Census method for estimating the population size of the endemic and threatened land snail Iberus gualtieranus gualtieranus

Iberus gualtieranus gualtieranus is an endemic and threatened land snail inhabiting south–eastern Spain. Because it seeks shelter in karstic fissures when inactive, detection is difficult, and censuses may be biased. In this study, a methodology is developed to take an adequate census of this subspecies. The census was performed in the population of Sierra Elvira when the probability of detection was the highest, minimizing the bias. The results show that this population is patchy and has about 500,000 specimens. However, this subspecies is probably vulnerable to extinction as only three isolated populations are known and it is threatened by several factors. The census method in this study may be useful to conserve this endemic species. Key words: Iberus g. gualtieranus, Census technique, Population size, Distribution.