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Demography and dynamics of mountain nyala Tragelaphus buxtoni in the Bale mountains National Park,Ethiopia

Current Zoology 2010年第6期56卷 660-669页

作者： Yosef MAMO Michelle A.PINARD Afework BEKELE Hawassa University Department of Wildlife and Eco-tourism University of Aberdeen Institute of Biological and Environmental Sciences Addis Ababa University Department of Biology

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）： 660q569, 2010].

关键词： Density Dynamics Group size mountain nyala Movement Sex ratio

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Habitat use by mountain nyala Tragelaphus buxtoni determined using stem bite diameters at point of browse, bite rates, and time budgets in the Bale mountains National Park, Ethiopia

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Current Zoology 2013年第6期59卷 707-717页

作者： Solomon A. TADESSE Butt P. KOTLER Mitriani Department for Desert Ecology Blaustein Institutes for Desert Research Ben-Gurion University of the NegevMidreshet Ben-Gurion 84990 Israel

We studied the habitat use of mountain nyala Tragelaphus buxtoni in the northern edge of the Bale mountains Na- tional 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 obser- vations, 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 fora- ging 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 of- fering 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 .

关键词： Behavioural indicators Bite rates mountain nyala Natural giving-up densities Non-invasive techniques Stem bite diameters Vigilance

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Assessing habitat quality of the mountain nyala Tragelaphus buxtoni in the Bale mountains, Ethiopia

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Current Zoology 2012年第4期58卷 525-535页

作者： Paul H. EVANGELISTA John NORMAN III Paul SWARTZINKI3,Paul SWARTZINKI3,Paul SWARTZINKI Nicholas E. YOUNG Natural Resource Ecology Laboratory Colorado State University Fort Collins CO 80524-1499 USA Natural Resource Conservation Service Shepardson Bldg. Colorado State University Fort Collins CO 80524 USA AECOM 1601 Prospect Pkwy Fort Collins CO 80303 USA

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 for-mulating 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 approxi- mately 18,610 km^2 （82.7% of our study area） is unsuitable or poor habitat for the mountain nyala, while 2,857 km^2 （12.7%） and 1,026 km^2 （4.6%） was ranked as good or optimal habitat, respectively. Our results not only reflected human induced habitat deg-radation, but also revealed an extensive area of intact habitat on the remote slopes of the Bale mountain＇s southern and southeast- ern escarpments. This study provides an example of the roles that expert knowledge can still play in modem 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 .

关键词： Expert knowledge FunConn model Habitat mapping Land cover mountain nyala Wildlife conservation

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