Red List of South African Species

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Least Concern (LC)
Assessors: Mike Perrin Matthew Child Ara Mondajem
Contributors: Claire Relton Nico Avenant Margaret Avery Rod Baxter Duncan MacFadyen Guy Palmer Peter Taylor Beryl Wilson
Reviewers: Mike Perrin Matthew Child Ara Mondajem

Rationale

Listed as Least Concern in view of its wide distribution within the assessment region, and its occurrence in numerous protected areas, including Kruger National Park. However, this species may become threatened in the near future as encroaching human settlements and industries degrade the woodlands needed by this species. Selective harvesting of tall trees for firewood and charcoal production, as well as wholesale destruction of woodlands by mining and agricultural expansion, threaten to cause population decline. For example, it is estimated that, between 1990 and 2006, 20% of woodland cover was lost to pine and Eucalyptus plantations and residential expansion in the Soutpansberg, Limpopo Province. Assuming the rate of loss is linear, 1.25% of woodland is lost per year in the region, which, if extrapolated across the province, could lead to a 12.5% decline in woodland cover over the next ten years and a suspected population decline. Similarly, models of fuelwood extraction from the Bushbuckridge region in Mpumalanga Province indicate that biomass in the area will be exhausted within 13 years at current rates of extraction. However, the relationship between woodland loss and population density is unknown, and more research is needed to estimate potential population decline. Remote sensing techniques (for example, Landsat imagery or LiDAR) should be used to assess tall tree loss at finer spatial scales and field surveys should be used to ground-truth the suspected impact on this species’ population. These data can then be used to estimate both the area of occupancy and the rate of population decline for this species. A reassessment will be needed when such data are available, as we suspect that this species may qualify for a threatened category. This species is a dietary specialist with a complex gastric anatomy containing microbial symbionts, which may negatively affect the colonisation of new woodland sites, particularly those containing different species composition. Thus significant rescue effects are doubtful. Key interventions for this species include the conservation of tall tree structure through protected area expansion, biodiversity stewardship and community engagement, and active rehabilitation of degraded sites.

Regional population effects: Possible through contiguous habitat or patches linked by corridors and dispersal across Botswana, Zimbabwe and Mozambique.

Distribution

This species ranges widely from southern Ethiopia and southern Somalia in the north, through East Africa, to southern parts of the Democratic Republic of the Congo, Angola and much of Zambia. From here, it ranges south to northeastern South Africa (northern KwaZulu-Natal, Mpumalanga, Limpopo, Gauteng and North West provinces) and Swaziland. The western limit of its distribution within the assessment region is unclear and may be more or less extensive than shown in Figure 1 (see Perrin 2013; Monadjem et al. 2015). For example, Power (2014) captured this species in the northeastern bushveld of the North West Province, where it often associates with human habitation, but there were no captures in the western district in the Kalahari, where one could expect them to be and all grass nests examined belonged to the Namaqua Rock Mouse Micaelamys namaquensis. Thallomys paedulcus and T. nigricauda are believed to be parapatric, possibly overlapping partially in a narrow contact zone (Taylor et al. 1995). Further vetting of museum records is required to delimit the respective distributions of T. nigricauda and T. paedulcus.

Population trend

Trend

It can be locally common in suitable habitats but populations are generally small and isolated (Perrin 2013). Although southern Africa is considered a stronghold for this species, it is uncommon. It is difficult to catch and researchers should consider putting traps in trees. For example, P.J. Taylor (unpubl. data) has not captured any individuals in the Soutpansberg Mountains, Limpopo Province, across a gradient of land-use types despite similar overall rodent densities. Worryingly, this corresponds to general woodland loss in the region as estimated by Landsat imagery (Munyati & Kabanda 2009).

Threats

The major threat to this species is woodland loss and degradation (Driver et al. 2012), especially of large mature trees that are potential cavity nesting sites (sensu Dean et al. 1999). Ongoing illegal commercial harvesting of tall trees for firewood or charcoal production is causing a decline in the habitat quality for this species, which is a noted problem in the North West Province (DACE 2008). Fuelwood extraction and plantation forestry has led to a 20% decrease in woodland cover in the Soutpansberg, Limpopo from 1996–2006 (Munyati & Kabanda 2009). In Limpopo Province specifically, urban expansion and agriculture, particularly overgrazing in ranchlands, are key drivers of woodland loss (Munyati & Kabanda 2009). Encroaching human settlements also put pressure on woodlands for supplementary firewood and charcoal production. For example, in the Bushbuckridge region of Mpumalanga, airborne light detection and ranging (LiDAR) modelling indicates that biomass will be exhausted within 13 years given unsustainable fuelwood extraction (Wessels et al. 2013).

Uses and trade

This species is not known to be traded or utilised in any form.

Conservation

It is present within a number of protected areas, including Kruger National Park. Although no interventions are necessary at present, several interventions could be trialled to prevent this species from becoming threatened in the future. For example, protected area expansion to protect and connect woodlands. This can be done formally or informally through conservancy formation and biodiversity stewardship schemes. Wildlife ranches and conservancies may be helping to conserve habitat for this species by protecting tall trees from charcoal harvesting. This should be encouraged. Harvest management for fuelwood extraction should also be considered. For example, Wessels et al. (2013), in their study area in Mpumalanga, suggested that a 15% annual reduction in consumption for eight years is required to reach sustainable fuelwood extraction levels.

Recommendations for land managers and practitioners:
  • Subpopulations should be monitored to record any changes in abundance and distribution. However, it should be considered that live-trapping in trees off the ground can be time-consuming, and population densities are likely to fluctuate.
  • Land managers should be encouraged to conserve woodlands and old trees.
Research priorities:
  • Rate of woodland loss across the species’ range and its effect on population trend. This can be achieved through the combined use of Landsat imagery and field surveys.
  • Urgent molecular analysis and taxonomic resolution of the species complex.
  • Analysis of museum records to more accurately delimit distribution.
Encouraged citizen actions:
  • Report sightings on virtual museum platforms (for example, iSpot and MammalMAP), especially outside protected areas. However, this species cannot be readily distinguished from T. nigricauda based on morphological characteristics.
  • Landowners can preserve Acacia trees, both living and dead.

References 

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,]
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