Small-scale field experiments provide important insights to restore the rock habitat of Australia's most endangered snake

Abstract

Habitat disturbance poses a major threat to biodiversity worldwide. The broad-headed snake (Hoplocephalus bungaroides) has become Australia's most endangered snake due to a dependence on rock habitats that are subject to high rates of human-induced degradation. The permanence of degradation can only be reversed by outcrop restoration. We constructed experimental outcrops near (<150 m) and far (>500 m) from roads and walking trails (access points). We tested two hypotheses over a 14-year period: that outcrop restoration can restore habitat quality, and that the frequency of outcrop degradation is influenced by distance from access points. We confirmed that habitat value was restored: lizard prey of the broad-headed snake was more abundant in constructed compared to natural outcrops; broad-headed snakes were detected equally in constructed and natural outcrops. Disturbance to constructed outcrops occurred more often and was more severe at near compared to far outcrops. The probability of occupancy by broad-headed snakes was 0.75 ± 0.13 in 29 far outcrops compared to 0.41 ± 0.11 in 35 near outcrops, suggesting a response to disturbance and more frequent poaching at near outcrops. Habitat restoration for the broad-headed snake should have its greatest value at locations far from access points. Restricting access should be a principal strategy to manage rock outcrop ecosystems. Outcrop disturbance is not unique to Australia. These findings have relevance to management of rock outcrops worldwide. Habitat restoration is an expensive conservation tool for endangered species, particularly if unsuccessful. Small-scale restoration experiments that aim to refine procedures should precede large-scale restoration.