ALIEN SPECIES

Brown tree snake (Boiga irregularis)

The brown tree snake is a nocturnal and arboreal snake that ranges from eastern Indonesia to the Solomon Islands and northern Australia. After World War II it was accidentally introduced to Guam, apparently as a hitchhiker on military cargo returning from use in the war in New Guinea. In the next three decades the snake spread throughout Guam and eventually resulted in the extinction of 9 of the island's 12 forest birds, half of its lizards, and perhaps some of its bats. It remains the leading cause of endangerment for the few remaining native vertebrates on Guam.

This snake has affected humans on Guam in a variety of ways too. Since 1980, Guam has suffered an average of one power outage every three days because the snakes cross powerlines and short out the circuits. And approximately 200 humans have suffered envenomation from the snake's bite. The brown tree snake lacks fangs, but has a weak venom that can be slowly conducted by enlarged rear teeth. These kind of teeth require the snake to chew on its victim for some time in order to allow the venom to penetrate the skin. Hence, the brown tree snake is not dangerous to adult humans who will not allow such chewing to occur. However, on Guam there have been many cases where the snakes have crept into cribs and envenomated infants (see photo at right), who are unable to protect themselves from the snakes. Several of these attacks have led to respiratory arrest in the infants, though no deaths have yet occurred because of the availability of rapid medical treatment in the hospitals. The island's previously thriving poultry industry has been devastated because the snake crawls into coops and eats the eggs and chicks. Many pet dogs and cats have been lost in a similar fashion.

Because of its secretive habits, the brown tree snake is adept at hiding itself in small spaces during the day and, consequently, is easily transported between islands in cargo shipments. Brown tree snakes have left Guam in this fashion several times, turning up in a variety of locations around the globe, such as Saipan, Wake, Tinian, Rota, Okinawa, Diego Garcia, Australia, and Texas. Between 1981 and 1994, seven brown tree snakes were accidentally transported to O`ahu in this manner and captured upon arrival. Most were found dead or dying near airport runways. As far as is known, brown tree snakes have not formed a self-sustaining population in Hawai`i. But constant vigilance is required to avert this disaster.

Because it has a similar climate and fauna, Hawai`i could expect to suffer many of the same negative ecological and economic consequences that Guam has if the brown tree snake were to become established here. Most of our remaining native forest birds would go extinct, power outages and cases of infant envenomation would probably be fairly frequent, and the tourist industry would possibly suffer from the negative publicity. To avoid this possibility, several state and federal government agencies have been working together for the past several years to ensure that the snake does not reach Hawai`i.

The first line of defense in keeping the brown tree snake out of Hawai`i involves the U.S. Department of Agriculture's program on Guam to keep the snakes out of the transportation network. This involves trapping and night searches to remove snakes from port facilities, inspection of outbound cargo and vehicles with snake-detection dogs, and research into new ways to lower snake population levels on Guam. Searches of inbound planes and cargo are conducted by Hawai`i Department of Agriculture (photo at left) as an additional guarantee against snakes arriving into the islands. This is the second line of defense. As a final measure, DLNR has trained staff and groups of volunteers from other agencies in appropriate methods of finding brown tree snakes in the field. In the event of a likely brown tree snake report, these teams are called into action to search for the snake in an effort to ensure that any brown tree snakes that do arrive here do not have a chance to establish a self-sustaining population. Teams occur on each of the main Hawaiian islands.

You can help protect Hawai`i from brown tree snakes too. No snake species are native to Hawai`i (although the small, harmless blind snake has become established here this century), and all have the potential to become problems should they establish here. So if you see a snake anywhere in Hawai`i, immediately report it to the proper authorities, such as the Department of Agriculture (586-PEST) or the police. If it is safe to do so, it is best to kill the snake (e.g., drive over it, beat it with any blunt object, cut it in half with a machete) before calling. If not, keep the snake in visual contact until authorities arrive. A prompt response is essential to ensuring that the snake does not escape and can be captured by the proper authorities.

For more information on brown tree snakes, visit http://reorg.nbii.gov/browntreesnake.

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