees were travelling around twilight hours, while when at the border of the fields they were foraging on crops mostly after twilight and in smaller parties. These results suggest that chimpanzees change their activity rhythm to access cultivated resources when human presence and surveillance is lower. This survey provides evidence of behavioral plasticity in chimpanzees in response to neighboring human farming activities, and emphasizes the urgent need to work with local communities to mitigate human-wildlife conflict related to crop-feeding.

Camera traps and guard observations as an alternative to researcher observation for studying anthropogenic foraging

Foraging by wildlife on anthropogenic foods can have negative impacts on both humans and wildlife. Addressing this issue requires reliable data on the patterns of anthropogenic foraging by wild animals, but while direct observation by researchers can be highly accurate, this method is also costly and labor‐intensive, making it impractical in the long‐term or over large spatial areas. Camera traps and observations by guards employed to deter animals from fields could be efficient alternative methods of data collection for understanding patterns of foraging by wildlife in crop fields. Here, we investigated how data on crop‐foraging by chacma baboons and vervet monkeys collected by camera traps and crop guards predicted data collected by researchers, on a commercial farm in South Africa. We found that data from camera traps and field guard observations predicted crop loss and the frequency of crop‐foraging events from researcher observations for crop‐foraging by baboons and to a lesser extent for vervets. The effectiveness of cameras at capturing crop‐foraging events was dependent on their position on the field edge. We believe that these alternatives to direct observation by researchers represent an efficient and low‐cost method for long‐term and large‐scale monitoring of foraging by wildlife on crops.

All-You-Can-Eat: Influence of Proximity to Maize Gardens on the Wild Diet and the Forest Activities of the Sebitoli Chimpanzee Community in Kibale National Park

Simple Summary

Understanding the resilience of primate populations to the threat of agricultural expansion is critical for effective conservation. Based on individual monitoring from morning to evening of wild chimpanzees in and around a protected area, we showed that the availability of maize at the forest edge had little effect on their activity budget by less resting and no impact on their wild diet and energy expenditure. In this area, large, caloric wild fruits are available year-round, and we observed no behavioral or dietary changes regarding wild resource availability either. Thus, the chimpanzees consume maize opportunistically as a bonus treat in their diet, and the presence of this nutritious resource does not seem to affect their role in seed dispersal and forest regeneration.

Abstract

Frugivorous primates have developed several strategies to deal with wild fruit scarcity, such as modifying their activity budget or enlarging their diet. Agricultural expansion threatens primate habitats and populations (e.g., disease transmission, agrochemical exposure), but it also increases crop feeding opportunities. We aimed at understanding whether maize presence close to the natural habitat of chimpanzees, a threatened species, would lead to significant behavioral modifications. We monitored 20 chimpanzees over 37 months in Kibale National Park, Uganda, with maize gardens at the forest edge. Based on focal nest-to-nest data, we analyzed their diet, activity budget, and energy balance depending on wild fruit and maize availability. We found that the Sebitoli area is a highly nutritive habitat for chimpanzees, with large and caloric wild fruits available all year long. The chimpanzees opportunistically consume maize and exploit it by resting less during maize season. However, no significant variation was found in daily paths and energy expenditures according to maize availability. No behavioral or energy modification was observed regarding wild resources either. Despite the availability of nutritious domestic resources, chimpanzees still exploit wild fruits and do not limit their movements. Thus, their contribution to seed dispersal and forest regeneration in this area is not affected.

Chimpanzee exposure to pollution revealed by human biomonitoring approaches

Wildlife is increasingly exposed to environmental pollution, but data illustrating to what extent this exposure can impact health and survival of endangered species is missing. In humans, hair matrix analysis is a reliable tool for assessing cumulative exposure to organic pollutants such as pesticides but has rarely been used in other primates for this purpose. LC/MS-MS and GC/MS-MS multi-residue methods were used to screen the presence of 152 organic pollutants and their metabolites belonging to 21 different chemical families in hair samples from our closest relative, the chimpanzee. Samples were collected from 20 wild chimpanzees in Sebitoli, Kibale National Park, Uganda and 9 captive chimpanzees in the Réserve Africaine de Sigean, France. In total, 90 chemicals were detected, 60 in wild chimpanzees and 79 in captive chimpanzees. The median concentrations of detected chemicals in captive individuals were significantly higher than those in wild chimpanzees. Hair from the captive individuals at RAS was sampled a second time after 6 months in an environment of reduced exposure to these pollutants (diet of organic food, decreased use of plastic food and water containers). The number of chemicals detected in captive chimpanzees reduced from 79 to 63, and their concentrations were also significantly reduced. In the present study we report for the first time the use of hair analysis to detect organic pollutants in primate hair. We conclude that both wild and captive chimpanzees are exposed to a large range of different chemicals through their diet. Our study provides surprising and alarming evidence that besides the direct threats of poaching, deforestation and diseases, wild chimpanzees might be endangered by indirect consequences of anthropic activities. As chimpanzees are our closest relatives, our results should be considered as an alert for human health as well.

Noninvasive Technologies for Primate Conservation in the 21st Century

Observing and quantifying primate behavior in the wild is challenging. Human presence affects primate behavior and habituation of new, especially terrestrial, individuals is a time-intensive process that carries with it ethical and health concerns, especially during the recent pandemic when primates are at even greater risk than usual. As a result, wildlife researchers, including primatologists, have increasingly turned to new technologies to answer questions and provide important data related to primate conservation. Tools and methods should be chosen carefully to maximize and improve the data that will be used to answer the research questions. We review here the role of four indirect methods—camera traps, acoustic monitoring, drones, and portable field labs—and improvements in machine learning that offer rapid, reliable means of combing through large datasets that these methods generate. We describe key applications and limitations of each tool in primate conservation, and where we anticipate primate conservation technology moving forward in the coming years.

Chimpanzees balance resources and risk in an anthropogenic landscape of fear

Human-wildlife coexistence is possible when animals can meet their ecological requirements while managing human-induced risks. Understanding how wildlife balance these trade-offs in anthropogenic environments is crucial to develop effective strategies to reduce risks of negative interactions, including bi-directional aggression and disease transmission. For the first time, we use a landscape of fear framework with Bayesian spatiotemporal modelling to investigate anthropogenic risk-mitigation and optimal foraging trade-offs in Critically Endangered western chimpanzees (Pan troglodytes verus). Using 12 months of camera trap data (21 camera traps, 6722 camera trap days) and phenology on wild and cultivated plant species collected at Caiquene–Cadique, Cantanhez National Park (Guinea-Bissau), we show that humans and chimpanzees broadly overlapped in their use of forest and anthropogenic parts of the habitat including villages and cultivated areas. The spatiotemporal model showed that chimpanzee use of space was predicted by the availability of naturalised oil-palm fruit. Chimpanzees used areas away from villages and agriculture more intensively, but optimised their foraging strategies by increasing their use of village areas with cultivated fruits when wild fruits were scarce. Our modelling approach generates fine-resolution space–time output maps, which can be scaled-up to identify human-wildlife interaction hotspots at the landscape level, informing coexistence strategy.

Insights into short- and long-term crop-foraging strategies in a chacma baboon (Papio ursinus) from GPS and accelerometer data

Crop-foraging by animals is a leading cause of human-wildlife "conflict" globally, affecting farmers and resulting in the death of many animals in retaliation, including primates. Despite significant research into crop-foraging by primates, relatively little is understood about the behavior and movements of primates in and around crop fields, largely due to the limitations of traditional observational methods. Crop-foraging by primates in large-scale agriculture has also received little attention. We used GPS and accelerometer bio-loggers, along with environmental data, to gain an understanding of the spatial and temporal patterns of activity for a female in a crop-foraging baboon group in and around commercial farms in South Africa over one year. Crop fields were avoided for most of the year, suggesting that fields are perceived as a high-risk habitat. When field visits did occur, this was generally when plant primary productivity was low, suggesting that crops were a "fallback food". All recorded field visits were at or before 15:00. Activity was significantly higher in crop fields than in the landscape in general, evidence that crop-foraging is an energetically costly strategy and that fields are perceived as a risky habitat. In contrast, activity was significantly lower within 100 m of the field edge than in the rest of the landscape, suggesting that baboons wait near the field edge to assess risks before crop-foraging. Together, this understanding of the spatiotemporal dynamics of crop-foraging can help to inform crop protection strategies and reduce conflict between humans and baboons in South Africa.

The Kibale Chimpanzee Project: Over thirty years of research, conservation, and change

Long-term primate field research programs contribute to the protection of endangered primate species and their vanishing habitats by informing and fostering local and international conservation programs. The Kibale Chimpanzee Project (KCP) has studied the Kanyawara community of wild chimpanzees continuously since 1987, investigating a wide range of behavioral, ecological, and physiological questions. The study area includes the northwest boundary of Kibale National Park, Uganda, and has experienced habitat change driven by multiple causes, including forest regeneration, an increasingly warmer and wetter climate, and impacts from the neighboring human population. Here, we review the history of research on Kanyawara chimpanzees and examine how their demography, diet, and social behavior have changed over the last 30+ years. While Kanyawara chimpanzees were protected from the major threats of poaching and habitat loss, respiratory diseases of human origin were a major source of mortality. Many individuals were also injured by wire hunting snares. Nevertheless, the study community has grown modestly in size, individuals have become increasingly gregarious, and birth rates have increased. These results are likely attributable to improved habitat productivity that can be traced to decades-long efforts by wildlife authorities and the associated research and conservation programs in Kibale. Overall, research has contributed both to understanding interactions among nutritional ecology, social behavior, physiology, and health of an endangered species, and also to conservation activities in the Kibale community through direct interventions, positive economic impacts, and conservation education programs.

Use of an embedded fruit by Nicobar Long-tailed Macaque Macaca fascicularis umbrosus: II. Demographic influences on choices of coconuts Cocos nucifera and pattern of forays to palm plantations

Adaptive pressures of human-induced rapid environmental changes and insular ecological conditions have led to behavioral innovations among behaviorally flexible nonhuman primates.  Documenting long-term responses of threatened populations is vital for our understanding of species and location-specific adaptive capacities under fluctuating equilibrium.  The Nicobar Long-tailed Macaque  Macaca fascicularis umbrosus, an insular sub-species uses coconuts Cocos nucifera, an embedded cultivar as a food resource and is speculated to have enhanced its dependence as a result of anthropogenic and environmental alterations.  We explored demographic patterns of use and abandonment of different phenophases of fresh coconuts.  To study crop foraging strategies, we recorded daily entry and duration of forays into coconut plantations.  We divided age-classes into early juvenile (13–36 months), late juvenile (37–72 months), and adults (>72 months) and classified phenophase of coconuts into six types.  Consistent with the theory of life history strategies, late juveniles were found to use a greater number of coconuts, which was considerably higher in an urban troop but marginally higher in a forest-plantation dwelling group.  Except in late juveniles, males consumed a higher number of coconuts than females in the remaining age-classes.  Owing to developmental constraints, juveniles of both types used higher proportion of immature coconuts though adults showed equitable distribution across phenophases.  Pattern of entries to plantations and duration of forays were uniform through the day in the urban troop but modulatory in the forest-plantation group, perhaps due to frequent and hostile human interferences.  Observations corroborating adaptations to anthropogenic disturbances are described. 

Sex Bias and Social Influences on Savanna Chimpanzee (Pan troglodytes verus) Nest Building Behavior

Many primates show sex differences in behavior, particularly social behavior, but also tool use for extractive foraging. All great apes learn to build a supportive structure for sleep. Whether sex differences exist in building, as in extractive foraging, is unknown, and little is known about how building skills develop and vary between individuals in the wild. We therefore aimed to describe the nesting behavior of savanna chimpanzees (Pan troglodytes verus) in Fongoli, Senegal to provide comparative data and to investigate possible sex or age differences in nest building behaviors and nest characteristics. We followed chimpanzee groups to their night nesting sites to record group (55 nights) and individual level data (17 individuals) on nest building initiation and duration (57 nests) during the dry season between October 2007 and March 2008. We returned the following morning to record nest and tree characteristics (71 nests built by 25 individuals). Fongoli chimpanzees nested later than reported for other great apes, but no sex differences in initiating building emerged. Observations were limited but suggest adult females and immature males to nest higher, in larger trees than adult males, and adult females to take longer to build than either adult or immature males. Smaller females and immature males may avoid predation or access thinner, malleable branches, by nesting higher than adult males. These differences suggest that sex differences described for chimpanzee tool use may extend to nest building, with females investing more time and effort in constructing a safe, warm structure for sleep than males do.

Comparing Methods for Assessing Chimpanzee (Pan troglodytes schweinfurthii) Party Size: Observations, Camera Traps, and Bed Counts from a Savanna–Woodland Mosaic in the Issa Valley, Tanzania

Studying animal grouping behavior is important for understanding the causes and consequences of sociality and has implications for conservation. Chimpanzee (Pan troglodytes) party size is often assessed by counting individuals or extracted indirectly from camera trap footage or the number of nests. Little is known, however, about consistency across methods for estimating party size. We collected party size data for wild chimpanzees in the Issa valley, western Tanzania, using direct observations, camera traps, and nest counts over six years (2012–2018). We compared mean monthly party size estimates calculated using each method and found that estimates derived from direct observations were weakly positively correlated with those derived from camera traps. Estimates from nest counts were not significantly correlated with either direct observations or camera traps. Overall observed party size was significantly larger than that estimated from both camera traps and nest counts. In both the dry and wet seasons, observed party size was significantly larger than camera trap party size, but not significantly larger than nest party size. Finally, overall party size and wet season party size estimated from camera traps were significantly smaller than nest party size, but this was not the case in the dry season. Our results reveal how data collection methods influence party size estimates in unhabituated chimpanzees and have implications for comparative analysis within and across primate communities. Specifically, future work must consider how estimates were calculated before we can reliably investigate environmental influences on primate behavior.

Forest fragments become farmland: Dietary Response of wild chimpanzees (Pan troglodytes) to fast-changing anthropogenic landscapes

Behavioral flexibility, including an ability to modify feeding behavior, is a key trait enabling primates to survive in forest fragments. In human-dominated landscapes, unprotected forest fragments can become progressively degraded, and may be cleared entirely, challenging the capacity of primates to adjust to the changes. We examined responses of wild chimpanzees (Pan troglodytes schweinfurthii) to major habitat change: that is, clearance of forest fragments for agriculture. Over 7 years, fragments in Bulindi, Uganda, were reduced in size by 80%. We compared the chimpanzees' diet at the start and end of this period of rapid deforestation, using data derived mainly from fecal analysis. Similar to other long-term study populations, chimpanzees in Bulindi have a diverse diet comprising over 169 plant foods. However, extensive deforestation seemed to impact their feeding ecology. Dietary changes after fragment clearance included reduced overall frugivory, reduced intake of figs (Ficus spp.; formerly a dietary "staple" for these chimpanzees), and reduced variety of fruits in fecal samples. Nevertheless, the magnitude of most changes was remarkably minor given the extent of forest loss. Agricultural fruits increased in dietary importance, with crops accounting for a greater proportion of fruits in fecal samples after deforestation. In particular, cultivated jackfruit (Artocarpus heterophyllus) became a "staple" food for the chimpanzees but was scarcely eaten before fragment clearance. Crops offer some nutritional benefits for primates, being high in carbohydrate energy and low in hard-to-digest fiber. Thus, crop feeding may have offset foraging costs associated with loss of wild foods and reduced overall frugivory for the chimpanzees. The adaptability of many primates offers hope for their conservation in fragmented, rural landscapes. However, long-term data are needed to establish whether potential benefits (i.e. energetic, reproductive) of foraging in agricultural matrix habitats outweigh fitness costs from anthropogenic mortality risk for chimpanzees and other adaptable primates.

Factors influencing wild chimpanzee (Pan troglodytes verus) relative abundance in an agriculture-swamp matrix outside protected areas

Human population growth and anthropogenic activities are exacerbating pressures on biodiversity globally. Land conversion is aggravating habitat fragmentation and non-human primates are increasingly compelled to live in forest-agricultural mosaics. In Sierra Leone, more than half of the wild chimpanzee population (Pan troglodytes verus) occurs outside protected areas and competes for resources with farmers. Our study area, in the Moyamba district in south-western Sierra Leone, is practically devoid of forest and is dominated by cultivated and fallow fields, swamps and mangroves. In this region, traditional slash-and-burn agriculture modifies annually the landscape, sparing swamps and mangroves and semi-domesticated oil palms (Elaeis guineensis). This study aimed to explore ecological and anthropogenic factors influencing chimpanzee relative abundance across this highly degraded and human-impacted landscape. Between 2015 and 2016, we deployed 24 camera traps systematically across 27 1.25x1.25 km grid cells. Cameras were operational over a period of 8 months. We used binomial iCAR models to examine to what extent anthropogenic (roads, settlements, abandoned settlements and human presence) and habitat variables (swamps, farmland and mangroves) shape chimpanzee relative abundance. The best model explained 43.16% of the variation with distance to roads and swamps emerging as the best predictors of chimpanzee relative abundance. Our results suggest that chimpanzees avoid roads and prefer to maintain proximity to swamps. There was no significant effect of settlements, abandoned settlements, mangroves or human presence. It appears that chimpanzees do not avoid areas frequented by people; although, our findings suggest temporal avoidance between the two species. We highlight the importance of studying chimpanzee populations living in anthropogenic habitats like agricultural-swamp matrixes to better understand factors influencing their distribution and inform conservation planning outside protected areas.

Nesting, sleeping, and nighttime behaviors in wild and captive great apes

The past few decades have seen a burgeoning of scientific studies on great apes' use of nests for sleeping in the wild, as well as their nesting behavior and sleep in captivity. We review recent advances in knowledge of these topics, with the aim of promoting information exchange between people working in the field and with captive great apes. We trace developments in research into nest-building techniques in adults and immatures, factors that influence selection of general sleeping sites and specific locations, social aspects of sleep, postures, and nighttime activities. We argue that exchanges of information deriving from studies of captive and wild apes are valuable for obtaining a better understanding of sleep-related adaptations in our nearest evolutionary neighbors, and conclude by making some recommendations regarding sleeping arrangements in captivity from a welfare perspective.

Facial dysplasia in wild forest olive baboons (Papio anubis) in Sebitoli, Kibale National Park, Uganda: Use of camera traps to detect health defects

BACKGROUND

Primate populations are in decline, mainly affected by agriculture leading to habitat loss, fragmentation but also chemical pollution. Kibale National Park (Uganda), Sebitoli forest, surrounded by tea and crop fields, is the home range of chimpanzees presenting congenital facial dysplasia. This study aimed to identify to what extent the same phenotypical features are observed in baboons (Papio anubis) of this area.

METHODS

A total of 25 390 clips recorded by 14 camera traps between January 2017 and April 2018 were analyzed.

RESULTS

We identified 30 immature and adult baboons of both sexes with nose and lip deformities. They were more frequently observed in the northwestern part of the area.

CONCLUSIONS

A possible effect of pesticides used in crops at the border of their habitat is suspected to alter the embryonic development. This study emphasizes the importance of non-invasive methods to detect health problems in wild primates that can act as sentinels for human health.

Nocturnal activity in wild chimpanzees (Pan troglodytes): Evidence for flexible sleeping patterns and insights into human evolution

OBJECTIVES

We investigated occurrences and patterns of terrestrial nocturnal activity in wild chimpanzees (Pan troglodytes) and modelled the influence of various ecological predictors on nocturnal activity.

METHODS

Data were extracted from terrestrial camera-trap footage and ecological surveys from 22 chimpanzee study sites participating in the Pan African Programme: The Cultured Chimpanzee. We described videos demonstrating nocturnal activity, and we tested the effects of the percentage of forest, abundance of predators (lions, leopards and hyenas), abundance of large mammals (buffalos and elephants), average daily temperature, rainfall, human activity, and percent illumination on the probability of nocturnal activity.

RESULTS

We found terrestrial nocturnal activity to occur at 18 of the 22 study sites, at an overall average proportion of 1.80% of total chimpanzee activity, and to occur during all hours of the night, but more frequently during twilight hours. We found a higher probability of nocturnal activity with lower levels of human activity, higher average daily temperature, and at sites with a larger percentage of forest. We found no effect of the abundance of predators and large mammals, rainfall, or moon illumination.

DISCUSSION

Chimpanzee terrestrial nocturnal activity appears widespread yet infrequent, which suggests a consolidated sleeping pattern. Nocturnal activity may be driven by the stress of high daily temperatures and may be enabled at low levels of human activity. Human activity may exert a relatively greater influence on chimpanzee nocturnal behavior than predator presence. We suggest that chimpanzee nocturnal activity is flexible, enabling them to respond to changing environmental factors.

Comparison of Three Methods to Assess the Potential for Bushpig-Domestic Pig Interactions at the Wildlife-Livestock Interface in Uganda

Bushpigs (Potamochoerus larvatus) are considered a nuisance to farmers because of their crop raiding habits. Through their incursions into farmlands, they may interact with free-ranging domestic pigs and potentially cause transmission of infectious diseases such as African Swine Fever (ASF). The role of the bushpig in the epidemiology of ASF is poorly known and one of the gaps of knowledge is precisely the nature of interaction between bushpigs and domestic pigs. Thus, in this study, we investigated the frequency of bushpig visits to crop fields in rural communities where ASF is endemic, at the edge of a wildlife protected area in northwestern Uganda, to better understand the potential for interaction and disease transmission. We used three methods (questionnaires, camera traps, and observations for tracks) to assess bushpig visits to farmland. These methods were implemented concurrently in 28 farms during rainy and dry seasons. The results obtained by each of the three methods were analyzed by generalized linear mixed models. Potential risk factors including crop type, season, and landscape characteristics related to bushpig ecology were tested as explanatory variables. A generalized linear model and the Kendall test were used to compare the results and consistency of the frequency values obtained by the three methods. A high percentage (75%) of interviewed farmers reported visits from bushpigs in 29.6% of assessed crops (n = 145), and a frequency of 0.014 +/-0.05 visits per night was obtained through camera-trapping. Bushpig tracks were detected in 36% of sessions of observation. Cassava (Manihot esculenta) and groundnut (Arachis hypogaea L.) crop fields were the most visited, and these visits were more common during the rainy than the dry season. Distances from crop sites to the boundary of the protected area and to the river also influenced visit frequency. Camera-trapping was the least sensitive method while questionnaires and track observations presented consistent and complementary results to characterize spatial and temporal visits of bushpig into the crop fields. Evidence from our study shows that when used in combination, these methods can provide useful data to improve our understanding of the interactions between bushpigs and domestic pigs at the wildlife-domestic interface.

Crop Foraging, Crop Losses, and Crop Raiding

Crop foraging or crop raiding concerns wildlife foraging and farmers’ reactions and responses to it. To understand crop foraging and its value to wildlife or its implications for humans requires a cross-disciplinary approach that considers the behavior and ecology of wild animals engaging in this behavior; the types and levels of competition for resources between people and wildlife; people's perceptions of and attitudes toward wildlife, including animals that forage on crops; and discourse about animals and their behaviors and how these discourses can be used for expressing dissent and distress about other social conflicts. So, to understand and respond to conflicts about crop damage, we need to look beyond what people lose, i.e., crop loss and economic equivalence, and focus more on what people say about wildlife and why they say it.

What, where and when: spatial foraging decisions in primates

When exploiting the environment, animals have to discriminate, track, and integrate salient spatial cues to navigate and identify goal sites. Actually, they have to know what can be found (e.g. what fruit), where (e.g. on which tree) and when (in what season or moment of the year). This is very relevant for primate species as they often live in seasonal and relatively unpredictable environments such as tropical forests. Here, we review and compare different approaches used to investigate primate spatial foraging strategies: from direct observations of wild primates to predictions from statistical simulations, including experimental approaches on both captive and wild primates, and experiments in captivity using virtual reality technology. Within this framework, most of these studies converge to show that many primate species can (i) remember the location of most of food resources well, and (ii) often seem to have a goal-oriented path towards spatially permanent resources. Overall, primates likely use mental maps to plan different foraging strategies to enhance their fitness. The majority of studies suggest that they may organise spatial information on food resources into topological maps: they use landmarks to navigate and encode local spatial information with regard to direction and distance. Even though these studies were able to show that primates can remember food quality (what) and its location (where), still very little is known on how they incorporate the temporal knowledge of available food (when). Future studies should attempt to increase our understanding of the potential of primates to learn temporal patterns and how both socio-ecological differences among species and their cognitive abilities influence such behavioural strategies.

Genetic analysis suggests dispersal among chimpanzees in a fragmented forest landscape in Uganda

Habitat fragmentation is a leading threat to global biodiversity. Dispersal plays a key role in gene flow and population viability, but the impact of fragmentation on dispersal patterns remains poorly understood. Among chimpanzees, males typically remain in their natal communities while females often disperse. However, habitat loss and fragmentation may cause severe ecological disruptions, potentially resulting in decreased fitness benefits of male philopatry and limited female dispersal ability. To investigate this issue, we genotyped nearly 900 non-invasively collected chimpanzee fecal samples across a fragmented forest habitat that may function as a corridor between two large continuous forests in Uganda, and used the spatial associations among co-sampled genotypes to attribute a total of 229 individuals to 10 distinct communities, including 9 communities in the corridor habitat and 1 in continuous forest. We then used parentage analyses to infer instances of between-community dispersal. Of the 115 parent-offspring dyads detected with confidence, members of 39% (N = 26) of mother-daughter dyads were found in different communities, while members of 10% (N = 5) of father-son dyads were found in different communities. We also found direct evidence for one dispersal event that occurred during the study period, as a female's sample found first in one community was found multiple times in another community 19 months later. These findings suggest that even in fragmented habitats, chimpanzee males remain in their natal communities while females tend to disperse. Corridor enhancement in unprotected forest fragments could help maintain gene flow in chimpanzees and other species amid anthropogenic pressures.

Rethinking Human-Nonhuman Primate Contact and Pathogenic Disease Spillover

Zoonotic transmissions are a major global health risk, and human-animal contact is frequently raised as an important driver of transmission. A literature examining zooanthroponosis largely agrees that more human-animal contact leads to more risk. Yet the basis of this proposition, the term contact, has not been rigorously analyzed. To understand how contact is used to explain cross-species spillovers, we conducted a multi-disciplinary review of studies addressing human-nonhuman primate (NHP) engagements and pathogenic transmissions and employing the term contact. We find that although contact is frequently invoked, it is employed inconsistently and imprecisely across these studies, overlooking the range of pathogens and their transmission routes and directions. We also examine a related but more expansive approach focusing on human and NHP habitats and their spatial overlap, which can potentially facilitate pathogenic transmission. Contact and spatial overlap investigations cannot, however, explain the processes that bring together people, animals and pathogens. We therefore examine another approach that enhances our understanding of zoonotic spillovers: anthropological studies identifying such historical, social, environmental processes. Comparable to a One Health approach, our ongoing research in Cameroon draws contact, spatial overlap and anthropological-historical approaches into dialog to suggest where, when and how pathogenic transmissions between people and NHPs may occur. In conclusion, we call for zoonotic disease researchers to specify more precisely the human-animal contacts they investigate and to attend to how broader ecologies, societies and histories shape pathogen-human-animal interactions.

Rethinking the Origin of Primates by Reconstructing Their Diel Activity Patterns Using Genetics and Morphology

Phylogenetic inference typically invokes nocturnality as ancestral in primates; however, some recent studies posit that diurnality is. Here, through adaptive evolutionary analyses of phototransduction genes by using a variety of approaches (restricted branch/branch-site models and unrestricted branch-site-based models (BS-REL, BUSTED and RELAX)), our results consistently showed that ancestral primates were subjected to enhanced positive selection for bright-light vision and relatively weak selection for dim-light vision. These results suggest that ancestral primates were mainly diurnal with some crepuscularity and support diurnality as plesiomorphic from Euarchontoglires. Our analyses show relaxed selection on motion detection in ancestral primates, suggesting that ancestral primates decreased their emphasis on mobile prey (e.g., insects). However, within primates, the results show that ancestral Haplorrhini were likely nocturnal, suggesting that evolution of the retinal fovea occurred within ancestral primates rather than within haplorrhines as was previously hypothesized. Our findings offer a reassessment of the visual adaptation of ancestral primates. The evolution of the retinal fovea, trichromatic vision and orbital convergence in ancestral primates may have helped them to efficiently discriminate, target, and obtain edible fruits and/or leaves from a green foliage background instead of relying on mobile insect prey.

GPS-identified, low-level nocturnal activity of vervets (Chlorocebus pygerythrus) and olive baboons (Papio anubis) in Laikipia, Kenya

OBJECTIVES

Except for owl monkeys (Aotus spp.), all anthropoid primates are considered strictly diurnal. Recent studies leveraging new technologies have shown, however, that some diurnal anthropoids also engage in nocturnal activity. Here we examine the extent to which vervets (Chlorocebus pygerythrus) and olive baboons (Papio anubis) are active at night.

MATERIALS AND METHODS

We deployed GPS collars with tri-axial accelerometer data loggers on 18 free-ranging adult females: 12 vervets spread among 5 social groups, and 6 olive baboons spread among 4 groups. Their locations were recorded every 15 min, and their activity levels, for 3 s/min over 7.5 months. We also used camera traps that were triggered by heat and movement at seven sleeping sites.

RESULTS

Travel was detected on 0.4% of 2,029 vervet-nights involving 3 vervets and 1.1% of 1,109 baboon-nights involving 5 baboons. Travel was mainly arboreal for vervets but mainly terrestrial for baboons. During the night, vervets and baboons were active 13% and 15% of the time, respectively. Activity varied little throughout the night and appeared unaffected by moon phase.

DISCUSSION

Our results confirm the low nocturnality of vervets and olive baboons, which we suggest is related to living near the equator with consistent 12-hr days, in contrast to other anthropoids that are more active at night. Since anthropoid primates are thought to have evolved in northern latitudes, with later dispersal to tropical latitudes, our results may have implications for understanding the evolution of anthropoid diurnality.

Activity and Habitat Use of Chimpanzees (Pan troglodytes verus) in the Anthropogenic Landscape of Bossou, Guinea, West Africa

Many primate populations inhabit anthropogenic landscapes. Understanding their long-term ability to persist in such environments and associated real and perceived risks for both primates and people is essential for effective conservation planning. Primates in forest-agricultural mosaics often consume cultivars to supplement their diet, leading to potentially negative encounters with farmers. When crossing roads, primates also face the risk of encounters with people and collision with vehicles. Chimpanzees (Pan troglodytes verus) in Bossou, Guinea, West Africa, face such risks regularly. In this study, we aimed to examine their activity budget across habitat types and the influence of anthropogenic risks associated with cultivated fields, roads, and paths on their foraging behavior in noncultivated habitat. We conducted 6-h morning or afternoon follows daily from April 2012 to March 2013. Chimpanzees preferentially used forest habitat types for traveling and resting and highly disturbed habitat types for socializing. Wild fruit and crop availability influenced seasonal habitat use for foraging. Overall, chimpanzees preferred mature forest for all activities. They showed a significant preference for foraging at >200 m from cultivated fields compared to 0-100 m and 101-200 m, with no effect of habitat type or season, suggesting an influence of associated risk. Nevertheless, the chimpanzees did not actively avoid foraging close to roads and paths. Our study reveals chimpanzee reliance on different habitat types and the influence of human-induced pressures on their activities. Such information is critical for the establishment of effective land use management strategies in anthropogenic landscapes.

Impending extinction crisis of the world's primates: Why primates matter

Nonhuman primates, our closest biological relatives, play important roles in the livelihoods, cultures, and religions of many societies and offer unique insights into human evolution, biology, behavior, and the threat of emerging diseases. They are an essential component of tropical biodiversity, contributing to forest regeneration and ecosystem health. Current information shows the existence of 504 species in 79 genera distributed in the Neotropics, mainland Africa, Madagascar, and Asia. Alarmingly, ~60% of primate species are now threatened with extinction and ~75% have declining populations. This situation is the result of escalating anthropogenic pressures on primates and their habitats-mainly global and local market demands, leading to extensive habitat loss through the expansion of industrial agriculture, large-scale cattle ranching, logging, oil and gas drilling, mining, dam building, and the construction of new road networks in primate range regions. Other important drivers are increased bushmeat hunting and the illegal trade of primates as pets and primate body parts, along with emerging threats, such as climate change and anthroponotic diseases. Often, these pressures act in synergy, exacerbating primate population declines. Given that primate range regions overlap extensively with a large, and rapidly growing, human population characterized by high levels of poverty, global attention is needed immediately to reverse the looming risk of primate extinctions and to attend to local human needs in sustainable ways. Raising global scientific and public awareness of the plight of the world's primates and the costs of their loss to ecosystem health and human society is imperative.