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The Galápagos tortoise or Galápagos giant tortoise (Geochelone nigra) is the largest living species of tortoise and fully grown adults can weigh up to and measure  long. They are among the longest lived of all vertebrates, with life expectancy in the wild estimated to be 150 years. They are native to seven volcanic islands of the Galápagos archipelago, lying west of Ecuador. The Spanish explorers who discovered the islands in the 16th century were purportedly struck by the resemblance of the tortoises' shells to the shape of a saddle known then as a "galápago", and this is popularly said to be the origin of the name of the archipelago. The particular size and shell shape of the tortoises varies between populations on different islands according to habitat.

Tortoise numbers have fallen dramatically from over 250,000 when first discovered to 10,000 in the modern day. The decline was brought about by the unchecked hunting of tortoises for meat and oil, habitat clearance for agriculture, and the introduction of vermin and destructive grazers to the once-isolated islands. Only ten subspecies of the original twelve exist in the wild, and one other subspecies (G. n. abingdoni) is represented by a single remaining male, nicknamed Lonesome George. However, conservation measures including the establishment of the Galápagos National Park and the Charles Darwin Foundation have had successes, and thousands of captive-bred juveniles have been released onto their home islands. The Galápagos giant tortoise has become the flagship species for conversation efforts throughout the Galápagos.

Taxonomy and phylogeny
See also Subspecies of Geochelone nigra

There were probably 12 subspecies of Geochelone nigra in the Galápagos Islands, although some recognise up to 15 subspecies. Only ten subspecies now exist in the wild, one on each of five main volcanoes of the largest island Isabela and the others on Santiago, Santa Cruz, San Cristóbal, Pinzón, and Española. The eleventh extant subspecies from Pinta Island is considered extinct in the wild and is represented by a single male specimen.

Before wide knowledge of their taxonomic differentiation, zoos acquired tortoises without knowing the island of origin. Production of fertile offspring from various pairings of these animals largely confirmed that the allopatric populations were subspecies and not distinct species. However, it is noted that captive crosses between tortoises from different island races result in lower fertility rates and higher mortality rates than crosses between members of the same island population and captives in mixed species groups normally direct subadult courtship only toward members of the same island population. The taxonomic status of the various races is not fully resolved, and some researchers consider the subspecies to be full species. Significant revisions to the taxonomy from the International Commission on Zoological Nomenclature in future may resolve this issue.

All subspecies of Galápagos tortoise evolved from a common ancestor that arrived from mainland South America theoretically by a rafting event of a pregnant female or a breeding pair on the Humboldt Current which diverts westwards towards the Galápagos Islands from the mainland at equatorial latitudes. The tortoises are bouyant and can breathe by extending their necks above the water, able to survive at least 6 months without food or fresh water accounting for the 1000km journey. The closest living relative (though not a direct ancestor) of the Galápagos giant tortoise is Chaco Tortoise (Geochelone chilensis), a much smaller species. The evolutionary divergence between G. chilensis and G. nigra probably occurred 6-12 million years ago, an evolutionary divergence preceding the formation of the oldest modern Galápagos Islands 5 million years ago. Modern molecular methods have also revealed new information on the relationships between the subspecies. Phylogeographic and population genetics approaches based on mitochondrial DNA analysis indicates that the oldest existing islands, Española and San Cristóbal, were colonized first (older island populations only harbour endemic haplotypes that define divergent, monophyletic clades) followed by several migration events via local currents to and between the other islands with tortoises. Limited mixing between isolated populations then resulted in the diversification into forms observed in the modern subspecies by the process of allopatric radiation.

The Pinta Island subspecies represented by Lonesome George is most closely related to the subspecies on the distant islands of San Cristóbal (hoodensis) and Español (chathamensis) 300km away, rather than Isabela as previously assumed. This may be explained by a strong local current from San Cristóbal towards Pinta. This information will inform attempts for the preservation of the abingdoni lineage and the search for an appropriate mate. Further developments include the discovery of an abingdoni hybrid male in the Volcan Wolf population on Isabela, raising the possibility that there are more undiscovered Pinta descendents which could facilitate the rescue of the subspecies from the brink of extinction

Mitochondrial DNA studies of tortoises on Santa Cruz show at least two genetically distinct lineages, and possibly three. Although currently recognised as a single subspecies (porteri), each lineage is more closely related to tortoises on other islands than to each other

The four named southern subspecies on Isabela (microphyes, vandenburghi, guentheri and vicina) are likely to be a single genetic unit derived from colonists from Santa Cruz, whereas a genetically distinct Volcan Wolf subspecies (becki) is probably the result of a separate colonisation event from San Salvador. This is consistent with the suggestion of some authorities that the southern populations on Isabela may be considered a single subspecies, with morphological differences attributable to geographical variation.

Phylogenetic analysis may also help to 'resurrect' the extinct galapagoensis subspecies of Floreana, which became extinct by the mid 1800s, just years after Charles Darwin's important visit. Tortoises from Isabela were found to to be a partial match for the genetic profile of Floreana specimens from museum collections, possibly indicating the presence of hybrids from a population transposed by humans from Floreana to Isabela. This permits the theoretical possibility of re-establishing a reconstructed subspecies from selective breeding of the hybrid animals.

In light of molecular phylogenetic analyses of testudinids, there are taxonomic justifications for elevating Chelonoidis (Fitzinger 1835) from subgenus to genus status. South American tortoises including the Galápagos Tortoises would belong in the genus Chelonoidis rather than Geochelone, a convention which is being adopted by some authorities.

Description
Naturalist Charles Darwin remarked "These animals grow to an immense size ... several so large that it required six or eight men to lift them from the ground." . The tortoises' gigantism was a preadapted condition for successful colonisation of remote oceanic islands rather than a new evolutionary adaptation to the island environment. Indeed fossil giant tortoises from mainland South America have been described which are consistent with current phylogenetic groupings )

NEED SADDLEBACK AND DOMEBACK IN THE IN THE SAME POSE PICS SIDE BY SIDE

The tortoises have a large bony shell (carapace) of a dull brown colour like their scales. The osseous plates of the shell are fused with the ribs in a rigid protective structure that is integral to the skeleton. A tortoise can withdraw its head, neck and forelimbs into its shell for protection. The legs have hard scales that also provide armour when withdrawn. Tortoises keep a characteristic scute pattern on their shell throughout life. These have annual growth bands but are not useful for aging as the outer layers are worn off. shell and skin black or dark brownish-gray; large, stumpy extremities with dry, scaly skin; 5 front claws, 4 on back; beaked, toothless jaw.

Galapagos tortoises are only surviving lineage of the giant tortoises in the world that show two different types of shell shapes. (Chiari et al 2009). Physical features relate to the habitat of each subspecies, and they exhibit a spectrum of shell shapes from 'saddleback' to 'domed', denoting upward arching of the front edge of the shell (resembling a saddle) versus a rounded convex surface (resembling a dome) respectively. There is no saddleback/domed dualism, as tortoises can be of intermediate type with characteristics of both. Larger islands with wet highlands (>800m) such as Santa Cruz and the Alcedo Volcano on Isabela have abundant vegetation near the ground. Tortoises here tend to have domed shells and re larger, with shorter necks and limbs. Small, dry islands such as Espanola and Pinzon which have low elevation (<500m) and are more limited in food and other resources are inhabited by tortoises exhibiting saddleback shells Caccone 2002 with a flatter shell which is flared over the neck and hind feet. In combination with longer necks and limbs, the unusual carapace structure is better adapted to browse tall vegetation such as cacti which grow in the arid environment. Indeed, on the dry islands the Galápagos Opuntia cactus has a taller, tree-like form, indicating an evolutionary arms race between progressively taller tortoises and correspondingly taller cacti. The distinctive saddle shape may have also been an adaptive change to dominance displays in the mating season, which are fought on the basis of neck height (see below). This correlates with the observation that saddleback males are more aggressive (Schafer and Krekorian 1983). When saddleback tortoises withdraw their head and forelimbs to protect themselves a large unprotected gap remains at the top of their shell opening, evidence of the lack of predation during the evolution of this structure. Saddleback tortoises are smaller than domed varieties, which may be an adaptation to the more limited resources. Alternatively, larger tortoises may benefit from their size in their relatively cooler habitats because it offers more thermal stability through a lower surface area to volume ratio (the rit edu site). Saddlebacks are also more territorial (Fritts, 1983; Fowler de Neira and Roe, 1984), possibly for similar reasons.

Ihe saddleback carapace probably evolved independently several times in the context of dry environments (Fritts (1983)), since genetic similarity based on blood proteins does not correlate with carapace shape (Marlow and Patton (1981)). However, the extinction of crucial populations by human activities confounds whether domed and saddleback carapaces of different populations are definitively mono- or polyphyletic. . Morphological divergence in tortoises is potentially a better indicator of present ecological conditions than of evolutionary relationships. Fritts 2008

Sexual dimorphism is most notable in saddleback populations, in which males have more angled and higher front openings. Males generally have a longer tail and a shorter, concave undershell with thickened knobs at the back edge to facilitate mating. Males are also larger than females: adult males weigh an average of 272 - 317 kg whilst females are 136 - 181 kg. . Males can be up to three times heavier than females. (Bonin et al 2006)

Behaviour
(DeVries 1984) (Fritts 1984) (Hayes et al.1988) (MacFarland 1972) (MacFarland & Reeder 1974) (Schafer & Krekorian 1983) (Swingland 1989) (Van Denburgh 1914)

The tortoises are slow-moving reptiles with an average long-distance walking speed of 0.3 km/h (Darwin 1898). However, marked individuals have been reported to have traveled 13 km in two days, and they can move at surprising speeds for their size when seeking to water-holes or nesting grounds. Travelling is done in the early morning and late afternoon.

On the wetter islands, the tortoises seasonally migrate down between drier, low elevations which become grassy plains in the wet season areas to more moist areas which remain meadows in the dry season at higher elevations (up to 2,000 ft On these islands, the tortoises appear to be gregarious, often found in large 'herds'. In contrast, saddleback subspecies from drier islands have a more solitary and territorial disposition.

As they are cold-blooded, the tortoises bask for 1-2 hours after dawn to absorb the sun's heat through their dark shells, then becoming active for 8–9 hours a day. They typically sleep for 16 hours a day, resting limbs extended during the day and drawing them in during the evening. They also rest in mud wallows or submerge themselves in rain-formed pools. This may be both a thermoregulatory response during cool nights and a protection from parasites such as mosquitoes and ticks (DeVries 1984). At night, they may rest in a 'pallet'- a snug depression in soft ground or dense brush- which probably helps to conserve heat. On the Alcedo Volcano, repeated use of the same sites for pallets by the large resident population has resulted in the formation of small sandy pits. rs. At night they sleep under bushes, beside trees, or under overhanging rocks (Carpenter, 1966). The tortoises can vocalise in aggressive encounters, whilst righting themselves if turned upside down and, in males, during mating. The latter is described as "rhythmic groans".

Diet
The tortoises are herbivorous animals with a diet comprising cactus, grasses, leaves, vines, and fruit. Fresh young grass is a favorite food of the tortoises, and others are the 'poison apple' (Hippomane mancinella) (toxic to humans), the endemic guava (Psidium galapageium), the water fern (Azolla microphylla), and the bromeliad (Tillandsia insularis). A tortoise spends most of the day eating, consuming an average of 70 - 80 lb per day, though inefficient digestion means that much of this passes through without nutritional benefit. As in all ectotherms, speed of digestion influenced by outside temperature. Higher temperature = higher metabolism, quicker digestion. In a study of diets in captive juvenile Galapagos tortoises, efficiency of digestion was found to be similar to that of horses, Asian elephants, and Indian rhinoceroses, all hindgut-fermenting herbivores. (Hatt et al 2005)

There is a very interesting relationship between tortoises and the various Opuntia species that inhabit the various islands. On those islands where there have never been any evidence of resident tortoise populations (e.g. Genovesa), the resident species O. helleri tends to spread low over the ground and has soft, flexible spines, whereas on islands that have established tortoise populations, the resident species, like O. echios on Santa Cruz tends to grow as trees. As young plants, the trunks are thickly covered with long, sharp spines which give way in older plants to a tough, tree-like bark. Thus, these Opuntias are inaccessable to the tortoise until the fruits, laden with seeds, fall to the ground, whereupon the tortoises eat them. The seeds pass unharmed through the tortoise's gut and are dropped as the tortoise wanders from place to place.

(Bonin et al. 2006) (MacFarland 1972) (Swingland 1989) (Van Denburgh 1914) Since they acquire most of their moisture from the dew and sap in vegetation (particularly the Opuntia cactus), tortoises can go for long periods without actually drinking. They can also survive for over a year being forcefully deprived of all liquids, breaking down their body fat producing water as a side product. Drink through their mouths; drink large quantities of water at a given time, and store it in their bladders and the "root of the neck". On arid islands, tortoises lick boulders for collection of morning dew, and Some boulders have depressions from centuries of use.

Mutualism
Small group of finches lands in front of or on the back of a tortoise Hop, in exaggerated way, facing head of tortoise. Tortoise rises up, lifts its head, stretches neck, and extends legs

Tortoises have a classic example of a mutualistic symbiotic relationship with some species of Galápagos finch and mockingbirds. In order to invite removal of ticks and other ecto-parasites by the finches, tortoises will raise themselves on all four legs and extend their necks. This is a clear visual signal, and enables the birds to reach otherwise inaccessible spots on the tortoise's body (especially on the rear legs, cloacal opening, neck, and skin between plastron and carapace). The finches benefit from the food source and the tortoises get rid of harmful parasites.

An unusual feeding behavior for gaining extra protein noted by Bonin et al (2006): Tortoise rises up high off the ground (similar to invitation to finches to come pick off ticks) If a bird goes underneath the tortoise to investigate the ground, the tortoise suddenly drops flat to the ground Tortoise steps back and eats the dead bird

Reproduction
(Darwin 1898) (De Vries 1984) (MacFarland et al. 1974) (Rostal et al. 1998) (Russello et al. 2007) (Swingland 1989)

Mating occurs at any time of the year, although it does have seasonal peaks between February and June in the humid uplands(de Vries 1984) during the rainy season. When two mature males meet in the mating season they will face each other, rise up on their legs and stretch up their necks with their mouths open to assess dominance. Occasionally, head-biting occurs, but usually the shorter tortoise will back off, leaving the other to mate with the female. In groups of tortoises from mixed island populations, saddleback males have an advantage over domebacks due to their longer necks.

The male sniffs the air when seeking a female, bellows loudly, DeSola (1930: 79-80) described the mating act as follows: "Making his advances he carefully approaches and observes her and if she shows any signs of response, i.e., as approach toward him, he will quicken his pace and commence the deeply resounding guttural tortoise shout. He collides against her heavily in a manner that appears fierce, bumping her carapace with his own for about five to eight minutes and often for longer periods. During this time he often nips at her legs but in so doing she never retracts her limbs, however brutal his attack may seem. Again he crashes against her while she views his antics unheeding. This constant concussion, appearing painful to the quiet observer, continues and then another hoarse bellow follows. Slowly but persistently he cleaves behind her and awkwardly mounts her from the posterior extremity. Inserting his penis (which before had been concealed and now protrudes from the cloacal vent) into her dilating cloaca, he stretches forth his long thick neck with its heavy head and straddles forward over the hinder neural and costal shields of her carapace. Stretching and tensely holding this equilibrium so difficulty obtained, as he is now fully mounted in a semihorizontal, somewhat slanting, spread-eagle position, the first spasmodic tupping action of their congress begins. Its preliminary jerky motion almost takes the observer unawares. Opening his strangely peculiar and diabolical face he gives vent to another yell, which sounds more shrill and piercing than the others. The female all the while is crouched with forelegs retracted and hinder limbs stretched strongly outward, uplifting and supporting his great weight and bulk."and bobs his head. Male follows the female, who almost always retreats. The male then rams the female with the front of his shell and bites her exposed legs until she withdraws them, immobilizing her. Copulation can last several hours with roaring vocalisations from the males. Their concave shell base allows males to mount the females from behind. It brings its tail which houses the penis into the female's cloaca.

After mating, the females journey up to several kilometres in July to November to reach nesting areas of dry, sandy coast. Nest digging can last from hours to days and is elaborate and exhausting. It is carried out blindly using only the hind legs to dig a 30 cm deep hole, into which she lays up to sixteen spherical, hard-shelled eggs that are 50mm across. The female makes a muddy plug for the nest hole out of soil mixed with urine and leaves the eggs to incubate. In rocky areas, the eggs are deposited randomly into cracks. Females may lay 4-5 clutches per season (rit edu) nests laid early in the season, which incubate during the cool season, will have a longer period of incubation and thus are likely to produce males, while nests that are laid late in the season and incubate mostly during the hot season will produce females. The young emerge from the nest after 3 to 8 months gestation later (December-April) and may weigh only 50 g and measure 6 cm. Temperature plays a role in the sex of the hatchling: if the nest temperature is lower, more males will hatch; if it is high, more females will hatch. When the young tortoises emerge from their shells, they must dig their way to the surface, which can take up to a month. All have domed carapaces, and subspecies are initially indistinguishable. Young tend to stay in warmer lowland areas (DeVries 1984). Some hatchlings trapped underground in nest if soil is too dry and baked. Other hatchlings drown if nest area is flooded. Young tortoises may die by falling into cracks, being crushed by falling rock, or being exposed to excessive heat stress.

Sex can be determined only when the tortoise is 15 years old, and sexual maturity is reached at around 20-25 in captivity, possibly 40 years in the wild ??Ref. The tortoises grow slowly for about 40 years until they reach their full size. Reproductive prime is considered to be from the ages of 60–90.

The Galápagos Hawk was formerly the sole native predator of the tortoise hatchlings, as Darwin remarked: "The young tortoises, as soon as they are hatched, fall prey in great numbers to buzzards". Now feral pigs, dogs, cats and black rats are effective predators of eggs and young tortoises.

Carpenter (1966Carpenter, C. C. 1966. Notes on the behavior and ecology of the Galápagos tortoise on Santa Cruz Island. Proc. Oklahoma Acad. Sci. (1965) 46: 28-32.) reported that as the male approaches, the female extends her head and he smells it. The female then turns and the male smells her tail and mounts, stretching his neck and tail to the fullest. Intromission follows and males emit bellows or grunts.

Human disturbance
Threats to survival Historical Prior to the 20th century, up to an estimated 200,000 were collected by whalers and other seafarers as a source of food. Based on ships' logs, 13,013 tortoises were collected during 189 visits between 1831 and 1838. (This number only includes ships whose logs were available.) Considering that collecting had occurred since the 17th century, this represents only a small fraction of actual captures. Settlers began moving to the islands in the 1800's; they killed tortoises for meat and oil and destroyed their habitat when clearing for pasture and fences. In 1897, one observer found 150 skeletons by a water hole, and 100 more half a mile away. Also observed at a nearby settlement: 1200 gallons of tortoise oil, representing 400 to 1200 large tortoises (1-3 gallons per tortoise) (Van Denburgh 1914). Non-endemic mammals introduced, which preyed on eggs and young, and competed for resources (goats, rats, dogs, donkeys, pigs, cats). Scientific collecting expeditions took 661 tortoises between 1888 and 1930 Since 1990 up to 120 tortoises thought to have been killed by poachers. Present Introduced mammals are still a threat The only endemic predator is the Galapagos Hawk, which preys on eggs and hatchlings Poaching and habitat destruction by humans continues. Wildfires

Hunting in coastal areas particularly depletes female population.

In the seventeenth century, pirates started to use the Galápagos islands as a base for resupply, restocking on food, water and repairing vessels before attacking Spanish coloniesin the South American mainland. The tortoises were collected and stored live on board ships where they could survive for at least a year without food or water, providing valuable fresh meat, whilst their diluted urine and water stored in their neck bags could also be used as drinking water. Of the meat, Darwin wrote: "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 nineteenth century, whaling ships and fur-sealers collected tortoises for food and many more were killed for high grade 'turtle oil' from the late 1800s onward. Darwin described this process thus: "beautifully clear oil is prepared from the fat. When a tortoise is caught, the man makes a slit in the skin near its tail, so as to see inside its body, whether the fat under the dorsal plate is thick. If it is not, the animal is liberated and it is said to recover soon from this strange operation." A total of over 15,000 tortoises is recorded in the logs of 105 whaling ships between 1811 and 1844. As hunters found it easiest to collect the tortoises living round the coastal zones, the least affected populations tended to be those in the highlands.

An estimated 200,000 animals were taken

Population decline accelerated with the early settlement of the islands, when they were hunted for meat, their habitat was cleared for agriculture and alien mammal species were introduced. Feral pigs, dogs, cats and black rats are effective predators of eggs and young tortoises, whilst goats, donkeys and cattle compete for grazing. In the twentieth century, increasing human settlement and urbanisation and collection of tortoises for zoo and museum specimens depleted numbers even more.

Conservation
Characteristics making them vulnerable to extinction: (Chiari et al. 2009) Slow growth rate Late sexual maturity Island endemism (found only on Galapagos Islands) Large body size

PICTURES: NEED PICTURES OF THE LOGO OF THE NATIONAL PARK AND THE DARWIN RESEARCH SERVICE FEATURING THE TORTOISES. RESEARCH THESE WEBSITES TOO. The Galápagos giant tortoise is now strictly protected. Geochelone nigra is listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. This listing requires that trade in the taxon 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 species. A period of inaction followed until 1959, when it declared all uninhabited areas in the Galápagos to be a National Park and established the Charles Darwin Foundation. In 1970 it was made illegal to capture or remove many species from the islands, including tortoises and their eggs. To halt the trade altogether, it became illegal to export the tortoises from Ecuador, captive or wild, continental or insular in provenance. United States Public Law 91-135 (1969) automatically prohibited the importation of Galápagos tortoises into the U.S.A. as their export was declared illegal. A 1971 decree made it illegal to damage, remove, alter or disturb any organism, rock or other natural object in the National Park. Today, all tour groups must be guided and are asked to stay on the paths to avoid disruption of all flora and fauna.

Young tortoises are raised in a programme by the Charles Darwin Research Station in order to bolster the numbers of the extant subspecies. Eggs are collected from places on the islands where they are threatened and when the tortoises hatch they are kept in captivity for four to five years when they have reached a size that ensures a good chance of survival and are returned to their original ranges. The Galápagos National Park Service systematically culls feral predators and competitors where necessary such as the complete eradication of goats from Pinta.

The conservation project begun in the 1970s successfully brought 10 of the 11 endangered subspecies up to guarded population levels. The most significant recovery was that of the Española Tortoise, whose breeding stock comprised 2 males and 11 females brought to the Darwin Station. Fortuitously, a third male was discovered at the San Diego Zoo and joined the others in a captive breeding program. These 13 tortoises gave rise to over 1000 tortoises now released into their home island. In all, 2500 individuals of all breeds have been reintroduced to the islands. Hood island: A breeding colony of 15 adults was established at the Charles Darwin Research Station (Caporaso, 1991Caporaso, F. 1991. The Galapagos tortoise conservation program: the plight and future for the Pinzón Island tortoise. In: K. R. Beaman, F. Caporaso, S. McKeown, and M. D. Graff (eds.), Proceedings of the first International Symposium on Turtles & Tortoises: Conservation and Captive Husbandry, pp. 113-116. Chapman Univ., California.), and through August 1972, 25 young G. hoodensis had been raised to be used to restock Española Island (MacFarland et al., 1974bMacFarland, C. G., J. Villa, and B. Toro. 1974b. The Galápagos giant tortoises (Geochelone elephantopus). Part II: Conservation methods. Biol. Conserv. 6: 198-212.). By the end of 1993, 575 have been released, with an additional 288 held at the CDR Station awaiting release (Cayot and Morillo, 1997). Recently discovered nests and live hatchlings indicate that the released tortoises are reproducing (Pritchard, 1996aPritchard, P. C. H. 1996a. The Galápagos tortoises: nomenclatural and survival status. Chelonian Res. Monogr. (1): 1-85.). 1971: Very successful captive breeding program at breeding center of the Charles Darwin Research Station and Galapagos National Park on Santa Cruz with 12 females and 3 males from Española (Milankovitch et al. 2004) Begun for restoration of a tortoise population on Española Some 1200 offspring hatched in captivity were repatriated over next 33 years In 1994 offspring in wild documented from individuals hatched in captivity

http://www.guardian.co.uk/environment/2010/jun/27/giant-tortoise-galapagos-saved-extinction Authorities decided to cull the invaders in the 1970s with teams of marksmen, but some goats survived, bred and perpetuated the problem until the 1990s when helicopters, dogs and radio tracking devices were used. The breakthrough was using "Judas" goats fitted with electronic collars to pinpoint the elusive herds. "Every month they would go back, shoot all of them except the Judas, go back a month later, shoot again and so on, until it was just the Judas left. Then it was shot," said Nicholls.

1999: mtDNA studies showing G. n. abingdoni's close relationship to populations from Espanola and San Cristobal island; May make breeding attempts more successful in the future if these tortoises are matched Previously, breeding used Isabela Island populations (Caccone et al. 1999). 2005: DNA analysis designates two genetically distinct significant populations on Santa Cruz and a third much smaller population, also distinct; at least the two most numerous should be considered a separate conservation units. (Russello et al 2005) Currently the taxonomy only recognizes a single taxon, G. n. porteri. Problems facing especially the Cerro Fatal population include poaching, agriculture encroaching on habitat, and lack of genetic variation. 2002-2010: Attempts to breed Lonesome George (G. n. abingdoni) have been unsuccessful, but there is still hope. Approx. 200 G. n. ephippium have been reintroduced to Pinzon Island (Ciofi et al. 2002). By 2001, some 2500 individuals have been reintroduced to the islands (CDFG 2001) Galapagos Conservancy project to restore tortoise population to Pinta Island: (Galapagos Conservancy 2010) Goats eliminated in 1999 from Pinta 39 sterilized hybrids tortoises to be released May 2010 to help bring ecological balance to the islands that these large herbivores provide re-creating a "pre-human" balanced ecosyste: http://www.guardian.co.uk/environment/2010/jun/27/giant-tortoise-galapagos-saved-extinction

Have been dubbed the "ecosystem engineers" of Galapagos Islands; are the largest herbivores. We can say with certainty that the ecological integrity of Española is being re-established." http://www.guardian.co.uk/environment/2010/jun/27/giant-tortoise-galapagos-saved-extinction Maintain well-worn pathways through brush; even humans sometimes make use of these routes As herbivores, keep understory of vegetation thinned, allowing light to penetrate for many endemic plants (galapagos.org website May 2010) Help disperse seeds from many plants A keystone species is a species that plays an essential role in the structure, functioning or productivity of a habitat or ecosystem at a defined level (habitat, soil, seed dispersal, etc).

By 2030 genetically appropriate individuals will have been released; this is facilitated by the recognition of hybrid individuals on nearby islands and in captive populations in zoos Descendants of tortoises from islands of Floreana, thought to be extinct, survive as hybrids on Isabella; the genetics of the hybrids match the DNA from museum specimens collected in late 1800s and early 1900s from Floreana.(Poulakakis et al 2008) (Parham 2008) Descendants of tortoises from island of Pinta include Lonesome George and newly recognized hybrid individuals from nearby Isabela Island; six museum specimens from Pinta Island aided in this genetic study. (Russello et al 2007) With selective breeding, these hybrids could in time, help restore "the genetic constitution" of the original population. (Poulakakis et al. 2008)

Notable individuals

 * Lonesome George is the only known living specimen of the Pinta Island Tortoise.[[Image:Lonesome George -Pinta giant tortoise -Santa Cruz.jpg|right|thumb|Lonesome George, the last surviving Pinta Tortoise]]
 * Harriet was the second oldest tortoise ever authenticated with an estimated age of 175 years at the time of her death in 2006 in Australia Zoo.