|Scientific Name:||Chelonoidis darwini (Van Denburgh, 1907)|
Chelonoidis darwini (Van Denburgh, 1907)
Chelonoidis nigra ssp. darwini (Van Denburgh, 1907)
Geochelone elephantopus ssp. darwini (Van Denburgh, 1907)
Geochelone nigra ssp. darwini (Van Denburgh, 1907)
Testudo darwini Van Denburgh, 1907
|Taxonomic Source(s):||Fritz, U. and Havas, P. 2007. Checklist of chelonians of the world. Vertebrate Zoology 57(2): 149-368.|
The previous Red List assessments for Galápagos tortoises treated the various allopatric island populations as subspecies of Chelonoidis nigra, as did several authors (Pritchard 1996; Caccone et al. 1999; Beheregaray et al. 2003; Fritz and Havas 2007; TTWG 2007, Rhodin et al. 2008). However, other authors have considered them as full species based on morphology (Bour 1980; Fritts 1983; Ernst and Barbour 1989) and more recently several researchers (Caccone et al. 2002; Russello et al. 2005, 2007; Poulakakis et al. 2008, 2012, 2015; Chiari et al. 2009) have treated most of them as full species based on congruent patterns of mitochondrial and nuclear variation. This elevated species-level taxonomy has been largely accepted by TTWG (2009, 2014) and TEWG (2015) for most phylogenetic lineages of Galápagos tortoises. This Red List assessment therefore now treats C. darwini as a full species, rather than retaining its previous subspecies ranking from earlier Red List assessments.
|Red List Category & Criteria:||Critically Endangered A1bde ver 3.1|
|Assessor(s):||Cayot, L.J., Gibbs, J.P., Tapia, W. & Caccone, A.|
|Reviewer(s):||Rhodin, A.G.J. & van Dijk, P.P.|
|Contributor(s):||IUCN Galapagos Tortoises Red Listing Workshop & Galapagos National Park Directorate|
|Facilitator/Compiler(s):||van Dijk, P.P. & Rhodin, A.G.J.|
From a historic population estimated at 24,000 animals (Gibbs, unpubl. data), direct exploitation in the 19th century (less than three generations in the past, at generation length of 60 years) severely reduced the population, with recruitment hindered by the impacts of introduced predators (pigs) and vegetation change caused by invasive herbivores (primarily goats and some donkeys). In the early 1970s, the population was estimated at 500-700 tortoises (MacFarland et al. 1974). Since then, more than 1,000 headstarted juvenile tortoises have been repatriated to Santiago. Another 245 juveniles remain in the Government of Ecuador’s Tortoise Centre on Santa Cruz. Overall, the population collapsed by more than 95% from historical levels less than three generations ago, qualifying the species for listing as Critically Endangered A1bde (the reasons for the decline are understood, have ceased and the population has started to recover). The previous assessment on the 1996 IUCN Red List of the subspecies Chelonoidis nigra ssp. darwini was Endangered C2a. This assessment also incorporates contributions from the international workshop on Galápagos tortoises convened by the Galápagos National Park Directorate in July 2012.
|Previously published Red List assessments:|
Chelonoidis darwini occurs on Santiago [formerly James Island or San Salvador] in the Galápagos Islands of Ecuador. Santiago has a total surface area of 585 sq. km, of which 240 sq. km (41%) could potentially sustain tortoises (Gibbs, unpubl. data).
|Range Map:||Click here to open the map viewer and explore range.|
Based on an estimated average density of one tortoise per hectare of suitable habitat, the pre-human population size was estimated to have been about 24,000 adults (Gibbs, unpubl. data). The population was estimated at 500-700 native tortoises in the early 1970s (MacFarland et al. 1974). This population has been augmented by over 1,000 repatriated juveniles. With the eradication of feral pigs in 1999, natural reproduction and recruitment on the island has increased.
|Current Population Trend:||Increasing|
|Habitat and Ecology:||Detailed life history data are not available for the wild populations of Chelonoidis darwini; observations on long-term captive animals indicate that the species matures at about 20 years of age and longevity of 100-150 years is expected; generation time is estimated at c. 60 years. The species has an intermediate to domed shell morphology indicating that it is primarily a grazer on low-growing vegetation.|
|Generation Length (years):||60|
|Movement patterns:||Not a Migrant|
|Use and Trade:||Tortoises on Santiago were subject to extensive overexploitation for food by sailors and settlers in the 18th and 19th centuries, from which they still have not recovered (Pritchard 1996).|
Tortoises on Santiago were subject to extensive overexploitation for food by sailors and settlers in the 18th and 19th centuries, from which they still have not recovered (Pritchard 1996). Eggs have been collected from the small population of adults that survived, and the resulting hatchlings headstarted at the Government of Ecuador’s Tortoise Centre on Santa Cruz and then repatriated at 4-5 years old. Natural, in situ recruitment was severely impacted by introduced pigs (eradicated in 1999). The impact of infestation of tortoise eggs by flies remains to be clarified. An introduced goat population, once estimated at 80,000 animals, caused major degradation of tortoise habitat. Goats were eradicated in 2003 and the vegetation began to recover. However, the absence of goats resulted in the spread of invasive non-native vegetation, particularly blackberry and, to a lesser extent, naranjilla and avocado. Blackberry creates dense thickets impossible for tortoises to penetrate. The risk of further introductions or re-introductions (goats) remains.
Legislation and regulations: Chelonoidis darwini is protected under Ecuadorian national law. It has been included in Appendix I of CITES since 1975, prohibiting all forms of commercial international trade. All of Santiago, and thus the entire native range of darwini, is protected as part of the Galápagos National Park. Further management of habitat and invasive species is needed, especially blackberry. The C. darwini population continues to be included in the Galápagos National Park Directorate’s tortoise captive rearing and repatriation program. Population monitoring and population genetics studies are highly desirable. Habitat restoration work may be needed to reduce the spread of introduced plants, which occurred following goat eradication.
|Citation:||Cayot, L.J., Gibbs, J.P., Tapia, W. & Caccone, A. 2016. Chelonoidis darwini. The IUCN Red List of Threatened Species 2016: e.T9020A82689845.Downloaded on 21 April 2018.|
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