Risk assessment models for establishment of exotic vertebrates in Australia and New Zealand Mary Bomford (2008) A report produced for the Invasive Animals Cooperative Research Centre i Invasive Animals Cooperative Research Centre Risk assessment models for establishment of exotic vertebrates in Australia and New Zealand. Report prepared for Invasive Animals Cooperative Research Centre Project 9.D.1: Invasive pest vertebrates: Validating and refining risk assessment models. Disclaimer: The views and opinions expressed in this report reflect those of the author and do not necessarily reflect those of the Australian Government or the Invasive Animals Cooperative Research Centre. The material presented in this report is based on sources that are believed to be reliable. Whilst every care has been taken in the preparation of the report, the author gives no warranty that the said sources are correct and accepts no responsibility for any resultant errors contained herein, any damages or loss whatsoever caused or suffered by any individual or corporation. Published by: Invasive Animals Cooperative Research Centre. Postal address: University of Canberra, ACT 2600. Office Location: University of Canberra, Kirinari Street, Bruce ACT 2617. Telephone: (02) 6201 2887 Facsimile: (02) 6201 2532 Email: [email protected] Internet: http://www.invasiveanimals.com ISBN: 978-0-9804999-7-1 Web ISBN: 978-0-9804999-8-8 © Invasive Animals Cooperative Research Centre 2008 This work is copyright. The Copyright Act 1968 permits fair dealing for study, research, information or educational purposes. Selected passages, tables or diagrams may be reproduced ii for such purposes provided acknowledgement of the source is included. Major extracts of the entire document may not be reproduced by any process. Cover design: Graphic Ark Cover images (left to right): Canada goose (Bill Jolly), stoat (Department of Conservation New Zealand), redfin perch (ACT Government) and brown anole (Carla Kishinami, Bishop Museum, Honolulu). Editor: Wendy Henderson (Invasive Animals Cooperative Research Centre) This document should be cited as: Bomford, M. (2008). Risk assessment models for establishment of exotic vertebrates in Australia and New Zealand. Invasive Animals Cooperative Research Centre, Canberra. Risk assessment models for establishment of exotic vertebrates Foreword Exotic vertebrates can establish wild pest populations that prey on livestock and poultry, compete with livestock for food, eat valuable crops and cause land degradation through overgrazing. Exotic vertebrates also prey on and compete with native species for food and other resources, and may directly and indirectly modify ecosystems. They may reduce the range and abundance of native species or even cause them to become extinct. Other harm potentially caused by exotic vertebrates includes spreading diseases and hybridising with native species. There is a risk that new exotic species could establish as wild pests in Australia. When animals escape or are illegally released they can start new populations in the wild that breed and spread. Once an exotic species is widespread, eradication is virtually impossible. Pre-import screening of exotic vertebrates is recognised as a primary and cost-effective tool to prevent the potential harm caused by exotic vertebrates. The Bureau of Rural Sciences produced this report for the Invasive Animals Cooperative Research Centre. The report provides information to assist government agencies increase public awareness and assess the risks posed by the import and keeping of exotic species. For example, the Australian Government Department of the Environment, Water, Heritage and the Arts has the agreement of the publisher and contributing authors to republish the information that is relevant to the risk assessment processes for assessing the suitability of exotic animals for live import into Australia. This agreement will facilitate the use of information and tools in this report for scientific-based risk assessment in informing decisions under the Environment Protection and Biodiversity Conservation Act 1999. iii Prof Tony Peacock Chief Executive Invasive Animals CRC Invasive Animals Cooperative Research Centre Contents Foreword ......................................................................................................................... iii Summary .......................................................................................................................... 1 Risk of establishment ............................................................................................1 Risk of adverse impact ..........................................................................................2 Glossary ........................................................................................................................... 4 1. Introduction ................................................................................................................. 5 1.1 Establishment .................................................................................................5 1.2 Impacts of exotic vertebrates ............................................................................8 1.2.1 Types of impact ...................................................................................8 1.2.2 Demonstrating impact ..........................................................................9 1.3 Assessing risk ...............................................................................................10 2. Exotic mammals and birds ......................................................................................... 12 2.1 Factors affecting the establishment success of exotic birds ....................................... 12 2.2 Factors affecting the establishment success of exotic mammals ..........................13 2.3 Risk assessment for the establishment of exotic mammals and birds introduced to Australia ..............................................................................14 2.4 Risk assessment for the establishment of exotic mammals and birds introduced to New Zealand .........................................................................15 2.5 Instructions for using the Australian Bird and Mammal Models ............................16 2.6 Instructions for using the New Zealand Bird and Mammal Models .........................29 iv 2.7 Factors affecting the pest status of exotic mammals and birds .............................32 3. Exotic reptiles and amphibians .................................................................................. 34 3.1 Introduction and release ................................................................................34 3.1.1 Reasons for introductions ...................................................................34 3.1.2 Reasons for release ...........................................................................35 3.1.3 Reasons for intentional or assisted spread ............................................37 3.1.4 Control and eradication ......................................................................37 3.2 Factors affecting the establishment success of exotic reptiles and amphibians .......38 3.2.1 Key factors affecting establishment success...........................................38 3.2.2 Other factors potentially affecting establishment success ........................42 3.3 Risk assessment for establishment of exotic reptiles and amphibians introduced to Australia ..............................................................................48 3.4 Instructions for using the Australian Reptile and Amphibian Model .......................51 3.5 Instructions for using the Bird and Mammal Model for reptiles and amphibians .......54 3.6 Instructions for using Bomford et al’s (2008) Reptile and Amphibian Model to rank establishment risk for exotic reptiles and amphibians introduced to Australia .....55 Risk assessment models for establishment of exotic vertebrates 3.7 Factors affecting assessments of the pest status of introduced reptiles and amphibians ........................................................................................61 3.7.1 Evidence reliability and impacts caused by confounding factors ................61 3.7.2 Sleepers, adaptation and niche changes................................................63 3.8 Adverse impacts and their significance for assessing pest status ..........................64 3.8.1 Competition for resources ...................................................................64 3.8.2 Predation ........................................................................................73 3.8.3 Habitat and ecological community impacts ............................................79 3.8.4 Potential to cause injuries ..................................................................82 3.8.5 Role as disease carriers and reservoirs ................................................83 3.8.6 Hybridisation with native species and other genetic changes ..................84 3.8.7 Social and economic impacts ...............................................................86 3.8.8 Other factors ...................................................................................88 3.9 Discussion of factors affecting pest status for introduced reptiles and amphibians ...90 4. Freshwater fish ........................................................................................................... 92 4.1 Factors affecting the establishment success of exotic freshwater