Aldabra giant tortoise
Aldabra giant tortoise | |
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Beauval Zoo , France
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Testudines |
Suborder: | Cryptodira |
Superfamily: | Testudinoidea |
Family: | Testudinidae |
Genus: | Aldabrachelys |
Species: | A. gigantea
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Binomial name | |
Aldabrachelys gigantea (Schweigger, 1812)
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Synonyms[6] | |
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The Aldabra giant tortoise (Aldabrachelys gigantea) is a
Many of the Indian Ocean species were thought to be driven to extinction by over-exploitation by European sailors, and they were all seemingly extinct by 1840 with the exception of the Aldabran giant tortoise on the island atoll of Aldabra.[9] Although some remnant individuals of A. g. hololissa and A. g. arnoldi may remain in captivity,[9] in recent times, these have all been reduced as subspecies of A. gigantea.[6]
Description
The carapace of A. gigantea is a brown or tan in color with a high, domed shape. The species has stocky, heavily scaled legs to support its heavy body. The neck of the Aldabra giant tortoise is very long, even for its great size, which helps the animal to exploit tree branches up to a meter from the ground as a food source. Similar in size to the famous Galápagos giant tortoise, its carapace averages 122 cm (48 in) in length. Males have an average weight of 250 kg (550 lb).[10]
Females are generally smaller than males, with average specimens measuring 91 cm (36 in) in carapace length and weighing 159 kg (351 lb).[11] Medium-sized specimens in captivity were reported as 70 to 110 kg (150 to 240 lb) in body mass.[12] Another study found body masses of up to 132 kg (291 lb) most commonplace.[13]
Nomenclature and systematics
This species is widely referred to as Aldabrachelys gigantea, but in recent times, attempts were made to use the name
Four
- A. g. gigantea (Schweigger, 1812:327),[3] Aldabra giant tortoise from the Seychelles island of Aldabra
- A. g. arnoldi (Bour, 1982:118),[15] Arnold's giant tortoise from the Seychelles island of Mahé
- A. g. daudinii † (A.M.C. Duméril & Bibron, 1835:123),[4] Daudin's giant tortoise, from the Seychelles island of Mahé (extinct 1850)[6]
- Seychelles giant tortoise, from the Seychelles islands of Cerf, Cousine, Frégate, Mahé, Praslin, Round, and Silhouette
The subspecific name, daudinii, is in honor of French zoologist François Marie Daudin.[16]
Genetic evidence suggests that A. gigantea is most closely related to the extinct giant tortoise Aldabrachelys abrupta from Madagascar, from which it is estimaged to have diverged from approximately 4.5 million years ago.[17]
Range and distribution
The main population of the Aldabra giant tortoise resides on the islands of the
Another isolated population of the species resides on the island of
Ecology
Habitat
A peculiar habitat has coevolved due to the grazing pressures of the tortoises: "tortoise turf", a comingling of 20+ species of grasses and herbs. Many of these distinct plants are naturally dwarfed and grow their seeds not from the tops of the plants, but closer to the ground to avoid the tortoises' close-cropping jaws.
As the largest animal in its environment, the Aldabra tortoise performs a role similar to that of the elephant. Their vigorous search for food fells trees and creates pathways used by other animals.
Feeding ecology
Primarily
Little fresh water is available for drinking in the tortoises' natural habitat, so they obtain most of their moisture from their food.
The Aldabra giant tortoise has two main varieties of shells, related to their habitat. Specimens living in habitats with food available primarily on the ground have more dome-shaped shells with the front extending downward over the neck. Those living in an environment with food available higher above the ground have more flattened top shells with the front raised to allow the neck to extend upward freely.[citation needed]
Tortoise turf
The Aldabra giant tortoise is a herbivorous animal, spending much of its time browsing for food in its surrounding well-vegetated environment. The Aldabra giant tortoise is known to be found in places that are commonly known as "tortoise turf". Tortoise turf is composed of:[22][23]
- Bacopa monnieri
- Boerhavia elegans
- Bulbostylis basalis
- Cassia aldabrensis
- Cyperus dubius
- Cyperus ligularis
- Cyperus obtusiflorus
- Dactyloctenium pilosum
- Eragrostis decumbens
- Euphorbia prostrata
- Euphorbia stoddartii
- Evolvulus alsinoides
- Fimbristylis cymosa
- Fimbristylis ferruginea
- Hypoestes aldabrensis
- Lagrezia madagascariensis
- Lepturus repens
- Mollugo spergula
- Panicum aldabrense
- Phyllanthus maderaspatensis
- Pleurostelma cernuum
- Plumbaga aphylla
- Pycreus pumilus
- Ruellia monanthos
- Sclerodactylon macrostachyum
- Sida parvifolia
- Solanum nigrum
- Sporobolus testudinum
- Sporobolus virginicus
- Tephrosia pumila
Behavior
Aldabra tortoises are found both individually and in herds, which tend to gather mostly on open grasslands. They are most active in the mornings, when they spend time grazing and browsing for food. They dig wallows, hide under shade trees or in small caves, as well as submerge themselves in pools to keep cool during the heat of the day.
Lifespan
Large tortoises are among the longest-lived animals. Some individual Aldabra giant tortoises are thought to be over 200 years of age, but this is difficult to verify because they tend to outlive their human observers.
As of 2022,
Breeding
Mating takes place between February and May, and in July-September
In captivity, oviposition dates vary. Tulsa Zoo[28] maintains a small herd of Aldabra tortoises and they have reproduced several times since 1999. One female typically lays eggs in November and again in January, providing the weather is warm enough to go outside for laying. The zoo also incubates their eggs artificially, keeping two separate incubators at 27 °C (81 °F) and 30 °C (86 °F). On average, the eggs kept at the latter temperature hatch in 107 days.[26]
Conservation
The Aldabra giant tortoise has an unusually long history of organized conservation. Albert Günther of the British Museum, who later moved to the Natural History Museum of London, enlisting Charles Darwin and other famous scientists to help him, worked with the government of Mauritius to establish a preserve at the end of the 19th century. The related, but distinct, species of giant tortoise from the Seychelles islands, Seychelles giant tortoise A. g. hololissa and Arnold's giant tortoise A. g. arnoldi, were the subject of a captive-breeding and reintroduction program by the Nature Protection Trust of Seychelles.[29][30]
A reference genome and low-coverage sequencing analyses has looked at revealing within- and among-island genetic differentiation within the Aldabra population, as well as assigning likely origins for zoo-housed individuals. This has managed to differentiate between individuals sampled on Malabar and Grande Terre and resolve the exact origin of zoo-housed individuals.[31]
References
- .
- ^ "Appendices | CITES". cites.org. Archived from the original on 2017-12-05. Retrieved 2022-01-14.
- ^ a b Schweigger, Augustus F. (1812). "Prodromus monographiae Cheloniorum". Königsberger Archiv für Naturwissenschaft und Mathematik 1:271–368, 406–462.
- ^ a b Duméril, André Marie Constant, and Bibron, Gabriel. (1835). Erpétologie Générale ou Histoire Naturelle Complète des Reptiles. Tome Second. Paris: Roret.
- ^ a b Günther, Albert C.L.G. 1877. The Gigantic Land-Tortoises (Living and Extinct) in the Collection of the British Museum. London: Taylor and Francis, 96 pp.
- ^ a b c d Turtle Taxonomy Working Group [van Dijk, P.P., Iverson, J.B., Rhodin, A.G.J., Shaffer, H.B., and Bour, R.]. 2014. Turtles of the world, 7th edition: annotated checklist of taxonomy, synonymy, distribution with maps, and conservation status. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B., and Mittermeier, R.A. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs 5(7):000.329–479 Archived 2014-07-15 at the Wayback Machine, doi:10.3854/ crm.5.000.checklist.v7.2014.
- ^ Pritchard, Peter C.H. (1979) Encyclopedia of Turtles. Neptune, New Jersey: T.F.H. Publications, Inc. Ltd.
- (PDF) from the original on 2022-11-02. Retrieved 2022-11-02.
- ^ (PDF) from the original on 2022-12-22. Retrieved 2022-11-02.
- ^ "ANIMAL BYTES – Aldabra Tortoise". Seaworld.org. Archived from the original on 2018-02-03. Retrieved 2015-11-02.
- ^ "ANIMAL BYTES – Aldabra Tortoise". Seaworld.org. Archived from the original on 2018-02-03. Retrieved 2015-11-02.
- PMID 18461169.
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- ^ Bour, Roger (1982). "Contribution à la connaisance des tortues terrestres des Seychelles: définition du genre endémique et description d'une espéce nouvelle probablement originaire des îles grantiques & bord de l'extinction". Comptes Rendus de l'Académie des Sciences 295: 117–122. (Dipsochelys arnoldi, new species, p. 118). (in French).
- ISBN 978-1-4214-0135-5.
- PMID 36630487.
- ^ Payne, Roger (2004-04-05). "Losing Aldabra". Voyage of the Odyssey. PBS. Archived from the original on 2021-05-16. Retrieved 2008-10-21.
- ^ "Marine Parks: St. Anne". Seychelles National Parks Authority. Archived from the original on 2016-04-16.
- ^ Lambert, Jonathan (2021-08-23). "A giant tortoise was caught stalking, killing and eating a baby bird". Science News. Archived from the original on 2021-08-23. Retrieved 2021-08-23.
- PMID 34428417.
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- ^ Hnatiuk, R.J. and L.F.H. Merton (1979) "Vegetation of Aldabra, a Reassessment" Archived 2012-03-27 at the Wayback Machine. Atoll Research Bulletin No. 239, The Smithsonian Institution
- ^ "'Clive of India's' tortoise dies". BBC News. BBC Online. 2006-03-23. Archived from the original on 2019-05-30. Retrieved 2014-01-23.
- ninemsn. Archived from the originalon 2016-03-27. Retrieved 2016-03-25.
- ^ .
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- ^ Collins, Dave. (1984) "Captive Breeding and Management of the Aldabra Tortoise". Presented to 8th International Herpetological Symposium, Jacksonville Zoo, Jacksonville, Fl.
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- ^ Swingland, Ian R. Aldabran Giant Tortoise. The Conservation Biology of Tortoises, Occasional Papers of the IUCN Species Survival Commission (SSC), No. 5, 1989.
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