Psammobates geometricus 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Testudines Testudinidae

Scientific Name: Psammobates geometricus
Species Authority: (Linnaeus, 1758)
Common Name(s):
English Geometric Tortoise
French Tortue Géométrique, Sakafi
Spanish Sacafi, Tortuga Geométrica
Chersine geometrica (Linnaeus 1758)
Chersinella geometrica (Linnaeus 1758)
Geochelone geometrica (Linnaeus 1758)
Hydrone geometrica (Linnaeus 1758)
Peltastes geographicus Gray 1869
Peltastes geometricus (Linnaeus 1758)
Testudo geometrica Linnaeus, 1758
Testudo luteola Daudin 1801
Testudo strauchi Lidth de Jeude 1893
Taxonomic Source(s): TTWG [Turtle Taxonomy Working Group: van Dijk, P.P., Iverson, J.B., Rhodin, A.G.J., Shaffer, H.B., and Bour, R.]. 2014. Turtles of the world, 7th edition: annotated checklist of taxonomy, synonymy, distribution with maps, and conservation status. Chelonian Research Monographs 5(7): 000.329-479, doi:10.3854/crm.5.000.checklist.v7.2014.
Taxonomic Notes: Wallin (1977) documented that the Linnaean type specimen of Psammobates geometricus is actually a specimen of Geochelone elegans with the type locality of "Asia". Hoogmoed and Crumly (1984) instead assigned the animal depicted by Piso (1658) as syntypical to P. geometricus and designated it as lectotype, and the type locality was restricted to "southwestern Cape Province, South Africa" by Baard (1991). No subspecies are currently recognized. Although earlier research showed no significant genetic distance among three seemingly isolated subpopulations (Cunningham et al. 2002), the phylogeographic relationships of these should be given further attention.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2acde+4acde ver 3.1
Year Published: 2015
Date Assessed: 2015-05-15
Assessor(s): Hofmeyr, M.D. & Baard, E.H.W.
Reviewer(s): Rhodin, A.G.J., van Dijk, P.P., Henen, B.T., Turner, A.A. & Juvik, J.O.
The Geometric Tortoise is assessed here as Critically Endangered based on an inferred population reduction of well over 80% in the past three generations (90 years) due primarily to anthropogenic land transformation, where the causes of destruction may not have ceased, based on direct observation (survey data) [A2a], a decline in area of occupancy, extent of occurrence and habitat quality [A2c], actual levels of documented exploitation [A2d], the effects of introduced feral pigs and other subsidized predators [A2e], and unintentional but severe mortality from fire affecting small residual subpopulations in limited habitat patches. These declines are considered likely to continue into the future for at least one generation (30 years) [A4acde].
Previously published Red List assessments:
1996 Endangered (EN)
1994 Vulnerable (V)
1990 Vulnerable (V)
1988 Vulnerable (V)
1986 Vulnerable (V)
1982 Vulnerable (V)

Geographic Range [top]

Range Description: The Geometric Tortoise is endemic to the Western Cape, South Africa. Historically, the species occurred from around Eendekuil and Piketberg in the north, southwards through the Swartland (Porterville, Hermon, Wellington, Paarl) to the Strand-Gordon's Bay area in the south, and eastwards in the Upper Breede River Valley, from Tulbagh in the north to just west of Worcester. It was also found in the Ceres Valley, in the northeast (Baard 1993). The range currently occupied has diminished markedly, but isolated populations are still found in the Paarl district, north of Wellington towards Porterville, between Tulbagh, Wolseley and Worcester, and in the Ceres Valley. Surveys and interviews by Baard (1993, unpubl. data) could not confirm suspected presence of this species in the Bot River and Villiersdorp area, or in the Darling area. The Darling record is based on two specimens collected from this area in 1905. No further locality data are available. Darling lies within the historic distribution of Granite and Shale Renosterveld, suggesting that this was the western extent of the species’ range.
Countries occurrence:
South Africa (Western Cape)
Estimated area of occupancy (AOO) - km2: 22
Continuing decline in area of occupancy (AOO): Yes
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 4034
Continuing decline in extent of occurrence (EOO): Yes
Extreme fluctuations in extent of occurrence (EOO): No
Continuing decline in number of locations: Yes
Extreme fluctuations in the number of locations: No
Lower elevation limit (metres): 70
Upper elevation limit (metres): 600
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: See 'Geographic Range' above for a description of range contraction since historic times. A total of 34 cited localities were known before 1993, when intensive surveys added 33 localities of (past) occurrence. All 67 localities were surveyed intensively in the mid-80s and early 90s, and continued occurrence was documented for 31 sites (Baard 1993). Population sizes differ immensely, but the largest population was estimated to contain between 1,500 and 3,400 tortoises in 1992 (Baard 1993), whereas the entire species was estimated to be between 700 and 800 by 2012 (Goode et al. 2012). Generation time is estimated at 30 years. Over 90% of its original habitat has been irreversibly converted to agriculture (Baard and Hofmeyr 2014). Populations in remaining habitat have suffered catastrophic declines from fire-induced mortality, with little indication of population recovery.
Current Population Trend: Decreasing
Additional data:
Number of mature individuals: 800 Continuing decline of mature individuals: Yes
Extreme fluctuations: No Population severely fragmented: Yes
Continuing decline in subpopulations: Yes
All individuals in one subpopulation: No

Habitat and Ecology [top]

Habitat and Ecology: Psammobates geometricus occurs in the Mediterranean climate region (mean annual rainfall 350-600 mm) of the southwestern part of the Western Cape of South Africa, at altitudes of about 70 to 600 m (Baard 1995a). It is found in the Fynbos Biome, primarily in the Northwest and Southwest Fynbos Bioregions, and peripherally in the West Coast Renosterveld Bioregion, in a number of Critically Endangered and Endangered vegetation types, including Alluvium Fynbos, Sand Fynbos, Shale Fynbos, Shale Renosterveld, Granite Renosterveld, and Silcrete Renosterveld (Rebelo et al. 2006). The general habitat comprises low-lying, undulating plains (seldom rocky terrain, but never koppies), with a dominant low to medium-high shrub layer, a strong restioid and ericoid presence, and an essentially annual, herbaceous understorey with perennial grasses (Baard 1995a). During the hot and dry season P. geometricus takes refuge in slightly damper microhabitats under dense vegetation (E. Baard pers. obs.). This tortoise does not dig its own burrows but occasionally uses the burrows of other animals. The Geometric Tortoise is a rather small tortoise; males average about 10.0 cm in carapace length (CL) and 200 g in mass, females average 12.5 cm CL and 430 g, respectively. Large females of greater than 20.0 cm CL with a mass of 680 to 850 g have been recorded (Baard 1990, 1995b; M. Hofmeyr unpubl. data). Males reach sexual maturity after 8 to 10 yrs, while females usually mature at 11 to 13 yrs of age, but may mature in 10 yrs (Baard 1995b, Goode et al. 2012; M. Hofmeyr unpubl. data in Hayward et al. In Prep. 2015). Females may produce one or more clutches of 1 to 5 eggs in suitable conditions; or skip egg production during adverse periods (M. Hofmeyr unpubl. data in Hayward et al. In Prep. 2015). Egg and hatchling survival rates may be very low (possibly up to 99% mortality in the first year), thus recruitment is slow and generation time is estimated as 30 years (M. Hofmeyr unpubl. data in Hayward et al. In Prep. 2015). Longevity has been estimated at about 40 years (Goode et al. 2012).
Systems: Terrestrial
Continuing decline in area, extent and/or quality of habitat: Yes
Generation Length (years): 30
Movement patterns: Not a Migrant

Use and Trade [top]

Use and Trade: The Geometric Tortoise is not utilized in great quantities, but occasional casual collection for local subsistence consumption occurs. Although infrequent, the illegal collection of specimens for the pet trade may be a potential threat.

Threats [top]

Major Threat(s): Human-induced habitat alteration, degradation and destruction, largely due to extensive agricultural development (wine and wheat farming), have led to the irreversible alteration of more than 90% of its habitat. Human settlement, invasive alien species (both woody and herbaceous species), predators (including invasive feral pigs), overgrazing by domestic stock, droughts and wildfires (Baard 1997) seriously threaten survival in remaining habitats. Within its severely fragmented range, these threats are exacerbated in small, isolated populations which may not remain viable. Although infrequent, the illegal collection of specimens for local subsistence consumption and for the pet trade may be potentially significant threats. The current conservation status is dire, and climate change, involving warmer and drier conditions (Midgley et al. 2005), is likely to seriously compromise the survival of remaining, fragmented populations (Hofmeyr et al. 2006). Subsidized native predators such as  Chacma Baboons, Black-backed Jackals, and Pied Crows now exist in Geometric Tortoise areas, sometimes in high numbers, due to anthropogenic landscape change and management practices. After the 2012 fire at Elandsberg, baboons took many tortoises from holding pens and baboons now exist in large populations on protected lands abutting  this reserve. The aggressive Pied Crow is increasingly common in mixed agricultural/native Fynbos tortoise habitat throughout the range of P. geometricus (Juvik and Hofmeyr 2015), and causes considerable tortoise mortality (Fincham and Lambrechts 2014). For several decades irrigation canals crossing the Ceres Valley's remaining Geometric Tortoise habitat have been acting as pitfalls, trapping and killing P. geometricus and other tortoise species in significant numbers (Juvik et al. 2014).

Conservation Actions [top]

Conservation Actions: Psammobates geometricus has been included in CITES Appendix I since 1975, banning all commercial international trade, and is afforded protection under South African legislation. Geometric Tortoises occur in a number of protected areas, although catastrophic wildfires have affected these populations on occasion, in particular the Elandsberg Nature Reserve fire in January 2012. Continued research into aspects of conservation biology is necessary in order to inform conservation measures. Securing conservation stewardship of remaining lowland habitats by landowners should be prioritized. More remaining habitat should be included into more formal conservation arrangements. A PHVA should be conducted, and a Conservation Action Plan (CAP) has already started and is being implemented; the CAP’s actions need to be prioritized. A Biodiversity Management Plan – Species (BMP-s) is being drafted and will need to be implemented (Hayward et al. In Prep. 2015).

Citation: Hofmeyr, M.D. & Baard, E.H.W. 2015. Psammobates geometricus. The IUCN Red List of Threatened Species 2015: e.T18398A76918966. . Downloaded on 01 December 2015.
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