The Galápagos tortoise or Galápagos giant tortoise (''Chelonoidis niger'') is a species of very large

tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a turtle shell, shell to protect from predation and other threats. The shell in tortoises is generally hard, ...

in the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Chelonoidis ''Chelonoidis'' is a genus of turtles in the tortoise family erected by Leopold Fitzinger in 1835. They are found in South America and the Galápagos Islands, and formerly had a wide distribution in the West Indies. The multiple subspecies of t ...

'' (which also contains three smaller species from mainland

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

). It comprises 15

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

(13

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

and 2

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

). It is the largest living species of

, with some modern Galápagos tortoises weighing up to . With lifespans in the wild of over 100 years, it is one of the longest-lived

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

. Captive Galapagos tortoises can live up to 177 years. For example, a captive individual, Harriet, lived for at least 175 years. Spanish explorers, who discovered the islands in the 16th century, named them after the Spanish '' galápago'', meaning "tortoise". Galápagos tortoises are native to seven of the

Galápagos Islands The Galápagos Islands (Spanish: , , ) are an archipelago of volcanic islands. They are distributed on each side of the equator in the Pacific Ocean, surrounding the centre of the Western Hemisphere, and are part of the Republic of Ecuador ...

Shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard ou ...

size and shape vary between subspecies and populations. On islands with humid highlands, the tortoises are larger, with domed shells and short necks; on islands with dry lowlands, the tortoises are smaller, with "saddleback" shells and long necks.

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...

's observations of these differences on the second voyage of the ''Beagle'' in 1835, contributed to the development of his theory of evolution. Tortoise numbers declined from over 250,000 in the 16th century to a low of around 15,000 in the 1970s. This decline was caused by

overexploitation Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term app ...

of the subspecies for meat and oil, habitat clearance for agriculture, and introduction of non-native animals to the islands, such as rats, goats, and pigs. The extinction of most giant tortoise lineages is thought to have also been caused by predation by humans or human ancestors, as the tortoises themselves have no natural predators. Tortoise populations on at least three islands have become extinct in historical times due to human activities. Specimens of these extinct taxa exist in several museums and also are being subjected to DNA analysis. 12 subspecies of the original 14-15 survive in the wild; a 13th subspecies ('' C. n. abingdonii'') had only a single known living individual, kept in captivity and nicknamed

Lonesome George Lonesome George ( es, Solitario George or , 1910 – June 24, 2012) was a male Pinta Island tortoise (''Chelonoidis niger abingdonii'') and the last known individual of the subspecies. In his last years, he was known as the rarest creat ...

until his death in June 2012. Two other subspecies, '' C. n. niger'' (the type subspecies of Galápagos tortoise) from

Floreana Island Floreana Island (Spanish: ''Isla Floreana'') is an island of the Galápagos Islands. It was named after Juan José Flores, the first president of Ecuador, during whose administration the government of Ecuador took possession of the archipelago. ...

and an undescribed subspecies from

Santa Fe Island Santa Fe Island (Spanish: ''Isla Santa Fe''), also called Barrington Island after admiral Samuel Barrington, is a small island of which lies in the centre of the Galápagos archipelago, to the south-east of Santa Cruz Island. Visitor access is ...

are known to have gone extinct in the mid-late 19th century. Conservation efforts, beginning in the 20th century, have resulted in thousands of captive-bred juveniles being released onto their ancestral home islands, and the total number of the subspecies is estimated to have exceeded 19,000 at the start of the 21st century. Despite this rebound, all surviving subspecies are classified as

Threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensat ...

by the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

. The Galápagos tortoises are one of two insular radiations of giant tortoises that still survive to the modern day; the other is ''

Aldabrachelys gigantea The Aldabra giant tortoise (''Aldabrachelys gigantea'') is a species of tortoise in the family Testudinidae. The species is endemic to the islands of the Aldabra Atoll in the Seychelles. It is one of the largest tortoises in the world.Pritchar ...

'' of

Aldabra Aldabra is the world's second-largest coral atoll, lying south-east of the continent of Africa. It is part of the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands of the Seychelles, with a distance of 1,120 k ...

and the

Seychelles Seychelles (, ; ), officially the Republic of Seychelles (french: link=no, République des Seychelles; Creole: ''La Repiblik Sesel''), is an archipelagic state consisting of 115 islands in the Indian Ocean. Its capital and largest city, V ...

in the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

, east of

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...

. While giant tortoise radiations were common in prehistoric times, humans have wiped out the majority of them worldwide; the only other radiation of tortoises to survive to historic times, ''

Cylindraspis ''Cylindraspis'' is a genus of recently extinct giant tortoises. All of its species lived in the Mascarene Islands (Mauritius, Rodrigues and Réunion) in the Indian Ocean and all are now extinct due to hunting and introduction of non-native pre ...

'' of the

Mascarenes The Mascarene Islands (, ) or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of the islands belonging to the Republic of Mauritius as well as the French department of Réunion. Their ...

, was driven to extinction by the 19th century, and other giant tortoise radiations such as a ''

Centrochelys ''Centrochelys'' is a genus of tortoise. It contains one extant species and several extinct species: * ''Centrochelys atlantica'' * ''Centrochelys burchardi'' * ''Centrochelys marocana'' * ''Centrochelys robusta'' * ''Centrochelys vulcanica'' * ...

'' radiation on the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

and another ''Chelonoidis'' radiation in the

Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...

were driven to extinction prior to that.

Taxonomy

Early classification

The Galápagos Islands were discovered in 1535, but first appeared on the maps, of

Gerardus Mercator Gerardus Mercator (; 5 March 1512 – 2 December 1594) was a 16th-century geographer, cosmographer and Cartography, cartographer from the County of Flanders. He is most renowned for creating the Mercator 1569 world map, 1569 world map based on ...

and

Abraham Ortelius Abraham Ortelius (; also Ortels, Orthellius, Wortels; 4 or 14 April 152728 June 1598) was a Brabantian cartographer, geographer, and cosmographer, conventionally recognized as the creator of the first modern atlas, the ''Theatrum Orbis Terraru ...

, around 1570. The islands were named "Insulae de los Galopegos" (Islands of the Tortoises) in reference to the giant tortoises found there.The first navigation chart showing the individual islands was drawn up by the pirate

Ambrose Cowley William Ambrosia Cowley was a 17th-century English people, English buccaneer who surveyed the Galápagos Islands during his circumnavigation of the world while serving under several Captains such as John Eaton (pirate), John Eaton, John Cook (pir ...

in 1684. He named them after fellow pirates or English noblemen. More recently, the Ecuadorian government gave most of the islands Spanish names. While the Spanish names are official, many researchers continue to use the older English names, particularly as those were the names used when Darwin visited. This article uses the Spanish island names. Initially, the giant tortoises of the Indian Ocean and those from the Galápagos were thought to be the same subspecies. Naturalists thought that sailors had transported the tortoises there. In 1676, the pre-Linnaean authority

Claude Perrault Claude Perrault (25 September 1613 – 9 October 1688) was a French physician and an amateur architect, best known for his participation in the design of the east façade of the Louvre in Paris.Johann Gottlob Schneider Johann Gottlob Theaenus Schneider (18 January 1750 – 12 January 1822) was a German Empire, German classicist and natural history, naturalist. Biography Schneider was born at Collm in Saxony. In 1774, on the recommendation of Christian Gottlob ...

classified all giant tortoises as ''Testudo indica'' ("Indian tortoise"). In 1812,

August Friedrich Schweigger August Friedrich Schweigger (8 September 1783 – 28 June 1821) was a German naturalist born in Erlangen. He was the younger brother of scientist Johann Salomo Christoph Schweigger (1779-1857). He studied medicine, zoology and botany at Erl ...

named them ''Testudo gigantea'' ("gigantic tortoise"). In 1834,

André Marie Constant Duméril André Marie Constant Duméril (1 January 1774 – 14 August 1860) was a French zoologist. He was professor of anatomy at the Muséum national d'histoire naturelle from 1801 to 1812, when he became professor of herpetology and ichthyology. His ...

and

Gabriel Bibron Gabriel Bibron (20 October 1805 – 27 March 1848) was a French zoologist and herpetologist. He was born in Paris. The son of an employee of the Museum national d'histoire naturelle, he had a good foundation in natural history and was hir ...

classified the Galápagos tortoises as a separate subspecies, which they named ''Testudo nigrita'' ("black tortoise"). RothschildTortoise

Recognition of subpopulations

The first systematic survey of giant tortoises was by the zoologist

Albert Günther Albert Karl Ludwig Gotthilf Günther FRS, also Albert Charles Lewis Gotthilf Günther (3 October 1830 – 1 February 1914), was a German-born British zoologist, ichthyologist, and herpetologist. Günther is ranked the second-most productive re ...

of the

British Museum The British Museum is a public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is among the largest and most comprehensive in existence. It docum ...

, in 1875. Günther identified at least five distinct populations from the Galápagos, and three from the Indian Ocean islands. He expanded the list in 1877 to six from the Galápagos, four from the

, and four from the

. Günther hypothesized that all the giant tortoises descended from a single ancestral population which spread by sunken

land bridge In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and Colonisation (biology), colonize new lands. A land bridge can be created by marine regre ...

s. This hypothesis was later disproven by the understanding that the Galápagos, the atolls of Seychelles, and the Mascarene islands are all of recent volcanic origin and have never been linked to a continent by land bridges. Galápagos tortoises are now thought to have descended from a South American ancestor, while the Indian Ocean tortoises derived from ancestral populations on Madagascar. At the end of the 19th century,

Georg Baur Georg Baur (1859–1898) was a German vertebrate paleontologist and Neo-Lamarckian who studied reptiles of the Galapagos Islands, particularly the Galápagos tortoises, in the 1890s. He is perhaps best known for his subsidence theory of the o ...

and

Walter Rothschild Lionel Walter Rothschild, 2nd Baron Rothschild, Baron de Rothschild, (8 February 1868 – 27 August 1937) was a British banker, politician, zoologist and soldier, who was a member of the Rothschild family. As a Zionist leader, he was present ...

recognised five more populations of Galápagos tortoise. In 1905–06, an expedition by the

California Academy of Sciences The California Academy of Sciences is a research institute and natural history museum in San Francisco, California, that is among the largest museums of natural history in the world, housing over 46 million specimens. The Academy began in 1853 ...

, with Joseph R. Slevin in charge of reptiles, collected specimens which were studied by Academy herpetologist

John Van Denburgh John Van Denburgh (August 23, 1872 – October 24, 1924) was an American herpetologist from California (who also used the name Van Denburgh in publications, hence this name is used below). Biography Van Denburgh was born in San Francisco and enr ...

. He identified four additional populations, and proposed the existence of 15 subspecies. Van Denburgh's list still guides the

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

of the Galápagos tortoise, though now 10 populations are thought to have existed.

Current species and genus names

The current specific designation of ''niger'', formerly feminized to ''nigra'' ("black" – Quoy &

Gaimard Joseph Paul Gaimard (31 January 1793 – 10 December 1858) was a French naval surgeon and naturalist. Biography Gaimard was born at Saint-Zacharie on January 31, 1793. He studied medicine at the naval medical school in Toulon, subsequent ...

, 1824b) was resurrected in 1984 after it was discovered to be the senior

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

(an older taxonomic synonym taking historical precedence) for the then commonly used subspecies name of ''elephantopus'' ("elephant-footed" – Harlan, 1827). Quoy and Gaimard's Latin description explains the use of ''nigra: "Testudo toto corpore nigro"'' means "tortoise with completely black body". Quoy and Gairmard described ''nigra'' from a living specimen, but no evidence indicates they knew of its accurate provenance within the Galápagos – the locality was in fact given as California. Garman proposed the linking of ''nigra'' with the extinct

Floreana Floreana Island (Spanish: ''Isla Floreana'') is an island of the Galápagos Islands. It was named after Juan José Flores, the first president of Ecuador, during whose administration the government of Ecuador took possession of the archipelago. ...

subspecies. Later, Pritchard deemed it convenient to accept this designation, despite its tenuousness, for minimal disruption to the already confused nomenclature of the subspecies. The even more senior subspecies synonym of ''californiana'' ("californian" – Quoy &

, 1824a) is considered a ''

nomen oblitum In zoological nomenclature, a ''nomen oblitum'' (plural: ''nomina oblita''; Latin for "forgotten name") is a disused scientific name which has been declared to be obsolete (figuratively 'forgotten') in favour of another 'protected' name. In its p ...

'' ("forgotten name"). Previously, the Galápagos tortoise was considered to belong to the genus ''

Geochelone ''Geochelone'' is a genus of tortoises. ''Geochelone'' tortoises, which are also known as typical tortoises or terrestrial turtles, can be found in southern Asia. They primarily eat plants. Species The genus consists of two extant species: A n ...

'', known as 'typical tortoises' or 'terrestrial turtles'. In the 1990s, subgenus ''

'' was elevated to generic status based on

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

evidence which grouped the South American members of ''Geochelone'' into an independent

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

(branch of the

tree of life The tree of life is a fundamental archetype in many of the world's mythological, religious, and philosophical traditions. It is closely related to the concept of the sacred tree.Giovino, Mariana (2007). ''The Assyrian Sacred Tree: A History ...

). This nomenclature has been adopted by several authorities.Tortoise & Freshwater Turtle Specialist Group. (2016). ''Chelonoidis nigra''. The IUCN Red List of Threatened Species

Subspecies

Within the archipelago, 14-15 subspecies of Galápagos tortoises have been identified, although only 12 survive to this day. Five are found on separate islands; five of them on the volcanoes of Isabela Island. Several of the surviving subspecies are seriously endangered. A 13th subspecies, '' C. n. abingdonii'' from

Pinta Island Pinta Island (Spanish: ''Isla Pinta''), also known as Abingdon Island, after the Earl of Abingdon, is an island located in the Galápagos Islands group, Ecuador. It has an area of and a maximum altitude of . Pinta was the original home to Lones ...

, is

since 2012. The last known specimen, named

, died in captivity on 24 June 2012; George had been mated with female tortoises of several other subspecies, but none of the eggs from these pairings hatched. The subspecies inhabiting

(''G. niger'') is thought to have been hunted to extinction by 1850, only 15 years after

's landmark visit of 1835, when he saw shells, but no live tortoises there. However, recent DNA testing shows that an intermixed, non-native population currently existing on the island of Isabela is of genetic resemblance to the subspecies native to Floreana, suggesting that ''G. niger'' has not gone entirely extinct. The existence of the '' C. n. phantastica'' subspecies of

Fernandina Island Fernandina Island (Spanish: ''Isla Fernandina'', named after King Ferdinand of Spain, the sponsor of Christopher Columbus) (formerly known in English as Narborough Island, after John Narborough) is the third largest, and youngest, island of the ...

was disputed, as it was described from a single specimen that may have been an artificial introduction to the island; however, a live female was found in 2019, likely confirming the subspecies' validity. Prior to widespread knowledge of the differences between the populations (sometimes called races) from different islands and volcanoes, captive collections in zoos were indiscriminately mixed. Fertile offspring resulted from pairings of animals from different races. However, captive crosses between tortoises from different races have lower fertility and higher mortality than those between tortoises of the same race, and captives in mixed herds normally direct courtship only toward members of the same race. The valid scientific names of each of the individual populations are not universally accepted, and some researchers still consider each subspecies to be distinct species. Prior to 2021, all subspecies were classified as distinct species from one another, but a 2021 study analyzing the level of divergence within the extinct West Indian ''Chelonoidis'' radiation and comparing it to the Galápagos radiation found that the level of divergence within both clades may have been significantly overestimated, and supported once again reclassifying all Galápagos tortoises as subspecies of a single subspecies, ''C. niger''. This was followed by the

Turtle Taxonomy Working Group The Turtle Taxonomy Working Group (TTWG) is an informal working group of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group (TFTSG). It is composed of a number of leading turtle taxonomists, with varying participation by individual partici ...

and the

Reptile Database The Reptile Database is a scientific database that collects taxonomic information on all living reptile species (i.e. no fossil species such as dinosaurs). The database focuses on species (as opposed to higher ranks such as families) and has entrie ...

later that year. The taxonomic status of the various races is not fully resolved. * ''Testudo californiana''
Quoy &

, 1824a (''nomen oblitum'') * ''Testudo nigra''
Quoy &

, 1824b (''nomen novum'') * ''Testudo elephantopus''
Harlan, 1827 (''nomen dubium'') * ''Testudo nigrita''
Duméril and

Bibron Gabriel Bibron (20 October 1805 – 27 March 1848) was a French zoologist and herpetologist. He was born in Paris. The son of an employee of the Museum national d'histoire naturelle, he had a good foundation in natural history and was hir ...

, 1834 (''nomen dubium'') * ''Testudo planiceps''

Gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...

, 1853 (''nomen dubium'') * ''Testudo clivosa''

Garman Garman is a surname or first name. Notable people with the name include: Sports * Ann Garman, All-American Girls Professional Baseball League player * Judi Garman (born 1954), American softball coach * Mike Garman (born 1949), American baseball pla ...

, 1917 (''nomen dubium'') * ''Testudo typica''

, 1917 (''nomen dubium'') * ''Testudo'' (''Chelonoidis'') ''elephantopus''
Williams, 1952 * ''Geochelone'' (''Chelonoidis'') ''elephantopus''
Pritchard, 1967 * ''Chelonoidis elephantopus''
Bour, 1980 ''C. n. nigra'' (

nominate subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

) * ''Testudo californiana''
Quoy &

, 1824a (''nomen oblitum'') * ''Testudo nigra''
Quoy &

, 1824b (''nomen novum'') * ''Testudo galapagoensis''

Baur Baur can refer to: People * A. C. Baur (1900–1931), American football player and stock broker * Alfred Baur, Swiss collector of Asian art * Eleonore Baur, only woman to participate in Munich Beer Hall Putsch * Erwin Baur, German geneticist and b ...

1889 ''C. n. abingdoni'' * ''Testudo ephippium''
Günther, 1875 (partim, misidentified type specimen once erroneously attributed to what is now ''C. n. duncanensis'') * ''Testudo abingdoni''
Günther, 1877 ''C. n. becki'' * ''Testudo becki''

Rothschild Rothschild () is a name derived from the German ''zum rothen Schild'' (with the old spelling "th"), meaning "with the red sign", in reference to the houses where these family members lived or had lived. At the time, houses were designated by sign ...

, 1901 ''C. n. chathamensis'' * ''Testudo wallacei''

1902 (''partim'', ''nomen dubium'') * ''Testudo chathamensis''
Van Denburgh, 1907 ''C. n. darwini'' * ''Testudo wallacei''

1902 (''partim'', ''nomen dubium'') * ''Testudo darwini''
Van Denburgh, 1907 ''C. n. duncanensis'' * ''Testudo ephippium''
Günther, 1875 (''partim'', misidentified type) * ''Geochelone nigra duncanensis''

, 1917 in Pritchard, 1996(''nomen nudum'') ''C. n. hoodensis'' * ''Testudo hoodensis''
Van Denburgh, 1907 ''C. n. phantastica'' * ''Testudo phantasticus''
Van Denburgh, 1907 ''C. n. porteri'' * ''Testudo nigrita''
Duméril and

, 1834 (''nomen dubium'') * ''Testudo porteri''

, 1903 ''C. n. vicina'' * ''Testudo microphyes''
Günther, 1875 * ''Testudo vicina''
Günther, 1875 * ''Testudo güntheri''

, 1889 * ''Testudo macrophyes''

, 1917 * ''Testudo vandenburghi''
De Sola, R. 1930 (''nomen nudum'') ; '' Chelonoidis nigra nigra'' * ''Testudo nigra'' Quoy & Gaimard, 1824 * ''Testudo californiana'' Quoy & Gaimard, 1824 * ''Testudo galapagoensis'' Baur, 1889 * ''Testudo elephantopus galapagoensis'' Mertens & Wermuth, 1955 * ''Geochelone elephantopus galapagoensis'' Pritchard, 1967 * ''Chelonoidis galapagoensis'' Bour, 1980 * ''Chelonoidis nigra'' Bour, 1985 * ''Chelonoidis elephantopus galapagoensis'' Obst, 1985 * ''Geochelone nigra'' Pritchard, 1986 * ''Geochelone nigra nigra'' Stubbs, 1989 * ''Chelonoidis nigra galapagoensis'' David, 1994 * ''Chelonoidis nigra nigra'' David, 1994 * ''Geochelone elephantopus nigra'' Bonin, Devaux & Dupré, 1996 * ''Testudo california'' Paull, 1998 (''

ex errore This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see List of Latin and Greek words commonly used in systematic names. Note that many of the abbreviat ...

'') * ''Testudo californianana'' Paull, 1999 (''ex errore'') ; ''

Chelonoidis nigra abingdonii The Pinta Island tortoise (''Chelonoidis niger ''), also known as the Pinta giant tortoise, Abingdon Island tortoise, or Abingdon Island giant tortoise, was a subspecies of Galápagos tortoise native to Ecuador's Pinta Island. The subspecies wa ...

'' * ''Testudo ephippium'' Günther, 1875 * ''Testudo abingdonii'' Günther, 1877 * ''Testudo abingdoni'' Van Denburgh, 1914 (''ex errore'') * ''Testudo elephantopus abingdonii'' Mertens & Wermuth, 1955 * ''Testudo elephantopus ephippium'' Mertens & Wermuth, 1955 * ''Geochelone abingdonii'' Pritchard, 1967 * ''Geochelone elephantopus abingdoni'' Pritchard, 1967 * ''Geochelone elephantopus ephippium'' Pritchard, 1967 * ''Geochelone ephippium'' Pritchard, 1967 * ''Chelonoidis abingdonii'' Bour, 1980 * ''Chelonoidis ephippium'' Bour, 1980 * ''Geochelone elephantopus abingdonii'' Groombridge, 1982 * ''Geochelone abingdoni'' Fritts, 1983 * ''Geochelone epphipium'' Fritts, 1983 (''ex errore'') * ''Chelonoidis nigra ephippium'' Pritchard, 1984 * ''Chelonoidis elephantopus abingdoni'' Obst, 1985 * ''Chelonoidis elephantopus ephippium'' Obst, 1985 * ''Geochelone nigra abingdoni'' Stubbs, 1989 * ''Chelonoidis nigra abingdonii'' David, 1994 * ''Chelonoidis elephantopus abingdonii'' Rogner, 1996 * ''Chelonoidis nigra abingdonii'' Bonin, Devaux & Dupré, 1996 * ''Chelonoidis nigra abdingdonii'' Obst, 1996 (''ex errore'') * ''Geochelone abdingdonii'' Obst, 1996 * ''Geochelone nigra abdingdoni'' Obst, 1996 (''ex errore'') * ''Geochelone nigra ephyppium'' Caccone, Gibbs, Ketmaier, Suatoni & Powell, 1999 (''ex errore'') * ''Chelonoidis nigra ahingdonii'' Artner, 2003 (''ex errore'') * ''Chelonoidis abingdoni'' Joseph-Ouni, 2004 ; '' Chelonoidis nigra becki'' * ''Testudo becki'' Rothschild, 1901 * ''Testudo bedsi'' Heller, 1903 (''ex errore'') * ''Geochelone becki'' Pritchard, 1967 * ''Geochelone elephantopus becki'' Pritchard, 1967 * ''Chelonoidis becki'' Bour, 1980 * ''Chelonoidis elephantopus becki'' Obst, 1985 * ''Chelonoidis nigra beckii'' David, 1994 (''ex errore'') * ''Chelonoidis elephantopus beckii'' Rogner, 1996 * ''Chelonoidis nigra becki'' Obst, 1996 ; ''

Chelonoidis nigra chathamensis ''Chelonoidis'' is a genus of turtles in the tortoise family erected by Leopold Fitzinger in 1835. They are found in South America and the Galápagos Islands, and formerly had a wide distribution in the West Indies. The multiple subspecies of t ...

'' * ''Testudo wallacei'' Rothschild, 1902 * ''Testudo chathamensis'' Van Denburgh, 1907 * ''Testudo elephantopus chathamensis'' Mertens & Wermuth, 1955 * ''Testudo elephantopus wallacei'' Mertens & Wermuth, 1955 * ''Testudo chatamensis'' Slevin & Leviton, 1956 (''ex errore'') * ''Geochelone chathamensis'' Pritchard, 1967 * ''Geochelone elephantopus chathamensis'' Pritchard, 1967 * ''Geochelone elephantopus wallacei'' Pritchard, 1967 * ''Geochelone wallacei'' Pritchard, 1967 * ''Chelonoidis chathamensis'' Bour, 1980 * ''Chelonoidis elephantopus chathamensis'' Obst, 1985 * ''Chelonoidis elephantopus wallacei'' Obst, 1985 * ''Chelonoidis elephantopus chatamensis'' Gosławski & Hryniewicz, 1993 * ''Chelonoidis nigra chathamensis'' David, 1994 * ''Chelonoidis nigra wallacei'' Bonin, Devaux & Dupré, 1996 * ''Geochelone cathamensis'' Obst, 1996 (''ex errore'') * ''Geochelone elephantopus chatamensis'' Paull, 1996 * ''Testudo chathamensis chathamensis'' Pritchard, 1998 * ''Cherlonoidis nigra wallacei'' Wilms, 1999 * ''Geochelone nigra chatamensis'' Caccone, Gibbs, Ketmaier, Suatoni & Powell, 1999 * ''Geochelone nigra wallacei'' Chambers, 2004 ; '' Chelonoidis nigra darwini'' * ''Testudo wallacei'' Rothschild, 1902 * ''Testudo darwini'' Van Denburgh, 1907 * ''Testudo elephantopus darwini'' Mertens & Wermuth, 1955 * ''Testudo elephantopus wallacei'' Mertens & Wermuth, 1955 * ''Geochelone darwini'' Pritchard, 1967 * ''Geochelone elephantopus darwini'' Pritchard, 1967 * ''Geochelone elephantopus wallacei'' Pritchard, 1967 * ''Geochelone wallacei'' Pritchard, 1967 * ''Chelonoidis darwini'' Bour, 1980 * ''Chelonoidis elephantopus darwini'' Obst, 1985 * ''Chelonoidis elephantopus wallacei'' Obst, 1985 * ''Chelonoidis nigra darwinii'' David, 1994 (''ex errore'') * ''Chelonoidis elephantopus darwinii'' Rogner, 1996 * ''Chelonoidis nigra darwini'' Bonin, Devaux & Dupré, 1996 * ''Chelonoidis nigra wallacei'' Bonin, Devaux & Dupré, 1996 * ''Cherlonoidis nigra wallacei'' Wilms, 1999 * ''Geochelone nigra darwinii'' Ferri, 2002 * ''Geochelone nigra wallacei'' Chambers, 2004 ; '' Chelonoidis nigra duncanensis'' * ''Testudo duncanensis'' Garman, 1917 (''

nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate descr ...

'') * ''Geochelone nigra duncanensis'' Stubbs, 1989 * ''Geochelone nigra duncanensis'' Garman, 1996 * ''Chelonoidis nigra duncanensis'' Artner, 2003 * ''Chelonoidis duncanensis'' Joseph-Ouni, 2004 ; '' Chelonoidis nigra hoodensis'' * ''Testudo hoodensis'' Van Denburgh, 1907 * ''Testudo elephantopus hoodensis'' Mertens & Wermuth, 1955 * ''Geochelone elephantopus hoodensis'' Pritchard, 1967 * ''Geochelone hoodensis'' Pritchard, 1967 * ''Chelonoidis hoodensis'' Bour, 1980 * ''Chelonoidis elephantopus hoodensis'' Obst, 1985 * ''Chelonoidis nigra hoodensis'' David, 1994 ; '' Chelonoidis nigra phantastica'' * ''Testudo phantasticus'' Van Denburgh, 1907 * ''Testudo phantastica'' Siebenrock, 1909 * ''Testudo elephantopus phantastica'' Mertens & Wermuth, 1955 * ''Geochelone elephantopus phantastica'' Pritchard, 1967 * ''Geochelone phantastica'' Pritchard, 1967 * ''Chelonoidis phantastica'' Bour, 1980 * ''Geochelone phantasticus'' Crumly, 1984 * ''Chelonoidis elephantopus phantastica'' Obst, 1985 * ''Chelonoidis nigra phantastica'' David, 1994 ; ''

Chelonoidis nigra porteri ''Chelonoidis'' is a genus of turtles in the tortoise family erected by Leopold Fitzinger in 1835. They are found in South America and the Galápagos Islands, and formerly had a wide distribution in the West Indies. The multiple subspecies of ...

'' * ''Testudo nigrita'' Duméril & Bibron, 1835 * ''Testudo porteri'' Rothschild, 1903 * ''Testudo elephantopus nigrita'' Mertens & Wermuth, 1955 * ''Geochelone elephantopus porteri'' Pritchard, 1967 * ''Geochelone nigrita'' Pritchard, 1967 * ''Chelonoidis nigrita'' Bour, 1980 * ''Geochelone elephantopus nigrita'' Honegger, 1980 * ''Geochelone porteri'' Fritts, 1983 * ''Chelonoidis elephantopus nigrita'' Obst, 1985 * ''Geochelone nigra porteri'' Stubbs, 1989 * ''Chelonoidis elephantopus porteri'' Gosławski & Hryniewicz, 1993 * ''Chelonoidis nigra nigrita'' David, 1994 * ''Geochelone nigra perteri'' Müller & Schmidt, 1995 (''ex errore'') * ''Chelonoidis nigra porteri'' Bonin, Devaux & Dupré, 1996 ; '' Chelonoidis nigra vicina'' * ''Testudo elephantopus'' Harlan, 1827 * ''Testudo microphyes'' Günther, 1875 * ''Testudo vicina'' Günther, 1875 * ''Testudo macrophyes'' Garman, 1917 * ''Testudo vandenburghi'' de Sola, 1930 * ''Testudo elephantopus elephantopus'' Mertens & Wermuth, 1955 * ''Geochelone elephantopus'' Williams, 1960 * ''Geochelone elephantopus elephantopus'' Pritchard, 1967 * ''Geochelone elephantopus guentheri'' Pritchard, 1967 * ''Geochelone elephantopus guntheri'' Pritchard, 1967 (''ex errore'') * ''Geochelone elephantopus microphyes'' Pritchard, 1967 * ''Geochelone elephantopus vandenburgi'' Pritchard, 1967 (''ex errore'') * ''Geochelone guntheri'' Pritchard, 1967 * ''Geochelone microphyes'' Pritchard, 1967 * ''Geochelone vandenburghi'' Pritchard, 1967 * ''Geochelone vicina'' Pritchard, 1967 * ''Geochelone elephantopus microphys'' Arnold, 1979 (''ex errore'') * ''Geochelone elephantopus vandenburghi'' Pritchard, 1979 * ''Chelonoides elephantopus'' Obst, 1980 * ''Chelonoidis elephantopus'' Bour, 1980 * ''Chelonoidis guentheri'' Bour, 1980 * ''Chelonoidis microphyes'' Bour, 1980 * ''Chelonoidis vandenburghi'' Bour, 1980 * ''Geochelone guentheri'' Fritts, 1983 * ''Chelonoidis elephantopus elephantopus'' Obst, 1985 * ''Chelonoidis elephantopus guentheri'' Obst, 1985 * ''Chelonoidis elephantopus microphyes'' Obst, 1985 * ''Chelonoidis elephantopus vandenburghi'' Obst, 1985 * ''Geochelone elephantopus vicina'' Swingland, 1989 * ''Geochelone elephantopus vicini'' Swingland, 1989 (''ex errore'') * ''Chelonoidis elephantopus guntheri'' Gosławski & Hryniewicz, 1993 * ''Chelonoidis nigra guentheri'' David, 1994 * ''Chelonoidis nigra microphyes'' David, 1994 * ''Chelonoidis nigra vandenburghi'' David, 1994 * ''Geochelone nigra elephantopus'' Müller & Schmidt, 1995 * ''Chelonoidis elephantopus vicina'' Rogner, 1996 * ''Geochelone elephantopus vandenburghii'' Obst, 1996 (''ex errore'') * ''Geochelone vandenburghii'' Obst, 1996 * ''Chelonoidis nigra microphyies'' Bonin, Devaux & Dupré, 1996 (''ex errore'') * ''Geochelone elephantopus microphytes'' Paull, 1996 (''ex errore'') * ''Geochelone elephantopus vandenbergi'' Paull, 1996 (''ex errore'') * ''Testudo elephantopus guntheri'' Paull, 1999 * ''Chelonoidis nigra vicina'' Artner, 2003 * ''Chelonoidis vicina'' Joseph-Ouni, 2004 * ''Geochelone nigra guentheri'' Chambers, 2004

Evolutionary history

All subspecies of Galápagos tortoises evolved from common ancestors that arrived from mainland South America by overwater dispersal. Genetic studies have shown that the

Chaco tortoise The Chaco tortoise (''Chelonoidis chilensis''), also known commonly as the Argentine tortoise, the Patagonian tortoise, or the southern wood tortoise, is a species of tortoise in the family Testudinidae. The species is endemic to South America. ...

of Argentina and Paraguay is their closest living relative. The minimal founding population was a pregnant female or a breeding pair. Survival on the 1000-km oceanic journey is accounted for because the tortoises are buoyant, can breathe by extending their necks above the water, and are able to survive months without food or fresh water. As they are poor swimmers, the journey was probably a passive one facilitated by the

Humboldt Current The Humboldt Current, also called the Peru Current, is a cold, low- salinity ocean current that flows north along the western coast of South America.Montecino, Vivian, and Carina B. Lange. "The Humboldt Current System: Ecosystem components and pr ...

, which diverts westwards towards the Galápagos Islands from the mainland. The ancestors of the genus ''

'' are believed to have similarly dispersed from Africa to South America during the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

. The closest living relative (though not a direct ancestor) of the Galápagos giant tortoise is the

(''Chelonoidis chilensis''), a much smaller subspecies from South America. The divergence between ''C. chilensis'' and ''C. niger'' probably occurred 11.95–25 million years ago, an evolutionary event preceding the volcanic formation of the oldest modern Galápagos Islands 5 million years ago.

Mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

analysis indicates that the oldest existing islands (Española and San Cristóbal) were colonised first, and that these populations seeded the younger islands via dispersal in a "stepping stone" fashion via local currents. Restricted

gene flow In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent a ...

between isolated islands then resulted in the independent evolution of the populations into the divergent forms observed in the modern subspecies. The evolutionary relationships between the subspecies thus echo the volcanic history of the islands.

Subspecies

Modern DNA methods have revealed new information on the relationships between the subspecies: Isabela Island The five populations living on the largest island, Isabela, are the ones that are the subject of the most debate as to whether they are true subspecies or just distinct populations or subspecies. It is widely accepted that the population living on the northernmost volcano, Volcan Wolf, is genetically independent from the four populations to the south and is therefore a separate subspecies. It is thought to be derived from a different colonization event than the others. A colonization from the island of Santiago apparently gave rise to the Volcan Wolf subspecies (''C. n. becki'') while the four southern populations are believed to be descended from a second colonization from the more southerly island of Santa Cruz. Tortoises from Santa Cruz are thought to have first colonized the Sierra Negra volcano, which was the first of the island's volcanoes to form. The tortoises then spread north to each newly created volcano, resulting in the populations living on Volcan Alcedo and then Volcan Darwin. Recent genetic evidence shows that these two populations are genetically distinct from each other and from the population living on Sierra Negra (''C. guentheri'') and therefore form the subspecies ''C. n. vandenburghi'' (Alcedo) and ''C. n. microphyes'' (Darwin). The fifth population living on the southernmost volcano (''C. n. vicina'') is thought to have split off from the Sierra Negra population more recently and is therefore not as genetically different as the other two. Isabela is the most recently formed island tortoises inhabit, so its populations have had less time to evolve independently than populations on other islands, but according to some researchers, they are all genetically different and should each be considered as separate subspecies. Floreana Island Phylogenetic analysis may help to "resurrect" the extinct subspecies of Floreana (''C. n. niger'') – a subspecies known only from

subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

remains. Some tortoises from Isabela were found to be a partial match for the genetic profile of Floreana specimens from museum collections, possibly indicating the presence of hybrids from a population transported by humans from Floreana to Isabela, resulting either from individuals deliberately transported between the islands, or from individuals thrown overboard from ships to lighten the load. Nine Floreana descendants have been identified in the captive population of the Fausto Llerena Breeding Center on Santa Cruz; the genetic footprint was identified in the genomes of hybrid offspring. This allows the possibility of re-establishing a reconstructed subspecies from

selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant mal ...

of the hybrid animals. Furthermore, individuals from the subspecies possibly are still extant. Genetic analysis from a sample of tortoises from Volcan Wolf found 84 first-generation ''C. n. niger'' hybrids, some less than 15 years old. The genetic diversity of these individuals is estimated to have required 38 ''C. n. niger'' parents, many of which could still be alive on Isabela Island. Pinta Island Lonesome George in profile

The Pinta Island subspecies (''C. n. abingdonii'', now extinct) has been found to be most closely related to the subspecies on the islands of San Cristóbal (''C. n. chathamensis'') and Española (''C. n. hoodensis'') which lie over 300 km (190 mi) away, rather than that on the neighbouring island of Isabela as previously assumed. This relationship is attributable to dispersal by the strong local current from San Cristóbal towards Pinta. This discovery informed further attempts to preserve the ''C. n. abingdonii'' lineage and the search for an appropriate mate for

, which had been penned with females from Isabela. Hope was bolstered by the discovery of a ''C. n. abingdonii'' hybrid male in the Volcán Wolf population on northern Isabela, raising the possibility that more undiscovered living Pinta descendants exist. Santa Cruz Island Mitochondrial DNA studies of tortoises on Santa Cruz show up to three genetically distinct lineages found in nonoverlapping population distributions around the regions of Cerro Montura, Cerro Fatal, and La Caseta. Although traditionally grouped into a single subspecies (''C. n. porteri''), the lineages are all more closely related to tortoises on other islands than to each other: Cerro Montura tortoises are most closely related to ''C. n. duncanensis'' from Pinzón, Cerro Fatal to ''C. n. chathamensis'' from San Cristóbal, and La Caseta to the four southern races of Isabela as well as Floreana tortoises. In 2015, the Cerro Fatal tortoises were described as a distinct taxon, '' donfaustoi''. Prior to the identification of this subspecies through genetic analysis, it was noted that there existed differences in shells between the Cerro Fatal tortoises and other tortoises on Santa Cruz. By classifying the Cerro Fatal tortoises into a new taxon, greater attention can be paid to protecting its habitat, according to Adalgisa Caccone, who is a member of the team making this classification. Pinzón Island When it was discovered that the central, small island of Pinzón had only 100–200 very old adults and no young tortoises had survived into adulthood for perhaps more than 70 years, the resident scientists initiated what would eventually become the Giant Tortoise Breeding and Rearing Program. Over the next 50 years, this program resulted in major successes in the recovery of giant tortoise populations throughout the archipelago. In 1965, the first tortoise eggs collected from natural nests on Pinzón Island were brought to the Charles Darwin Research Station, where they would complete the period of incubation and then hatch, becoming the first young tortoises to be reared in captivity. The introduction of black rats onto Pinzón sometime in the latter half of the 19th century had resulted in the complete eradication of all young tortoises. Black rats had been eating both tortoise eggs and hatchlings, effectively destroying the future of the tortoise population. Only the longevity of giant tortoises allowed them to survive until the Galápagos National Park,

Island Conservation Island Conservation is a non-profit organization with the mission to prevent extinctions by removing invasive species from islands. Island Conservation has therefore focused its efforts on islands with species categorized as Critically Endangere ...

, Charles Darwin Foundation, the Raptor Center, and Bell Laboratories removed invasive rats in 2012. In 2013, heralding an important step in Pinzón tortoise recovery, hatchlings emerged from native Pinzón tortoise nests on the island and the Galápagos National Park successfully returned 118 hatchlings to their native island home. Partners returned to Pinzón Island in late 2014 and continued to observe hatchling tortoises (now older), indicating that natural recruitment is occurring on the island unimpeded. They also discovered a snail subspecies new to science. These exciting results highlight the conservation value of this important management action. In early 2015, after extensive monitoring, partners confirmed that Pinzón and Plaza Sur Islands are now both rodent-free. Española On the southern island of Española, only 14 adult tortoises were found, two males and 12 females. The tortoises apparently were not encountering one another, so no reproduction was occurring. Between 1963 and 1974, all 14 adult tortoises discovered on the island were brought to the tortoise center on Santa Cruz and a tortoise breeding program was initiated. In 1977, a third Española male tortoise was returned to Galapagos from the San Diego Zoo and joined the breeding group. After 40 years' work reintroducing captive animals, a detailed study of the island's ecosystem has confirmed it has a stable, breeding population. Where once 15 were known, now more than 1,000 giant tortoises inhabit the island of Española. One research team has found that more than half the tortoises released since the first reintroductions are still alive, and they are breeding well enough for the population to progress onward, unaided. In January 2020, it was widely reported that Diego, a 100-year-old male tortoise, resurrected 40% of the tortoise population on the island and is known as the "Playboy Tortoise". Fernandina The ''C. n. phantasticus'' subspecies from Fernandina was originally known from a single specimen — an old male from the voyage of 1905–06. No other tortoises or remains were found on the island for a long time after its sighting, leading to suggestions that the specimen was an artificial introduction from elsewhere. Fernandina has neither human settlements nor

feral A feral () animal or plant is one that lives in the wild but is descended from domesticated individuals. As with an introduced species, the introduction of feral animals or plants to non-native regions may disrupt ecosystems and has, in some ...

mammals, so if this subspecies ever did exist, its extinction would have been by natural means, such as volcanic activity. Nevertheless, there have occasionally been reports from Fernandina. In 2019, an elderly female specimen was finally discovered on Fernandina and transferred to a breeding center, and trace evidence found on the expedition indicates that more individuals likely exist in the wild. It has been theorized that the rarity of the subspecies may be due to the harsh habitat it survives in, such as the

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

flows that are known to frequently cover the island.

Santa Fe

The extinct Santa Fe subspecies has not yet been described and thus has no

binomial name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

, having been identified from the limited evidence of bone fragments (but no shells, the most durable part) of 14 individuals, old eggs, and old dung found on the island in 1905–06. The island has never been inhabited by man nor had any introduced predators, but reports have been made of whalers hauling tortoises off the island. Later genetic studies of the bone fragments indicate that the Santa Fe subspecies was distinct, and was most closely related to ''C. n. hoodensis''. A population of ''C. n. hoodensis'' has since been reintroduced to and established on the island to fill in the ecological role of the Santa Fe tortoise. Species of doubtful existence The purported

Rábida Island Rábida Island (), is one of the Galápagos Islands. The island has also been known as Jervis Island named in honour of the 18th-century British admiral John Jervis. In Ecuador it is officially known as Isla Rábida. Wildlife In addition to ...

subspecies (''C. n. wallacei'') was described from a single specimen collected by the

in December 1905, which has since been lost. This individual was probably an artificial introduction from another island that was originally penned on Rábida next to a good anchorage, as no contemporary whaling or sealing logs mention removing tortoises from this island.

Description

The tortoises have a large bony shell of a dull brown or grey color. The plates of the shell are fused with the ribs in a rigid protective structure that is integral to the skeleton.

Lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship. Tortoises keep a characteristic

scute A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...

(shell segment) pattern on their shells throughout life, though the annual growth bands are not useful for determining age because the outer layers are worn off with time. A tortoise can withdraw its head, neck, and fore limbs into its shell for protection. The legs are large and stumpy, with dry, scaly skin and hard

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

. The front legs have five claws, the back legs four.

Gigantism

The discoverer of the Galápagos Islands, Fray Tomás de Berlanga, Bishop of Panama, wrote in 1535 of "such big tortoises that each could carry a man on top of himself." Naturalist Charles Darwin remarked after his trip three centuries later in 1835, "These animals grow to an immense size ... several so large that it required six or eight men to lift them from the ground". The largest recorded individuals have reached weights of over and lengths of . Size overlap is extensive with the

Aldabra giant tortoise The Aldabra giant tortoise (''Aldabrachelys gigantea'') is a species of tortoise in the family Testudinidae. The species is endemic to the islands of the Aldabra Atoll in the Seychelles. It is one of the largest tortoises in the world.Pritchar ...

, however taken as a subspecies, the Galápagos tortoise seems to average slightly larger, with weights in excess of being slightly more commonplace. Weights in the larger bodied subspecies range from in mature males and from in adult females. However, the size is variable across the islands and subspecies; those from

Pinzón Island Pinzón Island (Spanish: ''Isla Pinzón''), sometimes called Duncan Island (after Adam Duncan, 1st Viscount Duncan), is an island in the Galápagos Islands, Ecuador. Pinzón is home to giant Galápagos tortoises of the endemic subspecies '' Chel ...

are relatively small with a maximum known weight of and carapace length of approximately compared to range in tortoises from

Santa Cruz Island Santa Cruz Island (Spanish: ''Isla Santa Cruz'', Chumash: ''Limuw'') is located off the southwestern coast of Ventura, California, United States. It is the largest island in California and largest of the eight islands in the Channel Islands a ...

. The tortoises' gigantism was probably a trait useful on continents that was fortuitously helpful for successful colonisation of these remote oceanic islands rather than an example of evolved

insular gigantism Island gigantism, or insular gigantism, is a biological phenomenon in which the size of an animal species isolated on an island increases dramatically in comparison to its mainland relatives. Island gigantism is one aspect of the more general Fos ...

. Large tortoises would have a greater chance of surviving the journey over water from the mainland as they can hold their heads a greater height above the water level and have a smaller surface area/volume ratio, which reduces

osmotic Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region of ...

water loss. Their significant water and fat reserves would allow the tortoises to survive long ocean crossings without food or fresh water, and to endure the drought-prone climate of the islands. A larger size allowed them to better tolerate extremes of temperature due to

gigantothermy Gigantothermy (sometimes called ectothermic homeothermy or inertial homeothermy) is a phenomenon with significance in biology and paleontology, whereby large, bulky ectothermic animals are more easily able to maintain a constant, relatively high bod ...

. Fossil giant tortoises from mainland South America have been described that support this hypothesis of gigantism that pre-existed the colonization of islands.

Shell shape

Galápagos tortoises possess two main shell forms that correlate with the biogeographic history of the subspecies group. They exhibit a spectrum of carapace morphology ranging from "saddleback" (denoting upward arching of the front edge of the shell resembling a saddle) to "domed" (denoting a rounded convex surface resembling a dome). When a saddleback tortoise withdraws its head and forelimbs into its shell, a large unprotected gap remains over the neck, evidence of the lack of predation during the evolution of this structure. Larger islands with humid highlands over in elevation, such as Santa Cruz, have abundant vegetation near the ground. Tortoises native to these environments tend to have domed shells and are larger, with shorter necks and limbs. Saddleback tortoises originate from small islands less than in elevation with dry habitats (e.g. Española and Pinzón) that are more limited in food and other resources. Two lineages of Galápagos tortoises possess the Island of Santa Cruz and when observed it is concluded that despite the shared similarities of growth patterns and morphological changes observed during growth, the two lineages and two sexes can be distinguished on the basis of distinct carapace features. Lineages differ by the shape of the vertebral and pleural scutes. Females have a more elongated and wider carapace shape than males. Carapace shape changes with growth, with vertebral scutes becoming narrower and pleural scutes becoming larger during late

ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...

. ;Evolutionary implications In combination with proportionally longer necks and limbs, the unusual saddleback carapace structure is thought to be an adaptation to increase vertical reach, which enables the tortoise to browse tall vegetation such as the ''

Opuntia ''Opuntia'', commonly called prickly pear or pear cactus, is a genus of flowering plants in the cactus family Cactaceae. Prickly pears are also known as ''tuna'' (fruit), ''sabra'', ''nopal'' (paddle, plural ''nopales'') from the Nahuatl word f ...

'' (prickly pear) cactus that grows in arid environments. Saddlebacks are more territorial and smaller than domed varieties, possibly adaptations to limited resources. Alternatively, larger tortoises may be better-suited to high elevations because they can resist the cooler temperatures that occur with cloud cover or fog. A competing hypothesis is that, rather than being principally a feeding adaptation, the distinctive saddle shape and longer extremities might have been a

secondary sexual characteristic Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexual dimorphism, sexually dimorphic phenotypic traits that distinguis ...

of saddleback males. Male competition over mates is settled by dominance displays on the basis of vertical neck height rather than body size ( see below). This correlates with the observation that saddleback males are more aggressive than domed males. The shell distortion and elongation of the limbs and neck in saddlebacks is probably an evolutionary compromise between the need for a small body size in dry conditions and a high vertical reach for dominance displays. The saddleback carapace probably evolved independently several times in dry habitats, since genetic similarity between populations does not correspond to carapace shape. Saddleback tortoises are, therefore, not necessarily more closely related to each other than to their domed counterparts, as shape is not determined by a similar genetic background, but by a similar ecological one. ; Sexual dimorphism

Sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

is most pronounced in saddleback populations in which males have more angled and higher front openings, giving a more extreme saddled appearance. Males of all varieties generally have longer tails and shorter, concave plastrons with thickened knobs at the back edge to facilitate mating. Males are larger than females — adult males weigh around while females are .

Behavior

Routine

The tortoises are

ectotherm An ectotherm (from the Greek () "outside" and () "heat") is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature.Davenport, John. Animal Life a ...

ic (cold-blooded), so they bask for 1–2 hours after dawn to absorb the sun's heat through their dark shells before actively foraging for 8–9 hours a day.Swingland, I.R. (1989). Geochelone elephantopus. ''Galapagos giant tortoises''. In: Swingland I.R. and Klemens M.W. (eds.) ''The Conservation Biology of Tortoises.'' Occasional Papers of the IUCN Species Survival Commission (SSC), No. 5, pp. 24–28. Gland, Switzerland: IUCN. . They travel mostly in the early morning or late afternoon between resting and grazing areas. They have been observed to walk at a speed of . On the larger and more humid islands, the tortoises seasonally migrate between low elevations, which become grassy plains in the wet season, and meadowed areas of higher elevation (up to ) in the dry season. The same routes have been used for many generations, creating well-defined paths through the undergrowth known as "tortoise highways". On these wetter islands, the domed tortoises are gregarious and often found in large herds, in contrast to the more solitary and territorial disposition of the saddleback tortoises. Tortoises sometimes rest in mud wallows or rain-formed pools, which may be both a

thermoregulatory Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

response during cool nights, and a protection from

parasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

such as mosquitoes and ticks. Parasites are countered by taking dust baths in loose soil. Some tortoises have been noted to shelter at night under overhanging rocks. Others have been observed sleeping in a snug depression in the earth or brush called a "pallet". Local tortoises using the same pallet sites, such as on Volcán Alcedo, results in the formation of small, sandy pits.

Diet

The tortoises are

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

s that consume a diet of cacti, grasses, leaves, lichens, berries, melons, oranges and milkweed. They have been documented feeding on ''

Hippomane mancinella The manchineel tree (''Hippomane mancinella'') is a species of flowering plant in the spurge family (Euphorbiaceae). Its native range stretches from tropical southern North America to northern South America. The name "manchineel" (sometimes spel ...

'' (poison apple), the endemic

guava Guava () is a common tropical fruit cultivated in many tropical and subtropical regions. The common guava ''Psidium guajava'' (lemon guava, apple guava) is a small tree in the myrtle family ( Myrtaceae), native to Mexico, Central America, the ...

''Psidium galapageium'', the

water fern Water fern is a common name for several plants and may refer to: * Salviniales, an order of aquatic ferns * '' Austroblechnum lanceolatum'', syn. ''Blechnum chambersii'', lance water fern * '' Austroblechnum patersonii'', syn. ''Blechnum patersonii' ...

''Azolla microphylla'',

bromeliad The Bromeliaceae (the bromeliads) are a family of monocot flowering plants of about 80 genera and 3700 known species, native mainly to the tropical Americas, with several species found in the American subtropics and one in tropical west Africa, ...

''Tillandsia insularis'' and the Galápagos tomato ''Solanum cheesmaniae''. Juvenile tortoises eat an average of 16.7% of their own body weight in dry matter per day, with a digestive efficiency roughly equal to that of hindgut-fermenting herbivorous mammals such as horses and rhinos. Tortoises acquire most of their moisture from the dew and sap in vegetation (particularly the ''

'' cactus); therefore, they can survive longer than 6 months without water. They can endure up to a year when deprived of all food and water, surviving by breaking down their body fat to produce water as a byproduct. Tortoises also have very slow metabolisms. When thirsty, they may drink large quantities of water very quickly, storing it in their bladders and the "root of the neck" (the

pericardium The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...

), both of which served to make them useful water sources on ships. On arid islands, tortoises lick morning dew from boulders, and the repeated action over many generations has formed half-sphere depressions in the rock.

Senses

Regarding their senses, Charles Darwin observed, "The inhabitants believe that these animals are absolutely deaf; certainly they do not overhear a person walking near behind them. I was always amused, when overtaking one of these great monsters as it was quietly pacing along, to see how suddenly, the instant I passed, it would draw in its head and legs, and uttering a deep hiss fall to the ground with a heavy sound, as if struck dead." Although they are not deaf, tortoises depend far more on vision and smell as stimuli than hearing.

Mutualism

Tortoises share a mutualistic relationship with some subspecies of Galápagos finch and mockingbirds. The birds benefit from the food source and the tortoises get rid of irritating

ectoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s. Small groups of finches initiate the process by hopping on the ground in an exaggerated fashion facing the tortoise. The tortoise signals it is ready by rising up and extending its neck and legs, enabling the birds to reach otherwise inaccessible spots on the tortoise's body such as the neck, rear legs,

cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, a ...

l opening, and skin between plastron and carapace. Some tortoises have been observed to exploit this mutualistic relationship to consume birds seeking to groom them. After rising and extending its limbs, the bird may go beneath the tortoise to investigate, whereupon suddenly the tortoise withdraws its limbs to drop flat and kill the bird. It then steps back to eat the bird, presumably to supplement its diet with protein. Galapagos dominance display

Mating

Mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reproduc ...

occurs at any time of the year, although it does have seasonal peaks between February and June in the humid uplands during the rainy season. When mature males meet in the mating season, they face each other in a ritualised dominance display, rise up on their legs, and stretch up their necks with their mouths gaping open. Occasionally, head-biting occurs, but usually the shorter tortoise backs off, conceding mating rights to the victor. The behaviour is most pronounced in saddleback subspecies, which are more aggressive and have longer necks. The prelude to mating can be very aggressive, as the male forcefully rams the female's shell with his own and nips her legs. Mounting is an awkward process and the male must stretch and tense to maintain equilibrium in a slanting position. The concave underside of the male's shell helps him to balance when straddled over the female's shell, and brings his cloacal vent (which houses the penis) closer to the female's dilated cloaca. During mating, the male vocalises with hoarse bellows and grunts, described as "rhythmic groans". This is one of the few vocalisations the tortoise makes; other noises are made during aggressive encounters, when struggling to right themselves, and hissing as they withdraw into their shells due to the forceful expulsion of air. Galapagos egg and hatchling

Egg-laying

Females journey up to several kilometres in July to November to reach nesting areas of dry, sandy coast. Nest digging is a tiring and elaborate task which may take the female several hours a day over many days to complete. It is carried out blindly using only the hind legs to dig a -deep cylindrical hole, in which the tortoise then lays up to 16 spherical, hard-shelled eggs ranging from in mass, and the size of a billiard ball. Some observations suggest that the average

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

size for domed populations (9.6 per clutch for ''C. porteri'' on Santa Cruz) is larger than that of saddlebacks (4.6 per clutch for ''C. duncanensis'' on Pinzón). The female makes a muddy plug for the nest hole out of soil mixed with urine, seals the nest by pressing down firmly with her plastron, and leaves them to be incubated by the sun. Females may lay one to four clutches per season. Temperature plays a role in the sex of the hatchlings, with lower-temperature nests producing more males and higher-temperature nests producing more females. This is related closely to incubation time, since clutches laid early incubate during the cool season and have longer incubation periods (producing more males), while eggs laid later incubate for a shorter period in the hot season (producing more females).

Early life and maturation

Young animals emerge from the nest after four to eight months and may weigh only and measure . When the young tortoises emerge from their shells, they must dig their way to the surface, which can take several weeks, though their yolk sac can sustain them up to seven months. In particularly dry conditions, the hatchlings may die underground if they are encased by hardened soil, while flooding of the nest area can drown them. Subspecies are initially indistinguishable as they all have domed carapaces. The young stay in warmer lowland areas for their first 10–15 years, encountering hazards such as falling into cracks, being crushed by falling rocks, or excessive heat stress. The

Galápagos hawk The Galápagos hawk (''Buteo galapagoensis'') is a large hawk endemic to most of the Galápagos Islands. Description The Galapágos hawk is similar in size to the red-tailed hawk (''Buteo jamaicensis'') and the Swainson's hawk (''Buteo swainso ...

was formerly the sole native predator of the tortoise hatchlings; Darwin wrote: "The young tortoises, as soon as they are hatched, fall prey in great numbers to the buzzard". The hawk is now much rarer, but introduced feral pigs, dogs, cats, and black rats have become predators of eggs and young tortoises. The adult tortoises have no natural predators apart from humans; Darwin noted: "The old ones seem generally to die from accidents, as from falling down precipices. At least several of the inhabitants told me, they had never found one dead without some such apparent cause".

Sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...

is reached at around 20–25 years in captivity, possibly 40 years in the wild. Life expectancy in the wild is thought to be over 100 years, making it one of the longest-lived subspecies in the animal kingdom. Harriet, a specimen kept in

Australia Zoo Australia Zoo is a zoo located in the Australian state of Queensland on the Sunshine Coast, Queensland, Sunshine Coast near Beerwah, Queensland, Beerwah/Glass House Mountains National Park, Glass House Mountains. It is a member of the Zoo and A ...

, was the oldest known Galápagos tortoise, having reached an estimated age of more than 170 years before her death in 2006. Chambers notes that Harriet was probably 169 years old in 2004, although media outlets claimed the greater age of 175 at death based on a less reliable timeline.

Darwin's development of theory of evolution

Charles Darwin visited the Galápagos for five weeks on the second voyage of HMS ''Beagle'' in 1835 and saw Galápagos tortoises on San Cristobal (Chatham) and Santiago (James) Islands. They appeared several times in his writings and journals, and played a role in the development of the theory of evolution. Darwin wrote in his account of the voyage:

I have not as yet noticed by far the most remarkable feature in the natural history of this archipelago; it is, that the different islands to a considerable extent are inhabited by a different set of beings. My attention was first called to this fact by the Vice-Governor, Mr. Lawson, declaring that the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought ... The inhabitants, as I have said, state that they can distinguish the tortoises from the different islands; and that they differ not only in size, but in other characters. Captain Porter has described* those from Charles and from the nearest island to it, namely, Hood Island, as having their shells in front thick and turned up like a Spanish saddle, while the tortoises from James Island are rounder, blacker, and have a better taste when cooked.

The significance of the differences in tortoises between islands did not strike him as important until it was too late, as he continued,

I did not for some time pay sufficient attention to this statement, and I had already partially mingled together the collections from two of the islands. I never dreamed that islands, about fifty or sixty miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted.

Though the ''Beagle'' departed from the Galápagos with over 30 adult tortoises on deck, these were not for scientific study, but a source of fresh meat for the Pacific crossing. Their shells and bones were thrown overboard, leaving no remains with which to test any hypotheses. It has been suggested that this oversight was made because Darwin only reported seeing tortoises on San Cristóbal (''C. chathamensis'') and Santiago (''C. darwini''), both of which have an intermediate type of shell shape and are not particularly morphologically distinct from each other. Though he did visit Floreana, the ''C. niger'' subspecies found there was already nearly extinct and he was unlikely to have seen any mature animals. HMS Beagle 1832 longitudinal section larger

HMS Beagle 1832 longitudinal section larger

However, Darwin did have four live juvenile specimens to compare from different islands. These were pet tortoises taken by himself (from San Salvador), his captain

FitzRoy Fitzroy or FitzRoy may refer to: People As a given name *Several members of the Somerset family (Dukes of Beaufort) have this as a middle-name: **FitzRoy Somerset, 1st Baron Raglan (1788–1855) ** Henry Charles FitzRoy Somerset, 8th Duke of Beau ...

(two from Española) and his servant

Syms Covington Syms Covington (1816–1861) was a fiddler and cabin boy on HMS ''Beagle'' who became an assistant to Charles Darwin and was appointed as his personal servant in 1833, continuing in Darwin's service after the voyage until 1839. Originally named ...

(from Floreana). Unfortunately, they could not help to determine whether each island had its own variety because the specimens were not mature enough to exhibit morphological differences. Although the British Museum had a few specimens, their provenance within the Galápagos was unknown. However, conversations with the naturalist

, who had seen the mature tortoises of the Paris Natural History Museum confirmed to Darwin that distinct varieties occurred. Darwin later compared the different tortoise forms with those of

mockingbird Mockingbirds are a group of New World passerine birds from the family Mimidae. They are best known for the habit of some species mimicking the songs of other birds and the sounds of insects and amphibians, often loudly and in rapid succession. ...

s, in the first tentative statement linking his observations from the Galapagos with the possibility of subspecies transmuting:

When I recollect the fact that
rom Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * R ...
the form of the body, shape of scales and general size, the Spaniards can at once pronounce from which island any tortoise may have been brought; when I see these islands in sight of each other and possessed of but a scanty stock of animals, tenanted by these birds, but slightly differing in structure and filling the same place in nature; I must suspect they are only varieties ... If there is the slightest foundation for these remarks, the zoology of archipelagos will be well worth examining; for such facts would undermine the stability of subspecies.

His views on the mutability of subspecies were restated in his notebooks: "animals on separate islands ought to become different if kept long enough apart with slightly differing circumstances. – Now Galapagos Tortoises, Mocking birds, Falkland Fox, Chiloe fox, – Inglish and Irish Hare." These observations served as counterexamples to the prevailing contemporary view that subspecies were individually created. Darwin also found these "antediluvian animals" to be a source of diversion: "I frequently got on their backs, and then giving a few raps on the hinder part of their shells, they would rise up and walk away;—but I found it very difficult to keep my balance".

Conservation

Several waves of human exploitation of the tortoises as a food source caused a decline in the total wild population from around 250,000 when first discovered in the 16th century to a low of 3,060 individuals in a 1974 census. Modern conservation efforts have subsequently brought tortoise numbers up to 19,317 (estimate for 1995–2009). The subspecies ''C. n. niger'' became extinct by human exploitation in the 19th century. Another subspecies, ''C. n. abingdonii'', became extinct on 24 June 2012 with the death in captivity of the last remaining specimen, a male named Lonesome George, the world's "rarest living creature". All the other surviving subspecies are listed by the IUCN as at least "vulnerable" in conservation status, if not worse. Galápagos tortoise - Chelonoidis nigra on the Santa Cruz Island - Galapagos

Galápagos tortoise - Chelonoidis nigra on the Santa Cruz Island - Galapagos

Historical exploitation

An estimated 200,000 animals were taken before the 20th century. The relatively immobile and defenceless tortoises were collected and stored live on board ships, where they could survive for at least a year without food or water (some anecdotal reports suggest individuals surviving two years), providing valuable fresh meat, while their diluted urine and the water stored in their neck bags could be used as drinking water. The 17th-century English pirate, explorer, and naturalist

William Dampier William Dampier (baptised 5 September 1651; died March 1715) was an English explorer, pirate, privateer, navigator, and naturalist who became the first Englishman to explore parts of what is today Australia, and the first person to circumnav ...

wrote, "They are so extraordinarily large and fat, and so sweet, that no pullet eats more pleasantly," while Captain

James Colnett James Colnett (1753 – 1 September 1806) was an officer of the British Royal Navy, an explorer, and a maritime fur trader. He served under James Cook during Cook's second voyage of exploration. Later he led two private trading expeditions that ...

of the

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...

wrote of "the land tortoise which in whatever way it was dressed, was considered by all of us as the most delicious food we had ever tasted." US Navy captain David Porter declared, "after once tasting the Galapagos tortoises, every other animal food fell off greatly in our estimation ... The meat of this animal is the easiest of digestion, and a quantity of it, exceeding that of any other food, can be eaten without experiencing the slightest of inconvenience." Darwin was less enthusiastic about the meat, writing "the breast-plate roasted (as the Gauchos do "carne con cuero"), with the flesh on it, is very good; and the young tortoises make excellent soup; but otherwise the meat to my taste is indifferent." In the 17th century,

pirate Piracy is an act of robbery or criminal violence by ship or boat-borne attackers upon another ship or a coastal area, typically with the goal of stealing cargo and other valuable goods. Those who conduct acts of piracy are called pirates, v ...

s started to use the Galápagos Islands as a base for resupply, restocking on food and water, and repairing vessels before attacking

Spanish colonies The Spanish Empire ( es, link=no, Imperio español), also known as the Hispanic Monarchy ( es, link=no, Monarquía Hispánica) or the Catholic Monarchy ( es, link=no, Monarquía Católica) was a colonial empire governed by Spain and its prede ...

on the South American mainland. However, the Galápagos tortoises did not struggle for survival at this point because the islands were distant from busy shipping routes and harboured few valuable natural resources. As such, they remained unclaimed by any nation, uninhabited and uncharted. In comparison, the tortoises of the islands in the Indian Ocean were already facing extinction by the late 17th century. Between the 1790s and the 1860s,

whaling Whaling is the process of hunting of whales for their usable products such as meat and blubber, which can be turned into a type of oil that became increasingly important in the Industrial Revolution. It was practiced as an organized industry ...

ships and fur sealers systematically collected tortoises in far greater numbers than the buccaneers preceding them. Some were used for food and many more were killed for high-grade "turtle oil" from the late 19th century onward for lucrative sale to continental Ecuador. A total of over 13,000 tortoises is recorded in the logs of whaling ships between 1831 and 1868, and an estimated 100,000 were taken before 1830. Since it was easiest to collect tortoises around coastal zones, females were most vulnerable to depletion during the nesting season. The collection by whalers came to a halt eventually through a combination of the scarcity of tortoises that they had created and the competition from crude oil as a cheaper energy source. Galápagos tortoise exploitation dramatically increased with the onset of the California Gold Rush in 1849. Tortoises and sea turtles were imported into San Francisco, Sacramento and various other Gold Rush towns throughout Alta California to feed the gold mining population. Galápagos tortoise and sea turtle bones were also recovered from the Gold Rush-era archaeological site, Thompson's Cove (CA-SFR-186H), in San Francisco, California. Population decline accelerated with the early settlement of the islands in the early 19th century, leading to unregulated hunting for meat, habitat clearance for agriculture, and the introduction of alien mammal subspecies. Feral pigs, dogs, cats, and black rats have become predators of eggs and young tortoises, whilst goats, donkeys, and cattle compete for grazing and trample nest sites. The extinction of the Floreana subspecies in the mid-19th century has been attributed to the combined pressures of hunting for the penal colony on the relatively small island, the conversion of the grazing highlands into land for farming and fruit plantations, and the introduction of feral mammals. Scientific collection expeditions took 661 tortoises between 1888 and 1930, and more than 120 tortoises have been taken by poachers since 1990. Threats continue today with the rapid expansion of the tourist industry and increasing size of human settlements on the islands. The tortoises are down from 15 different types of subspecies when Darwin first arrived to the current 11 subspecies. Threats * Introduced mammals * Poachers * Destruction of habitat ** Characteristics that make tortoises vulnerable ** Slow growth rate ** Late sexual maturity ** Can only be found on Galápagos Islands ** Large size and slow moving Collection The tortoises of the Galápagos' island were not only hunted for the oil that they held for fuel but also once they were becoming more and more scarce people began to pay to have them in their collections, as well as being put into museums.

Modern conservation

Gigantic Turtle on the Island of Santa Cruz in the Galapagos

A gigantic galapagos tortuga on the island of santa cruz

The remaining subspecies of tortoise range in IUCN classification from

extinct in the wild A species that is extinct in the wild (EW) is one that has been categorized by the International Union for Conservation of Nature as known only by living members kept in captivity or as a naturalized population outside its historic range due ...

to vulnerable. Slow growth rate, late sexual maturity, and island endemism make the tortoises particularly prone to extinction without help from conservationists. The Galápagos giant tortoise has become a flagship subspecies for conservation efforts throughout the Galápagos. GalapagosTortoiseTourists

;Legal protection The Galápagos giant tortoise is now strictly protected and is listed on Appendix I of the Convention on International Trade in Endangered subspecies of Wild Fauna and Flora (CITES). The listing requires that trade in the

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

and its products is subject to strict regulation by ratifying states, and international trade for primarily commercial purposes is prohibited. In 1936, the Ecuadorian government listed the giant tortoise as a protected subspecies. In 1959, it declared all uninhabited areas in the Galápagos to be a

national park A national park is a nature park, natural park in use for conservation (ethic), conservation purposes, created and protected by national governments. Often it is a reserve of natural, semi-natural, or developed land that a sovereign state dec ...

and established the

Charles Darwin Foundation The Charles Darwin Foundation (Spanish: ''Fundación Charles Darwin'') was founded in 1959, under the auspices of UNESCO and the World Conservation Union. The Charles Darwin Research Station serves as headquarters for The Foundation, and is used ...

. In 1970, capturing or removing many subspecies from the islands (including tortoises and their eggs) was banned. To halt trade in the tortoises altogether, it became illegal to export the tortoises from Ecuador, captive or wild, continental, or insular in provenance. The banning of their exportation resulted in automatic prohibition of importation to the United States under Public Law 91-135 (1969). A 1971 Ecuadorian decree made it illegal to damage, remove, alter, or disturb any organism, rock, or other natural object in the national park.

Captive breeding

With the establishment of the Galapagos National Park and the CDF in 1959, a review of the status of the tortoise populations began. Only 11 of the 14 original populations remained and most of these were endangered if not already on the brink of extinction. The breeding and rearing program for giant tortoises began in response to the condition of the population on Pinzón, where fewer than 200 old adults were found. All of the hatchlings had been killed by introduced black rats, for perhaps more than a century. Without help, this population would eventually disappear. The only thing preserving it was the longevity of the tortoise. Its genetic resistance to the negative effects of

inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and o ...

would be another. Breeding and release programs began in 1965 and have successfully brought seven of the eight endangered subspecies up to less perilous population levels. Young tortoises are raised at several breeding centres across the islands to improve their survival during their vulnerable early development. Eggs are collected from threatened nesting sites, and the hatched young are given a head start by being kept in captivity for four to five years to reach a size with a much better chance of survival to adulthood, before release onto their native ranges. The most significant population recovery was that of the Española tortoise (''C. n. hoodensis''), which was saved from near-certain extinction. The population had been depleted to three males and 12 females that had been so widely dispersed that no mating in the wild had occurred. Fruitless attempts to breed one of the tortoises, Lonesome George for example, is speculated to be attributed to a lack of postnatal cues, and confusion over which would be the most appropriate genetic subspecies would be the most appropriate to mate him with on the islands. The 15 remaining tortoises were brought to the

Charles Darwin Research Station Charles is a masculine given name predominantly found in English and French speaking countries. It is from the French form ''Charles'' of the Proto-Germanic name (in runic alphabet) or ''*karilaz'' (in Latin alphabet), whose meaning was " ...

in 1971 for a captive breeding program and, in the following 33 years, they gave rise to over 1,200 progeny which were released onto their home island and have since begun to reproduce naturally. One of the tortoises, Diego, is one of the main drivers of a remarkable recovery of the ''hoodensis'' subspecies, having fathered between 350 and 800 progeny.

Island restoration

The Galápagos National Park Service systematically culls feral predators and competitors. Goat eradication on islands, including Pinta, was achieved by the technique of using "

Judas goat A Judas goat is a trained goat used in general animal herding. The Judas goat is trained to associate with sheep or cattle, leading them to a specific destination. In stockyards, a Judas goat will lead sheep to slaughter, while its own life is s ...

s" with radio location collars to find the herds. Marksmen then shot all the goats except the Judas, and then returned weeks later to find the "Judas" and shoot the herd to which it had relocated. Goats were removed from Pinta Island after a 30-year eradication campaign, the largest removal of an insular goat population using ground-based methods. Over 41,000 goats were removed during the initial hunting effort (1971–82). This process was repeated until only the "Judas" goat remained, which was then killed. Other measures have included dog eradication from San Cristóbal, and fencing off nests to protect them from feral pigs. Efforts are now underway to repopulate islands formerly inhabited by tortoises to restore their ecosystems (

island restoration The ecological restoration of islands, or island restoration, is the application of the principles of ecological restoration to islands and island groups. Islands, due to their isolation, are home to many of the world's endemic species, as well as ...

) to their condition before humans arrived. The tortoises are a keystone subspecies, acting as

ecosystem engineer An ecosystem engineer is any species that creates, significantly modifies, maintains or destroys a habitat. These organisms can have a large impact on species richness and landscape-level heterogeneity of an area. As a result, ecosystem enginee ...

s which help in plant

seed dispersal In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

and trampling down brush and thinning the understory of vegetation (allowing light to penetrate and germination to occur). Birds such as flycatchers perch on and fly around tortoises to hunt the insects they displace from the brush. In May 2010, 39 sterilised tortoises of hybrid origin were introduced to Pinta Island, the first tortoises there since the evacuation of Lonesome George 38 years before. Sterile tortoises were released so the problem of interbreeding between subspecies would be avoided if any fertile tortoises were to be released in the future. It is hoped that with the recent identification of a hybrid ''C. n. abingdonii'' tortoise, the approximate genetic constitution of the original inhabitants of Pinta may eventually be restored with the identification and relocation of appropriate specimens to this island. This approach may be used to "retortoise" Floreana in the future, since captive individuals have been found to be descended from the extinct original stock.

Applied science

The Galapagos Tortoise Movement Ecology Programme is a collaborative project coordinated by Dr Stephen Blake of the Max Planck Institute for Ornithology. Its goal is to assist the Galapagos National Park to effectively conserve giant tortoises by conducting cutting-edge applied science, and developing an inspirational tortoise-based outreach and education programme. Since 2009, the project team have been analysing the movements of giant tortoises by tracking them via satellite tags. As of November 2014, the team have tagged 83 tortoises from four subspecies on three islands. They have established that giant tortoises conduct migrations up and down volcanoes, primarily in response to seasonal changes in the availability and quality of vegetation. In 2015 they will start to track the movements of hatchling and juvenile tortoises, supported by the UK's Galapagos Conservation Trust.

Notes

References

External links

* ARKive �
images and movies of the Galápagos giant tortoise (''Geochelone'' spp.)

* ttp://galapagosconservation.org.uk/projects/galapagos-tortoise-movement-ecology-programme/ Galapagos Tortoise Movement Ecology Programme
'Extinct' Galapagos tortoise may still exist
{{DEFAULTSORT:Galapagos tortoise Tortoise, Galapagos Taxa named by Jean René Constant Quoy Taxa named by Joseph Paul Gaimard Reptiles described in 1824 Reptiles of Ecuador Turtles of South America

Taxonomy

Early classification

Recognition of subpopulations

Current species and genus names

Subspecies

Evolutionary history

Subspecies

Santa Fe

Description

Gigantism

Shell shape

Behavior

Routine

Diet

Senses

Mutualism

Mating

Egg-laying

Early life and maturation

Darwin's development of theory of evolution

Conservation

Historical exploitation

Modern conservation

Captive breeding

Island restoration

Applied science

See also

Notes

References

Further reading

External links