Feral goats (Capra hircus L.) in the Macleay River gorge system, north-eastern New South Wales, Australia. II. Impacts on rainforest vegetation
Philip Pisanu A B F , Paul Bayne A C , Robert Harden A D and Ann Eggert A EA NSW National Parks and Wildlife Service, c/- Zoology, University of New England, Armidale, NSW 2351, Australia.
B Current address: Department for Environment and Heritage South Australia, PO Box 39, Kingscote, SA 5223, Australia.
C Current address: 140 Mt Mitchell Road, Armidale, NSW 2530, Australia.
D Current address: 16 Perrott Street, Armidale, NSW 2530, Australia.
E Current address: 41 Redbank Road, Wauchope, NSW 2446, Australia.
F Corresponding author. Email: pisanu.phil@saugov.sa.gov.au
Wildlife Research 32(2) 111-119 https://doi.org/10.1071/WR03085
Submitted: 15 September 2003 Accepted: 21 December 2004 Published: 4 May 2005
Abstract
The impacts of feral goats in rainforests and thickets of the Macleay River system were studied. Rainforest floristics and diversity and goat browsing were measured over five years in a large-scale experiment with two experimental controls (density <1 goat km–2 and density ~20 goats km–2), and a goat-removal treatment (670-ha exclosure, initial density ~20 goats km–2). Feral goats browsed forb, shrub, tree and vine species. Sites with many goats were browsed at significantly higher levels than sites from which goats were removed and sites where goats occurred at very low density (<1 goat km–2). Contrary to findings in other studies, no plant species declined substantially where goat densities remained high throughout the study. Only the native forb Urtica incisa increased markedly following removal of goats. High goat numbers were not linked to increased exotic species abundances. At the community scale, species richness, diversity and evenness did not vary substantially among treatments in any year, nor did ordinations of sites (multidimensional scaling) reveal any pattern of site similarity between years that could be related to either goat presence or absence. Rainfall may have influenced plant density and masked the effects of feral goats. Rainforests in the region appear to be resilient to browsing under present feral goat densities, probably because goats feed predominantly in adjacent grassy woodlands and forests. However, we recommend a precautionary approach to feral goat management as these rainforests and thickets are of high conservation value.
Acknowledgments
Our sincere thanks to Glenn Cranfield and Lee-Anne Molony who provided invaluable field assistance during the project and to the landowners of the study area, Shane Andrews, Cliff Faint, Mike Saunders, Alan Waters, Phil Waters and New England Antimony Mines. We are also indebted to a number of staff at the University of New England: Graeme Moss for supervising AE, Ian Davies for statistical advice and John Williams for plant identification. Gwen Harden also assisted with plant identification and Chris Nadolny provided helpful criticism of the manuscript. Ken Pines and NPWS Armidale District Office assisted with the goat removal, which was undertaken in accordance with the protocols and procedures of the Feral Animal Aerial Shooting Training program (Anon. 1994) and the Australian Agricultural Council (Anon. 1991). The research was undertaken under NSW National Parks and Wildlife Service Scientific Investigation Licences A60 and B1655 and Animal Care and Ethics Committee Animal Research Authority #44.
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