Assessment of in situ nest decay rate for chimpanzees (Pan troglodytes ellioti Matschie, 1914) in Mbam-Djerem National Park, Cameroon: implications for long-term monitoring

Serge Alexis Kamgang,Mary Katherine Gonder,Tuneu Corral Carme,Ekwoge Enang Abwe,Kadiri Serge Bobo,Brice Sinsin

doi:10.1007/s10329-019-00768-3

Serge Alexis Kamgang, Mary Katherine Gonder + Show 4 more

Open Access

https://doi.org/10.1007/s10329-019-00768-3

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Abstract

Accurate assessment of great ape populations is a prerequisite for conservation planning. Indirect survey methods using nest and dung, and a set of conversion parameters related to nest decay rates, are increasingly used. Most surveys use the standing crop nest count (SCNC) method, whereby nests are counted along transects and the estimated nest density is converted into chimpanzee density using an often non-local nest decay rate. The use of non-local decay rate is thought to introduce substantial bias to ape population estimates given that nest decay rates vary with location, season, rainfall, nest shape, and tree species used. SCNC method has previously been applied in Mbam-Djerem National Park (MDNP) in Cameroon, for chimpanzee surveys using a non-local nest decay rate. This current study aimed to measure a local nest decay rate for MDNP and implications for chimpanzee population estimates in the MDNP. The mean nest decay rate estimated using a logistic regression analysis was 127 [95% CI (100–160)] days. Moreover, the results suggested that rainfall strongly influenced the nest decay rate over the early stage of the lifetime of the nests. The study confirms that estimates of chimpanzee density and abundance using non-local decay rates should be treated with caution. Our research emphasized the importance of using local nest decay rates and other survey methods which do not depend on decay rates to obtain more accurate estimates of chimpanzee densities in order to inform conservation strategies of these great apes in MDNP.

Highlights

2 Ministry of Forestry and Wildlife, Yaoundé, Cameroun 3 Department of Animal Biology, Plant Biology and Ecology, Autonomous University of Barcelona, Bellaterra, 08193 Barcelona, Spain (Guinness 2010) and sheltering most populations of African great apes (Fruth and Hohmann 1996; Williamson et al 2013). This forest and the fauna inhabiting it are threatened by habitat loss, fragmentation, bushmeat hunting, climate change, emerging infectious diseases, and other activities such as logging and mining
In Model 1, X is non-transformed while in Model 2, X is negative-inverse transformed and in Model 3, X is negativereciprocal root-transformed of chimpanzees in the Mbam-Djerem National Park (MDNP), which could to be useful for the long-term monitoring of populations across the park and adjacent areas
Our study aimed at assessing the nest decay rate for MDNP, which could be used to assess chimpanzee density in the area instead of using a non-local nest decay rate

Summary

Introduction

Autonomous University of Barcelona, Bellaterra, 08193 Barcelona, Spain (Guinness 2010) and sheltering most populations of African great apes (Fruth and Hohmann 1996; Williamson et al 2013) This forest and the fauna inhabiting it are threatened by habitat loss, fragmentation, bushmeat hunting, climate change, emerging infectious diseases, and other activities such as logging and mining Given its more limited geographical distribution and numbers, P. t. ellioti merits more urgent conservation action (Morgan et al 2011)

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