The study site is an area of coastal dunes in the southwest corner of Bold Park (3185700600S, 11584502100E), in City Beach, Perth. The site comprises areas Acacia I and Open I of Johnson (1980), with an abrupt (,5 m) transition between a
dense thicket of Acacia rostellifera bushes and low, sparse dune vegetation. Snails were censused in autumn or winter (late March to early August) each year from 1977 to 2010, along a transect across the two habitats. The transect comprised contiguous 5 m 5 m quadrats, except in the western (shoreward) portion of the Open habitat, where the dune vegetation was patchy and quadrats were placed within the inhabited vegetation only. The length of the transect sampled varied among years and low numbers of snails in the Open habitat in some years reduced the number of quadrats censused. Furthermore, over the course of the study the Acacia habitat spread 20 m
along the transect, reducing the area of the Open habitat. On
average, 15.5 quadrats were censused in the Acacia habitat
(range 7–23) and 7.7 quadrats in the Open habitat (range 4–
15).