Taxonomy
Early classification
The Galápagos Islands were discovered in 1535, but first appeared on the maps, ofRecognition of subpopulations
The first systematic survey of giant tortoises was by the zoologist Albert Günther of theCurrent species and genus names
The current specific designation of ''niger'', formerly feminized to ''nigra'' ("black" – Quoy &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'' fromEvolutionary 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 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, which diverts westwards towards the Galápagos Islands from the mainland. The ancestors of the genus ''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 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 fromSanta Fe
The extinct Santa Fe subspecies has not yet been described and thus has no binomial name, 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 subspecies (''C. n. wallacei'') was described from a single specimen collected by the California Academy of Sciences 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. Lichens can grow on the shells of these slow-moving animals. Tortoises keep a characteristic scute (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 Scale (zoology), scales. 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, 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 are relatively small with a maximum known weight of and carapace length of approximately compared to range in tortoises from Santa Cruz Island (Galápagos), Santa Cruz Island. 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 Island gigantism, insular gigantism. 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-to-volume ratio, surface area/volume ratio, which reduces Osmosis, osmotic 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. 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. ;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'' (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 sex characteristics, secondary sexual characteristic of saddleback males. Male competition over mates is settled by dominance (ethology), dominance displays on the basis of vertical neck height rather than body size (#Reproduction, 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 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 Turtle shell#Plastron, 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 ectothermic (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 Thermoregulation, thermoregulatory response during cool nights, and a protection from Parasitism, parasites 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 herbivores that consume a diet of cacti, grasses, leaves, lichens, berries, melons, oranges and milkweed. They have been documented feeding on ''Manchineel tree, Hippomane mancinella'' (poison apple), the endemic guava ''Psidium galapageium'', the Mosquito fern, water fern ''Azolla microphylla'', Tillandsia, bromeliad ''Tillandsia insularis'' and the Solanum cheesmaniae, 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 ''Opuntia'' 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), 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 Mutualism (biology), mutualistic relationship with some subspecies of Darwin's finches, Galápagos finch and mockingbirds. The birds benefit from the food source and the tortoises get rid of irritating ectoparasites. 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, cloacal 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.Mating
Mating 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.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 (eggs), clutch 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-dependent sex determination, 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 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 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 List of long-living organisms, longest-lived subspecies in the animal kingdom. Harriet (turtle), Harriet, a specimen kept in Australia Zoo, 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, 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, Nicholas Lawson, 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. 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 Robert FitzRoy, FitzRoy (two from Española) and his servant Syms Covington (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 Gabriel Bibron, 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 mockingbirds, in the first tentative statement linking his observations from the Galapagos with the possibility of subspecies transmuting:
When I recollect the fact that [from] 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.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 wrote, "They are so extraordinarily large and fat, and so sweet, that no pullet eats more pleasantly," while Captain James Colnett of the Royal Navy 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 (naval officer), 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, pirates started to use the Galápagos Islands as a base for resupply, restocking on food and water, and repairing vessels before attacking Spanish colonization of the Americas, Spanish colonies 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 ships and Seal hunting, 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
The remaining subspecies of tortoise range in IUCN classification from extinct in the wild to Vulnerable species, 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 species, flagship subspecies for conservation efforts throughout the Galápagos. ;Legal protection The Galápagos giant tortoise is now strictly protected and is listed on Appendix I of the CITES, Convention on International Trade in Endangered subspecies of Wild Fauna and Flora (CITES). The 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 subspecies. In 1959, it declared all uninhabited areas in the Galápagos to be a national park and established the Charles Darwin Foundation. 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 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 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 culling, culls feral predators and competitors. Goat eradication on islands, including Pinta, was achieved by the technique of using "Judas goats" 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) to their condition before humans arrived. The tortoises are a keystone species, keystone subspecies, acting as ecosystem engineers which help in plant seed dispersal and trampling down brush and thinning the understory of vegetation (allowing light to penetrate and germination to occur). Birds such as Galapagos flycatcher, 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.See also
* List of species of Galápagos tortoise, List of subspecies of Galápagos tortoise * Galápagos wildlifeNotes
References
Further reading
* * * * *External links
* ARKive �