Turtles in Trouble: The World's 25+ Most Endangered - Wildlife ...

Turtles in Trouble: Top 25+ Endangered Tortoises and Freshwater Turtles—2011Geometric TortoisePsammobates geometricus (Linnaeus 1758); Family TestudinidaeAfrica: South AfricaIUCN Red List: EN, Endangered A1ac, B1+2c; SARCA/TFTSG Draft: CR, Critically EndangeredCITES: Appendix IThe Geometric Tortoise is an excellentexample of convergent evolutiondue to its striking resemblance to startortoises of India and Burma. However,this beautiful tortoise is not closely relatedto its Asian look-alikes, and canbe distinguished by the presence of anuchal scute on the anterior carapace. Asits Latin name suggests—psammos andbates means “inhabitant of the sands”—this species is found in low-lying areasof the Western Cape Province, South Africa,with acidic, sandy and nutrient-poorshale and alluvium soils with sparse vegetation,characterized by grasses and lowto medium-high shrubs.This species once occurred throughoutthe low-lying West Coast and inlandrenosterveld from Gordon’s Bay toPiketberg, and in the Upper Breede Riverand Ceres valleys. Although its historic range was nevervast, it now occupies only approximately 22 km 2 (8.5 sq.mi.)of highly fragmented remnants of suitable shale renosterveldand alluvium fynbos habitat in the Western Cape. Habitatdestruction for agriculture, mainly for vineyards and wheatfarming, degradation by invasive non-native plants and animals,coupled with fire suppression and increasing predatorpressure have been, and continue to be, the main threats tothe remaining habitat patches and populations.This small species does not exceed 20 cm in carapacelength, however, average adult sizes are more typically 10cm for males and 12.5 cm for females, exhibiting strongsexual dimorphism with females larger than males andpronounced differences in plastron concavity, shell shapeand tail size. Sexual maturity in females is reached in 8to 10 years. Generally active year-round, inactivity mayonly occur during the coolest months of the year (June toDistribution of Psammobates geometricus.Psammobates geometricus from South Africa. Photo by Atherton de Villiers.August). Breeding behavior and oviposition (1–5 eggs in1–3 clutches per year) occurs from September to Novemberwith hatchlings emerging 6–8 months later in March toMay. Geometric Tortoises may reach ages of up to 30 yearsand more.More than 90% of its former habitat has been destroyedand this species now occurs in a few small to medium-sizedpopulations in isolated patches of uncultivated land. Protectionmeasures include full legal protection, and populationsin both private and provincial nature reserves, as well asconservation stewardship contract nature reserves, occupyingareas of between 30 and ca. 1000 ha of suitable habitat.The most pressing conservation need for this species is theacquisition of more suitable native habitat, and more conservationstewardship nature reserves are being negotiatedwith private landowners. Management is required to preventhabitat alteration, and in this fire-adapted habitat, fireis required to maintain the open nature of the habitat and itsspecies diversity. However, small tortoise populations areextremely vulnerable to fires and up to 80% mortality canbe expected.This species does poorly in captivity and a highly managedin-situ breeding facility may be warranted. Becausethreats continue to operate in natural habitats, headstartingis, however, unlikely to improve the status of this species.A species conservation management plan is imminent, andthe South African Reptile Conservation Assessment has recentlydetermined the species to warrant Critically Endangeredstatus on the IUCN Red List, as noted by the Tortoiseand Freshwater Turtle Specialist Group.– 39 –