The successful eradication of introduced roof rats (Rattus rattus) from Buck Island using diphacinone, followed by an irruption of house mice (Mus musculus)
Gary W. Witmer A E , Frank Boyd C and Zandy Hillis-Starr DA USDA National Wildlife Research Center, 4101 Laporte Avenue,
B Fort Collins, CO 80521-2154, USA.
C USDA Wildlife Services, Extension Hall, Room 118, Auburn University, Auburn, AL 36849-5656, USA.
D Christiansted National Historic Site and Buck Island Reef National Monument, 2100 Church Street #100, Danish Custom’s House, Kings Wharf, St Croix, US Virgin Islands 00821, USA.
E Corresponding author. Email: Gary.W.Witmer@aphis.usda.gov
Wildlife Research 34(2) 108-115 https://doi.org/10.1071/WR06006
Submitted: 11 January 2006 Accepted: 19 February 2007 Published: 24 April 2007
Abstract
The United States National Park Service and the United States Wildlife Services made a planned and sustained effort to eradicate the introduced roof rats (Rattus rattus) from Buck Island Reef National Monument in the Caribbean Sea during 1998–2000. The rats were causing substantial damage to a variety of the 80-ha island’s floral and faunal resources. An island-wide grid of elevated bait stations containing anticoagulant (0.005% diphacinone; 50 ppm) rodenticide bait blocks were used to eradicate the rats. The bait stations were modified several times to assure ready access by rats while minimising access by non-target animals, especially crabs and birds. Numerous post-project trapping sessions over six years resulted in no rat captures, suggesting that, indeed, the rats had been eradicated from the island. No non-target losses resulting from the baiting program were observed by field personnel, but they noted what appeared to be a recovery of some of the island’s floral and faunal resources. There have been no depredations of endangered sea turtle nests since the eradication. Post-project monitoring sessions revealed the presence of a growing house mouse (Mus musculus) population on the island. The threats posed by, and potential management strategies for, this introduced pest species are being investigated. This is the first successful rat eradication on a sizable island, using diphacinone bait blocks with a unique, elevated bait-station system. Diphacinone can provide an alternative to the highly toxic brodifacoum and may help reduce non-target hazards in some situations, although several applications are generally required.
Acknowledgements
The rat-eradication project was conducted under Interagency Agreement No. 1443IA500009905 between the NPS and WS. We especially thank NPS Park Superintendent Joel A. Tutein for hosting WS and facilitating the work. NPS personnel, BrendaLee Phillips, Philippe Mayor and Kimberly Woody, assisted in many ways. Marianne Jensen, WS Budget Assistant, greatly assisted in the management of the project, personnel, and budget. Dr Earl Campbell, FWS (formerly with WS), provided useful advice on the project. The tireless efforts of WS field staff (Kelly Ladner, Chad Fuqua, Trae Noblett, Allen Gosser, Joyce Wakefield, Ashley Rossi, Pedro Quinones, Doug Hall, Ken Garner, Damon Hughes and James Rebholz) allowed the success of the project. We appreciate the review comments of Michael Fall, Susan Jojola and several anonymous reviewers.
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