Chimpanzees facing a dangerous situation: A high-traffic asphalted road in the Sebitoli area of Kibale National Park, Uganda

Threat of mining to African great apes

The rapid growth of clean energy technologies is driving a rising demand for critical minerals. In 2022 at the 15th Conference of the Parties to the Convention on Biological Diversity (COP15), seven major economies formed an alliance to enhance the sustainability of mining these essential decarbonization minerals. However, there is a scarcity of studies assessing the threat of mining to global biodiversity. By integrating a global mining dataset with great ape density distribution, we estimated the number of African great apes that spatially coincided with industrial mining projects. We show that up to one-third of Africa's great ape population faces mining-related risks. In West Africa in particular, numerous mining areas overlap with fragmented ape habitats, often in high-density ape regions. For 97% of mining areas, no ape survey data are available, underscoring the importance of increased accessibility to environmental data within the mining sector to facilitate research into the complex interactions between mining, climate, biodiversity, and sustainability.

Primates and disability: Behavioral flexibility and implications for resilience to environmental change

Congenital malformations, conditions, injuries, and illness can lead to long-term physical impairment and disability in nonhuman primates. How individual primates change their behaviors flexibly to compensate for their disabilities can inform our understanding of their resilience and ability to adjust to environmental change. Here, we synthesize the literature on nonhuman primates and disability, addressing the questions: how does disability influence behavior in primates? What insights can we take from the literature to better understand and predict the capacity of primates to modify their behaviors in the face of human-induced environmental change? We conducted a systematic review of the literature on spontaneous physical impairment and disability in captive, free-ranging, and wild primates. We surveyed 2807 articles on Web of Science and Scopus and identified 114 studies that fit our predetermined inclusion criteria. Behavioral plasticity, maternal and conspecific care, and the potential for innovation of novel behaviors allow many primates with disabilities to compensate when faced with challenges that are outside the scope of usual circumstances. We also found that 60% of the publications connected primate physical impairment and disability to human activities, suggesting an entangled relationship among humans, the environment, and primate disability. Disability and physical impairments provide an opportunity to examine how primates modify their behavior when presented with challenging conditions, and their potential resilience to a changing environment.

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.

Automated acoustic detection of Geoffroy's spider monkey highlights tipping points of human disturbance

As more land is altered by human activity and more species become at risk of extinction, it is essential that we understand the requirements for conserving threatened species across human-modified landscapes. Owing to their rarity and often sparse distributions, threatened species can be difficult to study and efficient methods to sample them across wide temporal and spatial scales have been lacking. Passive acoustic monitoring (PAM) is increasingly recognized as an efficient method for collecting data on vocal species; however, the development of automated species detectors required to analyse large amounts of acoustic data is not keeping pace. Here, we collected 35 805 h of acoustic data across 341 sites in a region over 1000 km² to show that PAM, together with a newly developed automated detector, is able to successfully detect the endangered Geoffroy's spider monkey (Ateles geoffroyi), allowing us to show that Geoffroy's spider monkey was absent below a threshold of 80% forest cover and within 1 km of primary paved roads and occurred equally in old growth and secondary forests. We discuss how this methodology circumvents many of the existing issues in traditional sampling methods and can be highly successful in the study of vocally rare or threatened species. Our results provide tools and knowledge for setting targets and developing conservation strategies for the protection of Geoffroy's spider monkey.

Illegal Harvesting within a Protected Area: Spatial Distribution of Activities, Social Drivers of Wild Meat Consumption, and Wildlife Conservation

The African tropical forests host an inestimable number of resources, including food, medicine, vegetal and animal species. Among them, chimpanzees are threatened with extinction by human activities affecting their habitats, such as forest product harvesting, and/or more directly, snaring and trafficking. We aimed to better understand the spatial distribution of these illegal activities, and the reasons for setting snares and consuming wild meat in an agricultural landscape (subsistence farming and cash crops) densely populated near a protected area (Sebitoli, Northern part of Kibale National Park, Uganda). To carry out this study, we combined GPS records of illegal activities collected with group counts (in total, n = 339 tea workers, 678 villagers, and 1885 children) and individual interviews (n = 74 tea workers, 42 villagers, and 35 children). A quarter of illegal activities collected (n = 1661) targeted animal resources and about 60% were recorded in specific areas (southwest and northeast) of the Sebitoli chimpanzee home range. Wild meat consumption, which is illegal in Uganda, is a relatively common practice among participants (17.1% to 54.1% of respondents depending on actor types and census methods). However, consumers declared that they eat wild meat unfrequently (0.6 to 2.8 times per year). Being a young man coming from districts contiguous to Kibale National Park particularly raises the odds of consuming wild meat. Such an analysis contributes to the understanding of wild meat hunting among traditional rural and agricultural societies from East Africa.

Survey of ticks and tick-borne pathogens in wild chimpanzee habitat in Western Uganda

BACKGROUND

Ticks and tick-borne pathogens significantly impact both human and animal health and therefore are of major concern to the scientific community. Knowledge of tick-borne pathogens is crucial for prescription of mitigation measures. In Africa, much research on ticks has focused on domestic animals. Little is known about ticks and their pathogens in wild habitats and wild animals like the endangered chimpanzee, our closest relative.

METHODS

In this study, we collected ticks in the forested habitat of a community of 100 chimpanzees living in Kibale National Park, Western Uganda, and assessed how their presence and abundance are influenced by environmental factors. We used non-invasive methods of flagging the vegetation and visual search of ticks both on human team members and in chimpanzee nests. We identified adult and nymph ticks through morphological features. Molecular techniques were used to detect and identify tick-borne piroplasmids and bacterial pathogens.

RESULTS

A total of 470 ticks were collected, which led to the identification of seven tick species: Haemaphysalis parmata (68.77%), Amblyomma tholloni (20.70%), Ixodes rasus sensu lato (7.37%), Rhipicephalus dux (1.40%), Haemaphysalis punctaleachi (0.70%), Ixodes muniensis (0.70%) and Amblyomma paulopunctatum (0.35%). The presence of ticks, irrespective of species, was influenced by temperature and type of vegetation but not by relative humidity. Molecular detection revealed the presence of at least six genera of tick-borne pathogens (Babesia, Theileria, Borrelia, Cryptoplasma, Ehrlichia and Rickettsia). The Afrotopical tick Amblyomma tholloni found in one chimpanzee nest was infected by Rickettsia sp.

CONCLUSIONS

In conclusion, this study presented ticks and tick-borne pathogens in a Ugandan wildlife habitat whose potential effects on animal health remain to be elucidated.

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.

Assessing the importance of artificial canopy bridge design for Costa Rican monkeys in an experimental setting

Although artificial crossing structures are increasingly implemented by conservationists and wildlife managers to connect fragmented wildlife habitat, the study of artificial crossing structure design, particularly of canopy bridges, is an emerging field of study in primatology. We address this issue by evaluating five competing bridge models with varying width, material stiffness, and substrate spacing. We assessed bridge preference and performance by sampling the behavior of three species of Costa Rican monkeys (Alouatta palliata: n = 4, Ateles geoffroyi: n = 3, Cebus imitator: n = 3). In a semi-wild setting, we used focal individual sampling with instantaneous recording once every minute for ten-minute intervals and all occurrences sampling whenever study subjects used the bridge. We hypothesized that monkeys prefer bridges that are more stable, and that are made of materials that resemble tree branches. During nearly 37 sampling hours we observed 119 crossing events. We found that study subjects prefer bridge models that are built using more rigid materials, such as the bamboo pole bridge, or wider bridges that offer more stability than narrower bridges. The bridge type and the materials used to build the bridges are both significant predictors of bridge use. While preference for bridges and their performance varies by species, the bamboo pole bridge model and the horizontal mesh bridge were preferred and performed best in our study. The simple liana bridge model was the least preferred by all species and performed poorly in comparison to the other models. Our findings will help us better understand how design and materials impact the use of canopy bridges by monkeys, which can help improve biological corridors and offer new information for the management and conservation of primates living near infrastructure corridors and other kinds of dangerous matrix.

Canopy bridges are an economical mitigation reducing the road barrier effect for three of four species of monkeys in Diani, Kenya

For primates, canopy bridges can reduce the road barrier effect. Yet little information exists to predict species bridge use. We examined bridge use across a 9 km suburban road in Diani, Kenya, in three survey years (Nbridges: 21 = 2004, 27 = 2011, 29 = 2020) by four sympatric species of monkeys. The asphalt road is 6 m wide with a 50 km/h speed limit. Roadside observers recorded ground () and bridge () crossings, crossing direction, and traffic volume. Colobus (Colobus angolensis palliatus), Sykes’ monkeys (Cercopithecus mitis albogularis), and vervets (Chlorocebus pygerythrus hilgerti) used the bridges while baboons (Papio cynocephalus cynocephalus) rarely did. Crossing rates (Sykes’>vervet>colobus>baboon) did not fit our predictions based on species’ attributes of stratum preference (arboreal>terrestrial) or body mass (small>large), while the interaction between these attributes was more informative. Crossings were bidirectional. Colobus crossed bridges during higher traffic volumes than on the ground, whereas we found the opposite for vervets. Sykes’ monkeys crossed at similar traffic volumes on the ground and bridges. The mean annual bridge cost was USD 157, deriving a cost per crossing as < USD 0.10, though it undervalues the savings in ecosystem services, tourism benefits, and contributions to protecting colobus, a vulnerable species. While we consider this highly economical, funders and road engineers will ultimately determine if it is so.

Impact of linear infrastructure on South Africa’s primate fauna: the need for mitigation

South Africa’s extensive linear infrastructure network (which includes roads and power lines) is severely impacting the country’s historically recognised five primate species: greater or thick-tailed bushbaby (Otolemur crassicaudatus), southern lesser bushbaby (Galago moholi), chacma baboon (Papio ursinus), vervet monkey (Chlorocebus pygerythrus) and samango monkey (Cercopithecus albogularis). We present South African mortality data from two different linear infrastructure types on a country wide scale, over a long-term sampling period. Using primate road mortality and power line electrocution data acquired from different data sources, we compare and discuss different mortality data collection methodologies, the resulting data quality and identify current limitations in understanding the direct impacts of linear infrastructure which have important implications for primate conservation planning. Between 1996-2021 a total of 483 primate mortalities were recorded on roads and power lines, the majority on the former. Vervet monkeys were most severely impacted by both linear infrastructure types whereas lesser bushbabies experienced the least number of mortalities. Both data sets showed numerous incidents where more than one individual was killed (roadkill: 4%, up to four killed in one incident; electrocutions: 13%, up to six killed in one incident). GPS coordinates were available for 61% of roadkill records and for 65% of electrocution records. Age or sex of carcasses were not available for electrocution records and only available for 11% of roadkill records. Although South Africa leads the African continent regarding roadkill and electrocution data collection, there are still areas in the collection protocol that can be improved and projects implementing mitigation measures (e.g. canopy bridges) to reduce primate roadkill are lacking. We argue that the mortality data presented here should form the basis for future mitigation implementation and recommend that linear infrastructure be more prominently recognised as a direct threat when developing national and international Red Lists.

Wildlife is imperiled in peri-urban landscapes: threats to arboreal mammals

Urbanization and deforestation impose severe challenges to wildlife, particularly for forest-living vertebrates. Understanding how the peri-urban matrix impacts their survival is critical for designing strategies to promote their conservation. We investigated the threats faced by brown howler monkeys (Alouatta guariba clamitans) in peri-urban regions of Rio Grande do Sul (RS) and Santa Catarina (SC) states, southern Brazil, by compiling negative interaction events (hereafter NIE) reported over more than two decades. We assessed the major NIEs, their distribution among age-sex classes, and the predictors of NIE-related mortality. After 20+ years of monitoring, we compiled 540 NIEs (RS = 248 and SC = 292). Electrocution by power lines was the most frequent cause of death or injury (37%), followed by dog attack (34%), vehicle collision (17%), and human mistreatment (12%). The occurrence of lethal injuries ranged from 5% to 69% depending on the type of NIE and on which state it occurred in. The overall post-NIE mortality was 56%. Adults of both sexes were the most affected individuals in both study regions. The minimal adequate GLM model explained 83% of the variation in NIE-related mortality. State, NIE type, and age-sex class were the main predictors of mortality. Overall, mortality was lower in SC and higher among adult females than in the other classes. We found that the survival of brown howler monkeys in the forest-urban interface is constrained by both the urban infrastructure and the growing interactions with humans and domestic and stray dogs (Canis familiaris). We propose the placement of aerial bridges, road signs and speed bumps in areas of frequent animal crossing, the sterilization of stray dogs, and the sensitization of local inhabitants on the importance of respecting and protecting wildlife to reduce their NIEs with humans and domestic animals in the forest-urban interface.

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.

Identifying and mitigating the impacts on primates of transportation and service corridors

Most primate populations are declining; 60% of species face extinction. The expansion of transportation and service corridors (T&S) (i.e., roads and railways and utility and service lines) poses a significant yet underappreciated threat. With the development of T&S corridors predicted to increase across primates' ranges, it is necessary to understand the current extent of its impacts on primates, the available options to mitigate these effectively, and recognize research and knowledge gaps. By employing a systematic search approach to identify literature that described the relationship between primates and T&S corridors, we extracted information from 327 studies published between 1980 and 2020. Our results revealed that 218 species and subspecies across 62 genera are affected, significantly more than the 92 listed by the IUCN Red List of Threatened Species. The majority of studies took place in Asia (45%), followed by mainland Africa (31%), the Neotropics (22%), and Madagascar (2%). Brazil, Indonesia, Equatorial Guinea, Vietnam, and Madagascar contained the greatest number of affected primate species. Asia featured the highest number of species affected by roads, electrical transmission lines, and pipelines and the only studies addressing the impact of rail and aerial tramways on primates. The impact of seismic lines only emerged in the literature from Africa and the Neotropics. Impacts are diverse and multifaceted, for example, animal-vehicle collisions, electrocutions, habitat loss and fragmentation, impeded movement and genetic exchange, behavioral changes, exposure to pollution, and mortality associated with hunting. Although several mitigation measures were recommended, only 41% of studies focused on their implementation, whereas only 29% evaluated their effectiveness. Finally, there was a clear bias in the species and regions benefiting from research on this topic. We recommend that government and conservation bodies recognize T&S corridors as a serious and mounting threat to primates and that further research in this area is encouraged.

One Health Perspectives on New Emerging Viral Diseases in African Wild Great Apes

The most recent emerging infectious diseases originated in animals, mainly in wildlife reservoirs. Mutations and recombination events mediate pathogen jumps between host species. The close phylogenetic relationship between humans and non-human primates allows the transmission of pathogens between these species. These pathogens cause severe impacts on public health and impair the conservation of habituated or non-habituated wild-living apes. Constant exposure of great apes to human actions such as hunting, deforestation, the opening of roads, and tourism, for example, contributes to increased interaction between humans and great apes. In spite of several studies emphasizing the risks of pathogen transmission between animals and humans, outbreaks of the reverse transmission of infectious agents threatening wildlife still occur on the African continent. In this context, measures to prevent the emergence of new diseases and conservation of primate species must be based on the One Health concept; that is, they must also ensure the monitoring of the environment and involve political and social aspects. In this article, we review and discuss the anthropological aspects of the transmission of diseases between people and wild primates and discuss new anthropozoonotic diseases in great apes in Africa from studies published between 2016 and 2020. We conclude that the health of great apes also depends on monitoring the health of human populations that interact with these individuals.

Consumption of cultivated subterranean plant organs by chimpanzees in a human-dominated landscape

Although chimpanzees (Pan troglodytes) are ripe fruit specialists, they sometimes consume other plant parts including subterranean organs like roots and tubers. Such plant parts, which include underground storage organs (USOs), have been found to play a key role in the diets of some chimpanzee populations as well as, potentially, our hominin ancestors. We report the confirmed consumption of subterranean plant organs of three species — sweet potatoes (Ipomoea batatas), yams (Dioscorea alata) and peanuts (Arachis hypogaea), as well as unconfirmed consumption of cassava (Manihot esculenta) — by chimpanzees in a human-dominated landscape in western Uganda. These observations point toward the dietary flexibility of chimpanzees inhabiting anthropogenic landscapes, though mechanisms of novel food acquisition, particularly for subterranean fruits and tubers, are not well understood. Dietary flexibility may help chimpanzees survive as natural forest resources disappear, but simultaneously may bring them into greater conflict with their human neighbours, thereby further imperilling them.

Road impact in a protected area with rich biodiversity: the case of the Sebitoli road in Kibale National Park, Uganda

While road network expansion is crucial for economic development, it can cause a notable disturbance of fauna, especially in protected area in terms of habitat fragmentation, risk of collision, and also indirect threat such as pollution. In this study, we monitored the 4.6-km long tarmac road crossing the Kibale National Park in Uganda, home to a rich variety of wild species including the endangered chimpanzees. We evaluated the effects of collisions and pollution, as well as the impact of the renovation process in terms of disturbance and the mitigation measures deployed. This survey reports the death of 24 wild animals killed by cars, including two chimpanzees. The atmospheric concentrations of O₃, NO₂, SO₂, and BTEX did not exceed recommended limits. More than 5000 plastic bottles were collected along the road within 4 months, and for the first time, the presence of BPA and BPS was detected in the hairs of wild chimpanzees. The road bisecting the Kibale National Park poses a high danger in terms of traffic and an underestimated risk related to plastic pollution. Measures (signpost, speed bumps) should be urgently deployed to decrease the risk posed by the renovated road for emblematic species such as chimpanzees, which are crucial for tourism and economy in Uganda.

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.

Interactions with humans are jointly influenced by life history stage and social network factors and reduce group cohesion in moor macaques (Macaca maura)

Human-wildlife encounters are becoming increasingly frequent across the globe, often leading people to interact with and feed wild animals and impacting animal behaviour and ecology. Although the nature of human-wildlife interactions has been well documented across a number of species, we still have limited understanding as to why some individual animals interact more frequently with humans than others. Additionally, we lack a comprehensive understanding of how these interactions influence animal social networks. Using behavioural data from a group of moor macaque monkeys (Macaca maura), we used permutation-based linear regression analyses to understand how life history and social network factors jointly explain interindividual variation in tendency to interact with humans along a provincial road in South Sulawesi, Indonesia. As our study group spent only a portion of their time in proximity to humans, we also examined how social network structure changes in response to human presence by comparing social networks in the forest to those along the road. We found that sex, individual network position, and associate network position interact in complex ways to influence individual behaviour. Individual variation in tendency to be along the road caused social networks to become less cohesive when in proximity to humans. This study demonstrates that nuanced intragroup analyses are necessary to fully understand and address conservation issues relating to human-wildlife interactions.

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.

Using road patrol data to identify factors associated with carnivore roadkill counts

As the global road network expands, roads pose an emerging threat to wildlife populations. One way in which roads can affect wildlife is wildlife-vehicle collisions, which can be a significant cause of mortality through roadkill. In order to successfully mitigate these problems, it is vital to understand the factors that can explain the distribution of roadkill. Collecting the data required to enable this can be expensive and time consuming, but there is significant potential in partnering with organisations that conduct existing road patrols to obtain the necessary data. We assessed the feasibility of using roadkill data collected daily between 2014 and 2017 by road patrol staff from a private road agency on a 410 km length of the N3 road in South Africa. We modelled the relationship between a set of environmental and anthropogenic variables on the number of roadkill carcasses, using serval (Leptailurus serval) as a model species. We recorded 5.24 serval roadkill carcasses/100 km/year. The number of carcasses was related to season, the amount of wetland, and NDVI, but was not related to any of the anthropogenic variables we included. This suggests that roadkill patterns may differ greatly depending on the ecology of species of interest, but targeting mitigation measures where roads pass through wetlands may help to reduce serval roadkill. Partnering with road agencies for data collection offers powerful opportunities to identify factors related to roadkill distribution and reduce the threats posed by roads to wildlife.

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.

Chimpanzees and death

Information about responses to death in nonhuman primates is important for evolutionary thanatology. This paper reviews the major causes of death in chimpanzees, and how these apes respond to cues related to dying and death. Topics covered include disease, human activities, predation, accidents and intra-species aggression and cannibalism. Chimpanzees also kill and sometimes eat other species. It is argued that, given their cognitive abilities, their experiences of death in conspecifics and other species are likely to equip chimpanzees with an understanding of death as cessation of function and irreversible. Whether they might understand that death is inevitable-including their own death, and biological causes of death is also discussed. As well as gathering more fundamental information about responses to dying and death, researchers should pay attention to possible cultural variations in how great apes deal with death.This article is part of the theme issue 'Evolutionary thanatology: impacts of the dead on the living in humans and other animals'.

Agricultural expansion as risk to endangered wildlife: Pesticide exposure in wild chimpanzees and baboons displaying facial dysplasia

Prenatal exposure to environmental endocrine disruptors can affect development and induce irreversible abnormalities in both humans and wildlife. The northern part of Kibale National Park, a mid-altitude rainforest in western Uganda, is largely surrounded by industrial tea plantations and wildlife using this area (Sebitoli) must cope with proximity to human populations and their activities. The chimpanzees and baboons in this area raid crops (primarily maize) in neighboring gardens. Sixteen young individuals of the 66 chimpanzees monitored (25%) exhibit abnormalities including reduced nostrils, cleft lip, limb deformities, reproductive problems and hypopigmentation. Each pathology could have a congenital component, potentially exacerbated by environmental factors. In addition, at least six of 35 photographed baboons from a Sebitoli troop (17%) have similar severe nasal deformities. Our inquiries in villages and tea factories near Sebitoli revealed use of eight pesticides (glyphosate, cypermethrin, profenofos, mancozeb, metalaxyl, dimethoate, chlorpyrifos and 2,4-D amine). Chemical analysis of samples collected from 2014 to 2016 showed that mean levels of pesticides in fresh maize stems and seeds, soils, and river sediments in the vicinity of the chimpanzee territory exceed recommended limits. Notably, excess levels were found for total DDT and its metabolite pp'-DDE and for chlorpyrifos in fresh maize seeds and in fish from Sebitoli. Imidacloprid was detected in coated maize seeds planted at the edge the forest and in fish samples from the Sebitoli area, while no pesticides were detected in fish from central park areas. Since some of these pesticides are thyroid hormone disruptors, we postulate that excessive pesticide use in the Sebitoli area may contribute to facial dysplasia in chimpanzees and baboons through this endocrine pathway. Chimpanzees are considered as endangered by IUCN and besides their intrinsic value and status as closely related to humans, they have major economic value in Uganda via ecotourism. Identifying and limiting potential threats to their survival such be a conservation priority.

Perceptions of challenges to subsistence agriculture, and crop foraging by wildlife and chimpanzees Pan troglodytes verus in unprotected areas in Sierra Leone

The 2009–2010 Sierra Leone National Chimpanzee Census Project estimated there was a population of 5,580 chimpanzees Pan troglodytes verus distributed across the country, with > 50% occurring outside protected areas. The census also highlighted the significance of competition between people and chimpanzees for resources in areas dominated by farming activities where wild chimpanzees forage on crops. We selected four study areas in two districts in Sierra Leone with high chimpanzee density in habitats dominated by agriculture, far from any protected areas. Our objectives were to assess farmers’ perceptions of the main challenges to their agricultural yields, and the wildlife involved in crop foraging, and their perceptions of chimpanzees in particular, as well as the main crop protection measures used. We conducted 257 semi-structured interviews with local farmers across the four study areas. We found that (1) farmers reported wild animals as the main challenge to their agricultural practices; (2) most complaints concerned cane rats Thryonomys swinderianus, which targeted almost all crop types, especially rice and cassava; (3) chimpanzees reportedly targeted 21 of the 23 crop types cultivated, but did so less often than cane rats, focusing particularly on oil palm, cassava and domestic fruits; (4) overall, chimpanzees were not among the top three most destructive animals reported; (5) chimpanzees were generally perceived as being more destructive than dangerous and as having declined since before the civil war; and (6) the main crop protection measure employed was fencing interspersed with traps. Our findings show the importance of investigating farmers’ perceptions to inform the development of appropriate conservation strategies aimed at promoting coexistence of people and wildlife in degraded landscapes.

Cultural influence of social information use in pedestrian road-crossing behaviours

Social information use is common in a wide range of group-living animals, notably in humans. The role it plays in decision-making could be a key to understanding how social groups make collective decisions. The observation of road-crossing behaviours in the presence of other individuals is an ideal means to study the influence of social information on decision-making. This study investigated the influence of culture on social information used by pedestrians in a potentially dangerous scenario, namely road crossing. We scored the collective crossing of pedestrians at four locations in Nagoya (Japan) and three locations in Strasbourg (France). French pedestrians cross against the lights much more often (41.9%) than Japanese ones (2.1%). Individuals deciding to cross the road were strongly influenced by the behaviour and the presence of other pedestrians, especially in Japan, where a stronger conformism was noted. However, Japanese pedestrians were half as likely to be influenced by social information as their French counterparts when crossing at the red light, as they were more respectful of rules. Men show riskier behaviour than women (40.6% versus 25.7% of rule-breaking, respectively), deciding quickly and setting off earlier than women. Further related studies could help target specific preventive, culture-specific solutions for pedestrian safety.

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.

Collective behaviour of wild Asian elephants in risky situations: how do social groups cross roads?

Among group-living animals, some members may derive benefit by following the decisions of other members. Free-ranging wild Asian elephants in Mudumalai National Park, southern India, must often cross roads and can be disturbed by vehicles. We assessed if measures of road and traffic characteristics serve as indicators of risk, and compared behaviours of different age classes during road-crossing events. More individuals displayed excitable behaviour on wider roads. A larger number of adults entered the road first, which is considered the most dangerous position, compared with immature elephants. Immature individuals tended to move ahead of others on the road, suggesting that it is more important for immature individuals to follow adults at the beginning of a crossing than to follow along for the entire crossing. These findings may suggest that less experienced group members derive benefit by following the decisions of experienced ones under risky situations.

Chimpanzees (Pan troglodytes) Flexibly Use Introduced Species for Nesting and Bark Feeding in a Human-Dominated Habitat

As habitat loss and fragmentation place growing pressure on endangered nonhuman primate populations, researchers find increasing evidence for novel responses in behavior. In western Uganda between the Budongo and Bugoma Forests, chimpanzees (Pan troglodytes schweinfurthii) inhabit a mosaic landscape comprising forest fragments, human settlements, and agricultural land. We recorded nests and feeding evidence of unhabituated chimpanzees in this region over a 12-mo period. We found extensive evidence of nesting in introduced tree species, including eucalyptus (Eucalyptus grandis), guava (Psidium guajava), cocoa (Theobroma cacao), and Caribbean pine (Pinus caribaea). In addition, we found instances of ground nesting, nest reuse, and composite nests constructed from branches of multiple trees. This evidence may indicate a lack of suitable nesting trees or attempts by chimpanzees to nest in areas of riparian forest that allow them to avoid human detection. We also found new evidence for eucalyptus bark feeding by chimpanzees. Such evidence suggests chimpanzees respond flexibly to mitigate anthropogenic pressures in human-dominated landscapes. The limits of such flexibility remain unknown. Further research is needed to examine systematically the factors influencing the use of such resources and to understand better the extent to which chimpanzees can persist while relying on them.

Cars kill chimpanzees: case report of a wild chimpanzee killed on a road at Bulindi, Uganda

Roads have broadly adverse impacts on wildlife, including nonhuman primates. One direct effect is mortality from collisions with vehicles. While highly undesirable, roadkills provide valuable information on the health and condition of endangered species. We present a case report of a wild chimpanzee (Pan troglodytes schweinfurthii) killed crossing a road in Bulindi, Uganda, where chimpanzees inhabit forest fragments amid farmland. Details of the collision are constructed from eyewitness accounts of pedestrians. Physical examination of the cadaver indicated good overall body condition; at 40 kg, the deceased female was heavier than usual for an adult female East African chimpanzee. No external wounds or fractures were noted. Coprological assessment demonstrated infection by several gastrointestinal parasites commonly reported in living wild chimpanzees. Histopathology revealed eosinophilic enteritis and biliary hyperplasia potentially caused by parasite infection. However, eosinophilia was not widely spread into the submucosa, while egg/cyst counts suggested low-intensity parasite infections compared to healthy female chimpanzees of similar age in nearby Budongo Forest. No behavioral indicators of ill health were noted in the deceased female in the month prior to the accident. We conclude that cause of death was acute, i.e., shock from the collision, and was probably unrelated to parasite infection or any other underlying health condition. Notably, this female had asymmetrical polythelia, and, while nursing at the time of her death, had one functioning mammary gland only. In Uganda, where primates often inhabit human-dominated landscapes, human population growth and economic development has given rise to increasing motor traffic, while road development is enabling motorists to travel at greater speeds. Thus, the danger of roads to apes and other wildlife is rising, necessitating urgent strategies to reduce risks. Installation of simple speed-bumps-common on Ugandan roads-would be effective in reducing risks to wildlife, and would also make roads safer for human pedestrians.

Nodular Worm Infections in Wild Non-human Primates and Humans Living in the Sebitoli Area (Kibale National Park, Uganda): Do High Spatial Proximity Favor Zoonotic Transmission?

BACKGROUND

Nodular Oesophagostomum genus nematodes are a major public health concern in some African regions because they can be lethal to humans. Their relatively high prevalence in people has been described in Uganda recently. While non-human primates also harbor Oesophagostomum spp., the epidemiology of this oesophagostomosis and the role of these animals as reservoirs of the infection in Eastern Africa are not yet well documented.

METHODOLOGY/PRINCIPAL FINDINGS

The present study aimed to investigate Oesophagostomum infection in terms of parasite species diversity, prevalence and load in three non-human primates (Pan troglodytes, Papio anubis, Colobus guereza) and humans living in close proximity in a forested area of Sebitoli, Kibale National Park (KNP), Uganda. The molecular phylogenetic analyses provided the first evidence that humans living in the Sebitoli area harbored O. stephanostomum, a common species in free-ranging chimpanzees. Chimpanzees were also infected by O. bifurcum, a common species described in human populations throughout Africa. The recently described Oesophagostomum sp. found in colobine monkeys and humans and which was absent from baboons in the neighboring site of Kanyawara in KNP (10 km from Sebitoli), was only found in baboons. Microscopic analyses revealed that the infection prevalence and parasite load in chimpanzees were significantly lower in Kanyawara than in Sebitoli, an area more impacted by human activities at its borders.

CONCLUSIONS/SIGNIFICANCE

Three different Oesophagostomum species circulate in humans and non-human primates in the Sebitoli area and our results confirm the presence of a new genotype of Oesophagostomum recently described in Uganda. The high spatiotemporal overlap between humans and chimpanzees in the studied area coupled with the high infection prevalence among chimpanzees represent factors that could increase the risk of transmission for O. stephanostomum between the two primate species. Finally, the importance of local-scale research for zoonosis risk management is important because environmental disturbance and species contact can differ, leading to different parasitological profiles between sites that are close together within the same forest patches.