IUCN threat status:

Endangered (EN)

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Geometric tortoise

The geometric tortoise is an endangered species of tortoise and one of three members of the genus, Psammobates. It is found in a very small section in the South-Western Cape of South Africa.

Identification[edit]

It has a very strong, black and yellow patterned carapace, used for defense against predators. The patterns are arranged in ray-like markings and help the tortoise blend in with its environment. This tortoise is very small, and a full grown tortoise can only reach about 5 to 6 inches in diameter.

While it shares much of its superficial outer appearance with its relatives in the genus Psammobates, it can be distinguished by the distinctively brightly coloured yellow stars of its shell scutes, the small nuchal and single axillary, the lack of buttock tubercles, and the only slightly upturned rear margins of the shell.

Habitat[edit]

The geometric tortoise is naturally restricted to the far south-western corner of the Western Cape Province, South Africa. It used to occur as far north as Picketberg, as far south as Gordons Bay and eastwards into the Breede River valley.[2]

The last population in Cape Town died out in the tiny Harmony Flats Reserve. The species was believed to be extinct in the 1960s, but a surviving population was discovered in 1972 and it now occurs in three isolated pockets where it is conserved. A population in the Ceres valley, one in the Tulbagh-Worcester valley, and a group surviving on the coastal lowlands to the southwest.

These colourful tortoises live only in lowland fynbos and renosterveld vegetation, meaning that their populations are easily isolated by mountains which they cannot cross.[3]

It is one of the rarest tortoise species in the world

Diet[edit]

The geometric tortoise's diet consists mainly of the leaves, flowers, and shoots of a wide range of indigenous fynbos and renosterveld plants and grasses. In particular however, it is restricted by this diet to Alluvial Fynbos and Shale Renosterveld vegetation types. Its very specific diet of local plant species means that it soon dies when kept in captivity.

Behaviour[edit]

They are said to hibernate in the months of June through September, or when their natural environment is not normal, or when in captivity. Little is known about their reproductive behavior. When the female is ready to lay eggs, she digs a hole in the ground and covers it with grass or other vegetation.

Threats and conservation[edit]

The geometric tortoise has lost 97% of its habitat, and only 200 to 300 exist today.[when?] It is threatened for a number of reasons, but mainly due to loss of habitat. Restricted as it is to fertile lowlands and valleys, the vast majority of its tiny natural range has been covered with farms and housing.[4] In addition, its eggs are a source of food for the African people and traders capture the adults for their shells which are used to make many different decorative items. This species is also preyed upon by other mammals, particularly introduced mammals such as pigs and dogs.

The South African government has set aside restricted park lands for this unique tortoise, and there are laws that prohibit the capture and the taking of its eggs.

References[edit]

  1. ^ Fritz Uwe; Peter Havaš (2007). "Checklist of Chelonians of the World". Vertebrate Zoology 57 (2): 289. ISSN 18640-5755. Archived from the original on 2010-12-17. Retrieved 29 May 2012. 
  2. ^ http://sabap2.adu.org.za/news.php?id=3019
  3. ^ http://etd.uwc.ac.za/usrfiles/modules/etd/docs/etd_init_6020_1173955498.pdf
  4. ^ [p1[action]=content&sm[p1][cntid]=2012&sm[p1][persistent]=1 "Rescuing the rare geometric tortoise"]. 
  • Library.thinkquest.org entry
  • Baard, E. H. W. 1989. The Ecology and Conservation Status of the Geometric Tortoise Psammobates geometricus: Preliminary Results Jour. Herp. Ass. Afr. (36): 72-72
  • Baard, E. H. W. 1991. A Review of the Taxonomic History of and some Literature on the Geometric Tortoise, Psammobates geometricus Jour. Herp. Ass. Afr. (39): 8-12
  • Baard, E.H.W. 1995. Growth, age at maturity and sexual dimorphism in the geometric tortoise, Psammobates geometricus Jour. Herp. Ass. Afr. (44): 10-15
  • Baard, E.H.W.; Mouton, P.L.N. 1993. A Hypothesis Explaining the Enigmatic Distribution of the Geometric Tortoise, Psammobates geometricus, in South Africa Herpetological Journal 3 (2): 65-67
  • Duméril, A.M.C., and G. Bibron. 1835. Erpétologie Générale ou Histoire Naturelle Complète des Reptiles, Vol. 2. Librairie Encyclopédique de Roret, Paris, iv + 680 p.
  • Ernst,C.H. and Barbour,R.W. 1989. Turtles of the World. Smithsonian Institution Press, Washington D.C. - London
  • Hoogmoed, M.S., and C.R. Crumly. 1984. Land tortoise types in the Rijksmuseum van Natuurlijke Histoire with comments on nomenclature and systematics (Reptilia: Testudines: Testudinidae). Zool. Meded. 58(15): 241-259.
  • Iverson, J.B. 1986. A Checklist with Distribution Maps of the Turtles of the World. Paust Printing, Richmond, Indiana. viii + 282 pp.
  • Linnaeus, C. 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Laurentii Salvii, Holmiæ. 10th Edition: 824 pp.
  • Piso, W. 1658. Historiae Naturalis and Medicae Indiae Occidentalis. Libri Quinque. pp. 105–106. In: W. Piso. De Indiae Utriusque re Naturali et Medica. Libri Quatordecim, Amstelaedami. 327 pp.
  • Rau, R. 1971. Weitere Angaben über die geometrische Landschildkröte, Testudo geometrica. Salamandra 7 (3/4):123-136

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