Chimpanzees balance resources and risk in an anthropogenic landscape of fear

Abstract

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.

Figure 1

Map and location of the study area in Caiquene–Cadique, Cantanhez National Park, Guinea-Bissau, West Africa. (a) Cantanhez National Park includes a road network and approximately 200 villages and settlements. (b) Map of Caiquene–Cadique study area showing the 21 camera trap sampling sites and respective 200 m buffers where availability of chimpanzee foods was quantified. The forest block is shown in green and the heterogeneous matrix outside the forest block includes cashew orchards and shifting cultivation fields shown in pink, roads, three villages, five settlements and four abandoned villages. (c) Estimated home range of Caiquene–Cadique chimpanzees using 100% minimum convex polygon (MCP) analysis of 1380 direct and indirect observations of chimpanzees collected between 2013 and 2018. MCP analyses were ran using the R package ADEHABITATHR version 0.4.19. The base layers in a-c panels consist of modified Copernicus Sentinel-2 data from 25 January 2017 (RGB colour and grey scale). Sentinel-2 imagery was downloaded from the Sentinel Hub, Sinergise Ltd (https://www.sentinel-hub.com/). All maps were created using QGIS version 3.10.5 (https://www.qgis.org).

Figure 2

Comparison of relative detection frequency (RDF) (a) and temporal activity patterns (b) between chimpanzees and humans during a 12-month period across 21 camera trap sampling sites in Caiquene–Cadique. ∆ is the coefficient of overlap^,. Values in brackets represent 95% confidence intervals.

Figure 3

Monthly variation in availability of chimpanzee key food sources in 2017–2018 in Caiquene–Cadique, Cantanhez National Park. Frequency of availability is the mean availability index of resource or group of resources k scaled by the total availability during the study period (12 months). Village foods include the combined availability of orange, lime and papaya ripe fruit; village and abandoned settlement foods include the combined availability of mango and baobab ripe fruit; wild fruit include the combined availability of ripe fruit of ten important chimpanzee food species (Supplementary Figs. S2–S3).

Figure 4

Predicted chimpanzee intensity of space use across their home range in Caiquene–Cadique in two time periods. December 2017 corresponded to the peak in availability of village fruits (orange, lime and papaya), June 2017 coincided with the peak in mango ripe fruit and wild fruits (Fig. 3). Circles indicate the location of villages (Cadique Nalu and Caiquene) and small settlements (unlabelled smaller circles); crosses represent abandoned villages. Prediction raster layers were created using the R package RASTER version 3.4-5. Figures were created using QGIS (https://www.qgis.org). See Movie S1 for predictions of chimpanzee intensity of space use across the 12-month study period.

Figure 5

Chimpanzees in Caiquene–Cadique often use the roads located at the centre of their home range and frequently feed on cultivated foods. The camera trap images (right) show a chimpanzee entering Caiquene village to feed on orange in October 2017.