Habitat Quality Assessed with a Habitat Suitability Model and Habitat Selection Revealed by Isodar Analysis for the Mountain Nyala (Tragelaphus buxtoni) in Munessa, Ethiopia
Keywords:
activity density, habitat suitability models, isodars, mountain nyala, MunessaAbstract
Knowledge of habitat quality and adaptive habitat selection behavior of endangered species such as the mountain nyala (Tragelaphus buxtoni) can be invaluable for conservation and management, but quantitative information is lacking. The objectives of this study were to: (1) investigate the environmental variables that determine the suitable habitats for the mountain nyala, and (2) apply the isodar technique to look for density-dependent habitat selection behavior in mountain nyala. Following transects aligned through three major habitat types, environmental variables and activity densities of mountain nyala were estimated. The fieldwork was carried out in the wet and dry season in Munessa, Ethiopia. In addition, with the help of a spotlight, night-time mountain nyala censusing was carried out during the dry season. The result revealed that mountain nyala didn’t show density-dependent habitat selection behavior in the wet season. However, during the dry season, the natural forest was the most suitable habitat for the mountain nyala, when crown diameter of trees and abundance of shrubs affected the habitat suitability. Significant isodars were obtained only across season and dry season comparisons between natural forest versus plantation and natural forest versus cleared vegetation habitats. The regression analyses revealed that the natural forest was qualitatively, but not quantitatively, more suitable than both the plantation and the cleared vegetation habitats. The isodars suggested that the strength of density-dependence was lower in the natural forest than either in the plantation or the cleared vegetation habitat. Spotlight censusing revealed that mountain nyala selected the cleared vegetation habitat during the night-time. The study demonstrated that habitat suitability models are important tools to evaluate the habitat quality for mountain nyala. Isodar analyses support the habitat suitability models by increasing our understanding on the qualitative and quantitative differences in density-dependent habitat selection by mountain nyala and thereby to enhance their conservation and management.
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