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11/2-13/5 2010

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The Reptiles of Galapagos.

 Due to the isolation, only 28 species of reptiles are found on the islands, and eighteen of these are endemic. There are members of five groups; Tortoises, iguanas, lizards, geckos and snakes. The surrounding sea hosts a few more species; both turtles and a snake. My photos of Galapagos' reptilians can be seen here.

 The Giant Tortoises of the Galapagos islands have named the islands. Their shell reminded the bishop of


Chelonoidis donfaustoi - "The new one"

 Panama (who made the first recorded of the islands) of a type of saddles: Spanish; "galápago". Somehow, their ancestors have made the more than 1000 kilometres journey cross the sea. Most belong to one species which use to have fourteen subspecies on the islands. The closest living relative of these Galapagos giant tortoises is Geochelone chilensis, a small tortoise found in Argentina. The split between Geochelone chilensis and the Galápagos lineage probably occurred 6-12 million years ago based on mitochondrial DNA analysis. 
 


The last living Geochelone elephantopus abingdoni; George.

There was once more than 250.000 of these giants on the islands. Now, only 15.000 is found. The adults have been eaten by sailors, the eggs by introduced rats, dogs and pigs. The Darwin Research Station have a breeding program, and they are re-introduced along with the clearing of invasive species on the islands.

 The Galapagos tortoise is an herbivore that eats cactus, grasses, leaves, vines, and fruit. Fresh young grass is a favourite food of the tortoises, and others are the Manzanillo; Hippomane mancinella, the endemic Galapagos guava; Psidium galapageium , the floating water fern; Azolla microphylla, and the bromeliad; Tillandsia insularis. They have tremendous water storage capacities, enabling them to survive the long arid season in the cold period.

 The social structure of the Galapagos tortoise is a dominance hierarchy based on the height to which the tortoise can stretch its head. They matures at 20-25 years of age and can live to they reach 200 years, reaching a weight up to 300 kilos. Compared to most tortoises, the birth rate of Galapagos tortoises is extremely low, a result of the lack of predators. Where many other tortoises can lay up to hundreds of eggs at a time, the Galapagos tortoise only lays between 2 and 16 eggs.

 The mating occurs at any time of the year, although it does have seasonal peaks between January and August. After mating, in June-December, the females journey up to several kilometres to reach nesting areas of dry, sandy ground, often near the coast. These eggs are laid in a 30 centimetre deep hole. The female makes a muddy plug for the nest hole out of soil mixed with urine and leaves the eggs to incubate, which takes between 120-140 days. Then it can take them up to a month to dig them selves free. These small, only six centimetre large replicas weight only 80 grams.


Old drawing of Geochelone elephantopus abingdoni

 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", and can be heard for a hundred meters around. They have a classic example of a mutualistic symbiotic relationship with some species of Galápagos finch.[9] The finch hops in front of the tortoise to show that it is ready and the tortoise then raises itself up high on its legs and stretches out its neck so that the bird can pick off ticks that are hidden in the folds of the skin (especially on the rear legs, cloacal opening, neck, and skin between plastron and carapace), thus freeing the tortoise from harmful parasites and providing the finch with an easy meal.

 The species; Geochelone elephantopus, Harlan 1827 (Synonym: Geochelone nigra, Quoy & Gaimard 1824 and Chelonoidis) have evolved into different subspecies on each island and habitats on the single island. That way, they have been able to survive in these sometimes Geochelone elephantopushostile habitats. These differences were noted by Captain Porter, even before Charles Darwin. Larger islands with more wet highlands such as Santa Cruz and the Alcedo Volcano on Isabela have lush vegetation near the ground. Tortoises here tend to have 'dome-back' shells. These animals have restricted upward head movement due to shorter necks, and also have shorter limbs. These are the heaviest and largest of the subspecies.

 Smaller, drier islands such as Espanola and Pinta are inhabited by tortoises with 'saddleback' shells comprising a flatter carapace which is elevated above the neck and flared above the hind feet. Along with longer neck and limbs, this allows them to browse taller vegetation. Saddlebacks are smaller in size than domebacks, namely Hood Island, as having their shells in front thick and turned up like a Spanish saddle. They tend to have a yellowish colour on lower mandible and throat. At one extreme, the Sierra Negra volcano population that inhabits southern Isabela Island has a very flattened "tabletop" shell. The tortoises from James Island are rounder and darker.

 The subspecies of Geochelone elephantopus:

Abingdon Island Tortoise; G. e. abingdoni Günther, 1877.
 Southern slopes of Pinta. Only one known purebred individual is alive; Lonesome George, and is currently maintained at the Charles Darwin Research Station. G. e. hoodensis are released on the island now.

Chatham Island Tortoise G. e. chathamensis Van Denburgh, 1907.
 San Cristóbal, now confined to the northeast. Heavily exploited and completely eliminated over much of its original range.

James Island Tortoise G. e. darwini Van Denburgh, 1907. West-central San Salvador.
 Large numbers of tortoises were removed from the island by whaling vessels. Then ntroduced goats reduced the coastal lowlands to deserts, and most nests and young are destroyed by feral pigs.

Duncan Island Tortoise G. e. duncanensis Garman, 1917 (syn. ephippium Günther, 1875). South-western Pinzón.
 Due to the first whalers, then the introduction of black rats some time before 1900, there is no natural breeding.

                               Photo of a present animal.
Charles Island Tortoise G. e. galapagoensis Baur, 1889
(syn. nigra/elephantopus). Floreana.
 Extinct by settlers, however in 2008, research into mitochondrial DNA in museum specimens of the Floreana race by Dr Caccone of Yale University suggested that a population from Floreana may have been transposed to Isabela.

Hood Island Tortoise G. e. hoodensis Van Denburgh, 1907. Española. Found on Espanola.
 This population was very heavily exploited by whalers in the nineteenth century and collapsed around 1850. 13 adults were found in the early 1970s and held at the Charles Darwin Research Station as a breeding colony. There have been bread 1000 young here.

Indefatigable Island Tortoise G. e. porteri Rothschild, 1903 (syn. nigrita). Santa Cruz. The main population occurs in southwest with a smaller population in the northwest. Depleted by heavy exploitation for oil at least until the 1930s. Reproductive success severely hampered for many years by the presence of feral dogs and pigs.

Volcán Wolf Tortoise G. e. becki Rothschild, 1901. Northern Isabela.
 Northern and western slopes of Volcano Wolf. Reproduction is successful!

Iguana Cove Tortoise G. e. vicina Günther, 1875. Eastern Isabela Island: Cerro Azul.
 A typical dome-shelled tortoise. Range overlaps with G. n. guentheri. This population was depleted by seamen and by extensive slaughter in the late 1950s and 60's by employees of cattle companies.

Sierra Negra Tortoise G. e. guntheri Baur, 1889. Isabela Island.
 Volcano Sierra Negra, one group in the east and another over the western and south-western slopes. Severely depleted by settlement and exploitation for tortoise oil which continued until the 1950s. The wild reproduction is successful in the east, but in the western-south-western area pigs, dogs, rats and cats are present as predators.

Volcán Darwin Tortoise G. e. microphyes Günther, 1875. Isabela Island: southern and western slopes of Volcano Darwin.
 Heavily exploited in the nineteenth century by whaling vessels, but wild reproduction is successful.

Volcán Alcedo Tortoise G. e. vandenburghi DeSola, 1930. Central Isabela Island: caldera and southern slopes of Volcano Alcedo.
 The largest population in the archipelago, wild reproduction successful.

The extinct:    
G. e. phantastica Van Denburgh, 1907. Fernandina.
 Known from only one male specimen found (and killed) by members of the 1906 San Francisco Academy of Sciences expedition. Could just be a stray individual.
Santa Fe Island Tortoise.
 There are only 2 records of whalers removing tortoises, and there are two eye-witness accounts of locals removing tortoises in 1876 and 1890.
G. e. wallacei. Rabida Island.
 This putative subspecies is known from only one specimen. Tracks were seen on Rabida in 1897 and a single individual was removed by the Academy of Sciences in 1906.  Could just be a stray individual.
The newly discovered : Eastern Santa Cruz Tortoise
Chelonoidis donfaustoi. Through DNA, it was discovered this tortoise belong to another species tha the other tortoises on Santa Cruz.. A population of about 250 animals are living in an arid inland area of the island. The species name, donfaustoi, honours former Galapagos National Park ranger Fausto Llerena Sánchez, known to his friends and colleagues as Don Fausto.
It is named within the new genera, but some might argue it should be Geochelone elephantopus donfaustoi.

The pictures of the vandenburghi, darwini, becki and donfaustoi
are nicked from other sites
.

 The snakes on the island include some species of the Alsphis family; Banded Galapagos Snake; Antillophis slevini, found on Isabela, Fernandina and Pinzon. The Galapagos Racer; Alsophis biseralis, the Hood Racer; Philodryas hoodensis which is only found on Espanola and the Striped Galapagos Snake; Antillophis steindachneri which is found on Seymour, Baltra, Rapida Santiago and northern Santa Cruz.

 Synonym for Alsophis is Philodryas and Dromiscus.

 The snakes, which all are small;  60-90 centimetres, are only found on the southern islands. They  feeding on insects, Lava Lizards, grasshoppers, geckos, finch nestlings and from young Marine Iguanas. They are quite similar looking, about two to three feet long, brown with yellowish longitudinal stripes.

 Galapagos snakes can be slightly poisonous to humans, and may use venom to kill its prey. They first catch the prey with their mouths and mainly kill by constriction: wrapping around the victim and squeezing so it cannot breathe. Although common and widespread, the snakes are not often seen as they are rather shy. Most islands have one or two of the species.

 The Iguanas are represented by three species, all endemic. The Marine Iguana; Amblyrhynchus cristatus is unique in that it is the only seagoing lizard in the world. The Land Iguana; Conolophus subcristatus, and the Santa Fe Land Iguana; Conolophus pallidus.

 The Marine Iguana; Amblyrhynchus cristatus are found on most or even all the islands of the Archipelago. Even though they may vary in size and colours from island to island but they are all considered to be a single species. The most colourful are found at Española, the biggest ones are located at Fernandina and Isabela and the smallest one can be seen at Genovesa. The feed on algae, found in the sea. They have to heat up for hours to do a 20 minutes dive. Older and larger animals swim further out to sea. They can grow to 80 or even 90 centimetres.

 The Land Iguana on Galapagos are divided into two species, Conolophus subcristatus and Conolophus pallidus, which are only found on Santa Fe. This particular species is paler in colour and has more prominent spines, moor drooping crest and redder eyes. Conolophus subcristatus are found on North Seymour, South Plaza, Baltra, Santa Cruz, Isabela and Fernandina. They feed on grass, centipedes, plants and especially Opuntia fruits and their yellow flowers. Land Iguanas are different from Marine Iguanas in that they do not have a square nose; they have pointed noses. They get to be around 90 centimetres long.

 The Lava Lizards; Tropidurus sp. are the most abundant Galapagos reptiles. All species of lizards found in Galapagos are differences in colour and shape, from 12,5-25 centimetres, which show the incredible way they have adapted to the environment of the Islands. They feed on insects, flowers and fruits.
 The seven species are: Tropidurus albemarlensis found on Santa Cruz, Fernandina, Santiago, Baltra, Santa Fe, Raida, Seymour, Daphne Major, and Plaza Sur.  Tropidurus habellii is found on Marchena. Tropidurus grayi  if found on Floreana. Tropidurus bivattatus is the San Cristobal species. Tropidurus delanonis is from Espanola. Tropidurus pacificus  is from Pinta while Tropidurus duncanensis  is from Pinzon.

 The Galapagos Geckos or Galapagos Leaf-toed Gecko: Phyllodactylus galapagoensis. are represented by six subspecies that all are endemic to the Islands. They are found on Santa Cruz, San Cristobal, Baltra, Isabela, and Floreana. They are all  greyish.  The subspecies are: Phyllodactylus galapagensis daphnensis, PhyllodactylusPhyllodactylus leei or not? galapagensis galapagensis, Phyllodactylus galapagensis maresi and Phyllodactylus galapagensis olschkii.

 Phyllodactylus barringtonensis is found on Santa Fe, Phyllodactylus bauri is both on Floreana and Pinta, while Phyllodactylus gilberti is only found on Wolf. San Cristobal Leaf-Toed Gecko; Phyllodactylus leei is another San Cristobal species.

 Some species that have been introduced to the islands: Gonatodes caudiscutatus on San Cristobal along with Lepidodactylus lugubris  and Phyllodactylus tuberculosus while Phyllodactylus reissi  have been brought in on Santa Cruz.

 The Green Sea Turtle; Chelonia mydas might be a subspecies due to the fact they are darker than other populations. They are found massively in the Galapagos Islands although in other locations of the world they are considered to be an endangered species. The Galapagos are an important feeding place for green sea turtles especially in the Islands of: Fernandina, Santa Cruz, and Isabela.

 Several other sea turtles can be seen: Hawksbill Turtle; Eretmochelys imbricata. The huge Leatherback Turtle; Dermochelys coriacea and Olive Ridley; Lepidochelys olivacea.

 Yellow-bellied Sea Snake; Pelamis platurus. The tail section has spots, and the body is yellow and black, this snake gets to be up to 85 centimeters long. The venom is dangerous, even more poisonous than the venom of the cobra snake. Fortunately, the Yellow-bellied Sea Snake is pretty rare, except for during the El Nino times, when waters get warmer because of the Nino current.

 Amphibians was not found on the islands, but roomers have it, that two species have been realised recently. Only the goods and the insane know why! 

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