Abstract:
Aim: One objective was to quantify the impact of the Giant Mole Rat (Tachyoryctes macrocephalus) on vegetation communities
and their composition. A second objective was to assess plant biomass (plant volume) via photography at the Sanetti Plateau.
Third objective was to assess spatial distribution of the Giant Mole Rat across the Bale Mountains. In order to do that a predictive
model has been applied.
Location: Bale Mountains in south-eastern Ethiopia.
Taxon: Tachyoryctes macrocephalus (Spalacideae). The species is related to other rats in eastern Africa and endemic to the Bale
Mountains.
Methods: The vegetation was sampled using a paired plot design along a transect from the southern to the northern rim of Sanetti
Plateau and at sites where Giant Mole Rats were most abundant. Therefore, a total of 94 plots were established, 47 on Giant
Mole Rat mounds and 47 in the zonal vegetation as control plots. Species identification and vegetation cover was investigated
and photographs taken for further analysis of plant biomass. GPS data of around 1200 Giant Mole Rat mounds were recorded
in order to upscale points on a larger area and detect the distribution of the Giant Mole Rat across the Bale Mountains. For that
purpose Sentinel-2 satellite data was used with spatial resolution of 10 m, using a Forward Feature Selection.
Results: We found out that the Giant Mole Rat is distributed across the whole Afroalpine zone of the Bale Mountains. It
concentrates on the northern part of the Sanetti Plateau, in Sodota and Morebawa in wet and swampy habitat structures. Giant
Mole Rats cover an area of 8301,16 ha and an estimated population density of 22 individuals/ha via upscaling could be proved.
The Giant Mole Rat provides advantages to plants that require mixed and heterogen soil characteristics. The genera of Alchemilla
and Salvia are examples for that and could be found on a major part of the Giant Mole Rat mounds. The genus of Helichrysum
is abundant in the normal vegetation pattern and is almost completely absent on the Mole mounds. The presence of Helichrysum
causes higher plant volume in the normal vegetation, which is 1,7 times higher than on the Mole mounds.
Main conclusions: Giant Mole Rats change habitat and plant community structures. Shrub or woody plants do not occur on
Giant Mole Rat mounds. The Giant Mole Rat is distributed across the whole Sanetti but most abundant in the northern part of
Sanetti, Sodota and Morebawa. It prefers wet and swampy habitat.
