Tachyoryctes splendens (Ruppell, 1835)

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 : 136-137

16.

African Root Rat

Tachyoryctes splendens

French: Rat-taupe est-africain / German: Ostafrika-Maulwurfsratte / Spanish: Rata de raices africana

Other common names: East African Mole-rat

Taxonomy. Bathyergus splendens Ruppell, 1835 ,

Gondar , Dembea Province, Ethiopia.

Excluding 1. macrocephalus , which is widely recognized as a distinct species, 19 named forms of Tachyoryctes have been described. G. G. Musser and M. D. Carleton in 2005 recognized twelve of these as distinct species, albeit with hesitation due to absence of studies assessing variation in the genus. They recognized ankoliae named by O. Thomas in 1909 from south-western Uganda and north-western Tanzania; annectans named by Thomas in 1891 from south-western Kenya; audax named by Thomas in 1910 from Aberdare Range, Kenya; daemon named by Thomas in 1909 from northern Tanzania; ibeanus named by Thomas in 1900 from southern Kenya; naivashae named by Thomas in 1909 from south-central Kenya; rex named by E. Heller in 1910 from Mount Kenya; ruandae named by E. Lonnberg and N. Gyldenstolpe in 1925 from eastern DR Congo, Rwanda, and Burundi; rudd: named by Thomas in 1909 from south-western Kenya, south-western Uganda, and north-western Tanzania; spalacinus named by Thomas in 1909 from Mount Kenya area; storey: named by Thomas in 1909 from southwestern Kenya; and splendens that they restrict to Ethiopia, Somalia, and north-western Kenya. Numerous approaches have been proposed to deal with diversity within 7. splendens , with one, seven, ten, twelve, and 14 species recognized by various authorities. In one of the only genus-wide assessments of morphological diversity, F. Beolchini and M. Corti in 2004 used geometric morphometrics and concluded that these should be treated as a single species. A. Monadjem and colleagues in 2015 highlighted the large size of rex and rejected the single species argument put forth by Beolchini and Corti. Their taxonomic treatment recognized twelve species, but they suggested that certain species warrant synonymizing. They specifically suggest that daemon , ibeanus , narvashae, and storeyi might be conspecific and that annectans and audax might also be the same species. Musser and Carleton in 2013 adopted the single species approach pending further study, which is followed here. Considerable diversity is clearly present within what is treated as 7. splendens , but arguments supporting specific systematic treatments have been very weak. L.. A. Lavrenchenko and colleagues in 2014 conducted the only molecular phylogenetic study to date on diversity within 7. splendens sensu lato. Their research was limited to Ethiopian populations and the cytochrome-b gene, but they still recovered four clades exhibiting species-level mitochondrial divergence. There is little doubt that additional study will recover instances of cryptic speciation across allopatric populations found throughout the distribution of 7. splendens . At present, however, available data do not appear to provide support for any particular taxonomic delineation proposed to date. Further study is needed. Monotypic.

Distribution. Disjunct distribution in East Africa, known from Ethiopia, NW Somalia, S Uganda, SW Kenya, E DR Congo, Rwanda, Burundi, and N Tanzania.

Descriptive notes. Head-body 159-268 mm, tail 49-95 mm; weight 140-330 g. Male African Root Rats are often slightly larger than females. They are robust and stocky, with short limbs. They are smaller than Giant Root Rats (7. macrocephalus ). Color ranges from ginger, cinnamon-brown,to black with lighter venter. Many individuals have white patches. Juveniles are usually black. Pelage color varies in different regions. Size also varies, although these differences might occur along ecological gradients and might not reflect taxonomic differences. Large orange incisors are visible externally when mouth is closed. Third digit on forelimbis longest; first digit is rudimentary. There are eight nipples: 2 pairs of pectoral + 2 pairs of inguinal. Diploid number is 2n = 48 or 50.

Habitat. Well-drained soils in savanna grasslands, and open forests in Afro-montane, Afro-alpine, and adjacent regions in East Africa. The African Root Rat occurs at elevations of 700-4150 m and is known from the highest mountains in Kenya and Tanzania. It is replaced by the Giant Root Rat at elevations above 3000 m in the Bale Mountains of Ethiopia. It is a pest of agricultural fields and gardens. It is usually found where annual rainfall is above 500 mm.

Food and Feeding. The African Root Rat eats stems and leaves, herbs, grass rhizomes, roots, bulbs, and tubers. Food plants are accessed from below or by digging a feeding opening. Entire plants may be pulled down into the burrow and carried to the nest for eating or storage. When feeding at the surface, a small foraging opening is made, and an individual collects plant material within easy reach. Foraging holes are plugged with dirt after an individual goes belowground. Dirt is brushed from plants with forelimbs while being held with incisors.

Breeding. Breeding of African Root Rats occurs year-round, but pregnant females are most numerous at the end of the rainy season. One to four young are born after gestation of 46-49 days. Young weighing 11-18 g are born naked and toothless, with eyes closed. They are weaned after c.35 days and establish their own burrows after c¢.80 days. Sexual maturity is reached at ¢.120 days. Females can become pregnant while nursing a previous brood. Average time betweenlitters is c.173 days.

Activity patterns. The African Root Rat is reported to be diurnal in the wild, active from 10:00 h until 19:00 h. Under laboratory conditions, however, it shows distinct preference for nocturnal activity. Individuals remain in burrows more than 75% of the time. It is a chisel-tooth digger, dislodging soil with extrabuccal incisors. Dirt is held while carried to the surface by being pressed between side of head and forelimb, and a mound is formed. Burrow temperatures in Kenya are ¢.23°C; decomposition of feces and food stores provides added heat. If exposed to temperatures above 30°C, the African Root Rat salivates and spreads saliva on its body for evaporative cooling. Long-term exposure to temperatures above 35-37°C is lethal.

Movements, Home range and Social organization. Burrow systems of African Root Rats are 15-44 m long and include foraging burrows, a nest chamber and a bolt-hole. Nest chambers include spaces for sleeping, food storage, and use as a toilet. Burrows are not shared, and individuals aggressively defend them. Individuals communicate seismically by tapping on burrow floors with upper incisors or on ceilings with heads. Neighbors respond with their own taps, patterns that appear specific to individuals. Individuals respond to threats by throwing their heads back, opening their mouths, and lunging forward while squeaking, snorting, and chattering teeth. Male African Root Rats emit a musk-like odor from glands beneath eyes and ears. The African Root Rat is patchily distributed, but where it is present, it can be abundant. Densities of 70-200 ind/ha have been reported. The African Root Rat is preyed on by common barn-owls (7yto alba ), raptors, small carnivores, and snakes.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The African Root Rat is common and can be found in protected areas. Resolution of taxonomic uncertainty for the African Root Rat is essential for prioritizing conservation concerns. It is an agricultural and horticultural pest, damaging cassava, sweet potato, peanut, lucerne, and maize crops, along with lawns and young trees.

Bibliography. Allen (1939), Beolchini & Corti (2004), Delany (1975), Ellerman (1941), Heller (1910), Hollister (1919), Hrouzkova et al. (2013), Jarvis (1969, 1973a, 1973b, 2013a, 2013b), Jarvis & Sale (1971), Katandukila et al. (2013), Lavrenchenko et al. (2014), Lonnberg & Gyldenstolpe (1925), McNab (1966), Misonne (1974), Monadjem et al. (2015), Musser & Carleton (1993, 2005, 2013a, 2013c), Schlitter, Agwanda & Corti (2008), Thomas (1891a, 1900a, 1909, 1910a).

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)

Distribution. Disjunct distribution in East Africa, known from Ethiopia, NW Somalia, S Uganda, SW Kenya, E DR Congo, Rwanda, Burundi, and N Tanzania.