Overview

Myosorex sclateri – Thomas & Schwann, 1905

ANIMALIA – CHORDATA – MAMMALIA – EULIPOTYPHLA – SORICIDAE – Myosorex – sclateri 

Common Names: Sclater’s Forest Shrew, Sclater’s Mouse Shrew, clater’s Tiny Mouse Shrew (English), Sclater se bosskeerbek (Afrikaans)

Synonyms: No Synonyms 

Taxonomic Note: 
Meester et al. (1986) recognised two subspecies: Myosorex cafer cafer and M. c. sclateri but biochemical and morphological data suggested elevation to full species status for both taxa (Maddalena and Bronner 1992, Kearney 1993). Myosorex sclateri and M. cafer are now both recognised species (Willows-Munro 2008). For details on the evolutionary history and relationships within the Myosorex genus see Willows-Munro and Matthee (2009) and Taylor et al. (2013). 

Red List Status: VU – Vulnerable, B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv) (IUCN version 3.1) 

Assessment Information

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

Reviewer: Russo, I.³ 

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

Previous Assessors: Taylor, P. & Baxter, R. 

Previous Reviewer: Child, M.F. 

Assessment Rationale 

This South Africa endemic species is a forest habitat specialist, occurring primarily in subtropical swamps, wetlands and coastal forests of the northern KwaZulu-Natal Province. This species cannot exist in transformed or degraded habitats and depends on intact ecotones between forest and moist grasslands. Its extent of occurrence (EOO), based on both museum and recent field records, is estimated to be 16,153 km², while its area of occupancy (AOO), based on all natural forest habitat remaining with the EOO in 2018, is estimated to be 684 km², while the IUCN method, that uses occurrence of the species within a 2 by 2 km grid, estimates the AOO as 160 km². The species is threatened by ongoing habitat loss and degradation, caused primarily by coastal development, human settlement expansion, forest clear-cutting for agriculture and overgrazing from livestock farming. Remote sensing data show that there was a 19.7% loss of natural habitat in the KwaZulu-Natal Province from 1994 to 2011, with an average loss of 1.2% per annum. There’s an estimated 12% loss of habitat between 2012 and 2022. Corroborating this, new national land-cover datasets reveal that, between 2000 and 2013, there has been a 5.6% and 1.1% rate of urban and rural expansion respectively in the KwaZulu-Natal Province. Remaining forest patches are fragmented, and the species is suspected to have poor dispersal rates. Thus, we list this species as Vulnerable B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv) due to its restricted range, the severely fragmented nature of remaining forest patches or subpopulations, and an inferred continuing decline in extent, occupancy and the number of subpopulations from ongoing coastal development as well as an inferred decline in habitat quality from expanding human settlements and thus potential for overgrazing and water abstraction.

Recent climate modelling research shows that suitable habitats for the species may expand by 2050, but this gain may be negated by the ongoing development in coastal areas, low dispersal capacity and inability to colonise new patches without assistance. Key interventions include protected area expansion of forest habitats, including the creation of corridors between patches to facilitate gene flow, as well as the enforcement of regulations restricting development sprawl and disturbance to protected forest/grassland ecotones. 

Reasons for Change 

Reason(s) for Change in Red List Category from the Previous Assessment: No change 

Red List Index 

Red List Index: No change

Recommended citation: Taylor P & da Silva JM. 2025. A conservation assessment of Myosorex sclateri. 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 

Sclater’s Forest Shrew is endemic to northern the KwaZulu-Natal Province, South Africa. It is restricted to moist lowland subtropical, scarp and coastal forests on the Maputaland coastal plain. Further field surveys are necessary to delimit its precise northern and eastern distributional limits. It is sympatric in some areas with the more widespread Myosorex varius. Its EOO, based on both museum and recent field records is estimated to be 16,153 km². Its AOO, based on all natural forest habitat remaining with the EOO in 2018, is estimated to be 684 km², while the IUCN method, that uses occurrence of the species within a 2 by 2 km grid, estimates the AOO as 160 km². 

Elevation / Depth / Depth Zones 

Elevation Lower Limit (in metres above sea level): (Not specified) 

Elevation Upper Limit (in metres above sea level): (Not specified) 

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 Sclater’s Forest Shrew (Myosorex sclateri) 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 not considered to be an emerging threat to this species as model predictions for the year 2050 show a gain in suitable areas (Taylor et al. 2016). However, the fragmented nature of forest patches is likely to persist, which may negate the benefit of suitable habitat expansion as individuals are restricted from colonising new areas. Additionally, range expansion is improbable since it is a coastal forest specialist and most of the areas included in the expanded range include unsuitable habitat which would not support populations of the species (Taylor et al. 2017).  

Population information

This species is not common, but it is regularly caught during surveys (P. Taylor unpubl. data). In Dukuduku Forest, it was the most abundant shrew species sampled (Rautenbach and Bronner 1989). More research is needed to estimate densities across its range to enable a calculation of population size.  

Population Information 

Current population trend: Declining. Inferred from ongoing forest habitat loss and degradation. 

Continuing decline in mature individuals: Unknown  

Number of mature individuals in population: Unknown  

Number of mature individuals in largest subpopulation: Unknown 

Number of subpopulations: Unknown, but may correspond to discrete forest patches.  

Extreme fluctuations in the number of subpopulations: (Not specified) 

Continuing decline in number of subpopulations: Yes. Inferred from ongoing forest loss. 

All individuals in one subpopulation: (Not specified) 

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

While M. sclateri  has been incorporated into phylogeographic studies for the genus (e.g., Willows-Munro & Matthee 2009), no specific population genetic study has been conducted on this species. Based on the limited distribution of the species in the assessment region and the knowledge of biogeographic barriers for other species within the genus (Willows-Munro & Matthee 2011), it is likely to exist as a single metapopulation. Because no other populations are thought to have gone extinct, the Convention on Biological Diversity’s Global Biodiversity Framework’s (GBF) complementary genetic indicator – proportion of populations maintained (PM) – would receive a value of 1.0 (1/1 populations remaining). 

No population size estimates are available for the species, and the species is not considered common. Therefore, it is not possible to quantify the GBF’s headline indicator – proportion of populations with an effective population size (Ne) > 500. It is highly recommended that a fine scale population genetic study be undertaken across its known distribution. This will enable the quantification of Ne and possibly identify whether additional genetic structure exists.  

Habitats and ecology

Sclater’s Forest Shrew is found near water in subtropical swamps and coastal forests. Skinner and Chimimba (2005) reported that it is present in grassland, wetland and reedbed habitats. Specimens have been collected close to grassland/forest ecotones, and thus the species may select habitats more similar to Myosorex varius than M. cafer (Taylor 1998). In Dukuduku Forest, it was one of the dominant shrew species found in grassland (containing sedges and reeds but no woody elements) and abundance peaked in February (Perrin & Bodbijl 2001). Not a lot is known about its biology or ecology, although it is likely to be similar to both M. cafer and M. varius.

Ecosystem and cultural services: Candidate for flagship species in forest biodiversity stewardship schemes. 

IUCN Habitats Classification Scheme 

Life History 

Generation Length: (Not specified) 

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 

General Use and Trade Information

There is no known subsistence or commercial use of this species.  

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

The main threat to shrews is the loss or degradation of moist, productive areas such as wetlands and rank grasslands within suitable forest habitat. The two main drivers behind this are abstraction of surface water and draining of wetlands through industrial and residential expansion, and overgrazing of moist grasslands, which leads to the loss of ground cover and decreases small mammal diversity and abundance (Bowland and Perrin 1989). An increase in overgrazing, resulting from continued rural expansion in the region (see below), may be a particularly severe threat for this species as it exists in lowland, productive areas that are desirable for grazing lands. Suppression of natural ecosystem processes, such as fire, can also lead to habitat degradation through bush encroachment or loss of plant diversity, and is suspected to be increasing with human settlement expansion. There are also clear overlaps and synergistic effects between these threats. Shrews have a high metabolic rate and thus rely on highly productive and complex environments, where small mammal diversity is highest (Bowland and Perrin 1993). Forests are protected by South African law, but they are still being degraded as a result of human encroachment for livestock grazing and fuelwood extraction. The forest biome has one of the highest proportions of threatened ecosystem types (Driver et al. 2012). Similarly, 65% of wetland ecosystem types are threatened (48% Critically Endangered, 12% Endangered and 5% Vulnerable; Driver et al. 2012). 

Current habitat trend: Overall, there was a 19.7% loss of natural habitat in KwaZulu-Natal Province from 1994 to 2011, with an average loss of 1.2% per year (Jewitt et al. 2015). If this rate of loss continued into the future, it is estimated to have a 12% loss of habitat between 2012 to 2022. Worryingly, a massive 7.6% of natural habitat was recently lost in KwaZulu-Natal in just six years (2005–2011). Correspondingly, Southern Coastal and Swamp Forest have declined by at least 1–3% between 2000 and 2013 (F. Daniels unpubl. data). Further analysis is needed to more accurately estimate rate of forest loss over the past ten years. Additionally, between 2000 and 2013, there has been a 5.6% and 1.1% rate of urban and rural expansion in KwaZulu-Natal Province respectively (GeoTerraImage 2015), which indicates both a loss of habitat and possibly an increase in human encroachment on forest and wetland resources, which we infer as increasing habitat degradation. 

Conservation

The main intervention for this species is the protection and restoration of wetlands and grasslands within and around forest patches. This species is present in some protected areas in the northern part of its range (such as Lake St), but there is a need to protect suitable habitat within the landscapes between protected areas. Biodiversity stewardship schemes should be promoted if landowners possess wetlands or grasslands close to core protected areas or remaining forest patches, and the effects on small mammal subpopulations should be monitored. Protecting such habitats may create dispersal corridors between forest patches that will enable adaptation to climate change.

All forests in South Africa are protected by law, although the degree to which this is enforced may vary. Legislation should be enforced to prevent development or human encroachment in key habitats, which includes increased enforcement of forest-related transgressions to minimise disturbance to existing forest patches, as well as stricter zonation on development to decrease fragmentation of remaining forests.

At the local scale, landowners and managers should be educated, encouraged and incentivised to conserve the habitats on which shrews and small mammals depend. Retaining ground cover is the most important management tool to increase small mammal diversity and abundance. This can be achieved through lowering grazing pressure (Bowland and Perrin 1989), or by maintaining a buffer strip of natural vegetation around wetlands (Driver et al. 2012). Research will be needed to set the recommended length of the buffer strip in various habitats, but 500 m may provide a good indication of ecological integrity (Driver et al. 2012). Small mammal diversity and abundance is also higher in more complex or heterogeneous landscapes, where periodic burning is an important tool to achieve this (Bowland and Perrin 1993). Similarly, the specific fire regime thresholds should be calibrated by research. Removing alien vegetation from watersheds, watercourses and wetlands is also an important intervention to improve flow and water quality, and thus habitat quality, for shrews. This can be achieved through the Working for Water Programme (for example, Marais et al. 2004). However, the subsequent effects on shrew subpopulations must be monitored to demonstrate success (sensu Richardson and van Wilgen 2004). Education and awareness campaigns should be employed to teach landowners and local communities about the importance of conserving wetlands and moist grasslands.

Recommendations for land managers and practitioners: 

• More accurate estimates of forest patch occupancy through extensive live-trapping and field surveys should be conducted through dedicated surveys by specialists and conservation authorities to accurately establish geographical range and potential biodiversity stewardship sites, thus informing spatial conservation planning. 

• Enforce regulations on developments that potentially impact on the habitat integrity of forests. 

• Landowners should be incentivised to stock livestock or wildlife at ecological carrying capacity and to maintain a buffer of natural vegetation around wetlands. 

Research priorities: 

• Further analysis of museum specimens is needed to correctly identify and delimit the distributions of M. cafer, M. sclateri and M. tenuis. 

• Research should be conducted to determine disturbance thresholds in various habitats (for example, ecological stocking rates, amount of natural vegetation needed to sustain a viable subpopulation, and fire intensity and frequency needed to sustain habitat complexity) needed by managers to conserve shrew species. 

• Additional information is needed on the distribution, natural history and threats to this species. 

Encouraged citizen actions: 

• Citizens are requested to submit any shrews killed by cats or drowned in pools to a museum or a provincial conservation authority for identification, thereby enhancing our knowledge of shrew distribution (carcasses can be placed in a ziplock bag and frozen with the locality recorded). 

Bibliography

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. 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. 

GeoTerraImage. 2015. Quantifying settlement and built-up land use change in South Africa. Pretoria. 

IUCN. 2020. The IUCN Red List of Threatened Species. Version 2020-2. Available at: www.iucnredlist.org. (Accessed: 13 June 2020). 

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. 

Kearney, T.C. 1993. A craniometric analysis of three taxa of Myosorex from Natal and Transkei. University of KwaZulu-Natal. 

Maddalena, T. and Bronner, G. 1992. Biochemical systematics of the endemic African genus Myosorex Gray, 1838 (Mammalia: Soricidae). Israel Journal of Zoology 38: 245-252. 

Marais, C., van Wilgen, B.W. and Stevens, D. 2004. The clearing of invasive alien plants in South Africa: a preliminary assessment of costs and progress: working for water. South African Journal of Science 100: 97-103. 

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. 

Perrin, M.R. and Bodbijl, T. 2001. Habitat selection and small mammal prey availability of the gaboon adder in Zululand (KwaZulu-Natal), South Africa. South African Journal of Wildlife Research 31: 115-126. 

Rautenbach, I.L. and Bronner G.N. 1989. The mammals of Dukuduku Forest – results of a survey conducted 1–7 October 1988. Department of Mammals, Transvaal Museum, Pretoria, South Africa. 

Richardson, D.M. and van Wilgen, B.W. 2004. Invasive alien plants in South Africa: how well do we understand the ecological impacts? South African Journal of Science 100: 45-52. 

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., Kearney, T.C., Peterhans, K., Julian, C., Baxter, R.M. and Willows-Munro, S. 2013. Cryptic diversity in forest shrews of the genus Myosorex from southern Africa, with the description of a new species and comments on Myosorex tenuis. Zoological Journal of the Linnean Society 169: 881–902. 

Taylor, P.J., Ogony L., Ogola, J. and Baxter, R.M. 2017. South African mouse shrews (Myosorex) feel the heat: using species distribution models (SDMs) and IUCN Red List criteria to flag extinction risks due to climate change. Mammal Research 62(2): 149-162. 

Willows-Munro S. 2008. The molecular evolution of African shrews (family Soricidae). Ph.D Thesis. University of Stellenbosch, Stellenbosch, South Africa. 

Willows-Munro, S. and Matthee, C.A. 2009. The evolution of the southern African members of the shrew genus Myosorex: understanding the origin and diversification of a morphologically cryptic group. Molecular Phylogenetics and Evolution 51: 394–398. 

Willows-Munro, S. and Matthee, C.A. 2011. Linking lineage diversification to climate and habitat heterogeneity: phylogeography of the southern African shrew Myosorex varius. Journal of Biogeography 38: 1976-1991.