Population Status, Distribution and Habitat Association of the Beisa oryx (Oryx beisa beisa) and Its Interactions with Sympatric Species in Alledeghi Wildlife Reserve, Ethiopia
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Date
2016-07
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Addis Ababa University
Abstract
Individual count of Beisa oryx (Oryx beisa beisa) was conducted in Alledeghi Wildlife
Reserve during September - December, 2015 which covered both wet and dry seasons.
Transect count method was used to determine the current population size, group size,
demographic composition, seasonal distribution and habitat association of Beisa oryx as well
as population status of the two co-occurring wild ungulates (Soemmering’s gazelle and
Gerenuk). Twelve parallel sampling transects were systematically placed perpendicular to the
baseline with a minimum distance of 2 km apart .The total transect length was 167 km, and
given that width of 0.6 km on both sides of each transect, about 200 km2 area (47.6% of the
census zone) was sampled during the study. The density of animals observed per transect was
used to calculate mean population density. Mean differences in population structure of the
species was compared using Tukey’s multiple mean tests. Habitat association and seasonal
variation of Beisa oryx and the other two co-occurring ungulates were compared using Chi
square test. The population estimate of Beisa oryx was 722. There was a decrease in
individuals by 22% compared to the 2009 and 2010 estimates. There was a considerable
difference in the number of animals observed during the wet and dry seasons (χ2 = 1252.934 df
= 1 P <0.001). A total of 101 herds of Beisa oryx were observed (67 and 34 herds during wet
and dry seasons, respectively). The difference was statistically significant (F1, 99 = 79.17, P
<0.001). Age structure was mainly dominated by adults (85%), followed by sub-adults (13%).
The sex ratio was dominated by females (55.6%). Mean population density of Beisa oryx and
the two co-occurring ungulates observed in different habitat types excluding seasons showed
non-significant difference.
Key words: Alledighe Wildlife Reserve, Beisa oryx, Density, Herd size, Habitat, Season
Description
Keywords
Alledighe Wildlife Reserve, Beisa Oryx, Density, Herd Size, Habitat, Season