No abstract

Chameleons of the Madagascan endemic genus Brookesia Gray are small to extremely small reptiles with a mostly terrestrial lifestyle, and due to their low mobility and their camouflage they are nearly invisible in the leaf litter of Madagascar's forests. The genus Brookesia is widely distributed (except in the arid south and south-west) but many Brookesia species are restricted to a relatively small area of the island (Glaw & Vences 2007). Speciation has been most prolific in the northern parts of Madagascar, an area that currently host about two-thirds of the 27 nominal Brookesia species (Raxworthy & Nussbaum 1995; Glaw & Vences 2007; Townsend et al. 2009).

The Madagascar spider tortoise Pyxis arachnoides is endemic to the coastal dry forests of south-west Madagascar. In recent years its range has been reduced by c. 71%, with the species now confined to eight fragmented populations occupying a total of 2,464 km 2 . These remaining populations are facing a significant threat of extinction because of habitat destruction and other anthropogenic pressures. We developed methodology for a line transect distance sampling survey and applied it systematically across the species' range. The resulting distance model estimated a mean density of 226.9 tortoises km −2 (95% confidence interval, CI, 168.1-306.3) and a total population of 664,980 (95% CI 492,680-897,550). Fragmentation of the species' range suggests the current population could be , 30% of the historical population. Of the remaining population 73.5% falls within protected areas. However, nine of these 12 protected areas are designated as IUCN category III, V or VI parks, allowing some extractive activities to be undertaken. The most effective strategy for the conservation of P. arachnoides would be to reduce the threats to this species and its habitat, and to develop and expand the current community-based conservation and poverty alleviation programmes in the region.