Impacts on Military from Brown Treesnakes
The Department of Defense (DoD) has been involved in many aspects of carrying out the advised measures for controlling and limiting expansion of the brown Treesnake, including major time commitments and money expenditures (in excess of $1 million yearly). The Military Brown Treesnake Control Program was organized to combine the efforts of agencies involved to concentrate on preventing the brown Treesnake from spreading to other islands or continents and lessening its impact on Guam. Impacts include time delays and potential dispersal of brown Treesnakes in routine military traffic, impacts on military training in the Western Pacific Region, and management of wildlife on military lands.
The Military Brown Treesnake Control Program/Impacts on Routine Military Traffic
Initiated in 1988, the Military Brown Treesnake Control Program involves the DoD working in concert with the U.S. Fish and Wildlife Service and Guam Department of Agriculture to provide technical training to reduce the risks of snakes leaving Guam in military traffic. Since 1993, the Department of Defense has joined forces with the U.S. Department of Agriculture's Animal Damage Control to combat exportation of brown Treesnakes from Guam. Specific responsibilities of this program include: managing and implementing operational control to prevent the dispersal of brown Treesnakes via military material aircraft and vessels; providing training and snake control supplies to Emergency Snake Control Teams in Hawaii and the Commonwealth of the Northern Mariana Islands (CNMI); providing personnel to monitor DoD training sites on Saipan and Tinian during DoD exercises; and assisting military inspectors searching outbound cargo prior to shipment during training exercises.
The DoD provides funding and the infrastructure from which Animal Damage Control personnel carry out inspections, training, brown Treesnake trapping, habitat modification, prey reduction, detector dog handling, and barrier construction. All brown Treesnake control activities are now performed by Animal Damage Control personnel and Andersen Air Force Base Traffic Management Office Quality Control Inspectors.
The purpose of inspections is to detect snakes in military traffic prior to leaving Guam. Normal military inspections involve passengers, accompanied luggage, personal property, DoD-owned and leased ships, aircraft, and crews, and Department of Defense cargo shipped from or transiting through Guam. Inspectors search for the snake while clearing outbound cargo containers, pallets, vehicles, and aircraft. Particular emphasis is placed on inspection of confined spaces favored by the snake as day hiding refugia (e.g., aircraft wheelwells, undercarriages of vehicles, and compartments). Snakes that are encountered in cargo areas and on perimeter fences are removed and killed.
The Military Brown Treesnake Control Program covers various military installations on Guam, including the major installations. Five of eight brown Treesnakes found in Oahu to date were associated with military aircraft or on military facilities; one was found on a taxiway shared by military and civilian aircraft, one in the landing gear of a commercial airliner, and one in the Customs Area of Honolulu International Airport. A live brown Treesnake arrived in Texas in a military household goods shipment from Guam. Because of these dispersals, cargo handlers and aircraft ground crews in Hawaii have been sensitized to the need for intensive post-operational checks of Guam-arriving vessels and aircraft and routinely conduct visual examination of these conveyances, with particular attention to wheelwells or confined spaces.
Impact on Military Exercises
Military exercises originating on Guam are monitored closely to avoid dispersing brown Treesnakes upon arrival. Many exercises involve the use of fixed-wing aircraft and helicopters for transport to airfields or tactical landing zones, parachuting into drop zones, boats to beaches or swimming to beaches across the reef, and amphibious assault vehicles or air cushion landing craft to beaches. Regular military training occurs on Tinian Island in the CNMI, 100 miles north-northeast of Guam. The U.S. military leases approximately 18,000 acres of Tinian for training purposes. Since supplies and equipment to support exercises are shipped from Andersen Air Force Base and/or port facilities on Guam, military inspectors and Animal Damage Control personnel search for brown Treesnakes on transportation, equipment, and supplies used during exercises.
The limitations of snake exclusion efforts must be acknowledged. In some cases, personnel are routed from the U.S. mainland to Tinian before going to Guam to reduce risks of snakes being transported in equipment, supplies, and vehicles.
Management of Wildlife on Military Lands
Guam's Department of Agriculture monitors bird and bat populations including, but not restricted to: Mariana crows, island swiftlets, common moorhens, Micronesian starlings, various introduced bird species, and Mariana fruit bats. Snake control is attempted with tree barriers, habitat modification, and removal of snakes by hand when practical. The Department has also provided logistic support for snake control through access to laboratories, cages, storage facilities, and a mouse colony for trap bait. Department staff participate in various control planning and projects through cooperative involvement.
To protect active Mariana crow nests from brown tree snake predation, the Natural Resource program at Andersen Air Force Base purchased electrical and solar-powered barrier equipment. The objective of the effort is to prevent snakes from climbing tree trunks during nesting seasons using electric barriers wrapped around tree trunks. Despite these efforts, snakes have continued to gain access to these trees, nests have been lost, and crow populations are at precariously low levels. Since the early 1980s, only four young are known to have fledged successfully, and the crow population is now composed of mostly older adults. However, it is believed that these devices have helped to protect some Mariana crow nests from snake predation, and this technology may be applied to Micronesian kingfisher nesting sites pending reintroduction in the future.
A wild game exclosure constructed by Andersen Air Force Base at Northwest Field to keep out pigs and deer has been converted to a pilot project to exclude snakes from a 24-ha area of forested habitat. Control of the snakes is accomplished using a combination of trapping and a perimeter barrier to reduce re-invasions by snakes. In this space, the Guam rail has been reintroduced and is successfully reproducing. It is hoped that this technology can be extended to aid in future opportunities to recover wildlife.