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We studied the habitat use of mountain nyala Tragelaphus buxtoni in the northern edge of the Bale Mountains National Park, Ethiopia. The aims of this study were to: (1) measure and quantify habitat-specific stem bite diameters of mountain nyala foraging on common natural plant species in two major habitat types (i.e. grasslands versus woodlands), and (2) quantify the bite rates (number of bites per minute) and the activity time budgets of mountain nyala as functions of habitat type and sex-age category. We randomly laid out three transects in each habitat type. Following each transect, through focal animal observations, we assessed and quantified stem diameters at point of browse (dpb), bite rates, and time budgets of mountain nyala in grasslands versus woodlands. Stem dpb provide a measure of natural giving-up densities (GUDs) and can be used to assess foraging costs and efficiencies, with greater stem dpb corresponding to lower costs and greater efficiencies. The results showed that stem dpb, bite rates, induced vigilance, and proportion of time spent in feeding differed between habitats. In particular, mountain nyala had greater stem dpb, higher bite rates, and spent a greater proportion of their time in feeding and less in induced vigilance in the grasslands. In addition, adult females had the highest bite rates, and the browse species Solanum marginatum had the greatest stem dpb. Generally, grasslands provide the mountain nyala with several advantages over the woodlands, including offering lower foraging costs, greater safety, and more time for foraging. The study advocates how behavioural indicators and natural GUDs are used to examine the habitat use of the endangered mountain nyala through applying non-invasive techniques. We conclude that the resulting measures are helpful for guiding conservation and management efforts and could be applicable to a number of endangered wildlife species including the mountain nyala [Current Zoology 59 (6) : 707–717, 2013].

Populations of the endangered mountain nyala Tragelaphus buxtoni are significantly threatened by the loss of critical habitat. Population estimates are tentative, and information on the species’ distribution and available habitat is required for formulating immediate management and conservation strategies. To support management decisions and conservation priorities, we integrated information from a number of small-scale observational studies, interviews and reports from multiple sources to define habitat parameters and create a habitat quality model for mountain nyala in the Bale Mountains. For our analysis, we used the FunConn model, an expertise-based model that considers spatial relationships (i.e., patch size, distance) between the species and vegetation type, topography and disturbance to create a habitat quality surface. The habitat quality model showed that approximately 18,610 km2 (82.7% of our study area) is unsuitable or poor habitat for the mountain nyala, while 2,857 km2 (12.7%) and 1,026 km2 (4.6%) was ranked as good or optimal habitat, respectively. Our results not only reflected human induced habitat degradation, but also revealed an extensive area of intact habitat on the remote slopes of the Bale Mountain’s southern and southeastern escarpments. This study provides an example of the roles that expert knowledge can still play in modern geospatial modeling of wildlife habitat. New geospatial tools, such as the FunConn model, are readily available to wildlife managers and allow them to perform spatial analyses with minimal software, data and training requirements. This approach may be especially useful for species that are obscure to science or when field surveys are not practical [Current Zoology 58 (4): 525–535, 2012].

We studied the population dynamics of endangered mountain nyala Tragelaphus buxtoni between 2003–2005 in the Bale Mountains National Park. Line-transect sampling and total count methods were used to gather data on demographics and movement patterns. The population’s age-group composition was 58% adults, 25% sub-adults, 9% juveniles, 5% calves and 3% unidentified with a female-male sex ratio of 2:1. Population density was found to be significantly different between the two sub-populations (Dinsho Sanctuary and Gaysay/Adelay). A significant difference was found for age-group composition across the two sub-populations except adult females, sub-adult males and calves. The Dinsho sub-population was an isolated group. Separation and containment of the mountain nyala population could have negatively affected their ability to search for habitat requirements and mates from distant areas. The population varied between 830–908 individuals (95% CI), a reduction of 45% from earlier reports. However, the mean population density increased due to contraction of the species’ habitat range. We observed a population decrease of 2%–5% per year over the course of our study. Many of the assessed demographic parameters did not significantly change over the three years. This suggests that the decrease in nyala population was not due to random variations in reproduction. Anthropogenic factors such as competition with livestock for forage, habitat encroachment and poaching by the local people might have been partly responsible for the depleted population in our study areas [Current Zoology 56 (6): 660–669, 2010].