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

distributed in seven small and fragmented populations (Marino 2003a). One of at least nineteen
species of mammals restricted to the Afroalpine grasslands and heathlands of Ethiopia (Yalden
and Largen 1992), Ethiopian wolves evolved in the isolation of this huge mountain massif, which
comprises 80% of Africa’s land above 3000m a.s.l. (Yalden 1983; Malcolm and Ashenafi 1997).
The dominant herbivores in these high altitudes are rodents, particularly molerats (Rhyzomidae)
and grass rats (Muridae), adapted to the extreme diurnal temperature fluctuations, and these are
the main prey of Ethiopian wolves (Sillero-Zubiri and Gottelli 1995a; Sillero-Zubiri et al. 1995a,
1995b). As top predators of the Afroalpine ecosystem, Ethiopian wolves attain densities as high
as 1.2 adult per km² in prime habitats (Sillero-Zubiri and Gottelli 1995b) and adult wolves have
no known predators except man. Ironically, the specialisation on Afroalpine rodents that was once
the basis of the species’ success is now the force that constrains Ethiopian wolves to a fragmented
habitat (Yalden and Largen 1992; Marino 2003), and heightens the risk of local extinctions in the
face of stochastic and anthropogenic factors (Sillero-Zubiri and Macdonald 1997; Haydon et al.
2002, 2007).
Study Area
Field studies of Ethiopian wolves in the Bale Mountains began full-time in 1988, and still continue,
having expanded to other populations in Ethiopia since 1997. Most work has taken place in four study
areas: Web Valley (3450 m a.s.l.), Sanetti Plateau (4000 m a.s.l.), Morebawa (3600-3800 m a.s.l.),
and Tullu Deemtu (3800-4300 m a.s.l.) in the central massif of the Bale Mountains National Park
of southern Ethiopia (7°S, 42°E). This is the largest realm of Afroalpine habitat in Africa, spanning
over 1,000 km² and harbouring over half of the global Ethiopian wolf population (Marino 2003a;
Randall et al. this edition). The first three study areas represent typical open-grassland Afroalpine
habitat and sustain the highest wolf densities (ca. 1.2 wolf/km² in Web and Sanetti, ca. 0.9 wolf/km2 in Morebawa) (Gottelli and Sillero-Zubiri 1992; Sillero-Zubiri 1994; Tallents 2007). Tullu Deemtu
is characterised by Helichrysum dwarf-scrub, also a common habitat type, which sustains a much
lower wolf density (ca. 0.25 wolf/km²).
The Solitary Wolf as the Top Predator of the Afroalpine Rodent Community
Diet
The diet of Ethiopian wolves was studied by scat analysis (689 droppings) and 946 hours of watching
focal animals that yielded 811 attempts to kill prey, of which 361 corresponded to successful kills/
feeds (Sillero-Zubiri and Gottelli 1995a). Rodents accounted for 96% of all prey occurrences in
droppings and 97% by volume of undigested faecal material. Wolf prey included six rodent species,
Stark’s hare Lepus starkii, cattle, birds, insects and undigested sedge leaves, Carex monostachya.
Giant molerat Tachyoryctes macrocephalus – mean weight 618 g - was the main component in the
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 62