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

Rendille, Samburu, and Elmolo) (Kassam 1996). This composite group developed a common
identity by sharing the exploitation of the same ecological and economic niche under the hegemony
of the Borana, who established in the area the “Borana peace” (naga Borana) in the 17th century
(Ibid.).
Even if a genealogical relationship between Gabarra and Gabra is possible, it is more likely
that both names simply indicate Oromo otherness. In fact, the name Gabra derives from the words
gabaro or gebbar, used by Oromo to refer to those who are not of pure Oromo descent (Baxter et
al. 1996). The etymology of the term derives from the word garba indicating bodies of standing
water (Kassam 2006), in opposition to hora (mineral spring), from which pure Oromo (Horomo)
originated (Ibid.).
Ecology
During the survey, some direct evidence of visitation of the horas by wildlife was identified: warthogs,
forest hogs and bushbucks were found at the majority of sites, a lion was hunting cattle and horses at
hora Waticha and numerous tracks of warthogs and bushbucks were found at Gamo Sof Omar. The
questionnaire gave similar results, where warthogs, bushbucks and forest hogs we described as the
most common visitors, attracting predators such as lions and leopards. Informants also reported that
mountain nyala visit many horas in the forest, as far south as the coffee area (hora Higan).
While the use of salt licks by animals is widely reported, a specific use of mineral springs is
apparently documented only for the North American moose and white-tailed deer (Betchtold 1996).
The abundance of sodium in Ethiopian hydrothermal waters, and in BMNP in particular (Hillman
1988), could be an important resource for wildlife as documented for other cases of salt licking
(Bechtold 1996; Matsubayashi et al. 2006; Mills and Milewski 2007). The phenomenon of saltlicking
at the horas, or of preferential grazing in glades associated with horas, should be investigated
and monitored.
Horas and glades appear to be strongly associated in space: if Hora Rasa is considered to be
a single site, 25 out of the 32 sites surveyed were found in glades. Extreme rockiness and surface
water was characteristic of the five sites in the forest, while in glades the degree of rockiness varied
greatly. One possible explanation for the association is that horas fill with sediment over time giving
rise to glades, for example Riripha, Ataui, and the many dry horas in Hora Rasa.
The hypothesis derived from this research for the evolution of horas is as follows. Horas
originate in rocky patches of the forest, where hydrothermal water emerges through the cracked
rocks. Hydrothermal sediments associated with the stream tend to create a clay deposit on top of the
emerging rocks, progressively impeding the flow of water to the surface. Such clay deposits will be
waterlogged to different extents and different depths.
Waterlogging could be the main impediment to tree establishment in these clay deposits,
as it was suggested for other glades in Africa, with a similarly flat surface and sharp boundaries
(Backeus 1992). Waterlogging impedes aeration and creates acidic soil conditions. In the case of
sodium-rich environments, waterlogging would also lower the levels of sodium toxicity for plants
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 236