Geometric Tortoises lived in the coastal lowlands known as the renosterveld. This is a fire-prone, endangered type of shrub land habitat found in the semi-arid and sub-humid areas of southern Cape Province, South Africa. The renosterveld makes up part of the Fynbos biome, which has a chaparral, or Mediterranean climate. These tortoises were found at elevations within 80 meters above sea level. Over 90 percent of this habitat has now been converted to farmland or suburban and urban uses. Over half of remaining Geometric Tortoises live on one private nature reserve containing about 1000 hectares of useable habitat. (Boycott and Bourquin, 2000; Cowling, et al., 1986; Cunningham, et al., 2002; Hildyard, 2001; Kemper, et al., 1999)
This species is sexually dimorphic; males have longer tails and concave plastrons. Males are also known to be smaller than females, with average adult carapace lengths of 100 mm and 125 mm and masses of 200 g and 430 g, respectively. The largest specimens found had carapace lengths of 120 mm for a male and 200 mm for a female. The heaviest specimens had masses of 270 g for a male and 600 g for a female. (Baard, 1989; Boycott and Bourquin, 2000)
This is an oviparous species. Juveniles and sub-adults grow at an average of 10.45 mm per year, and adult males and females grow at 1.70 mm and 1.56 mm per year, respectively. This rapid growth results in two yearly annuli added to the carapace scutes. It is unclear if this species has environmental sex determination or genetic sex determination. Males mature at a carapace length of about 90 mm; size at maturity for females in unreported but they undoubtedly mature at a larger size than males. (Baard, 1989; Baard, 1995b; Baard, 1996; Boycott and Bourquin, 2000)
The mating behavior of (Boycott and Bourquin, 2000)in the wild has not been extensively observed or reported. In captivity, mating has occurred from January through March and in May and September.
After reaching maturity at five to eight years, individual Geometric Tortoises may live for over 30 years. Other than this, there has not been any significant research on the lifespan of these tortoises. Limits on lifespan include habitat destruction and fires and, to a lesser extent, predation and illegal collection for the pet trade. (Baard, 1989; Baard, 1996; Boycott and Bourquin, 2000)
Geometric Tortoises have a relatively specialized diet; they have been documented to eat various grasses including Briza maxima, Cynodon dactylon, Themeda triandra, Ehrharta calycina, and Pentaschistis curvifolia, as well as members of the geophyte genera Oxalis and Pelargonium. It has been noted that geometric tortoises use a "grab and pull" method of eating, so plants with high tensile strength are often avoided. When food and non-food plants are compared, (Balsamo, et al., 2004; Boycott and Bourquin, 2000; Henen, et al., 2005)has been found to eat food plants with high levels of phosphorus, iron, soluble carbohydrates, and low levels of acid detergent fiber and lipids. In captivity these tortoises eat various fruits, garden weeds, succulents, the shells of crushed snails and even softened chicken bones. This suggests possible scavenging in the wild.
Hyalomma truncatum, Rhipicephalus gertrudae, Amblyomma marmoreum, Amblyomma sylvaticum, and Ornithodoros compactus were found to parasitize , but the potential for disease transmission has not been studied. (Baard, 1996; Horak, et al., 2006; Kemper, et al., 1999)does not burrow, so its effects on its ecosystem are the result of its place in the food web. The food plants are kept in check by , which in turn serves as a food source for birds and other predators. However, with the large amount of habitat destruction and deadly fires, is rare, just as the renosterveld habitat itself is rare. In a study of South African reptile parasites, the ticks
Despite being endangered and protected by law, Geometric Tortoises were (and may still be) sold in the pet trade and used for medicinal purposes. There are, however, benefits that (Baard, 1989; Boycott and Bourquin, 2000; Kemper, et al., 1999; Petersen, et al., 2012)provides to humans that are not harmful to the species. A wide range of research has been conducted on in relation to species conservation and habitat conservation because of the rarity of the tortoises and of the renosterveld in which they live. The reserves that were established for Geometric Tortoises help to preserve other species, boost ecotourism and to increase interest in research and education.
There are no known adverse effects ofon humans.
yellow mongoose has been introduced to the area and serves as a predator to , causing further population decline. (Baard, 1989; Balsamo, et al., 2004; Boycott and Bourquin, 2000; Leuteritz and Ekbia, 2008)is the rarest chelonian in Africa. Up to 97% of its renosterveld habitat has been lost due to human development and fires, making gravely endangered. The species is listed on the IUCN Red List as Endangered, and is a CITES Appendix I species, meaning it is threatened with extinction and may only be traded in exceptional circumstances. Because it is not native to the United States, the species is absent from the US Federal List and the State of Michigan List. Another cause for the decline of is invasive plant species such as members of the genus Acacia, which replace the native plants that serve as food sources for the tortoises. It has also been suggested that the
The small geographic range ofis due to the small range in which the renosterveld habitat exists. This habitat range is still being reduced and converted into land for agriculture. It may also be noted that no subspecies of are recognized.
There has been some confusion over Carl Linnaeus's description of Testudo geometrica, which was eventually proven to be Geochelone elegans (Indian Star Tortoise), not as previously thought. (Baard, 1989; Baard, 1993; Boycott and Bourquin, 2000)
Hunter Craig (author), Michigan State University, James Harding (editor), Michigan State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
an animal that mainly eats leaves.
an animal that mainly eats fruit
An animal that eats mainly plants or parts of plants.
Animals with indeterminate growth continue to grow throughout their lives.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the business of buying and selling animals for people to keep in their homes as pets.
an animal that mainly eats dead animals
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
Auffenberg, W. 1977. Display Behavior in Tortoises. Integrative and Comparative Biology, 17/1: 241-250. Accessed November 29, 2013 at http://icb.oxfordjournals.org/content/17/1/241.short.
Baard, E. 1995. A preliminary analysis of the habitat of the geometric tortoise,Psammobates geometricus. South African Journal of Wildlife Research, 25/1: 8-13. Accessed November 03, 2013 at http://www.sabinet.co.za/abstracts/wild/wild_v25_n1_a2.html.
Baard, E. 1995. Growth, age at maturity and sexual dimorphism in the geometric tortoise, Psammobates geometricus. The Journal of the Herpetological Association of Africa, 44/1: 10-15. Accessed November 03, 2013 at http://www.tandfonline.com/doi/abs/10.1080/04416651.1995.9650383#.UpkmksRDtFt.
Baard, E. 1989. The Conservation Biology of Tortoises. Glaad, Switzerland: IUCN. Accessed November 29, 2013 at http://books.google.com/books?id=pL2vyHjC4akC&pg=PA87&dq=geometric+tortoise&hl=en&sa=X&ei=jhmZUt6LOpfhoASu3YHIBw&ved=0CDoQ6AEwAA#v=onepage&q=geometric%20tortoise&f=false.
Baard, E. 1993. Distribution and status of the geometric tortoise Psammobates geometricus in South Africa. Biological Conservation, 63/3: 235-239. Accessed November 30, 2013 at http://www.sciencedirect.com/science/article/pii/000632079390718G.
Baard, E. 1996. THE CONSERVATION BIOLOGY OF SOUTH AFRICAN TORTOISES - PERSPECTIVES AND OPPORTUNITIES. The Desert Tortoise Council 1995 Symposium, 15: 4-9. Accessed November 29, 2013 at http://www.deserttortoise.org/ocr_DTCdocs/1995DTCProceedings-OCR.pdf.
Balsamo, R., M. Hofmeyr, B. Henen, A. Bauer. 2004. Leaf biomechanics as a potential tool to predict feeding preferences of the geometric tortoise Psammobates geometricus. African Zoology, 39/2: 175-181. Accessed November 29, 2013 at http://126.96.36.199/usrfiles/importcms/gen11Srv7Nme54_2531_1210050507/Balsamo_Zool.pdf.
Boycott, R., O. Bourquin. 2000. The Southern African Tortoise Book. KwaZulu-Natal, South Africa: O. Bourquin.
Cowling, R., S. Pierce, E. Moll. 1986. Conservation and utilisation of South Coast renosterveld, an endangered South African vegetation type. Biological Conservation, 37/4: 363-377. Accessed November 29, 2013 at http://www.sciencedirect.com/science/article/pii/0006320786900789.
Cunningham, J., E. Baard, E. Harley, C. O'Ryan. 2002. Investigation of genetic diversity in fragmented geometric tortoise (Psammobates geometricus) populations. Conservation Genetics, 3/3: 215-223. Accessed November 29, 2013 at http://link.springer.com/article/10.1023/A:1019909515202#page-1.
Henen, B., M. Hofmeyr, R. Balsamo, F. Weitz. 2005. Lessons from the food choices of the endangered geometric tortoise Psammobates geometricus. South African Journal of Science, 101/9-10: 435-438. Accessed November 29, 2013 at http://apps.webofknowledge.com.proxy1.cl.msu.edu/full_record.do?product=WOS&search_mode=Refine&qid=2&SID=2F5xhccsBrUEXm7SksB&page=1&doc=2.
Hildyard, A. 2001. Endangered Wildlife and Plants of the World. United States: Marshall Cavendish Corporation. Accessed November 29, 2013 at http://books.google.com/books?id=wFdWlrnz_uoC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false.
Hofmeyr, M., U. van Bloemestein, B. Henen, C. Weatherby. 2012. Sexual and environmental variation in the space requirements of the Critically Endangered geometric tortoise, Psammobates geometricus. Amphibia-Reptilia, 33: 185-197. Accessed November 29, 2013 at http://www.ingentaconnect.com/content/brill/amre/2012/00000033/00000002/art00003.
Horak, I., I. McKay, B. Henen, H. Heyne, M. Hofmeyr, A. De Villiers. 2006. Parasites of domestic and wild animals in South Africa. XLVII. Ticks of tortoises and other reptiles. Onderstepoort Journal of Veterinary Research, 73: 215-227. Accessed November 30, 2013 at http://www.ojvr.org/index.php/ojvr/article/viewFile/148/143.
Iverson, J., C. Balgooyen, K. Byrd, K. Lyddan. 1993. Latitudinal variation in egg and clutch size in turtles. Canadian Journal of Zoology, 71/12: 2448-2461. Accessed November 29, 2013 at http://www.nrcresearchpress.com/doi/abs/10.1139/z93-341#.Uplg58RDtFs.
Kemper, J., R. Cowling, D. Richardson. 1999. Fragmentation of South African renosterveld shrublands: effects on plant community structure and conservation implications. Biological Conservation, 90/2: 103-111. Accessed November 29, 2013 at http://www.sciencedirect.com/science/article/pii/S000632079900021X.
Leuteritz, T., H. Ekbia. 2008. Not All Roads Lead to Resilience: a Complex Systems Approach to the Comparative Analysis of Tortoises in Arid Ecosystems. Ecology and Society, 13/1: 1. Accessed November 29, 2013 at http://www.ibcperu.org/doc/isis/8549.pdf.
Petersen, L., E. Moll, R. Collins, M. Hockings. 2012. Development of a Compendium of Local, Wild-Harvested Species Used in the Informal Economy Trade, Cape Town, South Africa. Ecology and Society, 17/2: 26. Accessed November 30, 2013 at http://www.ecologyandsociety.org/articles/4537.html.