Wildlife Research Wildlife Research Society
Ecology, management and conservation in natural and modified habitats

Testing island biosecurity systems for invasive rats

James C. Russell A D , Brent M. Beaven B , Jamie W. B. MacKay A , David R. Towns C and Mick N. Clout A
+ Author Affiliations
- Author Affiliations

A School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.

B Stewart Island Field Centre, Department of Conservation, PO Box 3, Stewart Island 9846, New Zealand.

C Research, Development & Improvement Division, Department of Conservation, Private Bag 68908, Auckland 1145, New Zealand.

D Corresponding author. Email: j.russell@auckland.ac.nz

Wildlife Research 35(3) 215-221 https://doi.org/10.1071/WR07032
Submitted: 9 March 2007  Accepted: 25 September 2007   Published: 20 May 2008


Rats continue to invade rat-free islands around the world, and it remains difficult to successfully intercept them before they establish populations. Successful biosecurity methods should intercept rats rapidly, before they can establish a population. Current island biosecurity practice employs techniques used for high-density rat eradication, assuming that they will be equally effective on low-density invaders. However, such approaches are often untested. Adult male Norway rats (Rattus norvegicus) were individually released onto forested rat-free islands in New Zealand to test methods of detecting and eliminating a single invader. Only half the rats released were caught within a two-week timeframe, although the mean time to interception was just under 14 days. Permanent island biosecurity surveillance systems performed better than contingency responses. Success rates were higher on islands where complete coverage could be obtained, although surveillance systems using multiple devices eventually detected most invading rats. For some rats a change of methods was necessary. Single invading rats left a rat-free island despite the presence of excessive natural food resources. With surveillance systems comprising an array of tested island biosecurity devices, and where necessary a contingency response using alternative methods, it should be possible to maintain islands as rat-free even when they have a high reinvasion rate.


Thanks to Phred Dobbins, Dane Springmeyer, Melanie Harsch, Alex Hoffmeier, Lucas Morgan and Sarah Hagopian for rat monitoring on Ulva. Thanks to Jo Peace and Jane Dudley for rat monitoring on the Noises. Thanks to the Department of Conservation rodent dog team members Fin Buchanan and Natasha Coad (Jak, Tama and Macy) who provided their services free of charge. We are grateful to the Neureuter family trust for permission to work on The Noises, and Ngati Manuhiri and Department of Conservation Warkworth for permission to work on Hawere. Thanks also to the Department of Conservation Auckland Area Office boat crew for field transport, and the Leigh Marine Laboratory for access to boating equipment. Thanks to John McCallum for permission to trap rats on Pakihi Island and the Karamuramu (Quarry) Island workers for regular transport to Pakihi. Paul Keeling (‘Ditch’) helped advise on methods of detecting and trapping small mammals. This research was funded by the Department of Conservation and performed with University of Auckland animal ethics approval and Department of Conservation high-impact research approval. Financial support was provided to JCR by the New Zealand Department of Conservation, a Top Achiever Doctoral Scholarship, University of Auckland Doctoral Scholarship and Edward and Isabel Kidson Scholarship. Amanda Todd, Mike Thorsen, Charlie Daugherty and three anonymous referees provided useful comments on earlier versions of the manuscript.


Airey A. T., and O’Connor C. E. (2003). Consumption and efficacy of rodent baits to Norway rats. DOC Science Internal Series 148. Department of Conservation, Wellington.

Bramley, G. N. , Waas, J. R. , and Henderson, H. V. (2000). Responses of wild Norway rats (Rattus norvegicus) to predator odors. Journal of Chemical Ecology 26, 705–719.
CrossRef |

Brigham A. J., and Sibley R. M. (1999). review of the phenomenon of neophobia. In ‘Advances in Vertebrate Pest Management’. (Eds D. P. Cowan and C. J. Feare.) pp. 67–84. (Filander Verlag: Furth.)

Brown, K. P. , Moller, H. , Innes, J. , and Alterio, N. (1996). Calibration of tunnel tracking rates to estimate relative abundance of ship rats (Rattus rattus) and mice (Mus musculus) in a New Zealand forest. New Zealand Journal of Ecology 20, 271–275.

Burbidge, A. A. (2004). Montebello Renewal: Western Shield review – February 2003. Conservation Science Western Australia 5, 194–201.

Burwash, M. D. , Tobin, M. E. , Woolhouse, A. D. , and Sullivan, T. P. (1998). Laboratory evaluation of predator odors for eliciting an avoidance response in roof rats (Rattus rattus). Journal of Chemical Ecology 24, 49–66.
CrossRef |

Chappell R. (2004). Motutapere Island rodent invasion 2004. Internal report, file ISL 0013. Department of Conservation, Coromandel.

Clout M. N., and Russell J. C. (2006). The eradication of mammals from New Zealand islands. In ‘Assessment and Control of Biological Invasion Risks’. (Eds F. Koike, M. N. Clout, M. Kawamichi, M. De Poorter and K. Iwatsuki.) pp. 127–141. (IUCN: Gland.)

Courchamp, F. , Chapuis, J.-L. , and Pascal, M. (2003). Mammal invaders on islands: impact, control and control impact. Biological Reviews 78, 347–383.
CrossRef | PubMed |

Cowan, P. E. (1977). Neophobia and neophilia: new-object and new-place reactions of three Rattus species. Journal of Comparative and Physiological Psychology 91, 63–71.
CrossRef |

Cunningham D. M., and Moors P. J. (1996). Guide to the identification and collection of New Zealand rodents. Occasional Publication No. 4, 3rd edn. Department of Conservation, Wellington.

Dilks P. J., and Towns D. R. (2002). Developing tools to detect and respond to rodent invasions of islands: workshop report and recommendations. DOC Science Internal Series 59. Department of Conservation, Wellington.

Esler A. E. (1975). Goat Island, Leigh. Unpublished report. Botany Division, Department of Scientific and Industrial Research, Auckland.

Hoare, J. M. , and Hare, K. M. (2006). The impact of brodifacoum on non-target wildlife: gaps in knowledge. New Zealand Journal of Ecology 30, 157–167.

Howald, G. , Donlan, C. J. , Galván, J. P. , Russell, J. C. , and Parkes, J. , et al. (2007). Invasive rodent eradication on islands. Conservation Biology 21, 1258–1268.
CrossRef | PubMed |

Inglis, I. R. , Shepherd, D. S. , Smith, P. , Haynes, P. J. , Bull, D. S. , Cowan, D. P. , and Whitehead, D. (1996). Foraging behaviour of wild rats (Rattus norvegicus) towards new food and bait containers. Applied Animal Behaviour Science 47, 175–190.
CrossRef |

Jay, M. , Morad, M. , and Bell, A. (2003). Biosecurity, a policy dilemma for New Zealand. Land Use Policy 20, 121–129.
CrossRef |

Lacey, E. A. , and Solomon, N. G. (2003). Social biology of rodents: trends, challenges, and future directions. Journal of Mammalogy 84, 1135–1140.
CrossRef |

Macdonald D. W., Mathews F., and Berdoy M. (1999). The behaviour and ecology of Rattus norvegicus: from opportunism to kamikaze tendencies. In ‘Ecologically-based Rodent Management’. (Eds G. R. Singleton, L. A. Hinds, H. Leirs and Z. Zhang.) pp. 49–80. (Australian Centre for International Agricultural Research: Canberra.)

MacKay, J. W. B. , and Russell, J. C. (2005). Ship rat Rattus rattus eradication by trapping and poison-baiting on Goat Island, New Zealand. Conservation Evidence 2, 142–144.

McFadden I. (1991). Rat invasion – Noises Islands. Internal report, file FAU 609-01. Department of Conservation, Auckland.

Mittermeier R. A., Gil P. R., Hoffman M., Pilgrim J., Brooks T., Mittermeier C. G., Lamoreux J., and da Fonseca G. A. B. (2005). ‘Hotspots Revisited: Earth’s Biologically Richest and Most Endangered Terrestrial Ecoregions.’ (Conservation International; Washington, DC.)

Moors P. J. (1985a). Eradication campaigns against Rattus norvegicus on the Noises Islands, New Zealand, using brodifacoum and 1080. In ‘Conservation of Island Birds’. (Ed. P. J. Moors.) Technical Publication No. 3. pp. 143–155. (International Council for Bird Preservation: Cambridge.)

Moors, P. J. (1985b). Norway rats (Rattus norvegicus) on the Noises and Motukawao Islands, Hauraki Gulf, New Zealand. New Zealand Journal of Ecology 8, 37–54.

Moors, P. J. , Atkinson, I. A. E. , and Sherley, G. H. (1992). Reducing the rat threat to island birds. Bird Conservation International 2, 93–114.

O’Connor, C. E. , and Eason, C. T. (2000). Rodent baits and delivery systems for island protection. Science for Conservation 150,[Department of Conservation: Wellington.]

Orueta, J. F. , Aranda, Y. , Gómez, T. , Tapia, G. G. , and Sanchez-Mármol, L. (2005). Successful eradication of invasive rodents from a small island through pulsed baiting inside covered stations. Biological Invasions 7, 141–147.
CrossRef |

Pitman, R. L. , Ballance, L. T. , and Bost, C. (2005). Clipperton Island: pig sty, rat hole and booby prize. Marine Ornithology 33, 193–194.

Russell J. C. (2007). Invasion ecology and genetics of Norway rats on New Zealand islands. Ph.D. Thesis, University of Auckland.

Russell J. C., and Clout M. N. (2005). Rodent incursions on New Zealand islands. In ‘Proceedings of the 13th Australasian Vertebrate Pest Conference’. (Eds J. Parkes, M. Statham and G. Edwards.) pp. 324–330. (Landcare Research: Lincoln.)

Russell, J. C. , Towns, D. R. , Anderson, S. H. , and Clout, M. N. (2005). Intercepting the first rat ashore. Nature 437, 1107.
CrossRef | PubMed |

Russell J. C., Towns D. R., and Clout M. N. (in press). Review of rat invasion biology: implications for island biosecurity. Science for Conservation. Department of Conservation, Wellington.

Russell P. A. (1983). Psychological studies of exploration in animals: a reappraisal. In ‘Exploration in Animals and Humans’. (Eds J. Archer and L. I. A. Birke.) pp. 22–54. (Van Nostrand Reinhold: Cambridge.)

Smith, D. A. , Ralls, K. , Davenport, B. , Adams, B. , and Maldonado, J. E. (2001). Canine assistants for conservationists. Science 291, 435.
CrossRef |

Sowls A. L., and Byrd G. V. (2002). Preventing rat introductions to the Pribilof Islands, Alaska, USA. In ‘Turning the Tide: the Eradication of Invasive Species’. (Eds C. R. Veitch and M. N. Clout.) p. 413. (IUCN SSC Invasive Species Specialist Group, IUCN: Gland.)

Spurr E. B., O’Connor C. E., Morriss G. A., and Turner J. (2006). Bait station preferences of Norway rats. DOC Research & Development Series 255. Department of Conservation, Wellington.

Spurr E. B., Morriss G. A., Turner J., O’Connor C. E., and Fisher P. (2007). Bait station preferences of ship rats. DOC Research & Development Series 271. Department of Conservation, Wellington.

Taylor, K. D. , Hammond, L. E. , and Quy, R. J. (1974). The reactions of captive wild rats (Rattus norvegicus) to human odour and to the odour of other rats. Mammalia 38, 581–590.

Thomas B. W., and Taylor R. H. (2002). history of ground-based rodent eradication techniques developed in New Zealand, 1959–1993. In ‘Turning the Tide: the Eradication of Invasive Species’. (Eds C. R. Veitch and M. N. Clout.) pp. 301–310. (IUCN SSC Invasive Species Specialist Group, IUCN: Gland.)

Thomas, M. D. , Brown, J. A. , and Henderson, R. J. (1999). Feasibility of using wax blocks to measure rat and possum abundance in native forest. Proceedings of the New Zealand Plant Protection Conference 52, 125–129.

Thorsen, M. , Shorten, R. , Lucking, R. , and Lucking, V. (2000). Norway rats (Rattus norvegicus) on Frégate Island, Seychelles: the invasion, subsequent eradication attempts and implications for the island’s fauna. Biological Conservation 96, 133–138.
CrossRef |

Towns D. R., Daugherty C. H., and Atkinson I. A. E. (1990). Ecological restoration of New Zealand islands. Conservation Sciences Publications No. 2, Department of Conservation, Wellington.

Towns, D. R. , Atkinson, I. A. E. , and Daugherty, C. H. (2006). Have the harmful effects of introduced rats on islands been exaggerated? Biological Invasions 8, 863–891.
CrossRef |

Wace, N. M. (1986). The rat problem on oceanic islands – research is needed. Oryx 20, 79–86.

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