Red List of South African Species

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Near Threatened (NT)
Assessors: Margaretha Hofmeyr Thomas Leuteritz Ernst Baard
Facilitators: Graham Alexander Krystal A Tolley
Reviewers: Anders Rhodin B.T. Henen Peter Paul van Dijk Graham Alexander Adriaan Jordaan Jody Taft

Rationale

The species Psammobates tentorius is widespread and still relatively common, but populations are scattered and few and declining at approximately 10-20% on average over three generations, and therefore considered to be Near Threatened under criterion A4ce; it was previously assessed in 2013 (and published in 2017) as Least Concern. The two subspecies P. t. tentorius and P. t. verroxii are both assessed at this time as Least Concern, but the third subspecies, P. t. trimeni, is assessed as Endangered, A4ce (see separate account for that taxon). The range of P. t. trimeni is small and restricted to a few vegetation units of the western Succulent Karoo, which are under continued pressure. A combined soil and veld degradation index (Hoffman et al. 1999) showed moderate degradation for the taxon’s habitat in the Northern Cape. Bourne et al. (2012) indicated that the Namaqua district (western Northern Cape) experiences multiple impacts from overgrazing, destructive or illegal mining, and unsustainable land use involving ploughing of natural veld for fodder cropping, uncontrolled harvesting of natural products, and irresponsible tourism activities in sensitive areas. The same processes occur in the taxon’s southern habitat in the Western Cape Province, which is severely impacted by cultivation and land degradation (Rouget et al. 2004). Unfortunately, habitat degradation and destruction of the taxon’s sensitive habitat is continuing (Schoeman et al. 2013) and may escalate. Predictions are that climate change will bring an increase in temperature and a decrease in rainfall, with increased aridity in the western Succulent Karoo (Bourne et al. 2012). Such changes would increase grazing pressure in this region, which is expected to affect the status of P. t. trimeni adversely. It is estimated that >30% of the taxon’s habitat has been destroyed over the past 40 years (1.5 generations) and that future changes in habitat over the next 40 years (1.5 generations) will be at least of equal proportions, with a total reduction in population size in excess of 50%. Available information indicates that Pied Crow (Corvus albus) predation on this taxon is increasingly severe, with anthropogenic facilitation having led to increased abundance of this species in western South Africa over the past three decades (Cunningham et al. 2016), making increased predation on P. t. trimeni highly likely, especially in conjunction with the current (and predicted prevailing) South African drought. Consequently, P. t. trimeni is assessed to be Endangered under criterion A4ce. This taxon was also considered Endangered at a Tortoise and Freshwater Turtle Specialist Group Red Listing workshop in 2013 (TTWG 2014, 2017).

Distribution

Psammobates tentorius is restricted to South Africa and Namibia. The distribution ranges of the three recognized subspecies overlap, and there remains some uncertainty about their exact limits. Of the three subspecies, P. t. tentorius occurs furthest to the south, and is morphologically most distinctive in the southeastern portion of its range. Its range extends from Fort Brown in the Eastern Cape to Touws River in the Western Cape. Further north, the range extends to Victoria West and the Kamiesberg Mountains in the Northern Cape. Genetic evaluation has shown that local populations of the northwestern localities (Kamiesberg Mountains) belong to P. t. tentorius instead of their traditional assignment to P. t. trimeni. The distribution of P. t. trimeni is concentrated in the Namaqualand Sandveld and Richtersveld Bioregions and extends peripherally into the Namaqualand Hardeveld Bioregion. Although P. t. trimeni is on record as present in southwestern Namibia (Griffin 2003), its occurrence there has not been verified despite extensive sampling for genetic studies (M.D. Hofmeyr pers. obs.). Psammobates t. verroxii has a wide distribution throughout the Nama Karoo in the Northern Cape and penetrates the Western Cape and possibly the Eastern Cape peripherally. Its range extends across the Orange River into Namibia, as far north as Mariental (Griffin 2003). Genetic evaluation, however, has shown that populations north and south of the Orange River differ from each other (Hofmeyr et al. 2016).

Population trend

Trend

Although Psammobates tentorius is widespread, population density is generally low throughout its range (Branch 2008), and populations appear to be declining slowly. Populations of the restricted subspecies P. t. trimeni appear to be declining more rapidly than the other subspecies (M.D. Hofmeyr pers. obs.).

Threats

Known threats for Psammobates tentorius include road mortality, veld fires, electrocution by livestock/game fences, and overgrazing from domestic livestock (Cunningham and Strauss 2005, Cunningham 2006) as well as predation by small carnivores, eagles, honey badgers, goshawks, crows, monitor lizards, and ostriches (Branch 1989, Malan and Branch 1992, Lloyd and Stadler 1998, Visagie 2011). Available information indicates that Pied Crow (Corvus albus) predation on this taxon is increasingly severe, with anthropogenic facilitation of Pied Crows having led to increased abundance in western South Africa over the past three decades (Cunningham et al. 2016), making increased predation on P. t. trimeni highly likely. Trade is low but illegal collection is still likely, particularly for P. t. trimeni, which is the most colourful subspecies (Cunningham 2006, Branch 2008). Threats are lowest for P. t. verroxii because its distribution is wide and mainly in areas with low human density. The range of P. t. tentorius is relatively large, but populations in some regions may be threatened by land degradation (Hamann and Tuinder 2012). The range of P. t. trimeni is the smallest of all subspecies and more restricted than initially thought after genetic results showed that it does not occur in the eastern parts of Namaqualand (M.D. Hofmeyr and S.R. Daniels unpubl. data). Habitat in the distribution of P. t. trimeni is threatened by mining activities (e.g., for diamonds, sand, copper, granite, sandstone, and gypsum), the inevitable expansion of human settlements in such areas, and overgrazing by livestock. Rouget et al. (2004) ranked the Succulent Karoo second highest for mining pressure of the nine terrestrial priority areas identified in South Africa. A combined soil and vegetation degradation index placed the western Northern Cape in the second highest degradation category (Hoffman et al. 1999). Latest climate change predictions show that although the western Succulent Karoo will remain relatively stable, the coast-hugging habitat of P. t. trimeni will be impacted under all climate change scenarios (Driver et al. 2012). Overall, threats facing P. t. trimeni are high.

Uses and trade

Because of its small size, Psammobates tentorius is not a significant food source for humans, but like P. oculifer (Cunningham 2006), historically, its shell may have been used by indigenous peoples as decorative snuff containers or storage boxes for personal effects. Between 1981 and 2015, 259 live P. tentorius were recorded in the international trade (96% South African exports) with the majority (72%) being declared as captive bred. The main importing countries were Japan, U.S., and Czech Republic. However, South Africa also imported many scientific specimens from Namibia (UNEP-WCMC 2017). This species fares poorly in captivity (Branch 1989).

Conservation

Psammobates tentorius is included in CITES Appendix II and is protected in South Africa by provincial nature conservation ordinances and biodiversity laws at regional level. In Namibia, the Tent Tortoise is protected under the 1975 Nature Conservation Ordinance and the recent Parks and Wildlife Management Act as Vulnerable, Protected Game, and Specially Protected (Cunningham 2006). Tent Tortoises are known to occur in the Karoo National Park, Camdeboo National Park (formerly Karoo Nature Reserve), Anysberg Nature Reserve, Goegap Nature Reserve, Tankwa Karoo National Park, Akkerendam Nature Reserve, Tierberg Karoo Research Centre, and Augrabies Falls National Park in South Africa, and Sperrgebiet, Ai-Ais/Hunsberg reserve and Hardap Recreation Resort in Namibia (Branch 1989, Boycott and Bourquin 2000, Griffin 2003, Leuteritz and Hofmeyr 2007).

Ecological field studies were undertaken for P. t. tentorius on reproduction, movement, diet, and population dynamics in the southern Karoo near Prince Albert, South Africa (Leuteritz and Hofmeyr 2007) and for P. t. verroxii on clutch size, diet, home range, activity pattern, resting site selection, and orientation in the Nama Karoo of southern Namibia (Cunningham and Simang 2008). Ongoing studies include the taxonomic status of the species complex, as well as distribution ranges and niche modelling of genetic lineages (M.D. Hofmeyr unpubl. data). Conservation measures to protect the habitat of P. t. trimeni are essential, as well as basic research on the taxon's demographics, ecology, and status.

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