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| The Galápagos Tortoise |
Today, May 23, is World Turtle Day, sponsored yearly since 2000 by American Tortoise Rescue. The purpose is to bring attention to, and increase knowledge of and respect for, turtles and tortoises, and encourage human action to help them survive and thrive.
World Turtle Day is celebrated around the globe in a variety of ways, from dressing up as turtles or wearing green summer dresses, to saving turtles caught on highways, to research activities. Turtle Day lesson plans and craft projects encourage teaching about turtles in classrooms.
The Jones continue their trip in the Galápagos Islands. The family has visited the tortoises today, one of the most typical animals of these islands to celebrate this important day. They have rested on the grass and have revised the Reported Speech.
More info: Reported Speech & Download Reported Speech
Later, they have read a new chapter of Oscar Wilde's The Picture of Dorian Gray.
The Galápagos tortoise complex or Galápagos giant tortoise complex, Chelonoidis nigra and related species, are the largest living species of tortoise. Modern Galápagos tortoises can weigh up to 417 kg. Today, giant tortoises exist only on two remote archipelagos: the Galápagos Islands 1000 km due west of mainland Ecuador, and Aldabra in the Indian Ocean, 700 km east of Tanzania.
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| Galápagos Tortoises and some Jones |
The Galápagos tortoises are native to seven of the Galápagos Islands, a volcanic archipelago about 1,000 km west of the Ecuadorian mainland. With lifespans in the wild of over 100 years, it is one of the longest-lived vertebrates.
A captive individual lived at least 170 years. Spanish explorers, who discovered the islands in the 16th century, named them after the Spanish galápago, meaning tortoise. Shell size and shape vary between 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.
More information: Galápagos
Charles Darwin'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 3,000 in the 1970s. This decline was caused by overexploitation of the species for meat and oil, habitat clearance for agriculture, and introduction of non-native animals to the islands, such as rats, goats, and pigs.
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| Galápagos Tortoise and Claudia Jones |
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. Ten species of the original 15 survive in the wild; an 11th species, Chelonoidis abingdonii, had only a single known living individual, kept in captivity and nicknamed Lonesome George until his death in June 2012.
More information: National Geographic
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 species is estimated to have exceeded 19,000 at the start of the 21st century. Despite this rebound, the species as a whole is classified as vulnerable by the International Union for Conservation of Nature.
The Galápagos Islands were discovered in 1535, but first appeared on the maps, of Gerardus Mercator and Abraham Ortelius, around 1570. The islands were named Insulae de los Galopegos, Islands of the Tortoises in reference to the giant tortoises found there.
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| Galápagos Tortoises and some Jones |
In 1783, Johann Gottlob Schneider classified all giant tortoises as Testudo indica, Indian tortoise. In 1812, August Friedrich Schweigger named them Testudo gigantea, gigantic tortoise. In 1834, André Marie Constant Duméril and Gabriel Bibron classified the Galápagos tortoises as a separate species, which they named Testudo nigrita, black tortoise.
All species 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.
More information: Darwin Foundation
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 Chelonoidis are believed to have similarly dispersed from Africa to South America during the Oligocene.
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| Claudia Jones and some Galápagos Tortoise |
The closest living relative, though not a direct ancestor, of the Galápagos giant tortoise is the Chaco tortoise, Chelonoidis chilensis, a much smaller species from South America.
The divergence between Chelodonis chilensis and Chelodonis nigra probably occurred 6–12 million years ago, an evolutionary event preceding the volcanic formation of the oldest modern Galápagos Islands 5 million years ago.
More information: New Scientist
Mitochondrial DNA 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 between isolated islands then resulted in the independent evolution of the populations into the divergent forms observed in the modern species. The evolutionary relationships between the species thus echo the volcanic history of the islands.
More information: Live Science
We called him Tortoise because he taught us.
Lewis Carroll
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