Tachyoryctes macrocephalus (Ruppell, 1842)

Don E. Wilson, Russell A. Mittermeier & Thomas E. Lacher, Jr, 2017, Spalacidae, Handbook of the Mammals of the World – Volume 7 Rodents II, Barcelona: Lynx Edicions, pp. 108-142 : 137

17.

Giant Root Rat

Tachyoryctes macrocephalus

French: Rat-taupe géant / German: Riesenmaulwurfsratte / Spanish: Rata de raices gigante

Other common names: Big-headed Mole-rat, Giant Mole-rat

Taxonomy. Rhizomys macrocephalus Ruppell, 1842 ,

Shoa , Ethiopia.

Presence of 71. macrocephalus in the region known until 1995 as Shoa (= Shewa) Province, Ethiopia, is considered suspect. D. W. Yalden and M. J. Largen in 1992 suggested that type material was collected in Begemdir or Wollo Province in northern Ethiopia. No further records of 7. macrocephalus have been recorded from northern Ethiopia since the original description. In a cladistics analysis that included fossil and extant taxa, R. Lopez-Antonanzas and H. B. Wesselman in 2013 showed that the two living root rats are sister taxa with respect to the known fossil species 71. konjiti, 1 pliocaenicus, and 1. makooka. Two subspecies recognized.

Subspecies and Distribution.

T. m. macrocephalus Ruppell, 1842 — N Ethiopia; no records since original description. T. m. hecki Neumann & Rummler, 1928 — S Ethiopia, Bale Mts above 3000 m (Oromia Region).

Descriptive notes. Head-body 224-313 mm, tail 40-65 mm; weight 330-930 g. The Giant Root Rat is stocky and short-limbed, with relatively large head and shorttail. It has soft dense pelage that is silver, brown, or orange. Hairs are gray at bases. Up to three darker lines may be present on crown of head, and dark spot is present on eyelids. Interorbital width is narrow, causing eyes to be distinctively high on face. Subspecies heck: has longer (greater than 7 mm) anterior palatal foramen and zygomatic plate that slopes down to premaxillary-maxillary suture than the nominate subspecies. Large orange incisors are visible externally when mouth is closed. Diploid numberis 2n = 50.

Habitat. Restricted to alpine grassland habitat at elevations of 3000-4150 m. The Giant Root Rat prefers soil depths greater than 50 cm in swamp shore grasslands and mixed herbaceous moorlands. Moist soils are preferred. In the Bale Mountains of Ethiopia, the African Root Rat (7. splendens ) is replaced by the Giant Root Rat at elevations above 3000 m.

Food and Feeding. The Giant Root Rat feeds on grasses and forbs such as Festuca (Poaceae) and Alchemilla (Rosaceae) . Food is gathered by opening a hole to the surface and consuming plant material within easy reach of the opening. An individual usually keeps its hindquarters in the opening to facilitate quick escape into the burrow. When food in an area is depleted, the Giant Root Ratseals the opening and creates a new burrow elsewhere. A mouthful of food is collected in short foraging bouts of 6-8 minutes and is taken belowground for consumption.

Breeding. Little information is available. Female Giant Root Rats appear to have one young perlitter.

Activity patterns. The Giant Root Rat is diurnal and active from 08:00 h to 16:00 h. Aboveground activity comes in short bursts, roughly ten bouts in dry season adding up to an hour of activity, with fewer during rainy season.

Movements, Home range and Social organization. Only a single Giant Root Rat is present in each burrow system. Burrows are up to 90 m long and 12-15 cm in cross section belowground, with openings c.8 cm. An individual's burrow system may be up to 360 m*. All burrow entrances are closed nightly. Densities of 6 ind/ha, 24 ind/ha, 60 ind/ha, and 90 ind/ha have been reported. The ground can feel spongy when Giant Root Rats occur at high densities because ofits burrows. It may reach 50-60% of total rodent biomass in certain locations. The Giant Root Rat is a preferred prey of the Ethiopian Wolf (Canis simensis), representing up to 47% (by volume) of its diet. Other predators include owls and probably raptors.

Status and Conservation. Classified as Endangered on The IUCN Red List. The Giant Root Rat can be present in very high concentrations, butits distribution is restricted and is dependent on a unique ecosystem. Much of its known distribution is in Bale Mountains National Park, but overgrazing by livestock threatens grasslands. It is not clear if the northern subspecies, macrocephalus , persists.

Bibliography. Corti & Lavrenchenko (2008), Lopez-Antonanzas & Wesselman (2013), Monadjem et al. (2015), Sillero-Zubiri et al. (1995a), Yalden (1985, 2013a), Yalden & Largen (1992).

Figures

1. Altai Zokor (Myospalax myospalax), 2. Steppe Zokor (Myospalax aspalax), 3. Armand’s Zokor (Mpyospalax armandii), 4. Manchurian Zokor (Myospalax psilurus), 5. Khingan Zokor (Myospalax epsilanus), 6. Fontanier’s Zokor (FEospalax fontaniern), 7. Gansu Zokor (Fospalax cansus), 8. Qinling Zokor (Fospalax rufescens), 9. Plateau Zokor (FEospalax bailey), 10. Rothschild’s Zokor (Eospalax rothschildi), 11. Smith’s Zokor (Eospalax smithu), 12. Chinese Bamboo Rat (Rhizomys sinensis), 13. Hoary Bamboo Rat (Rhizomys pruinosus), 14. Indomalayan Bamboo Rat (Rhizomys sumatrensis), 15. Lesser Bamboo Rat (Cannomys badius), 16. African Root Rat (Tachyoryctes splendens), 17. Giant Root Rat (Tachyoryctes macrocephalus), 18. Oltenia Blind Mole-rat (Spalax istricus), 19. Mehely’s Blind Mole-rat (Spalax antiquus), 20. Bukovina Blind Mole-rat (Spalax graecus), 21. Podolsk Blind Mole-rat (Spalax zemni), 22. Sandy Blind Mole-rat (Spalax arenarius), 23. Greater Blind Mole-rat (Spalax microphthalmus), 24. Giant Blind Mole-rat (Spalax giganteus), 25. Kazakhstan Blind Mole-rat (Spalax uralensis), 26. Lesser Blind Mole-rat (Nannospalax leucodon), 27. Anatolian Blind Mole-rat (Nannospalax xanthodon), 28. Middle East Blind Mole-rat (Nannospalax ehrenbergi)

Subspecies and Distribution. T. m. macrocephalus Ruppell, 1842 — N Ethiopia; no records since original description. T. m. hecki Neumann & Rummler, 1928 — S Ethiopia, Bale Mts above 3000 m (Oromia Region).