Keeping brown tree snakes from Guam from getting a foothold in Hawai'i could be a good deal tougher after May 31 when money for a program that checks for the snakes on military airplanes and ships departing Guam for Hawai'i runs out, federal and state officials say.

Some $2 million requested by U.S. Sen. Daniel K. Inouye's office to keep the snakes from hitching a ride on military ships and cargo leaving Guam may not be granted due to the elimination of congressional "add-ons," officials said.

If a congressional appropriation is not available, the U.S. Department of Agriculture will no longer be able to search for the snakes on military facilities on Guam.

Ships and planes leaving from civilian facilities will continue to be inspected for the snakes, which can have a devastating effect on birds and lizards.

Money to stop brown tree snakes from being accidentally shipped from military air and sea ports in vehicles and cargo has been channeled through the Department of Defense — $1.7 million in 2006 — primarily through the Armed Forces Pest Management Board as a congressional add-on. Money to pay for the program was not allotted automatically in past years but was obtained through budget add-on funds in past years thanks to Inouye's efforts, state and federal officials said. But as part of the 2007 federal budget process, Congress eliminated the budget add-ons.

Department of Defense, USDA-APHIS and Inouye's office are working with state, territorial and federal agencies to try to find a solution.

The Hawai'i Department of Agriculture's detector dog program is the last line of defense to protect Hawai'i from a brown tree snake invasion. Dog and handler teams try to meet and inspect all military and civilian planes and ships arriving from Guam, but don't have the funding or staff available to adequately search military ships or planes, agency officials said.

The Wildlife Services Division of the U.S. Department of Agriculture runs the Brown Treesnake Interdiction Program on Guam.

The program's goal is to keep brown tree snakes out of the transportation network, preventing the snake from leaving Guam and getting to snake-free islands such as Hawai'i. Wildlife Services workers on Guam use dogs and handlers to inspect out-going cargo, ships and planes for brown tree snakes and conduct trapping programs for snakes around ports of exit.

Brown tree snakes were introduced onto Guam in the late 1940s or early 1950s as passive stowaways in a military cargo ship that moved material after World War II. They were first detected around the naval port in the 1950s, and they spread across the entire 549-square-mile island within 20 years.

The native range of brown tree snakes includes portions of Indonesia, New Guinea, the Solomon Islands and Northern Australia.

Brown tree snakes are responsible for the extinction of nine of the 12 native forest birds, two of 11 native lizards on Guam, and have contributed to the decline of native fruit bats. The snakes are also responsible for an average of 200 power outages per year, and snakebites are the cause of approximately one of every 1,200 emergency room visits on Guam.

Infants constitute a disproportionately high number of the snakebite victims on Guam, although no deaths have been reported.

A University of Hawai'i economic study estimates that if brown tree snakes were to become established in Hawai'i, it would cost our economy $405 million each year.

A total of eight brown tree snakes have been found alive or dead in Hawai'i since the mid-1980s.

All snakes were associated with the movement of civilian and military vehicles or cargo from Guam.