Successful rat eradication on Canna, Scotland

The National Trust for Scotland announced the successful removal of Brown Rats (Rattus norvegicus) from the island of Canna off the west coast of Scotland (57.0579°, -6.54564°). Part of the Inner Hebrides, Canna has been plagued with an estimated 10,000 rats threatening nesting Manx Shearwaters (Puffinus puffinus), European Shag (Phalacrocorax aristotelis), Atlantic Puffin (Fratercula arctica) and Razorbill (Alca torda). Human residents, some 13 islanders (down from 436 in 1821) were also troubled by the infestation. Eradication was complicated by the presence of a unique population of Wood Mice (Apodemus sylvaticus) of Norse lineage that needed to be captured and re-released after the program was complete. Beginning in 2005, 4,388 traps were placed following a carefully plotted grid across the five-mile-long island. Chocolate-flavored baits have been placed to detect rats by their distinctive nibblings and after 2 years the island has been declared officially rat-free. The project was funded by the European LIFE Nature fund and Scottish Natural Heritage and cost an estimated £500,000 or £50/rat. The Canna Wood Mice are not known to pose any threat to seabirds.

Nesting seabirds are rebounding quickly, with only 27 successful Razorbill nests in 2005 growing to 273 in 2007 and European Shag going from 48 pairs in 2005 to 72 pairs in 2007. Canna once held one of the largest Shag colonies in Europe. Manx Shearwater (once 1,500 nesting pairs) failed entirely as a breeder for the past 10 years but birds have continued to visit the island and have already raised at least one chick. Hopefully the population will quickly rebound to former numbers.