The northern Madagascar spider tortoise (Pyxis arachnoides brygooi), is endemic to the coastal Mikea forests of southwest Madagascar. Very little is known of P. a. brygooi's ecology; however, it is suspected that the range is now very fragmented, with remaining populations facing significant threats from habitat destruction and poaching for food and the pet trade. A line-transect survey was undertaken that systematically surveyed the suspected historical range of this subspecies. The results were incorporated into a GIS database, which revealed that the distribution was confined to 20.5% of the suspected historical range, across three fragmented populations covering 499.6 km². It appears that a zone of intergradation has developed in a transitional area between the southern range of P. a. brygooi and the northern range of P. a. arachnoides. The results of this survey are currently being applied to management plans for newly gazetted protected areas in the region, in an effort to safeguard these relatively small remaining populations.