Informing the space between zero and one: a standardised, scat-based approach to monitoring changes in habitat use by brush-tailed rock-wallabies (Petrogale penicillata)

Abstract

Rock-wallabies occupy outcrops, escarpments and cliffs that incorporate structurally complex refuges; because of this, local populations present methodological challenges for monitoring purposes. We describe the development and adaptive modification of a survey technique intended to measure changes in rock-wallaby activity on a site-by-site basis. Twenty spatially independent field sites were collectively sampled across two geological strata using transects consisting of regularly spaced sampling points, with concentric series of fixed-radius circular plots at each sampling point used to count numbers of fresh/recent and/or older rock-wallaby scats. The presence/absence of fresh and/or recently deposited scats was identified as likely to be the more sensitive measure of changing use. Indexes of Activity (IoA) at each field site were subsequently obtained by transect-based sampling at 10 m intervals using 2 m fixed-radius circular plots and recording the presence/absence of fresh/recent scats therein. Derived rock-wallaby IoA ranged between 0.13 and 0.94 across the 20 sites and were approximately normally distributed. Central tendency measures associated with the IoA metrics imply some potential to develop management-themed activity thresholds. Further refinement and potential applications of the approach are discussed.