Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

wildlife, especially the mountain nyala and Ethiopian wolf. Nyala and other antelopes compete
directly with livestock for food and nyala are absent from areas where livestock numbers are high
(Brown 1969). The Afroalpine habitat of BMNP has a simple and visible trophic structure with
Ethiopian wolves and a diverse assemblage of raptors feeding almost exclusively upon a guild
of burrowing rodents, including 10 species endemic to Ethiopia (Sillero-Zubiri and Gottelli 1995;
Sillero-Zubiri et al. 1995). The wolf’s diet is dominated by three rodent species endemic to Bale:
the giant molerat, Tachyoryctes macrocephalus, Blick’s grass-rat, Arvicanthis blicki and the blackclawed
brush-furred rat, Lophuromys melanonyx, (Sillero-Zubiri and Gottelli 1995). The rodents,
in turn, feed exclusively on forbs and grasses (Clausnitzer et al. 2003). All three rodent species are
diurnal and found at very high densities in the Afroalpine zone of Bale, reaching biomass levels
of 2,500-4,000 kg/km², rivalling that of large mammals on the Serengeti plains (Sillero-Zubiri et
al. 1995). There is evidence to suggest that cattle compete with rodents (Delany 1972), possibly
reducing the prey base of wolves and raptors in Bale. From a wildlife viewpoint, grazing is often a
form of interference competition (Happold 1995).
Historic and Recent Livestock Trends in the BMNP
Current knowledge of the extent and impact of grazing, along with the quantification of the threats
associated with it, is scarce and most management decisions have to be made with preliminary
rather than detailed or expert knowledge. While several projects in the past have been involved in
censusing livestock in BMNP, was only in the last few years that this project started to look at ways
of quantifying the impact of livestock grazing on the vegetation and rodents and modelling this
impact on higher-trophic levels (Ethiopian wolves and raptors). Such information is important for
determining what livestock carrying capacities are sustainable in the Afroalpine.
The Bale Mountains Research Project (Hillman, 1986) carried out regular surveys of wildlife
and livestock between 1983 and 1992 which were subsequently continued by the Ethiopian Wolf
Conservation Programme (EWCP) from 1996 to present. EWCP monitors every month livestock
abundance via line transect counts in Sanetti and Web Valley. Animals and people in Sanetti are
counted along the Goba-Rira road that traverses the plateau in an almost straight line for 31km
and covers three different types of wolf habitat (marginal, good and optimal). Counts in Web are
conducted along a specifically designed line-transect, a 20 km circuit that samples over 30 km2 of
optimal wolf habitat.
Marino and colleagues (2006) summarised the trends in livestock abundance in different
areas of the park (Web Valley, Western/Eastern/Central Sanetti) between 1987 and 2000 using
the EWCP transect data and Hillman’s data (1986). Livestock abundances increased consistently
throughout the monitoring period in all the study areas, with the exception of sheep and goats in
Web Valley, with the highest densities of livestock recorded during the wet season (April-October).
Highest livestock abundances were registered in the Web Valley, in optimal wolf habitat, where all
livestock types were over four times more abundant than elsewhere. The livestock transect data
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 201