403.

South East African Vlei Rat

Otomys auratus

French: Otomys doré / German: Sidostafrika-Lamellenzahnratte / Spanish: Rata de laguna de Africa suroriental

Taxonomy. Otomys irroratus auratus Wroughton, 1906,

Vredefort, northern Free State Province, South Africa .

Otomys auratus previously was included in O. irroratus but was shown to be a distinct species based on molecular grounds, most recently by A. Engelbrecht and colleagues in 2011. Populations within O. auratus have been shown to encompass all five cytotypes described by G. Contrafatto and colleagues in 1992. Two of these cytotypes are independently derived in populations of O. wrroratus, suggesting that chromosomal rearrangements played no role in speciation of these two sibling species. Nevertheless, according to N. Pillay and colleagues in two 1995 papers incipient speciation may be occurring due to chromosomallyinduced reproductive isolation of populations of the “Al”cytotype from high altitudes (above 1400 m) in the Drakensberg Mountains. Monotypic.

Distribution. Widespread throughout C plateau and Drakensberg of South Africa, Swaziland, and Lesotho, with isolated populations in Soutpansberg, N South Africa, and Eastern Highlands of Zimbabwe and neighboring Mozambique.

Descriptive notes. Head-body 133-202 mm, tail 58-120 mm, ear 17-5-26 mm, hindfoot 21-38 mm; weight 63-211 g. The South East African Vlei Rat is large and robust, with large blunt head,short tail, and shaggy fur. Dorsum is olive-brown to cinnamonbrown above and dark to paler gray below. Tail is short (c.60% of head-body length), darker above than below and sparsely haired. Ears are small and close to body. Upper incisors have one deep groove, and lower incisors have one deep and one shallow groove. M has four laminae, and M” has six or (very seldom) seven laminae. Diploid numbers vary 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 grasslands, typically in wetlands with long rank grass and, at higher elevations, sparser and shorter grasses. Where the South East African Vlei Rat co-occurs with the Southern African Vlei Rat ( O. irroratus), they are associated with plants on wetter soils, and the Angoni Vlei Rat ( O. angoniensis) is associated with drier habitats further away from water.

Food and Feeding. The South East African Vlei Rat mainly eats grasses. It can eat soft bark of pine saplings and become a problem in forest plantations.

Breeding. Females are polyestrous, with 3—4 births/year. Breeding is curtailed during cold dry seasonwhen food availability is reduced. Litters have 1-5 young. Gestation is 5-6 weeks. Young are born precocial, with erupted incisors capable of nipple-clinging on their mother. Sexual maturity is attained at ten weeks for females and 14 weeks for males.

Activity patterns. The South East African Vlei Ratis typically crepuscular.

Movements, Home range and Social organization. South East African Vlei Rats construct distinctive runways in grass. At a site near Pretoria, densities varied throughout the year from 17 ind/ha to 72 ind/ha. They are partly territorial (guarding immediate nest areas), with mean home ranges of1730 m? for males and 1252 m? for females. They are solitary and aggressive, with levels of aggression decreasing from scrotal males to perforate females to non-scrotal males to imperforate females.

Status and Conservation. Not assessed on The IUCN Red List. The South East African Vlei Rat is regionally listed as near threatened in South Africa due to potential impacts of climate change and land use and land cover changes. Occurrence in Soutpansberg declined considerably between 1923 and 2013.

Bibliography. Bronner et al. (1988), Contrafatto et al. (1992), Davis (1972, 1973), Davis & Meester (1981), Engelbrecht et al. (2011), Happold (2013a), Monadjem et al. (2015), Pillay, Willan & Meester (1995), Pillay, Willan, Meester & Cooke (1995), Taylor & Kumirai (2001), Taylor, Maree, van Sandwyk, Baxter & Rambau (2009), Taylor, Nengovhela et al. (2016).