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Walker, R. C., Rafeliarisoa, T. H., Currylow, A. F., & Louis, E. E. , The rapid decline in population density of southern madagascar’s tortoises - abstract. Unpublished paper presented at Program and Abstracts of the Tenth Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles.
Added by: Admin (06 Jan 2014 18:23:14 UTC) |
| Resource type: Conference Paper BibTeX citation key: Walker2012f View all bibliographic details  |
Categories: General Keywords: Astrochelys radiata, Habitat - habitat, Madagaskar - Madagascar, Pyxis arachnoides, Schildkröten - turtles + tortoises, Testudinidae Creators: Currylow, Louis, Rafeliarisoa, Walker Collection: Program and Abstracts of the Tenth Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles |
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| Abstract |
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Testudinidae Geochelone Of the four extant endemic tortoise species in Madagascar, one of the largest; the Radiated Tortoise (Astrochelys radiata) and one of the smallest; the Spider Tortoise (Pyxis arachnoides) are sympatric and endemic to the xeric spiny forests of coastal southern Madagascar. Both of these species share IUCN Red Listing as Critically Endangered and are listed in Appendix I of CITES. These species are exhibiting dramatic and precipitous population declines as a result of habitat loss and collection for the illicit international pet market and consumption locally as bush meat. Some authors have suggesting that more than hundreds of thousands of tortoises are removed from the wild each year southern Madagascar. To assess this perceived rapid decline, we devised a population density monitoring program using a conventional line distance sampling methodology, within the core of the range of both species. During February 2010 and February 2012, we repeated surveys across 28 and 17 1-km transects for Spider and Radiated Tortoises respectively, and analyzed the data through post stratification by year. Across this two-year period, we found a mean decrease in density of 37.5% spider and 28.6% Radiated Tortoises. Mean tortoise density dropped from 2.4 Spider (95% CL; 1.6-3.4) and 2.1 Radiated (95%CI 1.2-3.5) tortoises per hectare to a mean of 1.5 (95% CL; 0.8-2.8) and 1.5 (95% CI 0.7-3.3) animals per hectare. These catastrophic declines most likely represent one of the most rapid declines of any species of chelonian worldwide and are indicative of the fate faced by the two species of Dispsochelys tortoises that were rapidly driven to extinction soon after the colonization of Madagascar by humans, 2000 years ago. An effective and rapidly implemented strategy for addressing the anthropogenic threats facing these species is required to prevent a further extinction episode within Madagascar’s chelonians.
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