Tortoise

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Tortoises
An Aldabra giant tortoise (Aldabrachelys gigantea)
Scientific classification e
Kingdom:Animalia
Phylum:Chordata
Class:Reptilia
Order:Procolophonomorpha
Order:Testudines (=Chelonii)
Suborder:Cryptodira
Superfamily:Testudinoidea
Family:Testudinidae
Batsch, 1788
Type species
Testudo graeca
Linnaeus, 1758
Subgroups
 
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Tortoises
An Aldabra giant tortoise (Aldabrachelys gigantea)
Scientific classification e
Kingdom:Animalia
Phylum:Chordata
Class:Reptilia
Order:Procolophonomorpha
Order:Testudines (=Chelonii)
Suborder:Cryptodira
Superfamily:Testudinoidea
Family:Testudinidae
Batsch, 1788
Type species
Testudo graeca
Linnaeus, 1758
Subgroups

Tortoises (/ˈtɔːr.təs.ɪz/, Testudinidae) are a family of land-dwelling reptiles in the order Testudines. Like turtles, tortoises are shielded from predators by a shell. The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The tortoise endoskeleton has the adaptation of having an external shell fused to the ribcage. Tortoises can vary in size from a few centimeters to two meters. They are usually diurnal animals with tendencies to be crepuscular depending on the ambient temperatures. They are generally reclusive animals.

Use of the term "tortoise"[edit]

Although the word "tortoise" is used by biologists in reference to the family Testudinidae only, in colloquial usage, it is often used to describe many land-dwelling Testudines. The inclusiveness of the term depends on the variety of English being used.[1]

Biology[edit]

Birth[edit]

Adult male tortoise, South Africa
Young African Sulcata tortoise

Female tortoises dig nesting burrows in which they lay from one to 30 eggs.[2] Egg-laying typically occurs at night, after which the mother tortoise covers her clutch with sand, soil, and organic material. The eggs are left unattended, and depending on the species, take from 60 to 120 days to incubate.[3] The size of the egg depends on the size of the mother and can be estimated by examining the width of the cloacal opening between the carapace and plastron. The plastron of a female tortoise often has a noticeable V-shaped notch below the tail which facilitates passing the eggs. Upon completion of the incubation period, a fully formed hatchling uses an egg tooth to break out of its shell. It digs to the surface of the nest and begins a life of survival on its own. Hatchlings are born with an embryonic egg sac which serves as a source of nutrition for the first three to seven days until they have the strength and mobility to find food. Juvenile tortoises often require a different balance of nutrients than adults, so may eat foods which a more mature tortoise would not. For example, the young of a strictly herbivorous species commonly will consume worms or insect larvae for additional protein.

Lifespan[edit]

Adult tortoise

The number of concentric rings on the carapace, much like the cross-section of a tree, can sometimes give a clue to how old the animal is, but, since the growth depends highly on the accessibility of food and water, a tortoise that has access to plenty of forage (or is regularly fed by its owner) with no seasonal variation will have no noticeable rings. Moreover, some tortoises grow more than one ring per season and in some others, due to wear, some rings are no longer visible.[4]

Tortoises generally have the longest lifespans of any animal, and some individuals are known to have lived longer than 150 years.[5] Because of this, they symbolize longevity in some cultures, such as China. The oldest tortoise ever recorded, and one of the oldest individual animals ever recorded, was Tu'i Malila, which was presented to the Tongan royal family by the British explorer Captain Cook shortly after its birth in 1777. Tu'i Malila remained in the care of the Tongan royal family until its death by natural causes on May 19, 1965, at the age of 188.[6] The record for the longest-lived vertebrate is exceeded only by one other, a koi named Hanako whose death on July 17, 1977 ended a 226-year life span.[7]

The Alipore Zoo in India was the home to Adwaita, which zoo officials claimed was the oldest living animal until its death on March 23, 2006. Adwaita (sometimes spelled with two ds) was an Aldabra giant tortoise brought to India by Lord Wellesley, who handed it over to the Alipur Zoological Gardens in 1875 when the zoo was set up. West Bengal officials said records showed Adwaita was at least 150 years old, but other evidence pointed to 250. Adwaita was said to be the pet of Robert Clive.[8]

Harriet was a resident at the Australia Zoo in Queensland from 1987 to her death in 2006; she was believed to have been brought to England by Charles Darwin aboard the Beagle and then on to Australia by John Clements Wickham.[9] Harriet died on June 23, 2006, just shy of her 176th birthday.

Timothy, a spur-thighed tortoise, lived to be about 165 years old. For 38 years, she was carried as a mascot aboard various ships in Britain's Royal Navy. Then in 1892, at age 53, she retired to the grounds of Powderham Castle in Devon. Up to the time of her death in 2004, she was believed to be the United Kingdom's oldest resident.

Jonathan, a Seychelles giant tortoise living on the island of St Helena may be as old as 176[10] or 178 years.[11] If this is true, he could be the current oldest living animal on Earth.

Sexual dimorphism[edit]

Many species of tortoises are sexually dimorphic, though the differences between males and females vary from species to species. In some species, males have a longer, more protruding neck plate than their female counterparts, while in others, the claws are longer on the females.

In most tortoise species, the female tends to be larger than the male. The male plastron is curved inwards to aid reproduction. The easiest way to determine the sex of a tortoise is to look at the tail. The females, as a general rule, have smaller tails, dropped down, whereas the males have much longer tails which are usually pulled up and to the side of the rear shell.

General information[edit]

Giant tortoises move very slowly on dry land, at only 0.17 mph (0.27 km/h).[12] The fastest recorded tortoise speed is 5 mph.[13]

Diet[edit]

Baby tortoise feeding on lettuce

Most land-based tortoises are herbivores, feeding on grasses, weeds, leafy greens, flowers, and some fruits, although some omnivorous species are in this family. Pet tortoises typically require diets based on wild grasses, weeds, leafy greens and certain flowers. Certain species consume worms or insects and carrion in their normal habitats. Too much protein is detrimental in herbivorous species, and has been associated with shell deformities and other medical problems. As different tortoise species vary greatly in their nutritional requirements, it is essential to thoroughly research the dietary needs of an individual tortoise.

Taxonomy[edit]

The following species list largely follows Rhodin et al., 2010,[14] this is a work in progress.

Skeleton of a tortoise
Fossil of the extinct Ergilemys insolitus
Achilemys cassouleti, the most primitive testudine

Family Testudinidae Batsch 1788[15]

Subfamily Testudininae

Subfamily Xerobatinae Agassiz, L. 1857.[18]

In religion[edit]

Bas-relief from Angkor Wat, Cambodia, shows Samudra manthan-Vishnu in the centre, his turtle Avatar Kurma below, asuras and devas to left and right

In Hinduism, Kurma (Sanskrit: कुर्म) was the second Avatar of Vishnu. Like the Matsya Avatara also belongs to the Satya Yuga. Vishnu took the form of a half-man, half-tortoise, the lower half being a tortoise. He is normally shown as having four arms. He sat on the bottom of the ocean after the Great Flood. A mountain was placed on his back by the other gods so they could churn the sea and find the ancient treasures of the Vedic peoples.

Tortoise shells were used by ancient Chinese as oracle bones to make predictions.

The tortoise is a symbol of the Ancient Greek god, Hermes.

Cultural depictions[edit]

Gallery[edit]

See also[edit]

References[edit]

  1. ^ "Turtle". Sandiegozoo.org. Retrieved 2012-09-16. 
  2. ^ Highfield, Andy. "Tortoise Trust Egg F.A.Q". Tortoisetrust.org. Retrieved 2009-04-07. 
  3. ^ Highfield, Andy. "Tortoise egg incubation". Tortoisetrust.org. Retrieved 2009-04-07. 
  4. ^ Veterinary Services Department, Drs. Foster & Smith, Inc. "Shells: Anatomy and Diseases of Turtle and Tortoise Shells". Retrieved 2013-10-22. 
  5. ^ Moon, J. C.; McCoy, E. D.; Mushinsky, H. R.; Karl, S. A. (2006). "Multiple Paternity and Breeding System in the Gopher Tortoise, Gopherus polyphemus". Journal of Heredity 97 (2): 150–157. doi:10.1093/jhered/esj017. PMID 16489146.  edit
  6. ^ "Tortoise Believed to Have Been Owned by Darwin Dies at 176". Associated Press via FOXNews. 2006-06-26. 
  7. ^ "Will You Still Feed Me...". The Guardian. Retrieved 2013-01-08. 
  8. ^ "World | South Asia | 'Clive of India's' tortoise dies". BBC News. 2006-03-23. Retrieved 2009-04-07. 
  9. ^ Thomson, S., Irwin, S. and Irwin, T. (1995). "Harriet, the Galapagos tortoise: disclosing one and a half centuries of history". Intermontanus 4 (5): 33–35. 
  10. ^ Jonathan the 176-year-old tortoise revealed as world's oldest animal in Boer War photo Daily Mail, December 5, 2008
  11. ^ Boer War memento puts years on Jonathan the tortoise. The Times, December 4, 2008
  12. ^ 2003 Grolier Encyclopedia, The Great Book of Knowledge, The Speed of Animals, pp. 278.
  13. ^ 2007 Grolier Encyclopedia, The Great Book of Knowledge, The Speed of Animals, p. 297.
  14. ^ Anders G.J. Rhodin, Peter Paul van Dijk, John B. Iverson, and H. Bradley Shaffer. 2010. Turtles of the World, 2010 Update: Annotated Checklist of Taxonomy, Synonymy, Distribution, and Conservation Status
  15. ^ Batsch, A.J.G.C. 1788. Versuch einer Anleitung zur Kenntniss und Geschichte der Thiere und Mineralien. Erster Theil. Allgemeine Geschichte der Natur; besondre der Säugthiere, Vögel, Amphibien und Fische. Jena: Akademischen Buchandlung, 528 pp.
  16. ^ Testudinidae, The Reptile Database
  17. ^ Austin, J. J.; Nicholas Arnold, E. (2001). "Ancient mitochondrial DNA and morphology elucidate an extinct island radiation of Indian Ocean giant tortoises (Cylindraspis)". Proceedings of the Royal Society B: Biological Sciences 268 (1485): 2515. doi:10.1098/rspb.2001.1825.  edit
  18. ^ Agassiz, L. (1857). Contributions to the natural history of the United States of America. Vol. 1. Little, Brown and Co., Boston.

Further reading[edit]

External links[edit]