Red List of South African Species

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Near Threatened (NT)
Assessors: Galen Rathbun
Contributors: Matthew Child Harriet Davies-Mostert Lizanne Roxburgh
Reviewers: Hanneline Smit-Robinson

Rationale

This species is at the edge of its range within the assessment region where two disjunct subspecies occur: P. t. schwanni in north-eastern Limpopo and P. t. warreni in northern KwaZulu-Natal, both being restricted to intact riparian and coastal forest. The estimated area of occupancy for P. t. schwanni and P. t. warreni, based on remaining forest habitat, is 72 and 192 km2 respectively. Although P. t. warreni at least may represent a South African endemic, further taxonomic resolution is required before we assess it separately. Overall, the species qualifies for Endangered B2ab(ii,iii,v) based on restricted area of occupancy (264 km2 in South Africa) presumed small population size, and a continuing decline in woodland habitat as a result of human expansion over the past decade. In KwaZulu-Natal alone, there was a 7.6% loss of natural habitat from 2005 to 2011. As such, forest patches are likely to be severely fragmented, hindering dispersal of the species. Fragmentation further opens up forest patches for ongoing anthropogenic disturbances, such as incidental bushmeat hunting and removal of ground cover and thus represents a continuing decline in both mature individuals and habitat quality. However, the species occurs predominantly in large, well-managed protected areas, including the Great Limpopo Transfrontier Park (P. t. schwanni) and the Lubombo Transfrontier Conservation Area (P. t. warreni), so net population decline is unlikely. Additionally, rescue effects are possible (see below). Thus we downlist to Near Threatened B2ab(ii,iii,v). The key intervention for this species is further protected area expansion (especially transfrontier expansion) and connection of remaining forest patches. 

Regional population effects: This species is the second-most widespread sengi in Africa, occurring from central and eastern Africa south to the north-eastern corner of South Africa. The assessment region thus represents the edge of its range. Although sengis are not long-distance dispersers, the presence of both subspecies in major transfrontier conservation areas, with presumably intact forest corridors, leads us to suspect rescue effects are possible. However, P. t. schwanni may represent a unique subspecies/species, in which case rescue effects are not possible. This should be investigated and may require reassessment.

Distribution

This species is one of the most widespread sengis, occurring in forest, woodland, and thicket habitats in central and eastern Africa from DR Congo to northeastern South Africa. Their occurrence depends on the availability of suitable forest or woodland habitat with dense underbrush, which is discontinuous throughout their range (Skinner & Chimimba 2005). It is an edge-of-range species within the assessment region, occurring in woodland and forest habitats in Limpopo, KwaZulu-Natal and perhaps Swaziland. The subspecies P. t. warreni occurs in KwaZulu-Natal and may be a South African endemic form (Corbet & Hanks 1968), where their distribution is predominantly coastal (Rathbun 2005), whereas P. t. schwanni occurs in the riparian forests of the northern Limpopo and across the border to the north. Although it has not been recorded from Swaziland (Monadjem 1998), it may possibly occur there marginally in suitable forest habitats.

The estimated area of occupancy (AOO) globally is 2,485,700 km2 based on censored minimum convex polygon with no consideration of fragmented habitat. The estimated global extent of occurrence is 5,700,000 km2. Within the assessment region, the AOO is estimated to be 6,438 km2 based on occupied grid cells. However, if we use forest and woodland areas as a proxy for occupied habitat (Mucina & Rutherford 2006), the estimated AOO for P. t. schwanni and P. t. warreni, based on remaining forest habitat, is 72 and 192 km2 respectively; and thus 264 km2 for the species overall.

Population trend

Trend

Although widespread, the species is often only locally common because it is restricted to closed-canopy forest, woodlands, and thickets. Little information is available on densities. In Afzelia habitat within Arabuko-Sokoke Forest (Kenya), the estimated density was 1.2 animals / ha (FitzGibbon 1995). Using this density for the estimate AOO within the assessment region yields 31,680 individuals. However, there is no evidence that it is abundant. For example, as there was no overlap between the home ranges of adjoining pairs in Tembe Elephant Park, KwaZulu-Natal, low population density was assumed (Oxenham & Perrin 2009). Further studies should be conducted to determine density estimates for both subspecies within the assessment region.

It often foot-drums and thus attracts the attention of people in suitable habitat, but sightings are almost always of individuals. It builds and maintains characteristic and distinct paths through the leaf litter that are often composed of a straight series of clean oval patches, which can be used as an indicator of presence.

Threats

There are no major identified threats range-wide, although habitat loss through woodland clearing and subsistence snaring may have impacts on local subpopulations in the assessment region. If we assume that both woodland clearing and subsistence hunting increase with rural population density and settlement expansion, it is suspected there is an ongoing loss of habitat and mature individuals, especially the forests of KwaZulu-Natal (see below).

Uses and trade

FitzGibbon et al. (1995) documented subsistence hunting in coastal Kenya, which is assumed to continue to the present, but it is not known whether this species is hunted in South Africa. Given the increase in the human population along protected area edges in general (Wittemyer et al. 2008), one could assume that hunting pressure has increased, and may especially be prevalent in KwaZulu-Natal where many rural communities surround forest patches. However, bushmeat hunting of this species may be lower than expected from relative density based on model outputs (Rowcliffe et al. 2003).

Conservation

The species occurs in several protected areas (confirmed in northern Kruger National Park and protected areas in KwaZulu-Natal) within the assessment region, including Great Limpopo Transfrontier Park (P. t. schwanni) and the Lubombo Transfrontier Conservation Area (P. t. warreni). For example, they occur in Tembe Elephant Park (Oxenham & Perrin 2009), Isimangaliso Wetland Park and Bonamanzi Game Reserve. A comprehensive list of protected areas should be tallied. This species would benefit from protected area expansion to conserve woodland habitat and connect subpopulations existing in forest fragments. For example, a transfrontier conservation area in Maputaland that connects with the existing Lubombo Transfrontier Conservation Area has recently been proposed and would add 480 km2 of linking corridors between forest habitats and potentially generate US$18.8 million from game ranching (Smith et al. 2008). Such a protected area network would undoubtedly benefit this species.

Recommendations for land managers and practitioners: 
  • Land owners and communities should reduce stocking rates to conserve undergrowth.
Research priorities:
  • Field surveys to confirm occupancy rate across the assessment region. Continue to accumulate information on occurrence points (see www.sengis.org). Collect evidence to indicate population trends and status of habitats.
  • Genetic and phenotypic analyses to determine whether, if any, species-complexes are present across its distribution south of the Sahara. 
  • Studies to determine the extent and impact of snaring in South Africa.
Encouraged citizen actions:
  • Landowners can create conservancies to protect woodland habitat.

References 

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,]
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