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

Abstract

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.

Extensive Overlap in the Selection of Wild Fruits by Chimpanzees and Humans: Implications for the Management of Complex Social-Ecological Systems

“…resistant and survive slash-and-burn activities, and hence this species is found frequently in cultivated and fallow areas as well as forest edges. This situation is representative of that found in many other locales in West Africa (e.g., Humle and Matsuzawa, 2004;Garriga et al, 2019) and special attention should be given to the national and regional conservation of this shared resource.…”

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

“…Habitat fragmentation and agricultural expansion are linked to chimpanzee population declines throughout tropical Africa (Arcus Foundation, 2015). Nevertheless, chimpanzees show resilience to some habitat modifications, including agriculture, and can persist outside protected areas in fragmented, mosaic landscapes near people, provided they are not heavily hunted (Dunnett, van Orshoven & Albrecht, 1970; Garriga et al, 2019; Hockings & McLennan, 2016; McCarthy et al, 2015; McLennan, 2008). Their diets are broadly omnivorous (e.g., Goodall, 1986; Nishida & Uehara, 1983), but they prefer to eat fleshy fruits (Watts, Potts, Lwanga, & Mitani, 2012a; Wrangham, Conklin‐Brittain, & Hunt, 1998).…”

The macronutrient composition of wild and cultivated plant foods of West African chimpanzees (Pan troglodytes verus) inhabiting an anthropogenic landscape

“…Oil palm trees clearly provide the chimpanzees with high-quality food sources, all of which are available year-round (Bryson-Morrison et al, 2016). These findings provide nutritional support for the oil palm serving as a potentially critical resource for chimpanzees residing in human-impacted landscapes across West Africa, particularly, as emerging evidence suggests that oil palm trees are utilized extensively for food by such populations (Bessa et al, 2015;Brncic, Amarasekaran, & McKenna, 2010;Garriga et al, 2019;Humle & Matsuzawa, 2004;Yamakoshi, 1998). Nevertheless, differences have been reported in the extent of oil palm use and the number of parts consumed by chimpanzee populations in varying habitat types across Africa, and these differences are not always readily explained by environmental variables (Humle & Matsuzawa, 2004).…”

“…Bossou chimpanzees heavily depend on the oil palm for food (up to 15.9% of annual feeding time: Yamakoshi, 1998) and nesting (Humle & Matsuzawa, 2004). Recent evidence suggests that oil palm trees are also an important food and nesting resource for other chimpanzee communities residing in human‐impacted areas across West Africa (Guinea‐Bissau: Bessa, Sousa, & Hockings, 2015; Sousa, Barata, Sousa, Casanova, & Vicente, 2011; Côte d'Ivoire: Humle & Matsuzawa, 2004; Sierra Leone: Garriga et al, 2019; Guinea: Leciak, Hladik, & Hladik, 2005). The macronutrient content of the oil palm fruit and nut kernel, both of which are used in the production of palm oils, has been previously described (Agunbiade, Wiseman, & Cole, 1999; Akpanabiatu, Ekpa, Mauro, & Rizzo, 2001; Bora, Rocha, Narain, Moreira‐Monteiro, & Moreira, 2003; Kok, Ong‐Abdullah, Ee, & Namasivayam, 2011).…”