Red List of South African Species

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Least Concern (LC)

Rationale (Changed due to Same category and criteria)

Rhabdomys spp. are widespread, versatile and common species, coexisting with humans in disturbed, semi-urban and agricultural landscapes. Thus, all species are listed as Least Concern. Rhabdomys pumilio is restricted to the low-altitude coastal region within the Fynbos and Succulent Karoo Biomes from the Richtersveld in the west to Port Elizabeth in the Eastern Cape Province. Some Rhabdomys species are affected by overgrazing which reduces the ground cover on which the species depend and thus lead to local declines. However, R. pumilio does  not rely on ground cover as much and is thus not as adversely affected by overgrazing. Rhambdomys pumilio appears to require no direct conservation interventions at present. Research should focus on delimiting the geographical extent of all species and researching their ecological differences.

Distribution

Rhabdomys spp. are broadly distributed across southern and eastern Africa. Their extent of occurrence is wide, while the distribution at the local scale is probably patchy and discontinuous. It cannot be stipulated with certainty whether the current distribution differs significantly from the historical distribution. Rhabdomys, however, appears to be well adapted to agricultural and semi-urban areas, therefore human activities probably would not have led to a significant reduction in distribution range. Rhabdomys dilectus occurs within the Grassland and Savanna Biomes along the mesic eastern region of South Africa, Eswatini and Lesotho, while the xeric clades (R. pumilio, R. intermedius and R. bechuanae) occur within more arid to savanna habitats in central and western South Africa (Monadjem et al. 2015). Specifically:

  • Within the R. dilectus clade, R. d. chakae, which is endemic to the assessment region, occurs in the eastern regions of South Africa from the Soutpansberg Mountains in the north to the Eastern Cape Province in the south, extending into Eswatini and Lesotho (Castiglia et al. 2012, du Toit et al. 2012); while R. d. dilectus occurs in northern South Africa northwards through Zimbabwe, Malawi to East Africa, with an apparently isolated subpopulation on the plateau of Angola (Castiglia et al. 2012). The two subspecies appear parapatric (Happold 2013), but there is a known case of sympatry (Monadjem et al. 2015).
  • Rhabdomys bechuanae occurs widely in the central and western regions of South Africa (Free State, North-West and Northern Cape provinces), mostly north of the Gariep (Orange) River, northwards and westwards through Botswana to Namibia and extreme southwestern Angola (Monadjem et al. 2015).
  • Rhabdomys intermedius is endemic to the southern interior regions of South Africa where it occurs in a narrow band through the Karoo, wedged between R. pumilio on the coast and R. bechuanae further north (du Toit et al. 2012).
  • Rhabdomys pumilio is endemic to South Africa where it occurs along a narrow coastal strip within the Fynbos and Succulent Karoo Biomes from Port Elizabeth/Fort Beaufort in the east (Eastern Cape) to the mouth of the Gariep (Orange) River in the Richtersveld in the west (Northern Cape) (du Toit et al. 2012).
The proposed species within the xeric clades have mostly allopatric distributions with several zones of sympatry at the distribution margins with R. dilectus (see du Toit et al. 2012, Ganem et al. 2012). There are several sampling sites where more than one species was present, so-called contact zones. At this stage of our knowledge, these contact zones are in Fort Beaufort (Eastern Cape), Sandveld Nature Reserve, Soetdoring, Tussen-Die-Riviere (Free State), and Ezemvelo Nature Reserve, Rietvlei Nature Reserve, Irene and Carltonville (Gauteng). In the Sandveld Nature Reserve, R. bechuanae occurs in sympatry with R. d. dilectus and R. d. chakae. Rhabdomys intermedius was described from Cradock and Port Elizabeth in the Eastern Cape, as well as Deelfontein in the Northern Cape; this species mostly represents the central clade, when R. pumilio was split into three geographically distinct groups (du Toit et al. 2012).

Likewise, the distribution of R. bechuanae is mostly represented by the northern clade, which is known from Namibia, Botswana, as well as the Northern Cape and North-West provinces of South Africa (du Toit et al. 2012).

Further molecular research and vetting of museum specimens is needed to more accurately delineate the distribution ranges of the various species.

Population trend

Trend

No abundance information is available for this species and, although they can be locally and temporally abundant, their densities are known to fluctuate (Happold 2013). Fast growth, followed by population crashes, occur frequently. The species commonly occur in high numbers, often significantly higher than all other co-occurring small mammal species (Happold 2013). A comparative study between the Rhabdomys spp. in the arid Succulent Karoo and those in the moist grassland habitats of South Africa found that, as a result of increased rainfall levels, Rhabdomys in grassland regions exhibited much longer breeding seasons (Schradin and Pillay 2005). Additionally, high annual survival rates in the Succulent Karoo resulted in significantly higher population densities compared to drier grassland regions (Schradin and Pillay 2005). In the Succulent Karoo, average population densities of 36.6 ± 21.2 mice / ha (N = 5 groups) were reported in September, increasing to a peak of 171.1 ± 40.9 mice / ha (N = 7 groups) in December, and then declining through the rest of summer and into winter (Schradin and Pillay 2005). In other parts of South Africa, densities of 35–93 individuals / ha, and 30–300 individuals / ha were recorded in the Highveld grasslands (Brooks 1974) and the Cape Flats (David and Jarvis 1985), respectively.

Threats

No major threats have been recognised for this species complex, and given the extensive occurrence of these species and their ability to coexist with humans in agricultural and semi-urban areas, they are unlikely to be threatened in the near future. However, the various proposed species may be susceptible to range declines or shifts due to climate change (Rymer et al. 2013). Considering the lack of information regarding the ecology and distribution of this species complex, the extent to which each species may be affected by habitat shifts is largely uncertain.

Uses and trade

Rhabdomys is currently only being utilised for research and museum collections. It is an important research model to assess social evolution and ecological diversification.

Conservation

This species is located in many protected areas across its range.  No conservation interventions are deemed necessary for this species, although all Rhabdomys species are likely to benefit from the expansion of protected areas into suitable habitats. This is especially true for R. pumilio and the expansion of lowland fynbos protected areas in the Western Cape.

Research priorities:
  • Rate of future habitat loss in the Western Cape.
  • Species geographical distribution, morphometrics, genotyping of populations and taxonomic assessment. This includes vetting of existing museum specimens.
  • Species social and general biology.
  • Ecology and mechanisms of coexistence with other Rhabdomys species.
A multidisciplinary study (Eco-Rhab) into the adaptive ecological radiation of the Rhabdomys genus is currently (2014–2017) being conducted by Guila Ganem (Institute of Evolutionary Sciences), Neville Pillay (University of the Witwatersrand), Nico Avenant (The National Museum Bloemfontein), and Teresa Kearney (The Ditsong Museum of Natural History). More information is available at: http://www.southern-africa.aird.fr/science-in-southern-africa/research-projects/unravelling-the-ecology-of-radiation-in-the-african-striped-mouse.

Encouraged citizen actions:

  • Report sightings on virtual museum platforms (for example, iSpot and MammalMAP), especially outside protected areas. However, due to their morphological similarities, identification to species level may prove difficult, especially in zones of sympatry.

Lead agencies, Partners and Funders

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