A Comparison of Population Ecology of Beisa Oryx in Awash National Park and Alledeghi Wildlife Reserve, Ethiopia
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Date
2005-07
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Addis Ababa Universty
Abstract
Field study on a comparison of population ecology of Beisa oryx (Oryx beisa) was conducted
eveiy month from October to March, 2005 for six months in Ulala Sala and adjacent areas in
Awash National Park and for five months (November to March, 2005) in the selected study site
in Alledeghi Wildlife Reserve. The result indicated that an average of 220 individual of Beisa
oryx in Awash National Park and 335 individuals of Beisa oryx in the selected study site in
Alledeghi Wildlife Reserve. The mean group sizes of 17.6 individuals were found in the selected
study site in AWR, and 13.9 individuals were at Illala Sala and adjacent areas in Awash National
Park. The difference in mean group sizes of Beisa oryx between the two study areas was not
significant. However, they were found to be significant for mixed herds (P=0.008). The group
structure of the animals varied with seasons in Awash National Park and the selected study site in
Alledeghi Wildlife Reserve. Large herds were frequently observed during short rainy season in
grassland and smaller groups during the dry season in both study sites. Variation in monthly
group size did not exist in both study sites, The most cohesive herd is that of the female and her
immediate young. Single males were most common at Illala Sala and its adjacent areas in Awash
National Park and male-female group in the selected study site in Alledeghi Wildlife Reserve.
The mean number of calves in Awash National Park and the selected study site in Alledeghi
Wildlife Reserve showed significant differences between the two seasons at 0.05 level of
significance (P=0.039 and P~0.014). The females during dry and wet seasons are more numerous
than the males in both study sites. The animals were observed utilizing the grassland, shrub
grassland and wooded grassland habitats in both seasons in both study sites, however, there was
more utilization of grassland habitat (72.8% in ANP and 89.1% in Alledeghi Wildlife Reserve).
Distribution of group sizes in grassland and shrub grassland habitats of the two study sites
showed a high significant differences (P=0.003 and P=0.025, respectively). Grassland habitat was
the best preferred habitat of Beisa oryx. The changes in the distribution of habitat preference in
the two seasons showed that no significant differences. However, there was slightly significant
differences in the group sizes in grassland habitat of ANP between the two seasons (P=0.047).
Seasonal home range size varied in ANP. Wet season home range size (31km ) was larger than
that of dty season (25km ), Minimum Convex Polygon (MCP) method was used to calculate the home range. On the average about 52.61 % of Beisa oryx daytime were spent in feeding and
36.65%) in rest i .e. standing and lying down.
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Keywords
Beisa Oryx