Regional faunal decline – reptile occurrence in fragmented rural landscapes of south-eastern Australia
Geoff W. Brown A D , Andrew F. Bennett B and Joanne M. Potts A CA Arthur Rylah Institute for Environmental Research, Department of Sustainability and Environment, 123 Brown Street, Heidelberg, Vic. 3084, Australia.
B School of Life and Environmental Sciences, Deakin University, 221 Burwood Highway, Burwood, Vic. 3125, Australia.
C Present address: Centre for Research into Ecological and Environmental Modelling, The University of St Andrews, The Observatory, Buchanan Gardens, St Andrews, Fife KY16 9LZ, Scotland.
D Corresponding author. Email: geoff.brown@dse.vic.gov.au
Wildlife Research 35(1) 8-18 https://doi.org/10.1071/WR07010
Submitted: 22 January 2007 Accepted: 17 December 2007 Published: 17 March 2008
Abstract
Many species of reptiles are sedentary and depend on ground-layer habitats, suggesting that they may be particularly vulnerable to landscape changes that result in isolation or degradation of native vegetation. We investigated patterns of reptile distribution and abundance in remnant woodland across the Victorian Riverina, south-eastern Australia, a bioregion highly modified (>90%) by clearing for agriculture. Reptiles were intensively surveyed by pitfall trapping and censuses at 60 sites, stratified to sample small (<30 ha) and large (>30 ha) remnants, and linear strips of roadside and streamside vegetation, across the regional environmental gradient. The recorded assemblage of 21 species was characterised by low abundance and patchy distribution of species. Reptiles were not recorded by either survey technique at 22% of sites and at a further 10% only a single individual was detected. More than half (53%) of all records were of two widespread, generalist skink species. Multivariate models showed that the distribution of reptiles is influenced by factors operating at several levels. The environmental gradient exerts a strong influence, with increasing species richness and numbers of individuals from east (moister, higher elevation) to west (drier, lower elevation). Differences existed between types of remnants, with roadside vegetation standing out as important; this probably reflects greater structural heterogeneity of ground and shrub strata than in remnants subject to grazing by stock. Although comparative historical data are lacking, we argue that there has been a region-wide decline in the status of reptiles in the Victorian Riverina involving: (1) overall population decline commensurate with loss of >90% of native vegetation; (2) disproportionate decline of grassy dry woodlands and their fauna (cf. floodplains); and (3) changes to populations and assemblages in surviving remnants due to effects of land-use on reptile habitats. Many species now occur as disjunct populations, vulnerable to changing land-use. The status of reptiles in rural Australia warrants greater attention than has been given to date. Effective conservation of this component of the biota requires better understanding of the population dynamics, habitat use and dispersal capacity of species; and a commitment to landscape restoration coupled with effective ecological monitoring.
Acknowledgements
The efforts of many people, notably staff of the (then) Victorian Department of Natural Resources and Environment (NRE) at the Heidelberg (Arthur Rylah Institute for Environmental Research), Benalla, Nathalia and Cohuna offices, ensured the completion of this study and their input is gratefully acknowledged. In particular, members of the NRE ‘Remnant Habitat’ team, David Hespe, Steffan Krasna, Lindy Lumsden and John Silins, contributed mightily to the installation and monitoring phases of the project. ARIER colleagues Phoebe Macak and Arn Tolsma drafted the map, and Michael Scroggie provided comments on early drafts of this paper. Barbara Baxter (Department of Sustainability and Environment, East Melbourne) provided access to records of the Atlas of Victorian Wildlife database, and Joern Fischer (Australian National University) generously made available unpublished data. This study was funded by the Murray–Darling Basin Commission through its Natural Resources Management Strategy (NRMS) program.
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