Red List of South African Species

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Least Concern (LC)
Assessors: Peter Taylor David Jacobs Lientjie Cohen Teresa Kearney Kate MacEwan Leigh Richards Corrie Schoeman Theresa Sethusa Ara Monadjem
Contributors: Domitilla Raimondo Matthew Child
Reviewers: Peter Taylor David Jacobs Lientjie Cohen Teresa Kearney Kate MacEwan Leigh Rosanne Richards Corrie Shoeman Theresa Sethusa Ara Monadjem

Rationale

This newly described species is near endemic to the assessment region, occurring in riparian woodlands across the Limpopo Valley and the Soutpansberg, Blouberg and Waterberg Mountains of Limpopo Province. Recent field surveys have shown that, although essentially limited to one province of South Africa (with a small, isolated Zimbabwean population), the species is quite widespread so areas of occupancy and occurrence exceed thresholds for Vulnerable under Criterion B. While there is no evidence for decline in the species or its habitat as the Savannah biome is well protected within the assessment region, it is not common: colony sizes are small (possibly < 40 individuals) and the species appears to have a scattered occurrence in the landscape since it is limited by availability of roosting sites, and possibly suitable water sources. There are 19 known localities, which would yield a population size of 760 individuals within the assessment region. While this may be an underestimate due to unidentified localities, we assume the overall population is not significantly more than 1,000 mature individuals and list as Near Threatened D1. We urge further field surveys to identify further colonies and estimate population size more accurately. This species should be reassessed once such data are available as it may qualify for a more threatened listing.

Regional population effects: This species has intermediate wing loading (Aldridge & Rautenbach 1987; Norberg & Rayner 1987; Schoeman & Jacobs 2008), and thus dispersal capacity is limited. Additionally, as the Zimbabwean population appears to be isolated from the assessment region, we assume no rescue effects are possible.

Distribution

This species is known to occur in two isolated areas, the Lutope-Ngolanola confluence just south of the Zambezi Escarpment in Zimbabwe (one known locality), and the Limpopo Province of South Africa (19 localities) where it is associated with the Limpopo Valley and the Soutpansberg, Blouberg and Waterberg Mountains (Taylor et al. 2012, 2013). It is likely more widespread across savannah woodlands of the Limpopo and Zambezi valleys, and their escarpments (the Gwembe horst, and the Soutpansberg and Waterberg Mountains, respectively). Accurate delimitation of this species’ range is subject to further collecting and reappraisal of existing museum material previously assigned to R. hildebrandti (Taylor et al. 2012). The estimated extent of occurrence within the assessment region is 87,132 km2.

Population trend

Trend

This species is relatively widespread within the northern parts of the assessment region. However, colony sizes are very small (just a few individuals) and the species appears to have a scattered occurrence in the landscape as, for example, it is rarely collected with harp traps or recorded with bat detectors during surveys of the Soutpansberg. While Smithers (1971) recorded colonies of over 100 individuals of R. hildebrandti in Botswana, we assume the colony structure of R. smithersi is closer to that of R. cohenae, which roosts in colonies of up to 40 individuals. This would yield an overall population estimate of 760 individuals occurring in 19 localities in the assessment region. While it is likely that some localities have been missed, we assume that the overall mature population is not significantly more than 1,000 individuals, especially considering that some colonies are likely to be fewer than 40 individuals. This inference is supported by the observation that it is limited by the availability of roosting sites and possibly suitable water sources. Further monitoring is necessary to determine population size and trend more accurately.

Threats

There are no known major threats to this species at present as much of its range occurs throughout the Soutpansberg, Blouberg and Waterberg ranges of Limpopo Province where human impacts and habitat transformation are not yet severe. The threat of extensive planned coal, platinum, natural gas (fracking) and other mining developments over much of the Limpopo Valley and the foothills of the Soutpansberg and Waterberg mountains and the Mahabeng Plateau (Desmet et al. 2013), however, could impact heavily on subpopulations through roosting and foraging habitat loss, noise, air and water pollution and water abstraction leading to degradation of riparian habitats. For example, R. smithersi was amongst five bat species recorded for the first time at Gatkop Cave (compared to surveys in the 1960s and 1980s), Limpopo Province, in December 2011 when thousands of M. natalensis use the cave, which may indicate a loss of other roost sites in the region (Kearney et al. 2016).

Suppression of fire, together with over-grazing of cattle and game, and climate change (sensu Sherwin et al. 2013) has resulted in serious bush encroachment of savannahs across much of its range (for example, the western Soutpansberg) which has been shown to have a negative effect on biodiversity generally (for example, Taylor et al. 2016). In the eastern Soutpansberg, afforestation and alien plant invasions have considerably altered natural habitats (sensu Armstrong & van Hensbergen 1996; Armstrong et al. 1998). Limpopo Province is extremely drought-prone and water-stressed and is projected to experience climate change (Erasmus et al. 2002; Boko et al. 2007). Since the species seems to be dependent on water sources for drinking, extreme droughts in the area have had potentially devastating effects on wildlife generally.

Uses and trade

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

Conservation

In the assessment area, the species is recorded from many protected areas, including Greater Mapungubwe Transfrontier Conservation Area, Kruger National Park, Nwanedi Nature Reserve, Blouberg Nature Reserve, Wolkberg Wilderness Area and Legalameetse Nature Reserve. Not counting the Zimbabwean population, the majority of the species’ range within South Africa is included within two UNESCO Biosphere Reserves, the Vhembe and Waterberg Biosphere Reserves. Defining and refining core and buffer areas is a critical part of the ongoing management of these reserves. Roosting sites of bats should be included in determining the location of such zones within biosphere reserves. This means that important bat underground (natural and man-made) roosts (including those of R. smithersi) should be included wherever possible in core or buffer areas where developments (including mining) would have to be regulated. Such conservation zonation plans (including Strategic Environmental Frameworks, EMFs) would inform planning by Provincial Nature Conservation (including the protected areas expansion strategy) and municipal Integrated Development Plans (IDPs), thereby affording protection to roosting sites.

Recommendations for land managers and practitioners:
  • Landowners should implement best land-use management practices to maintain sustainability and limit disturbance at roosting sites. To achieve this, ecological advisory services and training are needed.
Research priorities:
  • Field surveys and niche modelling to more accurately delimit distribution range, and to identify key roost sites for protection.
  • Further vetting of R. hildebrandti specimens to more accurately delimit distribution range.
  • Investigating patterns of movement to establish level of demographic and genetic exchange between colonies and quantifying the effects on transformation/fragmentation on such processes. This would also enable a more accurate estimate of population size and trend.
Encouraged citizen actions:
  • Limit disturbance to roost sites.
  • Avoid or limit the use of pesticides/insecticides for agricultural and household purposes as this can potentially negatively affect the prey base and lead to poisoning of individuals of this species and bats in general.

References 

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