|An Aldabra giant tortoise (Aldabrachelys gigantea)|
Tortoises (pron.: //, Testudinidae) are a family of land-dwelling reptiles in the order Testudines. Like their marine relatives, 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 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.
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.
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.
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 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, 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.
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.
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.
|This section's factual accuracy may be compromised due to out-of-date information. (April 2012)|
The following species list largely follows Rhodin et al., 2010, this is a work in progress.
Family Testudinidae Batsch 1788
Subfamily Xerobatinae Agassiz, L. 1857.
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.
Baby Testudo marginata emerges from its egg
Young (3.5 years) Sulcata tortoise Geochelone sulcata
African spurred tortoise from the Oakland Zoo
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