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The South West Madagascar Tortoise Survey Project

  • Wednesday, 05 May 2010 23:00
Walker, R.C.J. - End of phase 2 preliminary report to donors and supporters


This summary report documents phase two of the South West Madagascar Tortoise Survey Project (formally the Madagascar Spider Tortoise Conservation and Science Project). The project has redirected focus during this second phase, to concentrate research and survey effort for
both of southern Madagascar’s threatened tortoise species; Pyxis arachnoides and Astrocheys radiata.

The aims and objectives of this three phase project, were developed during the 2008 Madagascar Tortoise and Freshwater Turtle IUCN/SSC Red Listing and Conservation Planning Meeting held in Antananarivo, Madagascar.

This project now has five research objectives:

  • Establish the population density and current range of the remaining populations of P. arachnoides and radiated tortoise A. radiata.

  • Assess the response of the spider tortoises to anthropogenic habitat disturbance and alteration.

  • Assess the extent of global internet based trade in Madagascar’s four endemic, Critically Endangered tortoise species.

  • Assess the poaching pressure placed on radiated tortoises for the local tortoise meat trade.

  • Carry out genetic analysis on the three subspecies of spider tortoise and confirm that they are indeed three subspecies and at what geographical point one sub species population changes into another.

The field work undertaken during this second phase was undertaken by a team of British, American and Malagasy researchers from a number of conservation and research institutions.

This second phase concentrated effort in surveying the current range of the common spider tortoise sub species; P. a. arachnoides. Results show that populations are extinct within the vicinity of Toliara, however there are reasonably healthy and intact populations between the
 Onilahy and Linta Rivers.

Results suggest that there is a zone of intergradation in the Linta River region whereby P. a. arachnoides and P. a. oblonga mix within a  transitional zone, similar to the intergradation discovered between P. a. brygooi and P. a. arachnoides during phase one of the project towards the north of the species range. This intergradation has prompted a genetics study whereby ~300 blood samples were collected across P. arachnoides’ range encompassing individuals from all three subspecies, plus the two populations of intergrades between these sub species,
undertaken during this second phase.

This second phase of the project undertook a comprehensive population and poaching pressure assessment of the remaining populations of radiated tortoises A. radiata, in the coastal zone between Toliara and Cap Sainte Marie Special Reserve. Results suggested the northern  extremities of the species’ range now only spreads as far north as Tsimanampetsotsa National Park region. Tortoises occurred in greatest numbers within and around the Cap Sainte Marie region. Evidence of poaching pressure was greatest between the Linta and Menarandra Rivers.

The third year of this projects’ capture recapture study to investigate the effects of habitat disturbance to a population of P. arachnoides, revealed a year on year decline (2003, 2009 and 2010).

During this second phase of the project, a Madagascar tortoise internet trade monitoring program was set up, leading to the reporting of two suspicious trade activities of these CITES Appendix I species to the relevant national wildlife trade enforcement authorities.

Phase two of the project supported and facilitated the fieldwork of a herpetology PhD student from the University of Antananarivo, undertaking studies into the biogeography of A. radiata.

Results documenting phase one of this project to date comprise five manuscripts submitted to peer review journals. Results of the range wide population assessment of P. a. brygooi were presented at the 7th Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles (August 2009). Further to this results gained exposure through a number of media outlets.

The project continues to work alongside WWF Madagascar and the Turtle Survival Alliance through the provision of results to these NGOs, with the aim of formulating sound conservation management initiatives for the long term survival of these threatened species.

Phase two of this project stayed within its £11,070 ($16,900) budget.

Phase one and two of this project comprise what is the most comprehensive assessment to date into the conservation status of P. arachnoides and A. radiata.