Human-induced pressures such as climate and land-use changes in the Anthropocene disproportionately threaten island ecosystems and the endemic species they host. Shedding light on the ecological needs of island species is key to the conservation of these fragile ecosystems and their unique species. Here we present the ecological needs of a bat species endemic to Sardinia, the long-eared bat Plecotus sardus, and analyse the relationship between this Critically Endangered species and the insular environment at different spatial scales to inform action for its conservation. We show that besides displaying a unique phenology and roost use, the species is closely associated with the dry broadleaf forests of native oaks Quercus ilex and Quercus suber at all scales and, in contrast, is negatively affected by coniferous stands, open pastures and urban environments. Our results not only provide key information for the conservation of P. sardus but also provide insights into the unique adaptations of insular endemic species to the fragile island ecosystems, highlighting the importance of ecological studies to informing conservation in biodiversity hotspots. We also demonstrate that protection and restoration of key habitats, particularly within 2 km of roosts, are key to protecting the few known reproductive colonies.