Overview

Otomys laminatus – Thomas & Schwann, 1905

ANIMALIA – CHORDATA – MAMMALIA – RODENTIA – MURIDAE – Otomys – laminatus 

Common Names: Laminate Vlei Rat, KwaZulu Vlei Rat (English)
Synonyms: fannini, mariepsi, pondoensis, silberbaueri   

Taxonomic notes: It is possible that the two disjunct populations represent different species (Monadjem et al. 2015). Further molecular research is needed. Five subspecies were recognised by Roberts (1951) but it is likely that the four eastern forms are synonymous with the nominate form (Meester et al. 1986).   

Red List Status: VU, Vulnerable B2ab(ii,iii,v) (IUCN version 3.1) 

Assessment Information

Assessors: Taylor, P.¹ & da Silva, J.M.² 

Reviewer: Oosthuizen, M.³  

Institutions: ¹University of the Free State,²South African National Biodiversity Institute, ³University of Pretoria 

Previous Assessors and Reviewers: Taylor, P., Baxter, R.& Child, M.F. 

Previous Contributors: Roxburgh, L., Avenant, N., Avery, M., MacFadyen, D., Monadjem, A., Palmer, G. & Wilson, B. 

Assessment Rationale 

This endemic species is restricted to moist grasslands and shrublands and occurs in three isolated subpopulations in the Western Cape (Paarl and Cape Town areas) and eastern grasslands of the Drakensberg of Kwazulu-Natal and Mpumalanga provinces. These three subpopulations may represent separate species and should be reassessed following taxonomic resolution. The estimated area of occupancy (AOO), based on remaining natural fynbos and grassland habitat in all occupied grid cells, is 5,293 km². However, since it relies on moist areas, effective AOO could be as low as 95 km² based on 32 m buffer of natural vegetation around remaining wetlands. There has been 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. There is also a continuing loss of habitat from agricultural expansion, human settlement sprawl and mining. In KwaZulu-Natal alone, there was a 1.2% loss per annum of natural habitat from 1994 and 2011, which means there has been / will be a 12% loss of habitat over a ten-year time period. Climate change is also an emerging threat predicted to significantly reduce area of occupancy in the future (P. Taylor unpubl. data) and may synergise negatively with ongoing land-use change. Additionally, the species is naturally rare, and population size may well be below 10,000 mature individuals based on its current patchy distribution and specialised habitat requirements. However, density estimates are needed to confirm population size and further vetting of museum records is required to delimit its distribution more accurately. Thus, under a precautionary purview, the species is listed as Vulnerable B2ab(ii,iii,v) based on projected declines in habitat and fragmented habitat patches. Although the AOO is likely an underestimate, the true occupancy is not likely to be significantly over 2,000 km².  

Red List Index 

Red List Index: Uplisted 

Reason for change: Based on projected declines in habitat and fragmented habitat patches.  

Recommended Citation: Taylor P & da Silva JM. 2025. A conservation assessment of Otomys laminatus. In Patel T, Smith C, Roxburgh L, da Silva JM & Raimondo D, editors. The Red List of Mammals of South Africa, Eswatini and Lesotho. South African National Biodiversity Institute and Endangered Wildlife Trust, South Africa.

Regional Distribution and occurrence

Geographic Range 

Endemic to South Africa with a patchy distribution in three distinct areas in i) the Western Cape (Paarl and Cape Town areas), ii) the eastern foothills of the central and northern Drakensberg from the Eastern Cape to central KwaZulu-Natal and iii) the Wakkerstroom area of Mpumalanga province (Monadjem et al. 2015). It occurs in the Afromontane-Afroalpine, Highveld and occasionally in the Coastal Forest Mosaic biotic zones (Taylor 2013). Otomys species are generally associated with mesic grasslands and moorlands within alpine, montane and sub-montane regions of Southern, Central, East and West Africa (Monadjem et al. 2015). This species occurs on mid-level grasslands from sea level up to at least 2,000 m asl. It has been referred to in various publications as being recorded from Eswatini but the records for this country have no specimen basis (A. Monadjem pers. comm. 2015). Barn Owl (Tyto alba) pellet analysis reveals a potentially wider distribution in the Western Cape Province than previously recorded (Avery et al. 2005). However, further vetting of museum specimens is needed to delimit distribution more accurately. 

Elevation / Depth / Depth Zones 

Elevation Lower Limit (in metres above sea level): 0 

Elevation Upper Limit (in metres above sea level): 2000 

Depth Lower Limit (in metres below sea level): (Not specified) 

Depth Upper Limit (in metres below sea level): (Not specified) 

Depth Zone: (Not specified) 

Map 

Figure 1. Distribution records for Laminate Vlei Rat (Otomys laminatus) within the assessment region (South Africa, Eswatini and Lesotho). Note that distribution data is obtained from multiple sources and records have not all been individually verified.

Biogeographic Realms 

Biogeographic Realm: Afrotropical 

Occurrence 

Countries of Occurrence 

Large Marine Ecosystems (LME) Occurrence 

Large Marine Ecosystems: (Not specified) 

FAO Area Occurrence 

FAO Marine Areas: (Not specified) 

Climate change

Climate change is an emerging threat predicted to significantly reduce area of occupancy in the future and may synergise negatively with ongoing land-use change. Further research is needed on the effect of climate change on this species. 

Population information

It is considered to be uncommon. For example, it is much less common than Otomys irroratus although occurring in similar habitats (Taylor 2013). However, it is occasionally common; for example, it was the only species of Otomys trapped in a pine plantation (N = 56; P. J. Taylor unpubl. data). The population size is currently unknown but there is very low trapping success for this species throughout its range. As such, there may be fewer than 10,000 mature individuals.  

Population Information 

Current population trend: Declining  

Continuing decline in mature individuals: Yes  

Number of mature individuals in population: Unknown  

Number of mature individuals in largest subpopulation: Unknown  

Number of subpopulations: Three 

Severely fragmented: Yes. Two major subpopulations are isolated from each other. Additionally, most grassland patches are fragmented throughout its range. 

Quantitative Analysis 

Probability of extinction in the wild within 3 generations or 10 years, whichever is longer, maximum 100 years: (Not specified) 

Probability of extinction in the wild within 5 generations or 20 years, whichever is longer, maximum 100 years: (Not specified) 

Probability of extinction in the wild within 100 years: (Not specified) 

Population genetics

Based on available occurrence records, the species appears to exist as three geographically isolated subpopulations, which is expected to limit gene flow; and hence correspond to distinct genetic units. This needs to be confirmed through a population genetic study; however, samples are currently unavailable to test this.  

As a whole, the population size for the species is thought to be below 10,000 individuals (see Population section), If this size is distributed across the three subpopulations, each subpopulation may be thought to contain approximately 3,000 individuals, translating to Ne between 300-1,000 individuals (assuming a Nc/Ne conversion ratio of 0.1-0.3).  Density and genetic diversity estimates are needed to confirm this.  

Habitats and ecology

It occurs in mesic sub-montane grasslands along the Drakensberg foothills and has also been recorded from coastal forests as well as Restio-dominated coastal and mountain fynbos (De Graaff 1981, Taylor et al. 1994, Taylor 1998). Specifically, it inhabits moist habitats such as wetlands and marshes. It may also occur in pine plantations (Taylor 2013), but more research is necessary to determine the extent of this habitat use. It is not known whether it occurs in agricultural landscapes.  

It is probably entirely vegetarian, feeding on shoots and stems of grasses, Restio and small shrubs (De Graaff 1981). Otomys species are generally K-selected, giving birth usually to one or two offspring (maximum five), which are precocial (Monadjem et al. 2015). They have a number of predators including felids, jackals, mongooses, genets, snakes and different owl species (Otomys skulls typically comprise the bulk of owl pellets) (Monadjem et al. 2015). 

Ecosystem and cultural services: Vlei rats are important food for a number of mammalian predators, as well as raptors such as Marsh Owls (Asio capensis) and Barn Owls (Skinner & Chimimba 2005; Monadjem et al. 2015). For example, Vlei rats are favoured food by the Serval (Leptailurus serval) (Bowland 1990), so their range expansion could be interrelated (Power 2014). 

IUCN Habitats Classification Scheme 

Life History 

Age at Maturity: Female or unspecified: (Not specified) 

Age at Maturity: Male: (Not specified) 

Size at Maturity (in cms): Female: (Not specified) 

Size at Maturity (in cms): Male: (Not specified) 

Longevity: (Not specified) 

Average Reproductive Age: (Not specified) 

Maximum Size (in cms): (Not specified) 

Size at Birth (in cms): (Not specified) 

Gestation Time: (Not specified) 

Reproductive Periodicity: (Not specified) 

Average Annual Fecundity or Litter Size: (Not specified) 

Natural Mortality: (Not specified) 

Does the species lay eggs? (Not specified) 

Does the species give birth to live young: (Not specified) 

Does the species exhibit parthenogenesis: (Not specified) 

Does the species have a free-living larval stage? (Not specified) 

Does the species require water for breeding? (Not specified) 

Movement Patterns 

Movement Patterns: (Not specified) 

Congregatory: (Not specified) 

Systems 

System: Terrestrial, Freshwater (=Inland waters) 

General Use and Trade Information

This species is not known to be traded or utilised in any form.  

General notes regarding trade and use of this species: (Not specified) 

Local Livelihood: (Not specified) 

National Commercial Value: (Not specified) 

International Commercial Value: (Not specified) 

End Use: (Not specified) 

Is there harvest from captive/cultivated sources of this species? (Not specified) 

Harvest Trend Comments: (Not specified) 

Threats

There are three main threats that may cause significant population decline in the future: 

• Grassland and wetland habitat loss from agricultural expansion, human settlement sprawl and mining. 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 32 m buffer) and riparian areas have been transformed or lost to agricultural land use (Pence 2012). Habitat loss due to land transformation in the surrounding matrix further isolates wetlands from one another and exacerbates the degradation of individual wetlands. For example, sugarcane and forestry plantations are often planted right up to wetlands edges, not respecting the appropriate buffer. In KwaZulu-Natal alone, there an average loss of natural habitat of 1.2% per annum between in 1994 and 2011 from agriculture, plantations, built environments and settlements, mines and dams (Jewitt et al. 2015). Although no specific rates of habitat loss are available, 61% of Mpumalanga’s land surface between 2000 and 2014 have come under pressure from prospecting applications (Lötter 2015). In Mpumalanga, only 51% of the grasslands are still natural and not previously ploughed and 40% of the grassland vegetation types are listed as threatened (Lötter et al. 2014). Water abstraction or filling in of wetlands from human settlement and industrial expansion also leads to habitat loss. Similarly, suppression of natural ecosystem processes, such as fire, can also lead to habitat degradation through bush encroachment or loss of plant diversity through alien invasive species, and is suspected to be increasing with human settlement expansion. Overall, 45% of our remaining wetland area exists in a heavily modified condition, due primarily to onsite modification from crop cultivation, coal mining, urban development, dam construction, and overgrazing (and thus erosion) and off-site modifications from disruptions to flow regime and deterioration of water quality (Driver et al. 2012). 
• Overgrazing the vegetation around wetlands reduces ground cover and thus leads to decreased small mammal diversity and abundance (Bowland and Perrin 1989, 1993). The expansion of wildlife ranching will have to be monitored in this regard, as game overstocking may also affect wetland condition. 
• Climate change is projected to reduce area of occupancy significantly by reducing temperate grasslands and fynbos habitats. For example, climate models for the similarly mesic-adapted species, O. irroratus, show a decline in area of occupancy of 12–24% by 2050 (Taylor et al. 2016).  

Overgrazing and climate change may synergise to cause non-linear and accelerating population decline. More research is needed to validate these hypotheses.   

Conservation

This species is presumably present in several protected areas, but these remain to be documented comprehensively. Mitigating habitat loss outside of protected areas is urgently. The following interventions should be implemented: 

• Using previously cultivated areas for development instead of remaining natural areas: In Mpumalanga, for example, old lands or previously ploughed areas now left fallow make up 8.9% of the grassland biome (Lötter 2015), and these areas should be prioritised for further development. Similarly, in KwaZulu-Natal, abandoned agricultural fields on marginal lands offer an opportunity for further development instead of transforming virgin land and at least 4% of the landscape is available for this (Jewitt et al. 2015) 
• Wetland conservation and restoration: land managers should maintain a vegetation buffer to reduce impacts of land-use practices (Driver et al. 2012). 
• Holistic management of ranchlands: including de-stocking, rotational grazing and buffering wetland vegetation, are encouraged. 

Recommendations for land managers and practitioners:  

• Land managers should decrease stocking rates to maintain vegetation around wetlands.  
• Prioritise old fields for development in systematic conservation planning.  

Research priorities:  

• Long-term, systematic monitoring is needed to establish subpopulation trends and threat levels, particularly in KwaZulu-Natal and Mpumalanga. 
• Fine scale studies on habitat loss and inferred impact on the species. 
• Effects of overgrazing on the density and viability of this species. 
• Effects of climate change on the species. 
• Effects of habitat connectivity on dispersal rates.  
• Further vetting of museum records to delimit distribution more accurately. 

Bibliography

Avery, D.M., Avery, G. and Palmer, N.G. 2005. Micromammalian distribution and abundance in the Western Cape Province, South Africa, as evidenced by Barn owls Tyto alba (Scopoli). Journal of Natural History 39: 2047–2071. 

Bowland, A.E. and Perrin, M.R. 1989. The effect of overgrazing on the small mammals in Umfolozi Game Reserve. Zeitschrift für Säugetierkunde 54: 251–260. 

Bowland, J.M. 1990. Diet, home range and movement patterns of serval on farmland in Natal. University of KwaZulu-Natal. 

Bowland, J.M. and Perrin, M.E. 1993. Wetlands as reservoirs of small-mammal populations in the Natal Drakensberg. South African Journal of Wildlife Research 23: 39–43. 

Driver, A., Sink, K.J., Nel, J.N., Holness, S., Van Niekerk, L., Daniels, F., Jonas, Z., Majiedt, P.A., Harris, L. and Maze, K. 2012. National Biodiversity Assessment 2011: An assessment of South Africa’s biodiversity and ecosystems. Synthesis Report. South African National Biodiversity Institute and Department of Environmental Affairs, Pretoria, South Africa. 

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Jewitt D., Goodman, P.S., Erasmus, B.F.N., O’Connor, T.G. and Witkowski, E.T.F. 2015. Systematic land-cover change in KwaZulu-Natal, South Africa: Implications for biodiversity. South African Journal of Science 111: 1–9. 

Lötter, M.C. 2015. Technical Report for the Mpumalanga Biodiversity Sector Plan – MBSP. Mpumalanga Tourism & Parks Agency, Mbombela. 

Meester, J.A.J., Rautenbach, I.L., Dippenaar, N.J. and Baker, C.M. 1986. Classification of Southern African Mammals. Monograph number 5. Transvaal Museum , Pretoria, South Africa. 

Monadjem, A., Taylor, P.J., Denys, C. and Cotterill, F.P.D. 2015. Rodents of Sub-Saharan Africa – a biogeographic and taxonomic synthesis. De Gruyter, Berlin/Munich/Boston. 

Pence, Q.D.K. 2012. Contribution of C.A.P.E. Business and Biodiversity Initiatives to conservation of critical biodiversity, landscape connectivity and ecological support areas: Post-baseline assessment (2010). A Green Choice Alliance project report. Conservation South Africa, Cape Town. 

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Skinner, J.D. and Chimimba, C.T. (eds). 2005. The Mammals of the Southern African Subregion. Cambridge University Press, United Kingdom, Cambridge. 

Taylor, P. 1998. The Smaller Mammals of KwaZulu-Natal. University of Natal Press, Pietermaritzburg, South Africa. 

Taylor, P.J. 2013. Otomys laminatus Laminate Vlei Rat (KwaZulu Vlei Rat). In: Happold, D.C.D. (ed.), Mammals of Africa Volume III: Rodents, Hares and Rabbits, pp. 586-587. Bloomsbury, London. 

Taylor, P.J., Nengovhela, A., Linden, J. and Baxter, R.M. 2016. Past, present, and future distribution of Afromontane rodents (Muridae: Otomys) reflect climate-change predicted biome changes. Mammalia 80: 359–375. 

Taylor, P.J., Richardson, E.J., Meester, J. and Wingate, L. 1994. New distribution records for six small mammal species in Natal, with notes on their taxonomy and ecology. Durban Museum Novitates 19: 59-66. 

de Graaff, G. 1981. The Rodents of Southern Africa: Notes on their Identification, Distribution, Ecology, and Taxonomy. Butterworths, Durban, Pretoria, South Africa.