Ape Abundance and Habitat Use in the Goualougo Triangle, Republic of Congo |
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| Authors: | David Morgan Crickette Sanz Jean Robert Onononga Samantha Strindberg |
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| Institution: | (1) Cambridge University, Wildlife Conservation Society, Brazzaville, Congo;(2) Max Planck, Institute for Evolutionary Anthropology, Leipzig, Germany;(3) Wildlife Conservation Society, Brazzaville, Congo;(4) Living Landscapes Program, Wildlife Conservation Society, Bronx, New York, USA |
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| Abstract: | Chimpanzee (Pan troglodytes troglodytes) and western gorilla (Gorilla gorilla gorilla) populations in central Africa are rapidly declining as a result of disease epidemics, commercial bushmeat hunting, and habitat
destruction. Our main objective was to estimate the absolute abundance and habitat utilization of chimpanzees and gorillas
in the intact forests of the Goualougo Triangle in the Republic of Congo, and in an adjacent area in which selective logging
will take place in the near future. The estimates provide a unique baseline for apes inhabiting an undisturbed environment.
A second objective was to compare estimates of abundance and patterns of habitat utilization generated by different techniques:
1) distance sampling of individual ape nests and nest sites along line transects, 2) direct observations of apes during reconnaissance
surveys, and 3) observations of ape traces during reconnaissance surveys. We completed a total of 222 km of line transect
surveys in 4 sampling areas, resulting in overall density estimates of 1.53 chimpanzees/km2 and 2.34 gorillas/km2 from nest sites. We generated a density estimate of 2.23 chimpanzees/km2 from direct observations during reconnaissance surveys of a semihabituated community in 1 of the 4 sampling areas. Habitat
use profiles that nest surveys depicted on transects differed from those of direct observations and traces we encountered
on reconnaissance surveys. We found the highest overall abundance of chimpanzee nests in monodominant Gilbertiodendron forest, whereas our direct observations showed that chimpanzees preferred mixed species forest. Transects that traversed
the core area of the community range had the highest encounter rates of chimpanzee nests and nest sites. Gorilla nests on
transects showed a preference only for mixed species forest with an open canopy, but direct observations and traces on reconnaissance
surveys clearly indicated that gorillas use several habitat types. We conclude by evaluating the precision of these nest surveys
and our ability to detect future trends in ape densities in the Goualougo Triangle.
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| Keywords: | abundance ape chimpanzee density direct observation distance sampling gorilla habitat utilization line transect surveys reconnaissance surveys |
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