Identifying unidirectional and dynamic habitat filters to faunal recolonisation in restored mine-pits

1. There is increasing evidence that passive faunal recolonisation of restored areas can take decades or even centuries, reducing benefits to biodiversity from restoration. Thus, there is a need to develop restoration and management strategies that facilitate and accelerate faunal recolonisation. This requires identification of habitat features that act as filters to slow or prevent recolonisation and whether those filters are temporally unidirectional or dynamic. 2. We investigated successional patterns of reptiles and mammals in restored mine-pits in south-western Australia to identify potential filters to faunal recolonisation. We sampled reptiles and small mammals using 30 trapping grids across each of four restoration ages (4, 8, 12 and 17-years old) and unmined forest and assessed vegetation structure to identify animalhabitat relationships. 3. Mammal communities in restored areas converged on unmined forest communities as restoration matured, and all species recolonised rapidly, indicating there were no filters to mammal recolonisation. In contrast, reptile communities did not converge in the same way, indicating there were filters that slowed or prevented reptile recolonisation. We identified three reptile species that were slow, or failed, to recolonise restored areas and a fourth species that rapidly recolonised but disappeared as restoration matured. We identified low coarse woody debris (CWD) volumes and high overstorey stem densities as likely filters; the former is a unidirectional filter that will decrease gradually over long time frames, possibly centuries, while the latter is a dynamic filter that fluctuates in its intensity over short time frames of years. 4. Synthesis and applications. Our study adds to growing evidence that filters to faunal recolonisation may be widespread in restored areas, with important implications for restoration practices. Firstly, examining individual species may more effectively identify filters than examining community successional patterns. Secondly, filters can persist over long time frames, possibly centuries, so management, such as the provision and accelerated development of CWD, may need to occur over similar time frames. Lastly, filters can be dynamic and repeated management interventions, such as thinning, may be required to overcome these filters. The growing evidence for filters suggests that facilitating faunal recolonisation is more complex than simply returning vegetation to restoration sites.