title: Rat eradication comes within a whisker! A case study of a failed project from the South Pacific.
abstract: To enhance their conservation value, several hundred islands worldwide have been cleared of invasive alien rats, Rattus spp. One of the largest projects yet undertaken was on 43 km(2) Henderson Island in the Pitcairn group, South Pacific, in August 2011. Following massive immediate mortality, a single R. exulans was observed in March 2012 and, subsequently, rat numbers have recovered. The survivors show no sign of resistance to the toxicant used, brodifacoum. Using pre- and post-operation rat tissue samples from Henderson, plus samples from around the Pacific, we exclude re-introduction as the source of continued rat presence. Microsatellite analysis of 18 loci enabled comparison of genetic diversity of Henderson rats before and after the bait drop. The fall in diversity measured by allele frequency change indicated that the bottleneck (N e) through which the breeding population passed was probably around 50 individuals, representing a census population of about 60-80 animals. This is the first failed project that has estimated how close it was to success.
authors.affiliation: Department of Zoology , University of Cambridge , Downing Street, Cambridge , UK.
authors.forename: W
authors.initials: W
authors.lastname: Amos
authors.affiliation: Department of Zoology, University of Cambridge, Downing Street, Cambridge, UK; School of Natural Science and Psychology, Liverpool John Moores University, Liverpool, UK.
authors.forename: H J
authors.identifier: 0000-0002-4455-6065
authors.initials: HJ
authors.lastname: Nichols
authors.affiliation: RSPB Centre for Conservation Science, Royal Society for the Protection of Birds , Sandy , UK.
authors.forename: T
authors.initials: T
authors.lastname: Churchyard
authors.affiliation: Department of Zoology , University of Cambridge , Downing Street, Cambridge , UK.
authors.forename: M de L
authors.initials: Mde L
authors.lastname: Brooke
keywords: Henderson Island; Pitcairn Islands; Rattus exulans; brodifacoum; genetic diversity; heterozygosity