The ground-based eradication of Norway rats (Rattus norvegicus) from the Isle of Canna, Inner Hebrides, Scotland

Seabird populations, particularly European shags (Phalacrocorax aristotelis) and Manx shearwater (Puffinus puffinus), on the Isle of Canna have been in decline for several years. Norway rats (Rattus norvegicus) were identified as the most likely factor. The Canna Seabird Recovery Project, developed as a result of this information, was a three year project incorporating the ground-based eradication of Norway rats (Phase I) followed by long-term monitoring, quarantine and contingency for rodents (Phase II) and continued long-term monitoring of the seabird populations (Phase III). The National Trust for Scotland (NTS) contracted Wildlife Management International Limited to direct the first and second phases of the project (August 2005-June 2008), with the assistance of NTS staff and volunteers. Techniques, problems, non-target species, (particularly wood mice (Apodemus sylvaticus) and white-tailed eagles (Haliaeetus albicilla)) issues, solutions and results of the operation on the permanently inhabited island are covered. Bait stations with cereal-based wax blocks containing diphacinone at 0.005% w/w were established on a fifty to one hundred metre grid over the island. Some offshore islets harboured rats, although some of the more sheer stacks did not. Interference with bait stations by non-target species was moderate to high, and bait stations required extra strengthening or protection to prevent damage or disturbance by cattle (Bos taurus), ponies (Equus caballus), sheep (Ovis aries), rabbits (Oryctolagus cuniculus) and hooded crows (Corvus corone cornix). Monitoring confirmed the successful eradication of rats from the Isle of Canna in June 2008. This provides another example of the effectiveness of ground-based rodent eradication techniques and provides an opportunity to restore the seabirds.