Saddle-backed Rodrigues giant tortoise
|Saddle-backed Rodrigues giant tortoise|
The saddle-backed Rodrigues giant tortoise (Cylindraspis vosmaeri) was a species of giant tortoises in the Testudinidae family. It was endemic to Rodrigues. The human exploitation caused the extinction of this species around 1800.
Both the saddle-backed tortoise, and its smaller domed relative, were descended from an ancestral species on Mauritius (an ancestor of Cylindraspis inepta), which colonised Rodrigues by sea many millions of years ago, and then gradually differentiated into the two Rodrigues species.
The saddle-backed Rodrigues tortoise was an exceptionally tall species of giant tortoises, with a long, raised neck and an upturned carapace, which gave it a giraffe-like body shape almost similar to that of a sauropod dinosaur.
It lived by browsing the taller vegetation, while its much smaller relative, the domed Rodrigues giant tortoise, grazed on low vegetation such as fallen leaves and grasses.
The saddle-backed tortoise was described by early colonists as a docile, gentle browser, with a tendency to gather in large herds, especially in the evening. An early Huguenot settler, in 1707, described the unusual group behaviour of these animals:
"There's one thing very odd among them; they always place sentinels, at some distance from the troop at the four corners of the camp, to which the sentinels turn their backs, and look with their eyes, as if they were on watch. This we have always observed of them; and this mystery seems the more difficult to be comprehended, for that these creatures are incapable to defend themselves..." (Leguat, 1707)
Behaviour and ecology
It has subsequently been discovered that the browsing herds of tortoises filled an essential role in the island's ecosystem and the regeneration of its forests. Among other roles, the tortoises ensured the dispersal and germination of the trees' seeds, as well as "terraforming" by maintaining forest clearings and pools.
In recognition of this fact, measures have been undertaken to introduce replacement species, in the form of similar giant tortoises from other parts of the world, to assist in the rebuilding of Rodrigues's devastated environment. The replacement species for the saddle-backed Rodrigues tortoise was chosen to be the Aldabra giant tortoise (Aldabrachelys gigantia) of the Seychelles, which is roughly similar in size, though very different in body form.
At the time of the arrival of human settlers, dense tortoise herds of many thousands were reported on Rodrigues. Typically for isolated island species, they were reported to have been friendly and unafraid of humans.
However, in the ensuing years, massive harvesting and exporting for food and the introduction of invasive alien species rapidly exterminated the tortoises. Tentative conservation efforts began in the 18th century, with the French Governor Mahé de Labourdonnais attempting to legislate against the "tortoise plundering" of Rodrigues. However the wholesale slaughter continued. Hundreds of thousands were loaded into ships' holds for food, or to be transported to Mauritius where they were burnt for fat & oil. Due to their unusually thin shells, many died from crushing as they were densely stacked in the base of ships.
In the final years, only smaller specimens were found, lingering in isolated mountainous refuges inland. A surviving tortoise was reported on the island in 1795, found at the bottom of a ravine. As late as 1802, there is mention of survivors reportedly being killed in the large fires used to clear the island's vegetation for agriculture, but it is not clear which of the two Rodrigues species these were, and which survived longest.
- Fritz Uwe; Peter Havaš (2007). "Checklist of Chelonians of the World". Vertebrate Zoology. 57 (2): 278–279. ISSN 1864-5755. Archived from the original (PDF) on 2010-12-17. Retrieved 29 May 2012.
- Leguat de la Fougère, François: Voyage et avantures de François Leguat & de ses compagnons en deux îles déserte des Indes Orientales. Amsterdam: J.J. de Lorme. 2 vols. 1707-8.
- Cheke, A., Hume, J.: Lost Land of the Dodo, An Ecological History of Mauritius, Réunion & Rordrigues. T & AD Poyser, London.2008.
- World Conservation Monitoring Centre 1996. Cylindraspis vosmaeri. 2006 IUCN Red List of Threatened Species. Downloaded on 28 July 2007.
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