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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"

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.

  • British English normally describes these reptiles as "tortoises" if they live on land and cannot swim.
  • American English tends to use the word "tortoise" for land-dwelling species, including members of Testudinidae, as well as other species, such as box tortoises, though use of "turtle" for all chelonians is as common.
  • Australian English uses "tortoise" for terrestrial species, including semiaquatic species that live near ponds and streams. Traditionally, a "tortoise" has feet (including webbed feet) while a "turtle" has flippers.

Biology

Birth

Female tortoises dig nesting burrows in which they lay from one to 30 eggs. 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. 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

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.

Tortoises generally have the longest lifespans of any animal, and some individuals are known to have lived longer than 150 years. 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. 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.

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.

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. 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 182 or 178 years. If this is true, he could be the current oldest living animal on Earth.

Sexual dimorphism

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

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

Diet

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

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

Family Testudinidae Batsch 1788

Subfamily Testudininae

  • Aldabrachelys
    • Aldabrachelys gigantea, Aldabra giant tortoise, common synonyms Geochelone gigantea, Dipsochelys gigantea
    • Aldabrachelys abrupta (extinct)
  • Astrochelys Gray, 1873
    • Astrochelys radiata, radiated tortoise
    • Astrochelys yniphora, angulated tortoise, (Madagascan) plowshare tortoise, angonoka
  • Chelonoidis Fitzinger, 1835.
    • Chelonoidis carbonaria, red-footed tortoise
    • Chelonoidis chilensis, pampas tortoise, South Argentine tortoise
    • Chelonoidis denticulata, Brazilian giant tortoise, yellow-footed tortoise
    • Chelonoidis nigra complex:
      • Chelonoidis abingdonii, Pinta Island giant tortoise, Abingdon Island giant tortoise (extinct)
      • Chelonoidis becki, Wolf Volcano giant tortoise, Cape Berkeley giant tortoise
      • Chelonoidis chathamensis, San Cristobal giant tortoise, Chatham Island giant tortoise
      • Chelonoidis darwini, San Salvador giant tortoise, James Island giant tortoise
      • Chelonoidis duncanensis, Pinzon giant tortoise, Duncan Island giant tortoise
      • Chelonoidis hoodensis, Espanola giant tortoise, Hood Island giant tortoise
      • Chelonoidis nigra, Floreana giant tortoise, Charles Island giant tortoise (extinct)
      • Chelonoidis phantastica, Fernandina giant tortoise, Narborough Island giant tortoise (extinct)
      • Chelonoidis porteri, Santa Cruz giant tortoise, Indefatigable Island giant tortoise
      • Chelonoidis vicina, Isabela Island giant tortoise, Albemarle Island giant tortoise
    • Chelonoidis petersi, Chaco tortoise, northern Argentine tortoise
  • Chersina
    • Chersina angulata, angulate tortoise, South African bowsprit tortoise
  • Colossochelys
    • Colossochelys atlas, Atlas tortoise (extinct)
  • Cylindraspis (all species extinct) following Austin and Arnold, 2001:
    • Cylindraspis indica, synonym Cylindraspis borbonica, Reunion giant tortoise
    • Cylindraspis inepta, saddle-backed Mauritius giant tortoise or Mauritius giant domed tortoise
    • Cylindraspis peltastes, domed Rodrigues giant tortoise
    • Cylindraspis triserrata, domed Mauritius giant tortoise or Mauritius giant flat-shelled tortoise
    • Cylindraspis vosmaeri, saddle-backed Rodrigues giant tortoise
  • Geochelone
    • Geochelone elegans, Indian star tortoise
    • Geochelone platynota, Burmese star tortoise
    • Geochelone sulcata, African spurred tortoise (Sulcata tortoise)
  • Hadrianus
    • Hadrianus corsoni (syn. H. octonarius)
    • Hadrianus robustus
    • Hadrianus schucherti
    • Hadrianus utahensis
  • Homopus
    • Homopus areolatus, Common Padloper, parrot-beaked tortoise, beaked Cape tortoise
    • Homopus boulengeri, Karoo Padloper, Karoo dwarf tortoise, Boulenger's Cape tortoise
    • Homopus femoralis, Greater Padloper, greater dwarf tortoise
    • Homopus signatus, Speckled Padloper, speckled padloper tortoise
    • Homopus solus, Nama Padloper, Berger's cape tortoise, synonym Homopus bergeri
  • Indotestudo
    • Indotestudo elongata, elongated tortoise, yellow-headed tortoise
    • Indotestudo forstenii, Forsten’s tortoise, East Indian tortoise
    • Indotestudo travancorica, Travancore tortoise
  • Kinixys
    • Kinixys belliana, Bell's hinge-back tortoise
    • Kinixys erosa, Forest hinge-back tortoise, serrated hinge-back tortoise
    • Kinixys homeana, Home's hinge-back tortoise
    • Kinixys lobatsiana, Lobatse hinge-back tortoise
    • Kinixys natalensis, Natal hinge-back tortoise
    • Kinixys spekii, Speke's hinge-back tortoise
  • Malacochersus
    • Malacochersus tornieri, pancake tortoise
  • Psammobates
    • Psammobates geometricus, geometric tortoise
    • Psammobates oculifer, serrated tent tortoise, Kalahari tent tortoise
    • Psammobates tentorius, African tent tortoise
  • Pyxis
    • Pyxis arachnoides, (Madagascan) spider tortoise
    • Pyxis planicauda, flat-backed spider tortoise, (Madagascan) flat-tailed tortoise, flat-tailed spider tortoise
  • Stigmochelys Gray, 1873
    • Stigmochelys pardalis, leopard tortoise
  • Testudo
    • Testudo graeca, Greek tortoise, spur-thighed tortoise, Moorish tortoise
    • Testudo hermanni, Hermann's tortoise
    • Testudo horsfieldii, Russian tortoise, steppe tortoise, Horsfield's tortoise, or Central Asian tortoise
    • Testudo kleinmanni, Egyptian tortoise, including Negev tortoise
    • Testudo marginata, marginated tortoise

Subfamily Xerobatinae Agassiz, L. 1857.

  • Gopherus
    • Gopherus agassizii, Mojave Desert tortoise, Agassiz's desert tortoise
    • Gopherus berlandieri, Texas tortoise, Berlandier's tortoise
    • Gopherus flavomarginatus, Bolson tortoise
    • Gopherus morafkai, Sonoran Desert tortoise, Morajak's desert tortoise
    • Gopherus polyphemus, gopher tortoise
  • Manouria
    • Manouria emys, Asian giant tortoise, brown tortoise (mountain tortoise)
    • Manouria impressa, impressed tortoise
  • Stylemys (Genus extinct)
    • Stylemys botti
    • Stylemys calaverensis
    • Stylemys canetotiana
    • Stylemys capax
    • Stylemys conspecta
    • Stylemys copei
    • Stylemys emiliae
    • Stylemys frizaciana
    • Stylemys karakolensis
    • Stylemys nebrascensis (syn. S. amphithorax)
    • Stylemys neglectus
    • Stylemys oregonensis
    • Stylemys pygmea
    • Stylemys uintensis
    • Stylemys undabuna

In religion

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

Gallery

See also

Turtles portal
  • Cultural depictions of turtles and tortoises
  • Giant tortoise
  • Jackson ratio

References

Further reading

  • Chambers, Paul (2004). A Sheltered Life: The Unexpected History of the Giant Tortoise. London: John Murray. ISBN 0-7195-6528-6. 
  • Ernst, C. H.; Barbour, R. W. (1989). Turtles of the World. Washington, DC: Smithsonian Institution Press. 
  • Gerlach, Justin (2004). Giant Tortoises of the Indian Ocean. Frankfurt: Chimiara. 
  • Antoinette C. van der Kuyl; Donato L. Ph. Ballasina; John T. Dekker; Jolanda Maas; Ronald E. Willemsen; Jaap Goudsmit (February 2002). "Phylogenetic Relationships among the Species of the Genus Testudo (Testudines: Testudinidae) Inferred from Mitochondrial 12S rRNA Gene Sequences". Molecular Phylogenetics and Evolution 22 (2): 174–183. doi:. ISSN . PMID . 

External links

  • , The Reptile Database
  • , Tortoise conservation information
  • : Conservation and care of turtles.