404.

Southern African Vlei Rat

Otomys irroratus

French: Otomys du fynbos / German: Siidafrika-Lamellenzahnratte / Spanish: Rata de laguna de Africa meridional

Taxonomy. Euryotis irrorata Brants, 1827,

near Constantia, Cape Town, Western Cape Province, South Africa .

Otomys irroratus previously was included in widespread O. tropicalis, but they were shown to be distinct species, most recently by P. J. Taylor and colleagues in 2011. Otomys irroratus previously included populations from Grassland biome of central and eastern South Africa and Zimbabwe, but these populations have been assigned to

O. auratus, thus restricting O. irroratus to Fynbos and Thicket biomes of Western Cape and Eastern Cape provinces, most recently by A. Engelbrecht and colleagues in 2011. Within O. irroratus sensu stricto, populations belong to the “C” and “B” cytotypes of G. Contrafatto and colleagues in 1992, which lack composite chromosome rearrangement found in cytotype “Al” from the Drakensberg Mountains. Monotypic.

Distribution. SW & S South Africa (Western and Eastern Cape provinces).

Descriptive notes. Head—body 130-190 mm, tail 85-114 mm, ear 19-25 mm, hindfoot 27-35 mm; weight 80-201 g. The Southern African Vlei Ratis large and robust, with large blunt head,shorttail, and shaggy fur; it isslightly smaller than the East African Vlei Rat ( O. tropicalis). Dorsum varies geographically from dark brown (Western Cape) to richer buff or cinnamon-brown (Eastern Cape). Venter is dark gray to pale grayish buff. Tail is short (c.60% of head-body length) and black above and below. Upper and lower incisors each have single groove, and second fainter groove is present on lower incisors. M, has four laminae, and M? hassix or very occasionally seven laminae. Nasals are characteristically sharply expanded anteriorly. Chromosomal complement varies considerably within O. irroratus sensu lato (2n = 23-32) due to presence or absence of composite tandem fusion rearrangement of pairs 7 and 12, addition of heterochromatic short arms on up to four chromosome pairs, and numerical variation in number of B chromosomes.

Habitat. Montane and submontane moist grasslands and heathlands associated with Fynbos and Thicket Biomesat elevations above 900 m. In the Western Cape, the Southern African Vlei Rat is typically found in valley bottoms near streams, while the Fynbos Vlei Rat ( O. karoensis) occurs higher up on slopes.

Food and Feeding. Diet consists of green plant material such as preferred grasses (e.g. Panicum, Poaceae) and herbs. Gut is modified for specialized herbivory, and coprophagy is practiced.

Breeding. In the Eastern Cape, breeding declined during mid-summer, linked to food availability rather than rainfall, and mean litter size was 1-5 young.

Activity patterns. The Southern African Vlei Rat is presumably diurnal or crepuscular.

Movements, Home range and Social organization. No information.

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

Bibliography. Contrafatto et al. (1992), Engelbrecht et al. (2011), Happold (2013a), Monadjem et al. (2015), Perrin (1980a, 1980b), Rambau et al. (2001), Taylor & Kumirai (2001), Taylor, Lavrenchenko et al. (2011), Taylor, Maree, van Sandwyk, Baxter & Rambau (2009).