Madagascar’s cryptic reptiles

by Alexandra Evans, MSc student. Supervisors: Profs. Jason Marshal and Graham Alexander.

Madagascar is home to a host of fascinating organisms that are found nowhere else on earth. Some species are restricted to a single lake or a particular type of forest, and exhibit unique adaptations to their habitats. It is this fine-scale endemicity, as well as considerable deforestation through logging and agriculture, that puts many of Madagascar’s rarer species at risk of extinction.Terrestrial reptiles are of particular concern, as there has not been sufficient research into their distribution patterns and habitat-use to know which areas to prioritise in conservation. More than 90% of Malagasy reptiles are endemic to the island. Of these, the forest species are of special interest to me – while surveying reptile presence in north-western Madagascar in 2017 with Operation Wallacea, I was struck by how the variety of species could change from one habitat patch to the next.






To get a realistic picture of the occurrence of rare or cryptic species can be challenging – on some surveys, it would be easy to miss a Malagasy ground boa hidden under some fallen leaves, or a Henkel’s leaf-tailed gecko camouflaged to a tree’s bark. I will be using occupancy modelling to tackle this issue of imperfect detection, along with satellite imagery to assess how factors such as vegetation structure (important for shelter, hunting and basking) and proximity to roads and settlements affect the occurrence of more than 50 species.
I am particularly interested in how the occurrence patterns of threatened reptile species compare to those of more common species. Species that are more sensitive to habitat changes have often been more isolated, spatially or otherwise, in their evolutionary histories, and so are highly reliant on specific resources – these species tend to be classified as Threatened by the IUCN, as they are most at risk of extinction from habitat transformation. Understanding which combinations of environmental conditions support these reptile species could go a long way in helping us to conserve areas support them.