Overview

Suncus infinitesimus – (Heller, 1912)

ANIMALIA – CHORDATA – MAMMALIA – EULIPOTYPHLA – SORICIDAE – Suncus – infinitesimus 

Common Names: Least Dwarf Shrew (English), Kleinste Dwergskeerbek (Afrikaans)

Synonyms: No Synonyms 

Taxonomic Note:
Suncus infinitesimus possibly represents a complex of at least two similar species. These species may prove to be endemic to the assessment region if the isolated records from east and central Africa pertain to different species. Further studies are needed to clarify the taxonomic status of populations currently allocated to this species. 

Red List Status: LC – Least Concern, (IUCN version 3.1) 

Assessment Information

Assessor: Russo, I.M.¹, da Silva, J. M.²

Reviewer: Smith, C.³ 

Institutions: ¹Cardiff University, ²South African National Biodiversity Institute, ³Endangered Wildlife Trust 

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

Previous Reviewer: Child, M.F. 

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

Assessment Rationale 

The Least Dwarf Shrew is widespread within the assessment region, occurring across many habitat types, including gardens, and is regularly sampled in suitable habitats. It is common and can be overlooked due to its small size. It is present in several protected areas, and there is no evidence for net population decline. Thus, we evaluate the species as Least Concern. However, we caution that, pending molecular research, the species may be split into several species that would most likely represent one or more endemic taxa. This requires reassessment once the taxonomy has been resolved. Key interventions include protected area expansion of moist grassland and riverine woodland habitats, as well as providing incentives for landowners to sustain natural vegetation around wetlands and keeping livestock or wildlife at ecological carrying capacity to avoid overgrazing. 

Regional population effects: There is a disjunct distribution between populations in the assessment region and the rest of its range. This species is also a poor disperser. Thus, no significant rescue effect is expected. 

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: Russo IM da Silva J M. 2025. A conservation assessment of Suncus infinitesimus. 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 

The Least Dwarf Shrew has a seemingly wide African distribution: it is found in South Africa and Kenya (Rumruti and Rongai), with additional isolated records from the Central African Republic and Cameroon. It possibly occurs in Uganda, however, this needs to be confirmed. Thus, there is a disjunct distribution between the South African population and populations in east and central Africa. Additionally, it is thought to be a species complex and molecular research may reveal the South African population to be an endemic species. Thus, we currently call this species Near Endemic. 

Within the assessment region, it occurs extensively in the Gauteng, Mpumalanga, KwaZulu-Natal and Eastern Cape Provinces, and marginally in the North West, Free State, and Western Cape Provinces (Skinner & Chimimba 2005). A single specimen has been collected from Malolotja Nature Reserve in the highveld region of Eswatini (Monadjem 1998). 

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 Least Dwarf Shrew (Suncus infinitesimus) 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 considered to be the principal emerging threat to this species (Ogony 2014), both due to loss of habitat and habitat degradation from drying out of wetlands and because shrews cannot tolerate extremes of temperature for long and thus their foraging time will be reduced. Because of their high metabolism, low dispersal capacity and short life spans, climate change may reduce the amount of suitable habitat available. 

Population Information

This species has an extremely small body size (2.5–3 g, Skinner & Chimimba 2005), and thus rarely triggers traps during field surveys. As such, it is often overlooked and may be more common than thought. For example, it probably occurs throughout the woodland areas of the eastern North West Province (Power 2014). Similarly, it was recently regularly sampled at Phinda Private Game Reserve, KwaZulu-Natal Province across multiple habitats (Rautenbach et al. 2014), and elsewhere in KwaZulu-Natal (J. Harvey unpubl. data). Considering it is rare in museum collections (P. Taylor pers. comm. 2015), this is an important finding.  

Population Information 

Current population trend: Unknown  

Number of mature individuals in population: Unknown 

Number of mature individuals in largest subpopulation: Unknown  

Number of subpopulations: Unknown  

Severely fragmented: No. Can utilise modified habitats, but poor dispersal ability may negate its broad habitat suitability. 

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

Continuing decline in number of subpopulations: (Not specified) 

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 numerous molecular studies have been undertaken on other Suncus species, particularly within Asia, no population genetics have been conducted for this species within the assessment region. Given the limited records and studies for this species, it is not possible to estimate the number of isolated subpopulations or their effective population size (Ne). 

Habitats and ecology

It has a broad habitat tolerance, occurring in primary forest, montane grassland, subtropical grassland savannah, bushveld and suburban or rural gardens (Taylor 1998; Skinner & Chimimba 2005). In Kenya (Rongai), it was found on agricultural land. At Phinda Private Game Reserve, KwaZulu-Natal Province, it was sampled in flood plain grasslands and woodlands (Rautenbach et al. 2014). Interestingly, it was sampled along with Dendromus mystacalis in Kikuyu (Pennisetum clandestinum) pastures in Umvoti Vlei Conservancy, KwaZulu-Natal Province, despite this habitat having a low small mammal abundance (Fuller & Perrin 2001). It is commonly associated with disused termite mounds from the species Trinervitermes trinervoides (Lynch 1983), presumably used for thermoregulation. They are insectivorous and have been recorded in Barn Owl pellets (Skinner & Chimimba 2005). In Eswatini, this species has been collected from a rocky outcrop in Highveld sour grassland (Monadjem 1998). 

Ecosystem and cultural services: An important prey species. 

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 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 & Perrin 1989, 1993). Suppression of natural ecosystem processes, such as severe fire, can also lead to habitat degradation through bush encroachment or loss of plant diversity through alien invasives, and is suspected to be increasing with human settlement expansion. There are also clear overlaps and synergistic effects between these threats. Across South Africa, 65% of wetland ecosystem types are threatened (48% of all wetland types are Critically Endangered, 12% – Endangered and 5% – Vulnerable; Driver et al. 2012). 

Current habitat trend: In KwaZulu-Natal Province alone, there was a 19.7% loss of natural habitat from 1994 to 2008, with an average loss of 1.2% per annum (Jewitt et al. 2015). If this rate of loss continues into the future, there will be an estimated 12% loss of habitat over 10 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). However, as long as natural vegetation is maintained around wetlands, rivers and artificial waterbodies, habitat for this species is suspected to remain stable. Additionally, the expansion of wildlife ranching may have a positive effect on this species as more termitaria are likely to be conserved on old fields or fallow lands. 

Conservation

The Least Dwarf Shrew is present in several protected areas across its range within the assessment region. The main intervention for this species is the protection and restoration of grasslands and wetlands. Biodiversity stewardship schemes should be promoted if landowners possess wetlands or grasslands close to core protected areas or remaining habitat patches, and the effects on small mammal subpopulations should be monitored. Protecting such habitats may create dispersal corridors between grassland patches. 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 & Perrin 1989), or by maintaining buffer strips of natural vegetation around wetlands (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 & Perrin 1993). 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. 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: 

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

Research priorities: 

• Molecular research is needed to ascertain the validity of the putative species complex. 

• Additional field surveys are needed to clarify and confirm the distribution of 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. 

Fuller, J.A. and Perrin, M.R. 2001. Habitat assessment of small mammals in the Umvoti Vlei Conservancy, KwaZulu-Natal, South Africa. South African Journal of Wildlife Research 31: 1-12. 

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

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. 

Lynch, C.D. 1983. The mammals of the Orange Free State, South Africa. Navorsinge van die Nasionale Museum Bloemfontein 18: 1-218. 

Monadjem A. 1998. The mammals of Swaziland. Conservation Trust of Swaziland and Big Games Parks, Mbabane, Swaziland. 

Ogony OL. 2014. Potential impacts of climate change on Mysorex species as a model for extinction risk of montane small mammals in South Africa. M.Sc. Thesis. University of Venda, Thoyandou, South Africa. 

Power, R.J. 2014. The distribution and status of mammals in the North West Province. Department of Economic Development, Environment, Conservation & Tourism, North West Provincial Government, Mahikeng. 

Rautenbach A, Dickerson T, Schoeman MC. 2014. Diversity of rodent and shrew assemblages in different vegetation types of the savannah biome in South Africa: no evidence for nested subsets or competition. African Journal of Ecology 52: 30-40. 

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.