Tagging and location preferences to inform post-release monitoring of the Greater Bermuda land snail Poecilozonites bermudensis

Abstract

The Greater Bermuda land snail Poecilozonites bermudensis was once thought to be extinct in the wild, however, recent captive population increases have allowed reintroductions to take place. Post-release monitoring of reintroduced individuals is a fundamental component of the reintroduction process and requires individuals or groups to be identifiable. In this study, a novel method of identification through tagging (using Alpha fluorescent tags glued to sanded and non-sanded shells) was assessed in a captive population (n=400) at Chester Zoo. Tag loss rate and snail survival was monitored over six months, and the location preferences of the snails within their tanks was also recorded under different conditions (day/night, dry/wet) in order to inform survey methods in their native habitat. The tagging method is recommended based on a 0% tag loss rate over the study period, although sanding was unnecessary and had a negative effect on survival. Environmental conditions should be taken into account when planning post-release monitoring surveys. Under dry daytime conditions, more snails were found in higher areas, whilst snails were more likely to be found in both high and rocky areas during wet daytime conditions. During darkness, most snails were found on rocks and in the leaf litter. A consistent low number of snails were found buried within the soil. These results will inform the post-release monitoring of this species, enabling more accurate population and survival estimates to be made, and could act as a model for other reintroduction projects for land snail species.