Tortoise

Tortoises
An Aldabra Giant Tortoise (Geochelone gigantea)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Cryptodira
Superfamily:	Testudinoidea
Family:	Testudinidae
Genera
Astrochelys Chersina Cylindraspis (extinct) Dipsochelys Geochelone Gopherus Homopus Indotestudo Kinixys Malacochersus Manouria Psammobates Pyxis Stylemys (extinct) Testudo

Tortoises or land turtles are land-dwelling reptiles of the family of Testudinidae, order Testudines. Like their marine cousins, the sea 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 has both an endoskeleton and an exoskeleton. Tortoises can vary in size from a few centimeters to two meters. Tortoises tend to be diurnal animals with tendencies to be crepuscular depending on the ambient temperatures. They are generally reclusive animals.

Use of the term "tortoise"

Adult male tortoise, South Africa

Although the word "tortoise" is used by biologists in reference to the family Testudinidae only, in common usage it is used to describe many land-dwelling turtles. 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.
• 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" by default is as common.
• Australian English uses "tortoise" for terrestrial species, including semi-aquatic species that live near ponds and streams. Traditionally a "tortoise" has feet (including webbed feet) while a "turtle" has flippers.

Biology

Birth

Young tortoise

Female tortoises dig nesting burrows in which they lay from one to thirty eggs.^[1] 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.^[2] 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 to facilitate 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 3 to 7 days until they have the strength and mobility to find food. Juvenile tortoises often require a different balance of nutrients than adults, and therefore may eat foods which a more mature tortoise would not. For example, it is common that the young of a strictly herbivorous species will consume worms or insect larvae for additional protein.

Lifespan

Desert Tortoise in Rainbow Basin near Barstow, California

There are many old wives tales about the age of turtles and tortoises, one of which being that the age of a tortoise can be deduced by counting the number of concentric rings on its carapace, much like the cross-section of a tree. This is not true, since the growth of a tortoise depends highly on the access of food and water. A tortoise that has access to plenty of forage (or is regularly fed by its owner) will grow faster than a Desert Tortoise that goes days without eating.

Tortoises generally have lifespans comparable with those of human beings, 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, almost the oldest individual animal 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. Tui Malila remained in the care of the Tongan royal family until its death by natural causes on May 19, 1965. This means that upon its death, Tui Malila was 188 years old.^[3] 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.^[4]

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 d's) 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. Zoo officials state they have documentation showing that Adwaita was at least 130 years old, but claim that he was over 250 years old (although this has not been scientifically verified). Adwaita was said to be the pet of Robert Clive.^[5]

Harriet, a resident at the Australia Zoo in Queensland, was apocryphally thought to have been brought to England by Charles Darwin aboard the Beagle. Harriet died on June 23, 2006, just shy of her 176th birthday.

Timothy, a spur-thighed tortoise, lived to be approximately 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 passing in 2004 she was believed to be the UK's oldest resident.

According to articles published by the Daily Mail and the Times in December 2008, Jonathan, a Seychelles Giant tortoise living on the island of St Helena may be as old as 176^[6] or 178 years.^[7] 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. Some believe that males grow quicker, while the female grows slower but larger. The male also has a plastron that 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 a smaller tail which is dropped down whereas the males have a much longer tail which is 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 miles per hour (0.27 km/h).^[8]

Diet

A baby tortoise feeding on lettuce.

Most land based tortoises are herbivores, feeding on grazing grasses, weeds, leafy greens, flowers, and some fruits. Pet tortoises typically require a diet based on wild grasses, weeds and certain flowers. Certain species occasionally consume worms or insects, but too much protein is detrimental as it can cause shell deformation and other medical problems. Cat or dog foods should not be fed to tortoises, as these do not contain the proper balance of nutrients for a reptile; in particular, they are too high in protein. Additionally, it should not be assumed that all captive tortoises can be fed on the same diet. As different tortoise species vary greatly in their nutritional requirements it is essential to thoroughly research the dietary needs of your individual tortoise. Commercial tortoise pellets should not be offered as despite their claims they are not formulated to meet the nutritional needs of any type of tortoise. Large pellets have been known to rupture the oesophagus which begins the onset of choking and can cause a slow painful death. The best approach to determining the proper diet is to consult a qualified veterinarian specialising in chelonian care.

Taxonomy

The following species list largely follows Ernst & Barbour (1989), as indicated by The Reptile Database. However, the newly erected genera Astrochelys, Chelonoidis, and Stigmochelys have been retained within Geochelone.

Skeleton of a tortoise

Fossil of the extinct Ergilemys insolitus

Achilemys cassouleti, the most primitive testudine^[9]

• Chersina
  • Chersina angulata, Bowsprit Tortoise
• Cylindraspis (All species Extinct)
  • Cylindraspis indica, synonym Cylindraspis borbonica
  • Cylindraspis inepta
  • Cylindraspis peltastes
  • Cylindraspis triserrata
  • Cylindraspis vosmaeri
• Dipsochelys
  • Dipsochelys abrupta (Extinct)
  • Dipsochelys arnoldi, Arnold's Giant Tortoise,
  • Dipsochelys daudinii (Extinct)
  • Dipsochelys dussumieri, Aldabra Giant Tortoise, common synonyms Geochelone gigantea, Aldabrachelys gigantea
  • Dipsochelys grandidieri (Extinct)
  • Dipsochelys hololissa, Seychelles giant tortoise
• Geochelone
  • Geochelone carbonaria, Red-Footed Tortoise; sometimes placed in distinct genus Chelonoidis
  • Geochelone chilensis, Chaco or Chilean Tortoise; sometimes placed in distinct genus Chelonoidis
  • Geochelone denticulata, Yellow-Footed Tortoise; sometimes placed in distinct genus Chelonoidis
  • Geochelone elegans, Indian Star Tortoise
  • Geochelone nigra, Galápagos Giant Tortoise; sometimes placed in distinct genus Chelonoidis
  • Geochelone pardalis, Leopard Tortoise; sometimes placed in distinct genus Stigmochelys or in Psammobates
  • Geochelone platynota, Burmese Star Tortoise
  • Geochelone radiata, Radiated Tortoise; sometimes placed in distinct genus Astrochelys
  • Geochelone sulcata, African Spurred Tortoise (Sulcata Tortoise)
  • Geochelone yniphora, Angulated Tortoise, Madagascan (Plowshare) Tortoise; sometimes placed in distinct genus Astrochelys
• Gopherus
  • Gopherus agassizii, Desert Tortoise
  • Gopherus berlandieri, Texas Tortoise
  • Gopherus flavomarginatus, Bolson Tortoise
  • Gopherus polyphemus, Gopher Tortoise
• †Hadrianus
  • Hadrianus corsoni (syn. H. octonarius)
  • Hadrianus robustus
  • Hadrianus schucherti
  • Hadrianus utahensis
• Homopus
  • Homopus aerolatus, Parrot-Beaked Cape Tortoise
  • Homopus boulengeri, Boulenger's Cape Tortoise
  • Homopus femoralis, Karroo Cape Tortoise
  • Homopus signatus, Speckled Cape Tortoise, Speckled Padloper
  • Homopus bergeri, Berger's Cape Tortoise, Nama padloper, synonym Homopus solus
• Indotestudo
  • Indotestudo elongata, Elongated Tortoise
  • Indotestudo forstenii, Travancore Tortoise, Forsten’s Tortoise
  • Indotestudo travancorica, Travancore Tortoise
• Kinixys
  • Kinixys belliana, Bell's Hinge-Backed Tortoise
  • Kinixys erosa, Serrated Hinge-Backed Tortoise
  • Kinixys homeana, Home's Hinge-Backed Tortoise
  • Kinixys lobatsiana, Lobatse Hingeback Tortoise
  • Kinixys natalensis, Natal Hinge-Backed Tortoise
  • Kinixys spekii, Speke's Hingeback Tortoise
• Malacochersus
  • Malacochersus tornieri, Pancake Tortoise
• Manouria
  • Manouria emys, Brown Tortoise (Mountain Tortoise)
  • Manouria impressa, Impressed Tortoise
• Psammobates
  • Psammobates geometricus, Geometric Tortoise
  • Psammobates oculifer, Serrated Star Tortoise
  • Psammobates tentorius, African Tent Tortoise
• Pyxis
  • Pyxis arachnoides, Madagascan Spider Tortoise
  • Pyxis planicauda, Madagascan Flat-Tailed 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
• Testudo
  • Testudo atlas, Atlas tortoise, Colossochelys (Extinct)
  • Testudo graeca, Greek Tortoise (Spur-Thighed Tortoise)
  • Testudo hermanni, Herman's Tortoise
  • Testudo horsfieldii, Russian Tortoise (Horsfield's Tortoise, or Central Asian Tortoise)
  • Testudo kleinmanni, Egyptian Tortoise, incl. Negev Tortoise
  • Testudo marginata, Marginated Tortoise
  • Testudo nabeulensis, Tunisian Spur-thigh Tortoise

In religion

The 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 that 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.

Cultural depictions

Gallery

A baby Testudo marginata emerges from its egg	A baby tortoise, less than a day old	Testudo graeca ibera, Testudo hermanni boettgeri, Testudo hermanni hermanni, Testudo marginata sarda	A young (3.5 years) Sulcata Tortoise Geochelone sulcata	A young, 20 year old Tanzanian Leopard Tortoise feeding on grass
Aldabra Giant Tortoise Geochelone gigantea	App 22 year old Leopard Tortoise	An African Spurred Tortoise from the Oakland Zoo	Pair of tortoises mate in a zoo	A boy rides tortoise at a zoo

References

Further reading

• Chambers, Paul (2004). A Sheltered Life: The Unexpected History of the Giant Tortoise. London: John Murray. ISBN 0719565286. 
• 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. 
• Kuyl, AC; Ph Ballasina, DL; Dekker, JT; Maas, J; Willemsen, RE; Goudsmit, J; et al. (Feb 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:10.1006/mpev.2001.1052. ISSN 1055-7903. PMID 11820839. 

External links

• A turtles website
• The Reptile Database
• Family Testudinidae (Tortoises) of The Reptile Database
• Tortoise Protection Group: Tortoise conservation and expert advice on tortoise care.
• Chelonia: Conservation and care of turtles.
• Lot of pictures, videos and informations