Choosing a rock: perspectives of a bush-rock collector and a saxicolous lizard

The illegal collection of loose surface rock ('bush-rock') from sandstone, granite and laterite outcrops, and its sale as decoration for suburban gardens, is widespread in southern Australia. We examined the microhabitat preferences of velvet geckos Oedura lesueurii, and the ways in which habitat availability for this species is affected by the removal of bush-rock. The geckos are found mostly under large (> 15 cm diameter) rocks lying on other rocks. These large rocks are much less common in disturbed outcrops than in undisturbed areas, because large rocks are the main target of rock collectors. Measurements on a sample of confiscated rocks suggest that rock thieves are selective with respect to rock shape as well as overall rock diameter, and hence that bush-rock removal may reduce the diversity of thermally distinctive shelters available to the lizards. In combination with laboratory studies showing that O. lesueurii use a complex series of structural and microclimatic criteria to select diurnal retreat sites, our fieldwork suggests that commercial bush-rock removal substantially degrades available habitat for these lizards, and presumably for other saxicolous fauna as well.