Brown tree snakes effectively removed from a large plot of land on Guam byperimeter trapping

The brown tree snake introduction to Guam has had serious environmental, ec onomic and social consequences. Trapping brown tree snakes in the vicinitie s of ports and other cargo staging facilities is central to a program imple mented to deter its dispersal from Guam. Trapping forested plots on their p erimeters has been an efficient and effective trap placement strategy for r emoving brown tree snakes from plots up to 8.4 ha. Here we examined whether this trap placement strategy was effective on a 17.8 ha plot, over twice t he size of plot for which there was solid evidence of perimeter trapping's efficacy. We found that brown tree snakes were removed according to an expo nential decay function. From 7 weeks on of trapping, snake captures had dec lined to low steady state levels that may best reflect population recruitme nt in the plot. After 22 weeks of trapping, both the plot interior and peri meter were trapped in a second phase designed to determine if the central p ortion of the plot contained reservoirs of brown tree snake populations. Th e second trapping phase lasted for 8 weeks and produced the same low, stead y state capture rates as the final 16 weeks of the first phase that used on ly perimeter trapping. Only five snakes were captured in the plot interior in the second phase. We concluded that perimeter trapping removed brown tre e snakes throughout the plot and the strategy could be applied to larger pl ots than demonstrated previously. Published by Elsevier Science Ltd.