Literaturdatenbank
Literaturdatenbank |
|
 |
|
Walker, R. C., Whitmore, N., Rafeliarisoa, T. H., & Hamylton, S. , The effect of habitat degradation on the long term survival of the critically endangered madagascar spider tortoise (pyxis arachnoides) - 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 Unpublished paper presented at Program and Abstracts of the Tenth Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles.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: Walker2012e View all bibliographic details  |
Categories: General Keywords: Habitat - habitat, Madagaskar - Madagascar, Pyxis arachnoides, Schildkröten - turtles + tortoises, Testudinidae Creators: Hamylton, Rafeliarisoa, Walker, Whitmore Collection: Program and Abstracts of the Tenth Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles |
Views: 4/586
Views index: 12% Popularity index: 3% |
| Abstract |
|
Testudinidae Pyxis arachnoides inhabits the dry, coastal forests of southwest Madagascar; a biologically unique ecoregion severely threatened by unsustainable subsistence agricultural practices. Using remotely sensed data, we established vegetation loss remains unabated within our study area at 1.2% year -1; consistent with ecoregion wide vegetation loss between 1990 and 2000. We monitored tortoise population density on four occasions over eight years and developed a stage class projection matrix to model the finite growth rate, matrix sensitivities and elasticities of the population. Monitoring revealed an actual mean population decline of 10.8% between 2003 and 2011. Our projection matrix model suggested the finite rate of growth to be =0.986, indicative of 1.4% year-1 decline for the duration of the existence of the population, with adult survival as the most sensitive parameter to overall survival of the population. Projection modeling suggests that the population would likely become functionally non-viable in approximately 170 years. As our study was heavily reliant on the use of surrogate data, more information is needed on pre-adult survival and wild reproductive rates. Our study site currently represents a population of exceptional density; therefore, other less dense populations, subjected to the further stresses of poaching will likely become functionally non-viable much sooner. This study highlights the utility of population projection matrices in determining the vulnerability of chelonians; a globally threatened taxon. In the case of the Spider Tortoise, well-coordinated development programs and tighter protected area management are required to address the poverty-induced drivers forcing this species closer to extinction.
Added by: Admin |