Rationale
This mountain fynbos, thicket and grassland endemic species is listed as Least Concern because it has a relatively wide distribution within the assessment region (including Western Cape, Northern Cape, Eastern Cape and Free State Provinces) and occupies habitats that are largely inaccessible and unlikely to be transformed on a significant scale. It is very common in high mountain fynbos, predominantly on rocky slopes and dense fynbos patches, and this habitat is not prone to being overgrazed. However, the effects of climate change on this species should be monitored and, should molecular research reveal a species complex, it will necessitate a reassessment.
Distribution
The species is endemic to South Africa and occurs in two disjunct regions, the Fynbos of the Cape Fold Belt Mountains of the Western Cape as well as in the grasslands of southern Drakensberg in northern Eastern Cape and the central plateau grasslands of the southern Free State (Monadjem et al. 2015). It has been reported as occurring in Lesotho but this appears to have been a misidentification. Specifically, in the Eastern Cape, they occur south of 32ºS from King William’s Town in the east to Port Elizabeth in the west, possibly as far as Bredasdorp (Taylor 2013). In the Western Cape, they occur in mountainous winter rainfall areas from the Cape Peninsula to Citrusdal (Taylor 2013). They also occur in summer rainfall areas of the southern areas of the Drakensberg range (north of 32ºS and west of Lesotho) and into the Free State (Taylor 2013). The two disjunct populations in Western Cape and northern Eastern Cape and Free State State may be distinct species although molecular and chromosomal data are currently lacking (Monadjem et al. 2015). However, individuals from the Free State are conspicuously smaller than other members of this species (Taylor et al. 2005). Further research is needed to resolve its taxonomic and thus geographical delimitations.
Population trend
Trend
While the population size or density is unknown, it is much less common that O. irroratus in the Eastern Cape (Taylor 2013). Recent surveys suggest it may be hybridising with O. irroratus, however, further genetic and chromosomal research is needed to determine the taxonomic status of these populations.
Threats
There are no major threats known, although habitat loss and degradation from wetland drainage, grassland loss and exotic vegetation, are all suspected to be minor threats. Additionally, hybridisation may be a problem for the eastern subspecies. Additionally, climate change may represent an emerging threat to the montane grassland habitats that this species predominantly occupies. Climate modelling for similarly mesic-adapted Otomys species reveals significant reductions in area of occupancy by 2050, particularly in the Western Cape region (Taylor et al. 2016). More research is needed to determine specific effects of climate change on O. karoensis.
Wetlands are the most threatened ecosystem in South Africa (Driver et al. 2012). The South African National Land-Cover change report found a 32.8% decline in natural wetlands nationally from 1990-2013/14, which is a combination of both genuine wetland loss through anthropogenic activities and the generally drier conditions currently that in 1990 (GeoTerraImage 2015). In the Western Cape, specifically, 31% of all wetlands (plus a 32m buffer) and riparian areas have been transformed/lost to agricultural land use (Pence 2012).
Uses and trade
This species is not known to be utilised or traded.
Conservation
This species occurs within several protected areas within the Western and Eastern Cape, although these are yet to be comprehensively documented. Although no specific interventions are necessary at present, the conservation and restoration of wetlands and grasslands would benefit this species. The following interventions are thus encouraged:
- Using previously cultivated areas for development instead of remaining natural areas.
- Land managers should maintain a vegetation buffer around wetlands to reduce impacts of land-use practices (Driver et al. 2012).
