An empirical evaluation of camera trapping and spatially explicit capture‐recapture models for estimating chimpanzee density

Abstract

Empirical validations of survey methods for estimating animal densities are rare, despite the fact that only an application to a population of known density can demonstrate their reliability under field conditions and constraints. Here, we present a field validation of camera trapping in combination with spatially explicit capture-recapture (SECR) methods for enumerating chimpanzee populations. We used 83 camera traps to sample a habituated community of western chimpanzees (Pan troglodytes verus) of known community and territory size in Taï National Park, Ivory Coast, and estimated community size and density using spatially explicit capture-recapture models. We aimed to: (1) validate camera trapping as a means to collect capture-recapture data for chimpanzees; (2) validate SECR methods to estimate chimpanzee density from camera trap data; (3) compare the efficacy of targeting locations frequently visited by chimpanzees versus deploying cameras according to a systematic design; (4) evaluate the performance of SECR estimators with reduced sampling effort; and (5) identify sources of heterogeneity in detection probabilities. Ten months of camera trapping provided abundant capture-recapture data. All weaned individuals were detected, most of them multiple times, at both an array of targeted locations, and a systematic grid of cameras positioned randomly within the study area, though detection probabilities were higher at targeted locations. SECR abundance estimates were accurate and precise, and analyses of subsets of the data indicated that the majority of individuals in a community could be detected with as few as five traps deployed within their territory. Our results highlight the potential of camera trapping for cost-effective monitoring of chimpanzee populations.

Distance sampling with camera traps

“…; Després‐Einspenner et al . ). However, multiple research objectives can be addressed, and useful data for multiple species obtained, if CTs are deployed according to a randomised design (MacKenzie & Royle ; Wearn et al .…”

“…We used point transect DS methods to estimate the density of Maxwell's duikers within the territory of the ‘east group’ habituated chimpanzee community in Taï National Park, Côte d'Ivoire (Després‐Einspenner et al . ; Fig. a).…”

Seasonal Variation in Physiology Challenges the Notion of Chimpanzees (Pan troglodytes verus) as a Forest-Adapted Species

“…For example, it is well established that chimpanzees in savanna habitats occur at lower densities than chimpanzees in more heavily forested habitats (e.g., Baldwin et al, 1982;Pruetz et al, 2002;Matthews and Matthews, 2004;Kouakou et al, 2009;Potts et al, 2009;Arandjelovic et al, 2011;Després-Einspenner et al, 2017). By definition, savanna-mosaic habitats have lower tree density and diversity than habitats with continuous forest cover (Crowther et al, 2015), which in turn is expected to necessitate larger chimpanzee home range size to maintain dietary requirements (Mitani and Rodman, 1979;Baldwin et al, 1982;Pruetz and Bertolani, 2009).…”

Listening and watching: Do camera traps or acoustic sensors more efficiently detect wild chimpanzees in an open habitat?

“…For instance, CT allows for individual identification, necessary to extract information on population abundance (e.g. Després‐Einspenner et al, ).…”

“…Seasonality influences activity patterns, ranging and feeding behaviour of chimpanzees (Doran, ), and may consequently influence chimpanzee detectability with CT and PAM. CT studies on chimpanzees have been conducted to study uncommon behaviour, for example stone throwing (Kühl et al, ) and crab hunting (Koops et al, ), but also for abundance and density estimation (Cappelle, Després‐Einspenner, Howe, Boesch, & Kühl, ; Després‐Einspenner, Howe, Drapeau, & Kühl, ) among others. Only a few studies have employed PAM with chimpanzees; those have focused on group ranging and territory use (Kalan et al, , ) and temporal patterns of vocalizations (Piel, ).…”