Substantial reductions of brown tree snake (Boiga irregularis) populations in blocks of land on Guam through operational trapping

Two plots of land on opposite sides of Apra harbor in Guam that had been operationally trapped to remove brown tree snakes were subjected to further trapping at greater intensity to assess the remaining populations of snakes. Trapping in both plots was only terminated after at least 4 weeks without a capture. Only 2 snakes were captured in a 4.2 ha plot and 4 were captured in a 6.5 ha plot. Tagged snakes were released into an adjacent plot that was across a road from the 6.5 ha plot and had a bordering trap line as a barrier to deter snakes from exiting it into other plots or wharf areas. None of these snakes was found to have passed through the barrier trap line and crossed the road. Operational trapping methods were concluded to be highly effective in this developed area where optimal forested snake habitat occurs in a patchy distribution.