1 Taunos

Testudo Ephippium Classification Essay


After collapse of the population in the 19th century due to targeted exploitation, mostly by whalers for food (Pritchard 1996), recruitment was prevented by predation of hatchlings by introduced Black Rats. The population has recently (last three decades) started to recover as a result of reintroduction of headstarted animals. A successful rat eradication campaign was carried out in December 2012, and the first in situ live hatchlings sighted in 2014. The historic effective population size has been estimated at around 850 adult individuals (Jensen and Russello unpubl. data); the census population on Pinzón in December 2014 was estimated at 486 animals of all age classes combined (~70% adult), with additional young animals held at the Galápagos National Park Directorate’s Tortoise Centre on Santa Cruz Island. Recent genetic analyses found that Pinzón tortoises maintain high levels of variation in situ despite their well-documented decline, although the effective population size (Ne) for this species is 50-60 (Garrick et al. 2015, Russello et al. unpubl. data). Generation time of the Pinzón Giant Tortoise is estimated at 60 years; while all of the native reproducing adults on Pinzón are well over 100 years of age, many of the head-started animals released between 1970–1990 are now reproducing. Thus within three past generations the population declined from its historic level of at least 900 to a low of 100–200 older adult animals in 1960, and has since increased to about 500 animals in the wild at present, of which not all are mature, representing a current population of mature adults at about half of historical levels, qualifying for Vulnerable A1abde. Genetic data show that founders of the captive population are a reasonably diverse and representative group, although the headstart cohorts are not representative of the wild population (Jensen et al. 2015). Future head-start activities should strive to collect eggs and hatchlings from all nesting zones  to ensure capturing the full extent and distribution of genetic variation. Notably, native reproduction is again underway as of December 2014 (Tapia et al. 2015). At fewer than 1,000 mature adults occupying a single subpopulation, the species also meets the criteria for Vulnerable D1. The size of Pinzón, and thus maximum extent of occurrence (EOO), is 18 sq. km., of which at most 9 sq. km. is occupied by suitable habitat (area of occupancy – AOO), qualifying for Vulnerable D2; with a range of less than 20 sq. km., the species will always qualify as Vulnerable D2 even if full historic population levels are restored. This assessment also incorporates contributions from the international workshop on Galápagos tortoises convened by the Galápagos National Park Directorate in July 2012. This species was previously listed on the Red List in 1996 as Chelonoidis nigra ssp. ephippium, and since 2007 as Chelonoidis nigra ssp. duncanensis, with a status assessment of Extinct in the Wild, a listing that was unfortunately inaccurate, as more than 100–200 wild individuals have always been known to persist on Pinzón. 

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Galápagos tortoise

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