The successful eradication of introduced roof rats (Rattus rattus) from Buck Island using diphacinone, followed by an irruption of house mice (Mus musculus)

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. The successful eradication of introduced roof rats (Rattus rattus) from Buck Island using diphacinone, followed by an irruption of house mice (Mus musculus) Wildlife Research, 2007, 34, 108–115 www.publish.csiro.au/journals/wr CSIRO PUBLISHING