Control and Containment Strategies on Guam: Visual Searches

Visual searches for brown Treesnakes are conducted regularly on Guam, particularly in port areas, other transportation facilities, and protected wildlife habitat. These areas benefit most from concentrated search efforts because of the magnitude of risk if even one snake manages to crawl into a cargo container or make a meal of an endangered Guam rail. Searches are combined with other techniques for control such as barriers and habitat modification to maximize prevention and capture success.

Searches are conducted primarily at night because this is when the snakes are actively foraging and easiest to detect. Spot lights or flood lights are used by operational control personnel to help locate snakes while traveling on foot or in slow moving vehicles. Snakes are often found on chain link fence perimeter presumably where they are searching for prey. While these snakes are relatively easy to spot, their neighbors in nearby vegetation are much more elusive and often escape discovery. In fact, Wildlife Service personnel removed 2,051 snakes from in and around the Guam International Airport in 1994 - 1998 using visual searches of fence lines and buildings, yet an additional 3,319 snakes were captured from the same area during the same period using traps. So while perimeter checks are employed for regularly patrolled areas, more encompassing population monitoring efforts call for researchers to don head lamps and canvas forest areas.

Concentrating visual searches in high-risk areas such as cargo loading docks and wildlife enclosures provides essential focused protection to these areas; however, visual searches are not applicable on an island-wide basis. A number of factors prohibit the use of this tactic on a larger scale: the rugged terrain on remote parts of the island is not safely traversable for people; researchers cannot haphazardly cross boundaries onto private property or high-security government areas; and the cryptic nature of the snake itself makes discovery and capture a formidable task, requiring highly trained and dedicated individuals to conduct the searches.

Control and Containment Strategies on Guam: Visual Searches

Canine Detection Teams

Habitat Modification

Physical Barriers

Trapping

Visual Searches

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