Assessment of Chimpanzee (Pan troglodytes) population and habitat in Kwitanga Forest, western Tanzania.
Date
2008-04-11T06:17:46Z
Authors
Ndimuligo, Sood A.
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Abstract
This study examined three aspects: estimation of chimpanzee (Pan troglodytes) population size
using nest density as a proxy, description of the plant community and assessment of human impacts
to chimpanzee habitat in Kwitanga forest, western Tanzania. The overall estimated mean
chimpanzee population density was 0.69(0.31–1.54) individuals per km2 and a mean population
size of 15(7-34) weaned individual chimpanzees in the forest. The natural vegetation in Kwitanga
consists mainly of miombo woodland, dominated by Brachystegia-Julbernadia tree species, poorly
developed riverine forest, cultivated land and oil palm plantation. Assessment of the abundance of
nesting trees in the landscape revealed that tree species composition along transects were
significantly different to nesting sites (trees surrounding the actual tree that contains a nest)
(Kolmogorov-Smirnov test: KSa = 2.0148; D = 0.3934: P < 0.05). Thirteen tree species were used
for nests; the most used species were B. bussei, B. utilis, B. mirophylla, J. globiflora and P.
tinctorius. The assessment on scarcity of nesting tree species in the landscape revealed that such
species were abundant by proportion (KSa = 0.5883; D = 0.2308; P > 0.05), and species-specific
density (Wilcoxon Z-test: Z = - 1.0265; U1= U2 = 13; p > 0.05). Trees in size classes between 10 cm
and 40 cm diameter dominated the forest. The study on size suitability showed that there were
significant differences (using ANOVA with Tukey’s HSD post hoc test) in tree diameter size
among the three groups: transects, nesting sites, and nesting trees. Nesting trees were unique in size
to the other two groups. The mean size of nesting trees was larger compared to both nesting sites
and transects (27 ± 1.1 cm; 23 ± 0.7 cm and 18 ± 0.5 cm) respectively. Similar differences existed
in tree densities between nesting sites and transects (Wilcoxon test: Z = 1.8104; U1 = 46, U2 = 61:
P< 0.05), with nesting sites presenting higher tree density. These results indicated scarcity in trees
of a size suitable for nesting, and nesting materials.. Nesting tree species occur in the landscape,
though their sizes and higher tree species density at nesting sites determined nesting location choice
and specific nesting tree selection. Tree felling indicated by stumps was the major threat to the
availability of suitable nesting trees, with a higher encounter rate of seven (7) stumps per km and
contributed 48 % of total human disturbance, followed by established fields in the forest. The
analysis on the direction of the major threat to the habitat revealed that, the main road cutting
through the forest is a key to tree felling. Encountered stumps declined with increased distance
from the main road towards the forest edge, with more stumps in between 0 -100 m (P< 0.05; log
(Y) = 1.7017 - 0.0007(X); R2 = 0.6705). Such findings implied that the prison inside the forest is a
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major cause of habitat decline. At least 30 tree species constituted the group of stumps. Julbernadia
globiflora and Uapaca kirkiana were the most felled tree species. High human disturbances
implied by higher human activities encounter rates, and overlapping tree size classes between felled
and standing trees were the major threats to chimpanzee habitat in Kwitanga forest. High
chimpanzee density and population size estimates in Kwitanga forest renders this area a potential
for conservation in the Greater Gombe Ecosystem Program. Kwitanga being the largest remaining
natural forest near Gombe National Park, it will increase habitat size to allow chimpanzee dispersal
and feeding area. Such movements across heterogeneous landscapes would allow long-term
survival through reduced competition, increased genetic diversity and ability to absorb minimal
environmental shocks
Description
Keywords
Chimpanzee, Population estimate, Habitat degradation, Conservation