|Scientific Name:||Chelonoidis niger (Quoy & Gaimard, 1824)|
Chelonoidis nigra ssp. nigra (Quoy & Gaimard, 1824)
Geochelone elephantopus ssp. galapagoensis (Baur, 1889)
Geochelone elephantopus ssp. nigra (Quoy & Gaimard, 1824)
Geochelone nigra ssp. galapagoensis (Baur, 1889)
Geochelone nigra ssp. nigra (Quoy & Gaimard, 1824)
Testudo californiana Quoy & Gaimard, 1824a
Testudo galapagoensis Baur, 1889
Testudo nigra Quoy & Gaimard, 1824b
|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 (now named Chelonoidis niger), 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 the more recent consensus among researchers (Caccone et al. 2002; Russello et al. 2005, 2007; Poulakakis et al. 2008, 2012, 2015; Chiari et al. 2009) is to treat most 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, but not all, phylogenetic lineages of Galápagos tortoises. This Red List assessment therefore now treats C. niger as a full species, rather than retaining its previous subspecies ranking from earlier Red List assessments. This species from Floreana has also been referred to in some recent literature as C. elephantopus, but that name is a nomen dubium (TTWG 2009) and should not be used for the this species. The spelling of the specific name was recently changed from nigra to niger as a result of the determination that the gender of the generic name Chelonoidis is actually masculine rather than feminine (Olson and David 2014).
|Red List Category & Criteria:||Extinct ver 3.1|
|Assessor(s):||van Dijk, P.P., Rhodin, A.G.J., Cayot, L.J. & Caccone, A.|
|Reviewer(s):||Gibbs, J.P. & Tapia, W.|
|Contributor(s):||IUCN Galapagos Tortoises Red Listing Workshop, Galapagos National Park Directorate|
|Facilitator/Compiler(s):||van Dijk, P.P.|
The species collapsed from an estimated historical population in the early 19th century of about 8,000 animals on Floreana (J.P. Gibbs unpubl. data), to extinction in the wild on Floreana sometime in the mid 1800s. No genetically pure live Floreana Tortoises are known to exist, although a small number of adults held in captivity contain historical Floreana genetic material, with at least one animal at up to 80% niger genome (Poulakakis et al. 2008, Russello et al. 2010, Garrick et al. 2012). Additionally, genetic analyses have identified many tortoises on Wolf Volcano on northern Isabela that have partial Floreana ancestry. Today an estimated 100 to 200 animals with partial Floreana tortoise ancestry remain on Wolf Volcano; so far 84 individuals have been identified from genetic analyses (Garrick et al. 2012). Although no living pure niger animals are confirmed, the possibility exists that some animals on Wolf Volcano may be genetically pure Floreana Tortoises. Overall, in the absence of confirmed genetically pure animals, Chelonoidis niger should continue to be considered Extinct until documented otherwise. "Chelonoidis nigra ssp. nigra" was assessed as Extinct in the 1996 IUCN Red List. This assessment incorporates knowledge contributions from the international workshop on Galápagos tortoises convened by the Galápagos National Park Directorate in July 2012.
|Previously published Red List assessments:|
Chelonoidis niger occurred on Floreana [formerly Santa María or Charles Island] in the Galápagos Islands of Ecuador. Floreana has a total surface area of 172.5 sq.km, of which ca 81 sq. km (47%) could potentially sustain tortoises (J.P. Gibbs unpubl. data).
Regionally extinct:Ecuador (Galápagos)
|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 8,000 adults (J.P. Gibbs unpubl. data). This species was exposed to intense exploitation by whalers in the early 1800s, collecting animals as provisions and to produce oil, with the last large loads of tortoises from Floreana recorded as occurring between 1831 and 1837 (Townsend 1925, Pritchard 1996). Available population information for Chelonoidis niger indicates that the population was not rare during the 1830s, but had collapsed by about 1850 (Pritchard 1996). Charles Darwin saw no live tortoises when he visited in 1835 and only a handful of tortoises appear to have been collected between 1840 and 1847, with final rapid extinction estimated to have occurred in about 1850 (Broom 1929, Steadman 1986). However, several individuals showing hybridization between C. niger and C. becki have recently been discovered on Wolf Volcano on northern Isabela, as well as some with partial ancestry from other islands, including Española and a few from southern Isabela, and some in captivity at the Galápagos National Park’s Tortoise Center on Santa Cruz Island, probably as a result of C. niger being released on Isabela by whalers or other mariners prior to the 1830s (as with C. abingdonii), suggesting that the taxon’s genome may not yet be fully extirpated (Poulakakis et al. 2008, Russello et al. 2010, Garrick et al. 2012, TEWG 2015). These hybrid individuals exhibit strong genetic signatures of Floreana tortoises, as established by genetic analysis of the type specimen, indicating that their ancestry involves C. niger ancestors possibly only one or two generations back.
|Habitat and Ecology:|
No specific information on the habitat preferences and ecology of Chelonoidis niger is available; in all likelihood its biology and diet would have been analogous with other saddlebacked Galápagos tortoise species, a morphological adaptation that increases the vertical range of foraging options, from grazing on herbaceous vegetation to browsing on shrubs and cactus during dry periods when low-growing vegetation is unavailable.
|Use and Trade:||
This species was exposed to intense exploitation by whalers and other seamen in the 1700s and early 1800s, collecting animals as provisions, with the last large loads of tortoises from Floreana recorded as occurring between 1831 and 1837 (Townsend 1925, Pritchard 1996).
The precise cause of extinction is not exactly known, but most likely involved a combination of direct exploitation by sailors and settlers, as well as the impacts of invasive species. Historically, Cheloniodis niger was exploited as food by sailors provisioning their ships; a settlement was established on the island by 1829 and later converted to a penal colony; pigs, dogs, cats, goats, donkeys, and cattle were introduced around 1832 with the introduction of Black Rats and house mice likely occurred around the same time.
Legislation and regulations: Chelonoidis niger is protected under Ecuadorian national law. It has been included in Appendix I of CITES since 1975, prohibiting all forms of commercial international trade. Most of Floreana (98%), and thus the historic range of niger, is protected as part of the Galápagos National Park.
|Citation:||van Dijk, P.P., Rhodin, A.G.J., Cayot, L.J. & Caccone, A. 2017. Chelonoidis niger. The IUCN Red List of Threatened Species 2017: e.T9023A3149101.Downloaded on 23 February 2018.|
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