A Survey of the Land Winkle <i>Pomatias elegans</i> (Müller, 1774) in the Burren, Co. Clare

Abstract

The first Irish colony of the land winkle Pomatias elegans was found in the Burren, Co. Clare, in 1976, but the site was never surveyed. From the 28 July to the 7 August 2000 the extent and abundance of the P. elegans population was established in this locality. Standard searches by three people for five minutes each were used to determine the distribution of the snails. Live specimens were found to occupy an area of approximately 9ha of limestone pavement south of the wall along the coastal road north of Cnoc an Bhoinrnn hill. Empty shells of P. elegans were found on a further 6ha of limestone immediately south of this area. No specimens were found in the area of grassland (5ha) that occurs within the limestone area. To estimate abundance, additional searches were camred out in standard areas of 2m2 following a stratified random sampling protocol. For this, the survey area was divided into rectangles of approximately 0.2ha using a differential GPS navigation system, and a single measurement was made at random within each rectangle. In order to estimate the fraction of the population that was found by this sampling procedure, a mark release-recapture sampling programme was carried out at three sites where the snail was known to be common. The mean density of P. elegans was calculated, and the minimum population was estimated to be 247,000 individuals. The precision of the sampling methods and the pressures of grazing and housing development on the site are bnrefly discussed.