Literaturdatenbank
Literaturdatenbank |
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Bourn, D., Gibson, C., Augeri, D., Wilson, C. J., Church, J., & Hay, S. I. (1999). The rise and fall of the aldabran giant tortoise population. Proceedings of the Royal Society of London - Biological Sciences, 266(1424), 1091–1100.
Added by: Admin (17 Aug 2008 18:54:42 UTC) Last edited by: Beate Pfau (19 Jun 2009 08:44:14 UTC) |
| Resource type: Journal Article BibTeX citation key: Bourn1999 View all bibliographic details  |
Categories: General Keywords: Aldabrachelys, Aldabrachelys gigantea, Geochelone, Habitat = habitat, Pazifik = Pacific, Schildkröten = turtles + tortoises, Systematik = taxonomy, Testudinidae Creators: Augeri, Bourn, Church, Gibson, Hay, Wilson Collection: Proceedings of the Royal Society of London - Biological Sciences |
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| Abstract |
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Testudinidae Geochelone gigantea Dipsochelys At the end of the 19th century, after prolonged and extensive harvesting, indigenous giant tortoises had been eliminated from all islands in the Indian Ocean, except Aldabra atoll, where only a few survived. With greatly reduced levels of exploitation during the 20th century, the population recovered to a revised estimated total of 129 000 in 1973 to 1974, when the first sample census was conducted. A repeat census in 1997 revealed a highly significant reduction in numbers over the past 24 years to an estimated total of 100,000. The great majority of tortoises are still found at relatively high density in south–eastern Grande Terre, where the number of animals has declined by more than a third. In contrast, low–density subpopulations on Malabar and Picard have almost doubled in size, but they represent less than 5% of the total population. Corroborative evidence for the crash in the Grande Terre subpopulation comes from two independent observations: a significant increase in tortoise mortality; and a significant decline in tortoise counts on long–term population monitoring transects. These population changes are attributed to natural population regulatory mechanisms, exacerbated by low rainfall years in the period 1980 to 1997, including two consecutive years of below average rainfall in 1995 to 1996 and 1996 to 1997. Added by: Admin Last edited by: Beate Pfau |