A noodle in a haystack: determining the conservation status of the rare and Data Deficient Ravensthorpe Range slider, Lerista viduata

Context One-seventh of the ~157,000 species assessed by the IUCN Red List of Threatened Species are Data Deficient (DD), with insufficient information to assess their extinction risk. Such a statistic is concerning from a conservation perspective because more than half are predicted to be threatened by extinction, yet they are generally neglected from conservation priority. Aims Here, we aimed to improve ecological knowledge, and inform the conservation status of, the DD Ravensthorpe Range slider (Lerista viduata), a historically rare skink confined to Western Australia’s Ravensthorpe Range. Methods A detailed framework was developed to improve data on attributes integral to the species’ IUCN Red List assessment (e.g. distribution, threats, population size): collation of historical records, fieldwork within and around its known range, preserved specimen analysis, on-ground and spatial analysis of threats, and inference from ecologically similar species. Key results We found that L. viduata is threatened under multiple IUCN Red List criteria (B1ab[i,ii,iii,v], B2ab[i,ii,iii,v], C2ab[ii], D2), and overall should be considered Critically Endangered. This status is based on its Extent of Occurrence (32 km2) being <100 km2, occurrence at one location (defined by the threat of fire), and an inferred continuing decline in its distribution and habitat parameters. The species’ small estimated population size (3,514–9,276 mature individuals) also renders it extinction prone. Conclusions We demonstrate that L. viduata, long perceived as DD, should be reclassified as Critically Endangered, and is of the utmost conservation concern. Implications Our study reiterates the need for DD species to receive greater consideration in conservation research and action.