Distribution, habitat associations and conservation implications of Sri Lankan freshwater terrapins outside the protected area network

Terrapins are integral to many freshwater ecosystems, yet are imperilled at a global scale. In Sri Lanka, terrapins are understudied; thus, much of their natural history and distribution status remain unknown. Such paucity of studies impedes conservation. In this study, 79 freshwater habitats located outside the protected area network of south-western Sri Lanka were surveyed to document current population densities and habitat use of two terrapin species: Indian black terrapin (Melanochelys trijuga thermalis) and flap-shelled terrapin (Lissemys ceylonensis). Local inhabitants were interviewed to assess human threats towards terrapins. Both species were recorded in low densities: 1–2 individuals ha−1. Indian black terrapin was found in half of the surveyed sites while flap-shelled terrapin occurred in one-third of the surveyed sites. Highly urbanized river basins had the lowest densities for both species while rural basins supported higher numbers. Basking was the predominant behaviour of both species and large woody debris and boulders were preferred as basking substrates, together with sparse-canopy aquatic habitats with intact marshlands. Overharvesting for meat was a major threat for terrapins. Most local inhabitants were unaware of legislation on terrapin conservation and the ecological importance of terrapins. Human threats such as pollution, modification of aquatic and wetland habitats, and loss of riparian forests were frequently observed in surveyed sites. Terrapin populations outside the protected area are at risk as evidenced by lower population densities and a multitude of human threats. A landscape-scale ecosystem-based conservation approach is recommended for Sri Lanka's terrapins with incorporation of lands with different management regimes (privately owned, municipality managed) into the protected area network. Current environmental legislation should be revised to support buffer zone delineation for aquatic habitats, wetland restoration, and landscape-scale connectivity.