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Brown Treesnakes

The brown treesnake, native to Australia, Indonesia, New Guinea and the Solomon Islands was brought to Guam accidentally through post World War II shipments of war materials. By the 1970s, native bird populations were absent from all but the northern third of Guam, and predation by the snakes was identified as the cause. Currently, of the 12 species of forest birds on Guam, only the Mariana crow, the Mariana gray swiftlet and the Micronesian starling survive in the wild, with the crow population near elimination on the island. The Guam rail and Micronesian kingfisher have been taken into captive breeding programs.

Bat populations declined along with the birds. Several species of lizards have become extinct or endangered due to the snakes. Additionally, brown treesnakes have become agricultural pests through depredations on chickens, pigeons, caged songbirds newborn pigs, kittens and puppies. The snakes are also economic pests as they climb utility poles and wires and cause frequent power outages.

Brown treesnakes may impact other islands in the future because they are well-suited to transport and are often found in military and commercial port areas. A federal program was implemented in 1993 to control the snakes and deter their dispersal from Guam. Reclamation of areas on Guam to benefit existing native wildlife, and detection of invasive populations outside Guam before they become a bigger problem are other objectives of the federal program.

It is estimated that the cost of brown treesnake-related power outages is conservatively $1 million per year and the cost of medical treatment of snake bites is $25,000 per year (Pimental et al. 1999). Control methods currently available include trapping, capturing through spotlight searches of fence lines, cargo inspection by detector dogs, oral toxicants, barriers, and cargo fumigation. Potential control methods and tools under investigation include dermal toxicants, repellents and irritants, contraception, and biological control.

Literature Cited

PIMENTAL, D., L. LACH, R. ZUNIGA, AND D. MORRISON. 2000. Environmental and economic cotsts of nonindigenous species in the United States. Bioscience 53: 53-65.

Links

Brown treensnake (Hawaii Department of Land and Natural Resources) http://www.aphis.usda.gov/lpa/pubs/fsheet_faq_notice/fs_wsbtsnake.html Invasivespecies.gov

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