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

By James Stanford¹, USGS Rapid Response Team Coordinator, Guam

Brown Treesnake, Boiga irregularis (photo by Isaac Chellman).

In an ill-fated attempt to reach a bird nest on a utility line, this Brown Treesnake caused an electrical short that triggered a power outage (USGS photo).

It has been more than 27 years since Dr. Julie Savidge (now of Colorado State University) and other biologists first took notice of the invasive Brown Treesnake on Guam and its impacts on the island’s native bird life. Today, we are well aware of at least three major impacts of the snake’s invasion legacy on Guam. First, this nocturnal, tree-dwelling snake has caused the extirpation of nearly every species of forest bird and has played a major role in reducing or eliminating several species of native lizards and at least one mammalian species. Second, Brown Treesnake bites are mildly venomous and often require medical attention, especially bites to infants and small children. Third, the snake causes frequent power outages when climbing along utility lines or coming into contact with exposed structure wiring. The annual cost associated with snake-induced power outages on Guam was recently estimated to be $4.5 million. On a populous island with many at-risk ecosystems such as Oahu, Hawaii, an established population of Brown Treesnakes would be even more ecologically and economically damaging, with costs possibly exceeding $400 million per year.

Numerous U.S. Federal, State, and Territorial agencies, as well as cooperators from other island republics, are currently involved in a large, coordinated effort to reduce the Brown Treesnake’s impacts on Guam and prevent it from reaching or becoming established on other islands or the continental United States. Much of this work is funded by the U.S. Department of the Interior’s Office of Insular Affairs and the Department of Defense. As part of these prevention efforts, the USGS has established a unique team that is on call 24/7 to respond to potential Brown Treesnake sightings throughout the Pacific region. The multi-agency Brown Treesnake Rapid Response Team is based on Guam at the USGS Brown Treesnake Research Laboratory, with 4 full-time employees. The team comprises approximately 60 trained members from many agencies who can be recruited to assist during a response situation.

To understand what is involved in defending snake-free islands against this unwanted, highly adaptable invader, you are invited to take an 18-month journey through a chronicle of “life as a USGS Rapid Response Team coordinator”...

28 February—It is mid-afternoon on Guam: bright, sunny, and hot, a typical Guam day. I am driving to the airport to pick up some very important cargo. Today can be viewed as the culmination of many months of hard work; or more accurately, a significant step in a long process requiring many more months of dedication and hard work. Today, components of the fledgling research project known in Brown Treesnake circles as “Dogs in the Woods” have reached their new home on Guam. As I arrive at the airport with my two new staff members (dog-handlers-in-training recently arrived from Montana), I can’t help but wonder how they and today’s cargo are going to change my average work day. The “cargo” consists of two black Labrador retrievers. I am amazed at their size. These are not the typical snake dogs (currently, Jack Russell terriers) used to search cargo and planes on Guam and other islands. These big, energetic canines will be asked to locate snakes in a variety of habitats, where their size will enable them to get through the dense, vine-laden forests covering large tracts of Guam and many other Pacific islands. Their height will also allow them to detect snake scent higher in the air column as the scent drifts down from the tops of trees — one of the Brown Treesnake’s favorite hunting sites.

Invasive species control agencies, such as those in State and Territorial governments and the U.S. Department of Agriculture’s Wildlife Services (USDA-WS), need improved methods for detecting snakes at very low densities. This is the case with sighting reports from snake-free locations such as Oahu and Saipan (Commonwealth of the Northern Mariana Islands). To address that need, the USGS and its cooperators are testing the feasibility and cost-effectiveness of using detector dogs to locate snakes in rapid-response situations. USGS scientists are also testing visual search techniques, bait stations, and trapping methods for hatchling to adult-sized snakes.

20 March, 1:05 am—A flight attendant crossing a small courtyard between wings of the Saipan International Airport almost steps on a Brown Treesnake. Immediately, she informs her boss, who calls the response hotline for snake sightings in Saipan. Within 30 minutes of the report, trained Rapid Response Team members from the local natural resources department are on the scene. At daybreak, I receive notification. While I await further confirmation via a formal interview with the flight attendant, I alert staff on Guam of potential deployment and begin packing gear and supplies for two weeks in the field. By noon, the officials in Saipan have requested the assistance of the USGS Rapid Response Team on Guam. Four trained biologists from the USGS Brown Treesnake Laboratory and I are on the next plane out. We spend the next two weeks at the Saipan airport, assisting the local agencies in searching for the sighted snake.

Local agencies are so concerned about Brown Treesnakes becoming established on Saipan that they bring out their cargo dog teams to conduct outside searches. This is the first time these highly trained dogs have been used on a response, and they are extremely effective—it is amazing how quickly they can “clear” areas in and around the hangers and other structures on the airport property.

This experience illuminates the importance and potential of our “Dogs in the Woods” project, investigating whether these larger animals can be as effective in forested areas as the Jack Russell terriers are in airports and seaports. Keeping in mind management needs for timeliness and cost-effectiveness on neighboring islands, our work is assessing three specific questions concerning dogs and snakes:

1. Can the dogs find a Brown Treesnake? If so, can they do it without becoming distracted by the myriad intoxicating (to a dog), non-target smells found in a tropical forest?
2. Is the program cost-effective, considering the costs of hiring dog handlers, acquiring dogs, training, transport, care and feeding? How would this expense compare with, say, a team of 10 human searchers and their associated costs?
3. To what extent are the dogs effective in different circumstances? Do detector dogs work as well in thick, vine-laden forest as they do in open yards and around urban structures? Are detector dogs useful in both low-wind and high-wind situations? Are detector dogs as adept at finding snakes in tall trees as they are at finding snakes near or at ground level?

Early September—The summer has flown by. My days were filled with advancing the “Dogs in the Woods” project and conducting training courses for Rapid Response Team members stationed on Saipan, Rota, Guam, and Oahu. Altogether 24 team members receive training during the year, of whom 11 are new. New team members are required to attend an 18-day course, composed of a mixture of lectures, workshops, and field training. (It takes a considerable amount of time to develop a good “search image” for Brown Treesnake.) Also, the training stresses safety during field work and when handling snakes, as well as how to process and respond to reports of sightings. Existing team members periodically take 5-day refresher courses that focus on night searching for Brown Treesnakes. In a typical year, we conduct two 18-day training courses for new Team members and two 5-day refresher courses for existing Team members.

The main focus of these training courses is for participants to become familiar with spotting and handling Brown Treesnakes and to be comfortable searching for them at night. Moreover, we cover threats posed by Brown Treesnakes and the steps that agencies are taking to reduce these threats. During each training course, we work intensively with partner agencies, such as the USDA-WS and the Guam Division of Aquatic and Wildlife Resources.

12 September—With training completed for the time being, the Hotline rings again, as if on cue. It is early morning and as I try to unscramble my brain, I hear a distant but friendly voice telling me that the caller has run across one of “my” snakes in Oklahoma. Oklahoma! I am now wide awake. It turns out that a Brown Treesnake somehow managed to enter a shipping container that left Guam several months previously and arrived safe, secure, and alive at a military base in Oklahoma. Unluckily for the snake, the individuals opening the container spotted it and recognized it as something that they did not want to get loose. It was promptly dispatched.

The quick and decisive action of the military personnel in Oklahoma eliminated any threat from this snake. Personnel immediately notified superiors, who then contacted the Rapid Response Team to receive further instructions. The specimen was shipped to the USGS Fort Collins Science Center in Fort Collins, Colorado, for positive identification, where it was confirmed to be a Brown Treesnake. The actions and immediate follow-up of the parties involved demonstrate the importance of educating not only Pacific islanders but also anyone receiving cargo arriving from Guam in order to eliminate the threat posed by these invasive and highly adaptable snakes.

Left: Brown Treesnake outreach poster (click here for a larger version); Right: Brown treesnake detector dog team and response team members train to find snakes on Guam (USGS photo).

November—I spend several weeks working with host-country officials on an outreach trip through the Federated States of Micronesia (FSM) and the Republic of the Marshall Islands (RMI). These countries (as well as the Republic of Palau, which I visited earlier in the year) all receive direct flights and cargo shipments from Guam, making them prime targets for Brown Treesnake invasions. My role on these outreach trips is to educate and develop effective working relationships with host-country personnel and increase public awareness of this invasive snake and its potential impacts.

Given our knowledge that snakes can and will stow away in planes and cargo ships, it is imperative that we work hand-in-hand with these countries to help reduce the threat of Brown Treesnake invasion. Outreach and education is one of the Rapid Response Team project’s main goals. Through these outreach trips we are increasing the likelihood that any arriving Brown Treesnake will be sighted, reported, and potentially captured.

March—More training. This time I am running the first-ever Rapid Response Team training for individuals from the FSM, RMI, and Palau, the countries I visited the previous year. I have only one week to teach 18 days’ worth of material. It’s a very long week, but everyone pulls through. More importantly, we now have trained, well-informed team members on the ground in these countries. One of the goals of the USGS Rapid Response Team office is to train team members on islands at high risk of Brown Treesnake invasion (those that receive plane flights and shipping from Guam). These new team members are vital in helping to ensure that their islands remain snake-free. They are the first and best line of defense after a sighting is reported: as island residents, they can respond quickly to local sightings and therefore stand a greater chance of finding and capturing an intruding snake.

Training is based in part on continuing USGS research into how snake size, prey type and density, and other factors influence the effectiveness of current tools for snake detection and capture. What we learn about snake behavior and ecology will inform development and refinement of control and interdiction methods that island officials and resource managers can use to keep their islands snake-free.

25 May—Another reported snake sighting has occurred just outside of Kolonia on Pohnpei, one of the main islands of the FSM, and we’re off! This time we deploy not only the Rapid Response Team members, but also the dog teams to see what they can do at this point in their training. It is also our first “dry run” of the logistics involved in transporting our canine teams internationally.

Late Summer—Another summer has passed, although on Guam it is hard to tell. We have trained another batch of Rapid Response Team members this year, including 17 new members. The “Dogs in the Woods” research project is moving along nicely. We learned a lot from the Pohnpei sighting as well: though we did not find a Brown Treesnake, secondary interviews conducted with the person reporting the sighting suggested that what was actually seen was a blind snake (Ramphotyphlops braminus). Blind snakes are common throughout the Pacific region. They are only a few inches in length, they live in the soil, and they pose no threat to humans. During the response, searchers saw several blind snakes near the sighting location. This response effort highlighted the need for increased training of sighting responders as well as improving the flow of information between key agencies and personnel throughout the region.

October again—The USGS is in the initial stages of a new research project involving the snake detector dog program. We will be using the dogs to help us locate radio-tagged snakes in the forest of northern Guam. From these searches we are expecting to increase our understanding of where snakes rest during periods of inactivity as well as honing our ability to interpret what the detector dogs, through their reactions, are telling us during a search. Both efforts should enable us to increase our snake-finding abilities and help prevent the ecological and economic losses that Guam has endured from being re-enacted on another island.

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 can be found at: http://www.fort.usgs.gov/resources/education/bts/bts_home.asp

¹FORT biologist James Stanford has been coordinating the USGS Brown Treesnake Rapid Response Team since 2004.