Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

used for comparison. The study revealed that the total population size of T. buxtoni in the study
area varied between 887 and 965 (95% CI) antelope, representing a reduction by about 48% from
what was reported in 1980’s. However, due to contraction of its habitat, the average densities of
mountain nyala have shown an increase from what was reported in 1980s. The population structure
consisted of 58% adults, 25% sub-adults, 9% juveniles and 5% calves, with a sex ratio of 2:1 (♀:♂).
Significance differences in most parameters such as density, age-group composition, recruitment
and sex ratios were observed between the population in the Dinsho sanctuary and that found in the
Gaysay/Adelay area. No conclusive evidence was found to suggest that demographic characteristics
of the species have made a significant contribution on observed decline in population size since the
1980s, because many life history traits (e.g., age structure, and group size) were similar between
1983-85 and 2003-05 periods.
Habitat Components
The general aim this research was to describe the basic components of the mountain nyala habitat
and assess how mountain nyala relates to them. The study area was divided into three parts, based
on the dominant vegetation and relative location. Random sampling in plots (100 m2 ) placed along
transects was used, with 69 plots were Gaysay grassland, 71 in Adelay woodland and 31 in Dinsho
woodland areas. The major parameters measured were: ground cover; incidence of browsing;
vegetation height; slope; altitude; canopy openness; visibility; and, tree density. Indices of habitat
suitability and use were based on mountain nyala abundance and incidences of browsing. Gaysay
grassland was found to be the most suitable while Dinsho woodland the least suitable habitat to
mountain nyala. Seven types of vegetation were identified in Gaysay grassland area with open
grassland vegetation covering the largest proportion (58%). In Dinsho woodland, five vegetation
groups were identified with Hygenia and Juniperus woodland covering the largest proportion (68%).
In Adelay woodland, Hygenia and Juniperus woodland covered the largest proportion (65%). When
all vegetation types are pooled together, levels of browsing decreased with increase in vegetation
height and increased with increase in patch size. However, positive correlations were reported
between levels of browsing and vegetation height for Helichrisum species and while negative
correlations were recorded for Artemesia and open grassland in terms of patch size. The study also
revealed that greater availability of vegetation does not necessarily result in higher use by mountain
nyala.
Interactions between Livestock and Mountain Nyala Habitat
The main aim of this study was to assess how the presence of livestock and local people affect
habitat availability, composition and structure to mountain nyala. Also, the research investigated
how livestock use of the area affects mountain nyala habitat use and preference. Parameters such as
presence and/or absence of both livestock and mountain nyala dung, levels of browsing, vegetation
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