Aldabra Tortoise

Scientific Classification

Common Name

 

Kingdom

Aldabra tortoise, giant tortoise

Phylum

Chordata

Class

Reptilia

Order

Testudines (somes sources cite as Chelonia)

Family

Testudinidae

Genus Species

Geochelone (land turtle) gigantea (giant)

Fast Facts

Description

They are dark gray to black in color with a highly domed thick carapace, a very long neck to aid in food gathering, and short, thick legs.

Male: Males have longer, thicker tails than females.

Size

Male: Mature males have an average carapace (shell) length of 122 cm (4 ft.)

Female: Adult female carapace length averages 91 cm (3 ft.).

Weight

Male: Adult males up to 250 kg (550 lb.) or more

Female: Mature females average 159 kg (350 lb.)

Diet

Though it feeds primarily on vegetation, the Aldabra tortoise is flexible and opportunistic in its diet. In order to obtain enough nourishment for survival, the tortoise may supplement its diet with small invertebrates and even carrion (including dead tortoises).

Incubation

Incubation is temperature dependant: in warm temperatures, eggs hatch in about 110 days; in cool temperatures, eggs take 250 days to hatch.
Clutch Size: Typically, the females lay between 4 to 14 eggs, of which less than one half are fertile. Within zoological settings, the average clutch size may be seen to increase, approaching 9 to 25 eggs.

Breeding Period

In healthy, uncrowded populations, a second clutch (laying) within the same breeding season is likely.

Sexual Maturity

Sexual maturity is determined by size rather than by age; most species begin to reproduce when they reach approximately half their full-grown size, usually around 25 years of age.

Life Span

Unknown, probably easily lives over 100 years

Range

The entire wild population of Aldabras is restricted to the Aldabra Atoll (a small group of coral islands in the island nation of Seychelles, north of Madagascar).

Habitat

There are many different habitats on the islands where tortoises can be found, including scrub, mangrove swamp, and coastal dune. The largest concentrations of tortoises are found on the grasslands called platins.

Population

Global: No data

Status 

IUCN: Vulnerable
CITES: Appendix II
USFWS: Not listed

Fun Facts

1. The Aldabra tortoise is the largest animal on the atoll. The tortoises fill a niche very similar to the one occupied by elephants in Africa and Asia. As with elephants, they are the main consumers of vegetation and noticeably alter the habitat during their search for food. Tortoises have been known to knock over small trees and shrubs to obtain nutritious leaves. This makes pathways and clearings within the forestlands for other animals. Seeds pass through the tortoise's digestive tract and eventually become food for many other species.
2. The Aldabra tortoise is one of the longest-lived animals on earth, if not the longest. No one knows exactly how long these animals are capable of living, but they are believed to easily surpass 100 years. So far, the tortoises studied have outlived the scientists studying them, and proper records have not been maintained.
   
    

Ecology and Conservation

The Aldabra tortoise is the only remaining species out of 18 former species of tortoise that once flourished on the islands of the Indian Ocean. The others went extinct because of hunting by sailors and the predation of eggs and hatchlings by introduced species such as rats, cats, and pigs.

This was one of the first species to be protected in order to ensure its survival for the future. Charles Darwin and other notable conservationists of the day along with the governor of Mauritius set aside a captive breeding population on Mauritius as well as protecting the Aldabra Atoll.

Bibliography

Bourn, D. "Reproductive Study of Giant Tortoises on Aldabra". J. Zool., London, Vol. 182, 1977, pp. 27-38.

Collins, David E. "Captive Breeding and Management of the Aldabra Tortoise." Presentation to 8th International Herpetological Symposium, Jacksonville Zoo, Jacksonville, FL, 1984.

Gibson, C.W.D. and Hamilton, J. "Population Processes in a Large Herbivorous Reptile: The Giant Tortoises of Aldabra Atoll." Occologia (Berlin), Spring-Summer, 1984, pp. 230-240.

Grubb, P. "The Growth, Ecology, and Population Structure of the Giant Tortoises on Aldabra." Phil. Trans. Roy. Soc. Lond. B, Vol. 260, 1971, pp. 327-372.

Peters, U.W. and E.P. Finne. "First Breeding of the Aldabra Tortoise at Sydney Zoo."

Pritchard, Peter C.H. Encyclopedia of Turtles. Neptune, New Jersey: T.F.H. Publications, Inc. Ltd., 1979.

Spratt, David M.J. "Operation Curiesue: A Conservation Programme for the Aldabra Giant Tortoise in the Republic of Seychelles." Int. Zoo Yb., Vol. 28, 1989, pp. 66-69.

Stearns, Brett C. "Captive Husbandry and Propagation of the Aldabra Giant Tortoise." Int. Zoo Yb., Vol. 27, 1988, pp. 98-103.

Stoddart, D. R. "Retrospect and Prospect of Aldabra Research." Nature, March 15, 1969, pp. 1004-1006.

Stoddart, D. R. "The Aldabra Affair." Biological Conservation, 1974, pp. 63-69.

Swingland, Ian R. "Securing the Tortoises Future." Country Life, August 30, 1984, pp. 568-569.

Swingland, Ian R. "Aldabran Giant Tortoise." The Conservation Biology of Tortoises, Occasional Papers of the IUCN Species Survival Commission (SSC), No. 5, 1989.

Swingland, Ian R. and Klemens, Micheal W. (ed). The Conservation Biology of Tortoises. Occasional Papers of the IUCN. Species Survival Commission (SSC) No. 5 1985.