The brown tree snake (Boiga irregularis) has caused major ecological and economic damage in Guam, the largest of the Mariana Islands. The snake is native to New Guinea and northern Australia. It has also been introduced to some Pacific islands in addition to Guam.

Brown tree snakes in their natural habitat range from 3–6 ft (0.9–1.8 m) in length. Some snakes in Guam are more than 10 ft (3 m) long. The snake's head is bigger than its neck, and its coloring varies with its habitat. In Guam, the snake's brown-and-olive-green pattern blends in with foliage.

The tree snake was accidentally brought to Guam by cargo ships during the years between the end of World War II (1945) through 1952. On Guam, there were no population controls such as predators that eat snakes. As a result, the snake population boomed. During the late 1990s, there were close to 13,000 snakes per square mile in some areas.

The snake's diet includes birds, and the United States Geographical Survey (USGS) said that the brown tree snake "virtually wiped out" 12 of Guam's native forest birds (three of which are now extinct). Furthermore, snakes crawling on electrical lines caused more than 1,200 power outages from 1978 through 1998.

The USGS and other agencies were working to contain snakes on Guam and stop their spread to Hawaii and other islands.