RAPID HERPETOFAUNAL SURVEYS WITHIN FIVE ISOLATED FORESTS ON SEDIMENTARY ROCK IN WESTERN MADAGASCAR

Among the most threatened Madagascar ecosystems are the dry deciduous forests situated in the western portion of the island. Associated with varying sedimentary geological substrates, a high degree of microendemism can be found within these habitats. However, they are biologically poorly known and under severe human pressure. We present the first scientific data related to the herpetofaunal communities of five forest relicts resting on sedimentary rock: the Makay sandstone Massif, the Ankara and Kelifely sandstone Tablelands, and the Nosy-Ambositra and Beronto Forests that repose on limestone outcrop. We recorded 70 species (55 reptiles, 15 amphibians) in these habitats. Approximately 97% (n = 68) of these species are endemic to Madagascar and 60% (n = 42) were found exclusively in forest habitats. Sixty-four (91%) of the species are considered endemic to the western dry deciduous forest. A single species was confined to rock outcrops. The field survey data indicate a south-north clinal change in the herpetofauna assemblages occurring at these sites, which is concordant with the north-south biogeographical patterns associated with primates.