Biological Conservation 67 (1994) 49-56 CHOOSING A ROCK: PERSPECTIVES OF A BUSH-ROCK COLLECTOR AND A SAXICOLOUS LIZARD Christine A. Schlesinger & Richard Shine* School of Biological Sciences A 08, The University of Sydney, NS W 2006, Australia (Received 12 September 1992; revised version received 19 January 1993; accepted 4 March 1993) Abstract The illegal collection of loose surface rock ('bush-rock ') j~'om sandstone, granite and laterite outcrops, and its sale as decoration for suburban gardens, is widespread in southern Australia. We examined the microhabitat pref- erences 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 dis- turbed outcrops than in undisturbed areas, because large rocks are the main target of rock collectors. Measure- ments 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. Keywords." Australia, gecko, habitats, rock. INTRODUCTION In areas where there has been extensive man-induced loss of habitat, detailed information on the specific habitat requirements of resident species, and on the nature and extent of degradation, can provide a basis for assessing the extent to which particular taxa are threatened by changes in habitat availability. This in- formation may assist in the formulation of appropriate management strategies (e.g. Saunders, 1979; Recher, 1980; Milne & Hejl, 1988; Lindenmayer et al., 1990, 1991). One widespread example of habitat degradation in southern Australia is the commercial and private harvesting of loose or partially exposed pieces of surface rock from bush-land in the areas surrounding large cities. The rock, which is used mainly for orna- * To whom correspondence should be addressed. Biological Conservation 0006-3207/93/$06.00 © 1993 Elsevier Science Publishers Ltd, England. Printed in Great Britain 49 mentation in suburban gardens, is colloquially known as 'bush-rock' in the Sydney region, and 'moss-rock' around Perth and Adelaide. Although the extent of habitat destruction caused by this harvesting within the Sydney basin is poorly docu- mented, the commercial demand for bush-rock has increased dramatically during the past few decades as the city has expanded. Although bush-rock collection from Crown Land and State Forests was outlawed five years ago, it is still legally permissible to collect rocks from freehold land with the approval of the local council. Illegal collection of rocks also continues on Crown Land, in State Forests and in National Parks over a wide area of coastal New South Wales (e.g. Harvey, 1989; J. Sanders, pers. comm.). Most bush-rock occurs on ridge tops, where large areas of sandstone are exposed. Unfor- tunately, urban development (in particular the building of roads) often follows these ridge-tops, directly adding to the destruction of sandstone habitats as well as making outcrops more accessible for rock thieves. The rocks which are being removed provide shelter for a variety of fauna, primarily invertebrates, amphib- ians, reptiles and small mammals, all of which are frequently found in crevices beneath rocks. Bush-rock collection has been implicated as a cause of the decline in numbers and range of the endangered broad-headed snake Hoplocephalus bungaroides (Hersey, 1980; Shine & Fitzgerald, 1989). As well as removing important shelter items, bush-rock collectors may cause consider- able damage to vegetation in surrounding bush areas in order to gain vehicular access to outcrops (L. Llewellyn, pers. comm.). No attempt has been made to quantify the extent of the damage resulting from these activities. The amount of physical damage caused by rock collecting is not obvious because (a) most harvesting is done illegally and is thus not documented and (b) little is known of what constitutes a 'normal' amount of rock in an area. To date, there are no records of how much rock has been taken, purely anecdotal knowledge of which areas have been most affected, and little information on the specific habitat requirements of the animals which rely on the rocks for shelter. Hence, although there is a general awareness of the problem, the lack of specific information precludes any positive steps to mitigate these concerns.