Rationale
The Lesser Dwarf Shrew is widespread within the assessment region, occurring across many habitat types, including gardens, and can be locally common. It presumably occurs in many protected areas and there is no evidence of net population decline, although ongoing habitat loss and degradation (particularly the loss of termitaria) may cause local declines or extinctions. Thus, we list this species as Least Concern. However, further field studies are needed to confirm its presence in protected areas and to more accurately delimit its distribution. Additionally, taxonomic studies may be necessary to determine whether this species represents a species complex. 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 keep livestock or wildlife at ecological carrying capacity.
Regional population effects: Although its habitat is connected and intact through the Greater Limpopo Transfrontier Park, and thus dispersal is technically possible between South Africa, Mozambique and Zimbabwe, the poor dispersal abilities of this species means there is unlikely to be a significant rescue effect.
Distribution
Distributional records are scattered for the Lesser Dwarf Shrew and further field studies are needed to more accurately delimit its distribution within the assessment region and across southern Africa (Skinner & Chimimba 2005). The core distribution is South Africa, Lesotho and Zimbabwe, but it has also been recorded from Mozambique, Zambia, Tanzania, eastern Democratic Republic of the Congo, Malawi, and Nigeria. Within the assessment region, they occur or have been recorded from all provinces, most widely in KwaZulu-Natal and Free State provinces. Although a recent survey did not find this species in North West Province (Power 2014), they are difficult to trap and this may not necessarily reflect population decline in the area. They have not been recorded from Swaziland (Monadjem 1998), but the Highveld grassland areas of the country may provide suitable habitat.
Population trend
Trend
This species is difficult to sample because of its small size, and more effort should be concentrated towards sampling disused termitaria. For example, Lynch (1986) found 56% of disused termitaria in his study were utilised by Lesser Dwarf Shrews. Barn Owl (Tyto alba) pellet analysis indicates they are common in the lake areas (for example, Sedgefield) of Western Cape Province and constitute the major prey item in some areas (Avery et al. 2005).
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 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 Critically Endangered, 12% Endangered and 5% Vulnerable; Driver et al. 2012).
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.
Uses and trade
There is no known subsistence or commercial use of this species.
Conservation
The Lesser Dwarf Shrew has been recorded from several protected areas across its range within the assessment region; for example, De Hoop Nature Reserve, Western Cape Province (Avery et al. 2005). Although no specific intervention is required at present, the protection and restoration of wetlands and grasslands would be beneficial to all shrew species. 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 habitat patches that will enable adaptation to climate change. 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 a buffer strip 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 and to maintain a buffer of natural vegetation around wetlands.
- Protect disused termitaria to provide microhabitats for this species.
Research priorities:
- Additional field surveys are needed to clarify and confirm the distribution of this species.
- Further molecular research may be needed to disentangle a possible species complex.
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).
