U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

Fall 2012


Human–Wildlife Interactions 6(2):212–221, Fall 2012


The brown treesnake (Boiga irregularis) is an invasive predator that was introduced on Guam as a stowaway in cargo after World War II. Since then, the population has exploded, attaining 50 to 100 snakes per ha in some areas. The snake has caused the extirpation of ten of the 12 native forest bird species on Guam. The U.S. Department of Agriculture, Wildlife Services, has a program to deter the spread of snakes from Guam to other islands. Hand capture from fences, trapping, toxic bait stations, and canine inspection of outbound cargo methods are used in the control program in various localized and accessible areas. We investigated aerial delivery of toxic baits as a potential method for a broader landscape control of brown treesnakes. Treated baits were deployed on 6-ha of forest at 37.5 baits per ha. Snake activity was reduced by 80 to 85% by the third application of toxicant. Non-target bait-take was limited. Of 80 telemetered baits aerially deployed, 30 (38%) baits were taken by snakes, one was taken by a toad (Bufo marinus), and one was taken by a monitor lizard (Varanus indicus). Mortality was observed in all 30 cases of bait-take by the snakes. No evidence of ill effects was observed in the toad or the monitor lizard after bait ingestion. Aerial delivery of toxic baits holds promise as an economical, targeted method to control invasive brown treesnakes over large areas of land.

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