Local Distribution and Habitats
Located just north of the Tropic of Capricorn, Heron Island (23°26′31.20″S 151°54′50.40″E) is a small coral cay, belonging to the Capricorn Group on the Southern Great Barrier Reef, Queensland, Australia (Rohde 1981). It is approximately 300 m and 900 m in diameter and is composed of mainly lithified coral sand and beachrock (Rohde 1981).
On Heron Island, P. sulcatus are predominantly found on beachrock formations that extends for the most parts, the southern beaches (Southside) and to a smaller extend on the northern side (North Beach) of the island (Rohde 1981). Populations of P. sulcatus are found to occur almost exclusively on the upper parts of the beachrock formation on the Southside of Heron Island, which are exposed during low tides (Rohde 1981). They occur in distinct, isolated clusters, mostly in crevices between adjacent rocks and depressions of beachrock during low water (Rohde 1981).
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Local environment on Heron Island and P. sulcatus habitat. (A) Aerial view of Heron Island.
The area highlighted in red (Southbeach), marked the area at which the population survey of
P. sulcatus was conducted in October 2011. Populations of P. sulcatus are found to occur
almost exclusively on the upper parts of the beachrock formation on the Southside of the
Island (B) Beachrock Environment found along Southbeach. (C) P. sulcatus exposed on the
beachrocks during low tide on Heron Island. (D) Beach Rock formation along Southbeach.
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A population density estimate survey was conducted during a field trip to the island on October 2011. Using stratified random sampling techniques and 100 1m X 1m transects, the density of P. sulcatus on the Southside of Heron Island was estimated to occur at approximately 22 individual snails per m2 of beachrock surveyed. Approximately 600 m of beachrock on the Southside of the island was covered during the survey in October 2011.
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