Rationale
(Changed due to Incorrect data used previously)
This South Africa endemic species is a forest habitat specialist, occurring primarily in subtropical swamps, wetlands and coastal forests of 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, based on both museum and recent field records, is estimated to be 15,972 km², while its area of occupancy (AOO), based on natural forest habitat remaining in 2014, is estimated to be 697 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. Recent remote sensing data show that 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 annum. If this rate of loss continues into the future, there will be an estimated 12% loss of habitat over the next 10 years. 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 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 colonize 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.
Distribution
Sclater’s Forest Shrew is endemic to northern 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 range limits. It is sympatric in some areas with the more widespread Myosoerx varius. Its extent of occurrence (EOO), based on both museum and recent field records, is estimated to be 15,972 km²; its EOO based on a minimum convex polygon around its mapped distribution attached to this assessment, is 22,984 km². Its area of occupancy (AOO), based on natural forest habitat remaining in 2014, is estimated to be 697 km².
Population trend
Trend
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.
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).
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. 2016).
Uses and trade
There is no known subsistence or commercial use of this species.
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 minimize 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 incentivized 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 more 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).
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).
