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

Multi-Agency Effort Aims to Reduce Invasive Brown Treesnakes on Guam Using Aerial Baits

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Gail Keirn (970) 266-6007

Carol Bannerman (301) 851-4093

WASHINGTON, August 29, 2013 -- The Wildlife Services program of the U.S. Department of Agriculture's Animal and Plant Health Inspection Service and partners from the Department of Defense (DoD), Department of the Interior, and the Guam Department of Agriculture will begin a series of aerial broadcasts of acetaminophen-treated mice baits this September to reduce the population of invasive brown treesnakes (BTS) on Guam.

“This effort is a culmination of over 15 years of research. Since 1995, WS scientists and operations personnel have systematically developed and evaluated tools and strategies to control brown treesnakes safely and effectively. These tools include snake traps, baiting stations, snake-sniffing detector dogs at ports and airports, chemical repellents, and fumigants,” states Daniel Vice, WS Assistant State Director on Guam.  “The successful aerial delivery of an effective chemical control agent is a critical next step towards developing a method for large area control of brown treesnakes and reaching snakes in remote and inaccessible areas of Guam.”

Starting in September and continuing for approximately 16 months, WS experts and their partners will deploy acetaminophen-treated dead mouse baits attached to biodegradable corn starch streamers designed to snag onto branches in the dense tree canopy where the snakes feed. The baits will be dropped from helicopters. The goal of the $1.3 million project funded by DoD's Environmental Security Technology Certification Program is to significantly reduce the BTS population at two, 55-hectare (135-acre) jungle sites within Andersen Air Force Base.  The results of the project will be documented and used to guide future efforts to control or eradicate the BTS population island-wide. 

Extensive scientific research, field observations, and video monitoring -- in addition to the findings of the environmental assessment required for this effort -- confirm that this method is humane to snakes and presents little risk to nontarget species. BTS ingesting the small dose of acetaminophen (80 milligrams) will die within about 24 hours with no signs of distress. Given the baits are hung in trees, distributed at low densities, and eaten quickly by the snakes, there will be very limited exposure of the baits to nontarget species.  Moreover, this project poses no risk to humans, and aquatic life will not be affected because there is no surface water present in the targeted areas.

The BTS is an invasive species unintentionally introduced to Guam in the late 1940s.  With no native predators, the snake's population in Guam has grown to an estimated 1 to 2 million.  The BTS is responsible for the extinction of most native bird, bat, and lizard species on the island.  The BTS has also caused extensive economic damage to the island’s economy and electrical grid, costing an estimated $1 to 4 million annually in lost productivity due to power outages. 

The unintentional movement of BTS as a result of shipping or travel represents a very real danger to all islands in the western Pacific basin and sections of the U.S. mainland.  The economic costs of potential BTS colonization to the Hawaiian Islands alone are estimated to be as high as $2 billion annually -- in addition to the severe ecological damage the snake would cause to native birds and other wildlife.  Since 1993, more than 150,000 BTS have been removed from the transportation system alone in Guam.  A result of these successful Federal, State, and local cooperative efforts is that no live BTS have been detected at Hawaiian ports-of-entry in almost 20 years. 

“Though our containment efforts have been highly successful and we’ve kept the snakes from getting off Guam, we’re now expanding our focus to remove snakes from the more remote areas on the island. With these new tools and strategies, our brown treesnake management efforts may soon be making even bigger strides toward our ultimate goal of reintroducing native birds to the island,” notes Vice. “It’s an exciting time to be working on this project.”

For more information on WS’ efforts to manage brown treesnakes and protect endangered species on Guam, please visit

The WS is a program with the USDA Animal and Plant Health Inspection Service.  Its mission is to provide Federal leadership and expertise to resolve wildlife conflicts to allow people and wildlife to coexist. The program’s efforts help people resolve wildlife damage to a wide variety of resources and to reduce threats to human health and safety. Funding for the WS Program is a combination of federal appropriations and cooperator-provided funds.

The National Wildlife Research Center is the research arm of the WS program.  It is the only Federal research organization devoted exclusively to resolving conflicts between people and wildlife through the development of effective, selective, and socially responsible methods, tools, and techniques.


Note to Reporters: To offer the news media an opportunity to observe these activities and learn more about the brown treesnake issue, a media event is scheduled for Tuesday, October 1, on Guam.  A required orientation session with agency representatives will begin at 8:00 am local time.  Demonstrations of the aerial bait drop, bait manufacturing, and other brown treesnake management activities will follow the orientation meeting and are expected to conclude by 1:00 pm.  Space for media representatives is limited and requests will be accommodated on a first-come, first-served basis. To participate, please contact Gail Keirn at 970-266-6007 ( by September 17, 2013 to ensure adequate time to obtain security clearance.



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