The initial impact of a predator exclosure sanctuary on small vertebrates in semi-arid Western Australia

Abstract

Predator exclosure reserves have become pivotal to conserving some threatened Australian mammalian fauna. However, the impact of predator exclosure reserves on resident (non-target) small vertebrates is less understood. Given the potential ecological consequences of fencing, and the contribution of small vertebrates to ecosystem processes, we investigated species' occupancy, and site colonization and extinction dynamics, inside and outside of a predator exclosure fenced area for nine small vertebrates (six reptile, three mammal). We conducted vertebrate surveying 4 years (2011–2014) pre- and 2 years (2015–2016) post-fence construction at the Australian Wildlife Conservancy Mt Gibson Sanctuary, in the semi-arid, critically endangered Wheatbelt Eucalypt Woodlands of Western Australia, to assess spatial and temporal trends in small mammal and reptile populations. Of nine species modelled, one reptile (Diplodactylus pulcher) decreased in occupancy inside of the fence following construction. We detected no negative impact of the predator exclosure fence on the remaining eight species. One native reptile species (Lerista kingi) and an introduced rodent (Mus musculus) increased occupancy inside (but not outside) the fenced area. Spatial and temporal occupancy inside and outside of the fenced area for all other modelled species was stable. Biotic (habitat) factors and stochastic interannual detectability were the most significant drivers of species' occupancy. Species-specific habitat associations were partially determined by site-based presence and absence probabilities. This suggests that the predator exclosure sanctuary either benefitted or had minimal impact on all but one modelled species. These results may be a useful reference for future fencing projects aimed at both conservation and land management.