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. 2023 Oct 20;10(2):13-23.
doi: 10.5194/pb-10-13-2023. eCollection 2023.

Djaffa Mountains guereza (Colobus guereza gallarum) abundance in forests of the Ahmar Mountains, Ethiopia

Chala Adugna Kufa  1   2 , Afework Bekele  1 , Anagaw Atickem  1 , Dietmar Zinner  3   4   5
Affiliations

Djaffa Mountains guereza (Colobus guereza gallarum) abundance in forests of the Ahmar Mountains, Ethiopia

Chala Adugna Kufa et al. Primate Biol. .

Abstract

The size and density of a population are essential parameters in primate ecology and conservation. Such information, however, is still scarce for many forest primate species. The Djaffa Mountains guereza (Colobus guereza gallarum) is an endemic Ethiopian taxon for which data about its distribution and population size are missing. Therefore, we aimed to estimate the abundance and population size of the Djaffa Mountains guereza in four forests in the Ahmar Mountains southeast of the Ethiopian Rift Valley. We conducted line-transect surveys in the forests. Within an area of 183 km2, we sampled 19 transects covering a distance of 75.9 km. We encountered 73 guereza clusters which most likely represent social groups. Since the detection distances and cluster sizes did not differ among the four forests, we applied a conventional distance sampling (CDS) model and estimated a population density of 20.6 clusters per square kilometer, i.e., 109.6 individuals per square kilometer or 20 061 individuals within the complete study area. This abundance is relatively high compared to other C. guereza taxa. However, given that the habitat and population of C. g. gallarum are already highly fragmented, further monitoring of the population and exploration of the possibilities of reconnecting its habitat should be priorities for the conservation of this taxon.

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Conflict of interest statement

At least one of the (co-)authors is a member of the editorial board of Primate Biology. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.

Figures

Figure 1
Figure 1
Male Djaffa Mountains guereza (Colobus guereza gallarum) in Hades Forest, 2021 (photo: Chala A. Kufa).
Figure 2
Figure 2
Geographic position of the study area in the Ahmar Mountains, Ethiopia, and locations of the four forest sites where we did the line-transect surveys on Djaffa Mountains guereza (DMG): Dindin Forest (DDF), Jallo Kuni-Muktar Wildlife Sanctuary (JKF, comprising two sites nearby: Jallo Sorroro Torgam – JST – and Kuni-Muktar Wildlife Sanctuary – KMWS), Hades Forest (HDF), and Gara Muleta Forest (GMF) (source of protected area shapefiles: UNEP-WCMC and IUCN, 2023).
Figure 3
Figure 3
Positions of transects (yellow lines) within the four forests used for DMG surveys from 2020 to 2021: DDF, JKF, HDF, and GMF. The maps show the extents of the study sites for each forested area. Base map: ©Google Earth.
Figure 4
Figure 4
Frequency histogram of observed perpendicular distances truncated at 50 m and the detection function (red line) for DMG (half-normal key function).
See this image and copyright information in PMC

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