Aim Snakes are more vulnerable to extinction than many other taxa. Additionally, their secretive behaviour makes it difficult to acquire the baseline ecological knowledge required to reliably evaluate extinction risks. Consequently, the conservation status of snakes has only been assessed for small populations; reliable methods for large-scale evaluation remain to be tested. In this study, we explored how habitat-suitability models (HSMs) could be used to provide relevant information to help

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... ess extinction risks and formulate appropriate conservation strategies for the Orsini's viper (Vipera ursinii), a rare, endangered snake species. Location Provence-Alpes-Côte d'Azur region in south-eastern France (c. 30,000 km²). Methods We developed a high-resolution HSM (50 9 50 m) using a large sample of species presence data and nine climatic and land cover predictors. We used this model to predict the potential distribution of the Orsini's viper as well as to investigate the main environmental drivers explaining this distribution. We also assessed the geographical barriers between local populations and tested whether forest cutting would reduce fragmentation. Results The occurrence of the Orsini's viper was strongly correlated with the annual cumulative temperature and with vegetation cover type. The total extent of suitable habitat covered 2.98% of the study area and was highly fragmented into 1417 distinct areas. Among these areas of suitable habitat, 21 were confirmed to have the species. These represented 22,134 ha and a potential carrying capacity of 168,000 individuals. Main conclusions Our HSM was consistent with the past assessment of the distribution of the Orsini's viper. Our HSM represents a sound benchmark for the distribution of the species and can provide a powerful tool to help with the search of new populations, the identification of areas for habitat restoration, the test conservation strategies and effects of climate change. We found that forest cutting may lead to reconnect close isolated areas of suitable habitat.