It has been 27 years since Dr. Julie Savidge and other biologists first took notice of the invasive Brown Treesnake’s impacts on Guam’s native birds. Savidge (now of Colorado State University) was one of the first to document the snake’s predatory role in the demise of the bird community on Guam. Today, we are aware not only of this snake’s invasion legacy on Guam but also of the growing threat it poses to other Pacific islands.

To prevent a similar ecological catastrophe, the U.S. Geological Survey, in partnership with other federal agencies and island governments, is developing ways to stop brown treesnake invasions. The devastation the snake has wrought on Guam, as well as the island’s role as a major transportation hub on the Pacific, underscores the critical nature of the work underway.

This nocturnal, tree-dwelling snake has attacked Guam on three fronts:

• Ecology — The snake has eliminated 11 of 13 species of forest bird and has reduced or eliminated several native lizard species and at least one mammalian species. Its ability to shift from eating birds to rodents or lizards has enabled the snake to reach and maintain densities of as many as 13,000 per square mile.
  

• Health — This mildly venomous snake can threaten human health, particularly that of infants and small children, which the snake seems to seek out for attack. In recent years, roughly one of every 1,000 emergency room visits on Guam has been due to brown treesnake bites.
  

• Economy — The snake triggers frequent power outages when climbing among utility lines or coming into contact with exposed wiring, costing Guam as much as $4.5 million per year.  If the snake invaded and became established on Oahu, Hawaii, with that island’s dense human population and many at-risk ecosystems, losses could exceed $400 million annually.

Numerous federal, state, and territorial agencies, as well as cooperators from other island nations, are coordinating efforts to reduce the snake’s ecological and economic impacts in the region. They are especially focused on methods of preventing the snake from reaching or becoming established on other islands or the continental United States. Much of this work is funded through the U.S. Department of the Interior’s Office of Insular Affairs and the Department of Defense.

USGS is leading the effort in three major areas of this work:

• Snake Detection and Capture Research — Detecting brown treesnakes is vital for preventing infestation of normally snake-free locations, such as Oahu and Saipan (Commonwealth of the Northern Mariana Islands). It takes only one gravid (pregnant) female snake to establish a population in a new location. Therefore, resource-management agencies in state and territorial governments and the U.S. Department of Agriculture’s Wildlife Services need research-proven methods to detect the snakes at very low densities. To address that need, USGS develops and   tests detection techniques at its research facilities on Guam.   In one study, USGS investigators are assessing expanding the use of detector dogs to locate the snakes in complex forested environments; USDA and others already use dogs to detect brown treesnakes at port facilities.   USGS scientists and their cooperators are also testing visual-search techniques, trapping methods and toxicants. These projects investigate how prey type and density, snake size and other factors influence the effectiveness of control tools for detecting and capturing snakes.
  

• Rapid Response Team Training — The Brown Treesnake Rapid Response Team plays a critical role in keeping the snake from establishing on islands other than Guam. The team, which USGS coordinates from Guam, is available to respond to snake sightings on otherwise snake-free islands throughout the Pacific region. Comprising approximately 60 trained personnel from   multiple agencies and cooperators throughout the Pacific, the team is on call 24/7. A key goal is to train members residing on islands with a high risk of snake invasion (those receiving   aircraft and shipping from Guam). Local team members are the first and best line of defense because they can respond quickly to sightings, increasing chances of finding and capturing a snake. Typically, when an islander reports a snake, the USGS Guam office also assists at the request of the agency involved in the response. Nonetheless, the USGS team is highly dependent on the availability and skill of trained local searchers.
   
    Initial training for team members includes an 18-day course on Guam. With the island’s abundance of brown treesnakes, opportunities for reinforcement of each trainee’s “search   image” (ability to spot these snakes in the forest) are frequent. The course involves a mixture of lectures, workshops and extensive field training. During the course, instructors stress safety during fieldwork and when handling snakes, as well as how to process and respond to reports   of sightings.
   
    Those already on the team periodically take five-day refresher courses that focus on snake-search techniques and incorporate insights from recent USGS research.
  

• Outreach and Education — This component of preventing invasions involves working with officials from the Federated States of Micronesia, the Republic of Palau and the Republic of the Marshall Islands. These countries receive direct flights and cargo shipments from Guam,   putting them at high risk of snake invasions. The Rapid Response Team coordinator’s role during trips to these islands is to increase public awareness of the snake and its potential impacts and to develop working relationships with host-country personnel.
   
    Residents are usually the first to become aware of a new invasive species in their area. However, for the team to harness local knowledge, residents must recognize the invader as new and worthy of reporting. They must also find and call a local phone number to report the sighting to someone who speaks their first language. USGS personnel help local authorities by publicizing the importance of reporting the snakes. They also provide materials that aid residents in recognizing the snakes and list phone numbers for reporting sightings. Furthermore, team leaders can offer local authorities the benefit of past experiences, sharing ways to work through jurisdictional concerns when consolidating pest-reporting pathways.
   
  Given that snakes successfully stow away in planes and cargo ships with alarming frequency, and that these carriers load and unload in Micronesia, working hand-in-hand with Pacific islanders is imperative. Through outreach and education — two of the Rapid Response Team’s main tools for maintaining vigilance — USGS is increasing the likelihood that arriving snakes will be sighted, reported and captured. Outreach and education efforts have contributed to the timely capture of brown treesnakes arriving in places as diverse as Pohnpei (Federated States of Micronesia); Oklahoma; Texas; Hawaii and Spain.

Preventing the spread of the invasive brown treesnake is critical to the economic welfare and ecological diversity of Pacific islands. More information regarding this snake and invasion threats is available at http://www.fort.usgs.gov/resources/education/bts/bts_home.asp

Other links:

Brown Treesnake (Boiga irregularis): A Fact Sheet for Pacific Island Residents and Travelers http://www.fort.usgs.gov/Products/Publications/pub_abstract.asp?PubID=21535

Control and Containment of the Brown Treesnake and Other Invasive Reptiles http://www.fort.usgs.gov/Research/research_tasks.asp?TaskID=2184

FORT identifies cargo stowaway as invasive Brown Treesnake

http://www.fort.usgs.gov/News/news_story.asp?WebID=050922

Stalking Snakes: Days (and Nights) in the Life of a Brown Treesnake Rapid Responder

http://www.fort.usgs.gov/StalkingSnakes/

Publications:

The disappearance of Guam's wildlife: new insights for herpetology, evolutionary ecology, and conservation. Available online at  http://www.fort.usgs.gov/products/publications/20013/20013.pdf