418.

African Grass Rat

Arvicanthis niloticus

French: Rat-roussard du Nil / German: Nil-Grasratte / Spanish: Rata de hierba de Africa

Other common names: African Arvicanthis, Nile Grass Rat, Unstriped Grass Rat

Taxonomy. Arvicola niloticus E. Geoffroy Saint-Hilaire, 1803,

Egypt.

Aruvicanthis niloticus is a widespread murid that overlaps geographically with several other Arvicanthis species. It was once the only species recognized within the genus, but chromosomal and molecular studies have revealed the presence of several cryptic species. As currently constituted, A. niloticus may still be a complex of several species; for example, distinct lineages

have been recognized in Ethiopia, and considerable phylogeographic structure (four distinct lineages) recognized acrossits North African range. Polytypic, but subspecific taxonomy requires reassessment.

Distribution. Widespread from Mauritania and Senegal E to Ethiopia, and S to Tanzania and SW Zambia; range extends N along Nile Valley to the Nile Delta in Egypt, with an isolated population in SW Arabia (Yemen).

Descriptive notes. Head—body 127-188 mm,tail 92-155 mm, ear 13-22 mm, hindfoot 30-36 mm; weight 89-160 g. The African Grass Rat, a medium-sized rat, has dorsal fur buffy brown, heavily flecked with yellow and black, with or without mid-dorsal black line, and ventral fur whitish to gray. Ears are small, rounded, and reddish. Tail is relatively long (¢.85% of head—body length), dark above, and whitish or pale brown below.

Limbs are relatively short, with four digits on forefoot (first digit is absent; fifth digit is highly reduced butstill bears aclaw) and five digits on hindfoot. Females have three pairs of nipples. At least three different karyotypes present in Ethiopia 2n = 56, 60, and 62.

Habitat. Savanna and grassland habitats near water, from more arid steppes to more mesic grasslands (200-1200 mm), as well as cultivated fields and villages, but not entering houses.

Food and Feeding. Diet includesleaves, shoots, and seeds of grasses, cultivated crops; it also eats insects(up to 10% of diet in wet season).

Breeding. Depending onrainfall, duration of the African Grass Rat’s reproductive season varies geographically, from five months in Senegal to twelve months in Uganda, high grasslands (1700 m) in Ethiopia, and irrigated fields along Nile River. Proportion of breeding females also varies annually, from 32% to 80%. Gestation period is 21-23 days, and average litter size varies in different habitats from 4-3 to 7-4 (range 2-10).

Sexual maturity is reached in two months, and longevity in the wild is less than one year.

Activity patterns. African Grass Rats are diurnal and terrestrial. They are also capable of climbing—e.g. to feed on fruits of Balanites aegyptiaca ( Zygophyllaceae). Populations can fluctuate during year—e.g. 0-80 ind/ha in grassland and 5-18 ind/ha in maize fields. Populations can increase explosively during outbreaks—e.g. 100 ind/ha after good rains in Sahel, and up to 600-800 ind/ha for short periods in rice fields in northern Senegal .

Movements, Home range and Social organization. African Grass Rats are colonial, living in nests in burrows.

Status and Conservation. Classified as Least Concern on The IUCN Red Last.

Bibliography. Abdel-Rahman, Ducroz et al. (2008), Abdel-Rahman, Taylor et al. (2009), Bekele & Leirs (1997), Castiglia et al. (2006), Dobigny et al. (2013), Ducroz, Granjon et al. (1997), Ducroz, Volobouev et al. (1998), Fisher (1991), Ghobrial & Hodieb (1982), Happold (1966b, 2013a), Harrison & Bates (1991), Monadjem et al. (2015), Neal (1981), Poulet (1982), Poulet & Poupon (1978), Rabiu & Fisher (1989), Rabiu & Rose (1997), Taylor & Green (1976).