Brown Tree Snake Problem in Guam

The U.S. territory of Guam, situated in the western Pacific Ocean, has historically been an island of rich biodiversity despite its relatively small size. The accidental introduction of the brown tree snake (Boiga irregularis) to the island, which previously had no native snakes, has become a cautionary tale of what can happen to an ecosystem when an invasive species remains unchecked.

Biology

The brown tree snake is a slender, rear-fanged arboreal snake that is active mostly at night. These snakes can reach lengths of up to 10 feet, but most brown tree snakes remain in the range of 3 to 4 feet. Brown tree snakes are opportunistic eaters, feeding on whatever is available, including rodents, lizards and birds, which has contributed to their success on Guam.

History

The brown tree snake, which is native to Papua New Guinea, Australia and the Solomon Islands, was thought to have been introduced to Guam accidentally via cargo ship shortly after World War II, according to the United States Geological Survey. Because of the lack of natural predators, the abundant food sources and the snake's adaptability, populations of brown tree snakes on Guam skyrocketed.

Misconceptions

Brown tree snakes are extremely abundant in the jungles of Guam. The United States Department of Agriculture reports population estimates of more than 20 individual snakes per acre for parts of Guam. In spite of this extreme population density, encounters with humans are much rarer than one might expect. Few people come into contact with brown tree snakes, and envenomation of adults is relatively uncommon.

Despite false rumors that the snakes seek out or try to ambush humans, the USDA claims that it is possible to reside on Guam for years without ever seeing a live brown tree snake.

Effects

The ecology of Guam has been affected in monumental ways since the introduction of the brown tree snake. Of the island's original 12 bird species, 10 have been hunted to extinction by the brown tree snake and the two remaining species are in jeopardy. The loss of these birds could have adverse effects on the plant life of the island as well, because of the fact that birds are primary distributors of seeds on the island.

Humans have also been adversely affected by brown tree snakes. The snakes are responsible for multiple power outages every year as they cross power lines and cause the circuits to short out. Many small pets fall prey to brown tree snakes as well.

Control

Control of brown tree snakes on Guam consists of both prevention and eradication. Incoming and outgoing ships and planes are checked extensively to prevent the spread of brown tree snakes to other islands. Specially trained dogs are used to sniff out potential snake passengers.

Brown tree snake traps, which are constantly monitored, are in place under the advisory of the USDA. Physical barriers have also been placed in order to isolate populations of tree snakes. Occasionally, snakes are captured by hand, though this process is inefficient. Alexandria Amand of the University of Minnesota reports that some researchers are developing species-specific diseases to help eradicate the snakes in larger numbers.

References

• U.S. Geological Survey: The Brown Treesnake on Guam
• United States Department of Agriculture Animal and Plant Health Insepection Service: The Brown Tree Snake
• Guam News Factor: Brown Tree Snake Eradication Program Helps Reduce Guam Power Outages
• Science Daily: Brown Tree Snake Could Mean Guam Will Lose More Than Its Birds
• University of Minnesota Department of Horticultural Science: Boiga irregularis (Brown Tree Snakes) on Guam and Its Effect on Fauna