Galapagos giant tortoise (Chelonoidis nigra)

Synonyms: Geochelone nigra, Geochelone spp., Testudo nigra
  
French: Tortue Éléphantine, Tortue Géante Des Galapagos
Spanish: Tortuga Gigante De Las Galápagos
KingdomAnimalia
PhylumChordata
ClassReptilia
OrderTestudines
FamilyTestudinidae
GenusChelonoidis (1)
SizeLength: up to 1.2 m (2)
Male weight: 51 - 320 kg (3) (4)

The Galapagos giant tortoise is classified as Vulnerable (VU) on the IUCN Red List (1).

Subspecies: The Charles Island tortoise (Chelonoidis nigra nigra) is classified as Extinct (EX) on the IUCN Red List and the Abingdon Island tortoise (Chelonoidis nigra abingdoni) is classified as Extinct in the Wild (EW). The Duncan Island tortoise (Chelonoidis nigra duncanensis) is classified by the IUCN as Extinct in the Wild (EW), although it is currently provisionally evaluated as Critically Endangered (CR) by the IUCN Tortoise and Freshwater Turtle Specialist Group in their 2010 conservation status assessment (1) (5) (6).

The Hood Island tortoise (Chelonoidis nigra hoodensis) is classified as Critically Endangered (CR) and the James Island tortoise (Chelonoidis nigra darwini), Sierra Negra tortoise (Chelonoidis nigra guentheri), Indefatigable Island tortoise (Chelonoidis nigra porteri) and Iguana Cove tortoise (Chelonoidis nigra vicina) are classified as Endangered (EN). The Volcan Wolf tortoise (Chelonoidis nigra becki), Chatham Island tortoise (Chelonoidis nigra chathamensis), Volcan Darwin tortoise (Chelonoidis nigra microphyes) and Volcan Alcedo tortoise (Chelonoidis nigra vandenburghi) are all classified as Vulnerable (VU) on the IUCN Red List (1) (5) (6).

The Narborough Island giant tortoise (Chelonoidis nigra phantastica) was not previously evaluated by the IUCN, but has been provisionally classified as Extinct (EX) by the IUCN Tortoise and Freshwater Turtle Specialist Group (5).

The Galapagos giant tortoise is also listed on Appendix I of CITES (7).

The enormous Galapagos giant tortoise (Chelonoidis nigra) was once so numerous that Spanish explorers of the region named the Galapagos archipelago after its extraordinary inhabitant; 'galapagos' means 'tortoise' in Spanish (8).

This giant reptile is the largest living tortoise, with relatively heavy limbs, a long neck and a heavy carapace that can reach lengths of up to 150 centimetres (2) (8). The different subspecies of the Galapagos giant tortoise illustrate the principal of ‘adaptive radiation’, where populations isolated on islands or on parts of larger islands within the Galapagos chain have adapted to different conditions, and now have distinct appearances (9). The subspecies can be generally separated into those with 'domed' shells, which occur on the larger, wetter islands, and smaller tortoises with 'saddleback' carapaces that are found on smaller islands with dry vegetation (10).

It is thought that the distinctive saddleback shell of some populations of the Galapagos giant tortoise enables its bearer to reach taller vegetation, with these tortoises also having longer limbs and necks (10).

The Galapagos giant tortoise is endemic to the islands of the Galapagos in the eastern Pacific Ocean (1).

During the dry season, the Galapagos giant tortoise is likely to be found on higher slopes, while after the rains many individuals come down to feed on the newly grass-covered flats (9).

The Galapagos giant tortoise spends a large part of the day grazing in small groups (2), feeding on a wide range of vegetation, from grasses and flowers to cactus fruits (9). During the rainy season a lot of time is spent wallowing in shallow pools, and at night the Galapagos giant tortoise can be found in depressions dug into the ground (10). On some islands, Galapagos finches clean parasites from the skin of the tortoise, with the tortoise raising itself up on its legs to facilitate the process (11).

The male Galapagos giant tortoise typically becomes territorial during the mating season (2), during which time rivals size each other up by standing tall on their legs and stretching their necks out, with the taller tortoise usually being dominant (11). The female tortoise lays a clutch of 2 to 16 eggs into a nest dug into sandy ground, which is then covered over with soil and leaves. The hatchlings emerge around 4.5 months later (11).

The Galapagos giant tortoise is one of the longest-lived of all vertebrates, and the oldest recorded individual reached the impressive age of 152 (3).

When mariners first began to arrive in the Galapagos Islands in the 1600s they captured giant tortoises and stored them live on ships as a source of meat (11). This trend continued and throughout the 19th century whaling ships took a large number of tortoises for food, whilst others were killed for turtle oil (11).

Today the greatest threat to the survival of the Galapagos giant tortoise comes from introduced species. Feral dogs, cats and rats predate juvenile tortoises before their carapace has fully developed, while goats and cattle compete with the Galapagos giant tortoise for vegetation (10). The population of the Galapagos giant tortoise originally numbered in the 100,000s (9), but following centuries of persecution it is estimated that a mere fraction of this population remains; three subspecies have become extinct and there is only one sole survivor of the Abingdon Island subspecies (C. n. abingdoni), known as 'Lonesome George' (10).

The Galapagos giant tortoise is fully protected within the Galapagos National Park, which was established by Ecuador in 1959 (11). International trade is also prohibited by the listing of this species on Appendix I of the Convention on International Trade in Endangered Species (CITES) (7).

The Charles Darwin Foundation and the Galapagos National Park Service have been running a highly successful tortoise-restoration programme since the 1970s, by raising hatchlings from eggs until they are robust enough to be released into the wild without falling victim to predation (9). One of their major achievements has been to increase the population of the Critically Endangered Hood Island tortoise (C. n. hoodensis), which numbered just 13 individuals in the 1970s but now boasts over 1,000 members in the wild (4) (9). It is hoped that these concerted conservation efforts will help to secure the future of this giant, iconic reptile.

For more information on the Galapagos tortoise see:

Authenticated (11/06/03) by Howard Snell. Head of Science, Charles Darwin Research Station.
http://www.darwinfoundation.org/

  1. IUCN Red List (January, 2011)
    http://www.iucnredlist.org/
  2. Burnie, D. (2001) Animal. Dorling Kindersley, London.
  3. American Museum of Natural History - Galapagos giant tortoise (April, 2003)
    http://www.amnh.org/nationalcenter/Endangered/tortoise/tortoise.html
  4. Marquez, C. (2003) Pers. comm.
  5. Turtle Taxonomy Working Group [Rhodin, A.G.J., van Dijk, P.P., Iverson, J.B. and Shaffer, H.B.]. (2010) Turtles of the world, 2010 update: annotated checklist of taxonomy, synonymy, distribution and conservation status. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B. and Mittermeier, R.A. (Eds.) Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Specialist Group. Chelonian Research Monographs, 5: 000.85-000.164. Available at:
    http://www.iucn-tftsg.org/wp-content/uploads/file/Accounts/crm_5_000_checklist_v3_2010.pdf
  6. Ernst, C.H., Altenburg, R.G.M. and Barbour, R.W. (1997) Turtles of the World. ETI Information Systems Ltd, Netherlands.
  7. CITES (April, 2003)
    http://www.cites.org/
  8. WWF (April, 2003)
    http://www.worldwildlife.org/
  9. Galapagos Online - Tortoises (April, 2003)
    http://www.galapagosonline.com/Galapagos_Natural_History/Birds_and_Animals/Animals/Tortoises.html
  10. Discover Galapagos - The Endangered Galapagos Giant Tortoise (April, 2003)
    http://www.discovergalapagos.com/tortoise.html
  11. Galapagos Conservation Trust - Galapagos giant tortoise (January, 2011)
    http://www.savegalapagos.org/galapagos/galapagos-giant-tortoise.shtml