Abstract
Increased human activities such as commodity-led deforestation, extension of agriculture, urbanization, and wildfires are major drivers of forest loss worldwide. In Cameroon, these activities cause a loss of suitable primate habitat and could ultimately threaten the survival of chimpanzees (Pan troglodytes). We derived independent estimates of the population size of the Endangered Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti) in Kom-Wum Forest Reserve, Cameroon, and surrounding unprotected forest areas through 1) direct observations, 2) camera trapping, 3) distance sampling, 4) marked nest counts, and 5) standing crop nest counts. In addition, we georeferenced signs of chimpanzee and human activity along line transects. We used a generalized linear mixed model to predict the occurrence of chimpanzees in response to edge length (measured as the perimeter of core forest patches), core area of forest patches (measured as area of forest patches beyond an edge width of 100 m), habitat perforation (measured as the perimeter of nonforested landscape within core forest patches), patch size(measured as area of forest patches), and forest cover. Chimpanzee density estimates ranged from 0.1 (direct observation) to 0.9 (distance sampling) individuals km−2 depending on estimation method with a mean nest group size of 7 ± 5.4 (SD). The mean encounter rate for signs of chimpanzee activity was significantly higher in mature forests (2.3 signs km−1) than in secondary forests (0.3 signs km−1) and above 1000 m elevation (4.0 signs km−1) than below 1000 m (1.0 signs km−1). The mean encounter rate for signs of human activity was significantly higher in secondary (8.0 signs km−1) than in mature forests (0.9 signs km−1). Secondary forests, habitat perforation, and edge length had a significant negative effect on the occurrence of chimpanzee signs. Overall, human activity and forest degradation affected the number of observed chimpanzee signs negatively. Regular antipoaching patrols and reforestation programs in degraded areas could potentially reduce threats to populations of endangered species and may increase suitable habitat area.
Highlights
Increasing human activities such as commodity-led deforestation, extension of agriculture, urbanization, and wildfires are major drivers of forest loss worldwide (Curtis et al 2018)
We considered all nests (N = 271) in standing crop nest count (SCNC) analysis, as it identifies nest decay rate (Plumptre and Reynolds 1996) but only nests encountered during the first transect survey (N = 158) for distance sampling analysis
This study shows that forest degradation resulting from human activity had a significant negative impact on the encounter rate of chimpanzee signs in Kom-Wum Forest Reserve, Cameroon
Summary
Increasing human activities such as commodity-led deforestation, extension of agriculture, urbanization, and wildfires are major drivers of forest loss worldwide (Curtis et al 2018). These activities cause habitat loss, fragmentation, and destruction of natural ecosystems (Estrada et al 2017; Haddad et al 2015). Some primates show flexibility in human dominated landscapes (McLennan et al 2017), habitat loss and degradation have resulted in a decline of about 75% of the world’s primate species, of which 60% are endangered (Estrada et al 2017, 2019) This situation makes it crucial to measure threats to primate populations by determining the population status and trends in density and distribution (Kühl et al 2008)
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