Rationale
The Greater Dwarf Shrew is widespread in the assessment region, occurring in a variety of habitats, including suburban gardens, and thus can tolerate slightly transformed landscapes. It occurs in a number of protected areas and can be locally common in suitable habitat, such as riverine woodland, sandveld and moist grasslands. There is no evidence to suggest a net population decline. However, we caution that molecular data, coupled with further field surveys to delimit distribution more accurately, are needed to determine whether the highveld grassland and subtropical grasslands subpopulations comprise separate species. If so, both species will need to be reassessed as high rates of grassland habitat loss in both regions may qualify one or both species for a threatened status.
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: 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 there is not suspected to be a significant rescue effect.
Distribution
Throughout the global range of the Greater Dwarf Shrew there are only a few scattered records (Skinner & Chimimba 2005). However, it is a widespread species that ranges through East Africa, Central Africa and southern Africa. Within the assessment region, it occurs in Mpumalanga, Limpopo, North-West and KwaZulu-Natal provinces. It also occurs in Malolotja and Mlawula Nature Reserves in Swaziland (Monadjem 1998). The known range of the species has been extended westwards into the Zeerust area of North West Province through recent field surveys (Power 2014).
Population trend
Trend
It can be locally common in suitable habitat and is regularly caught during field surveys. For example, it was regularly sampled recently at both Mkhuze Game Reserve and Phinda Private Game Reserve in KwaZulu-Natal Province in a variety of habitat types (Rautenbach et al. 2014; Delcros et al. 2015). Considering it is rare in museum collections (P. Taylor pers. comm.), these are important findings.
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 are Critically Endangered, 12% Endangered and 5% Vulnerable; Driver et al. 2012).
Climate change is considered to be the principal emerging threat to this species, 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
Greater Dwarf Shrew is present in several protected areas (including Kruger National Park) across its range within the assessment region. The main intervention for this species is the protection and restoration of wetlands and grasslands. 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.
Research priorities:
- Further 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).
