Use of acetaminophen for large-scale control of brown treesnakes

Because the brown treesnake (Boiga irregularis) has virtually extirpated th e avifauna on Guam and is a threat to other Pacific islands. the developmen t of alternative and efficient control methods is required. Therefore, we p erformed a large-scale field experiment to determine whether the acetaminop hen baits we developed could be used to reduce population levels of brown t reesnakes on Guam. Toxic baits were made by inserting 80 mg of acetaminophe n into dead neonatal mice, and these mouse bails were used to treat plots. Reference plots were baited with unadulterated baits. We used mark-recaptur e methods to estimate snake abundance on plots before treatment, monitored bait-take rates on treated plots for 30 days, and used mark-recapture to es timate snake populations post-treatment. Bait-take rates were reduced on tr eated plots by 83% relative to reference plots after 14 days, when they rea ched an asymptote. Using a robust design model in program MARK, snakes on r eference plots had higher apparent survival rates ((x) over bar = 0.3505) t han those on treated plots ((x) over bar = 0.0072) for the duration of the study, but estimates were influenced by snake movement between plots. When we accounted for movement using a multistrata model. survival on treated pl ots was estimated as zero. High mobility of brown treesnakes presents diffi culty for complete removal of snakes from large areas, but we conclude that acetaminophen baits may provide an effective and selective management tool for quickly and efficiently reducing populations of brown treesnakes on Gu am.