Patterns of habitat use by three threatened mammals 10 years after reintroduction into a fenced reserve free of introduced predators

Abstract

Introduced predators are a major driver of global biodiversity loss. Over the last 200 years, the distribution and abundance of critical-weight-range mammals in Australia has declined, with many species now locally extinct or confined to small isolated refuges. From 2004 onwards as part of a major conservation initiative, the Australian Wildlife Conservancy reintroduced three threatened mammal species, the Greater Bilby (Macrotis lagotis), Bridled Nailtail Wallaby (Onychogalea fraenata) and Numbat (Myrmecobius fasciatus), into an 8000-hectare area protected by conservation fencing at Scotia Sanctuary in semi-arid New South Wales. Our study examined habitat selection for these species following multiple generations in a fenced area free of introduced predators.We used nocturnal spotlighting and diurnal search transect data collected over a two-year period to identify habitat preferences for these species, a decade after release. We used a Distance Sampling approach to examine differences in detectability between vegetation types, and Chi-Squared tests to identify differences in habitat use relative to availability. We used a Utilization Distribution (UD) analysis to identify how the spatial distribution of habitat affected its usage at Scotia Sanctuary. Habitat use of each species was compared with the results of a study conducted shortly after initial releases.We found that patterns of habitat use for these species differed to those identified following their initial release. We found a strong preference for shrub vegetation communities for all species relative to availability, as well as some variation in habitat preferences between two fenced areas (Stage 1 and Stage 2). The UD analysis revealed patterns of habitat use for one species (Bilby) that were not apparent from Chi-squared analysis, highlighting the importance of considering the spatial heterogeneity and proximity of different vegetation types when identifying species preferences.Our results demonstrate that in the absence of introduced predators these threatened species are able to use all of the vegetation types available, and by altering their habitat use over time, to persist following reintroduction into contemporary contexts within their historic ranges.