Military installations across the country are battling wild hogs, snakes and other troublemaking species, according to a report by the National Wildlife Federation.

"Terrorists or natural disasters jump to mind" when one pictures threats to military readiness and homeland security, said Heidi Hirsh, natural resources specialist for the U.S. Marine Corps., which funded the report on behalf of the Defense Department. "But few people realize that we also face the threat of non-human invaders."

The report looked at a dozen case studies to provide a sample of the problem. Among the findings:

* Guam, home to an Air Force base and a Navy base, is infested with more than 2 million brown tree snakes, or 12,000 per square mile. They climb wires leading to transformers, creating shorts that lead to a blackout at least once a week. The snakes themselves sometimes die from the shock, but not always.

The brown tree snakes, native to the South Pacific and Australia, are thought to have arrived in Guam aboard a cargo ship after World War II. In addition to causing blackouts, they bite hundreds of residents a year (nonfatally), and have caused the extinction of nine of the island's 12 native bird species.

* Avon Park Air Force Range, a bombing and gunnery range in central Florida, battles wild hogs that descended from European wild boars. The hogs dig up soil along the runways, exposing insects, which draw large birds such as sandhill cranes. The birds and hogs cause the military to curtail flights to protect personnel and equipment, according to the military.

* Blister-causing invasive plants pose a health risk for soldiers at Fort McCoy in western Wisconsin. The base is home to 30 to 50 exotic plant species, including leafy spurge and wild parsnip. Leafy spurge exudes a milky latex that causes blisters, dermatitis and even blindness if rubbed into the eyes. Wild parsnip can cause severe blistering and skin discoloration.

The collaboration between the National Wildlife Federation and the military was not exactly a natural fit. The two have battled over the Pentagon's request to be exempted from setting aside critical habitat for the recovery of endangered species. Although Congress granted the request, the Pentagon invited environmental groups to see how it was protecting endangered species; that led to discussions of the problem of invasive species, and that led to the collaboration. The military paid $20,000 to commission the report.

The Defense Department manages 25 million acres with 350 species protected by the Endangered Species Act. Invasive species are the second-leading cause of population decline for threatened and endangered wildlife, behind habitat destruction, according to Corry Westbrook, the federation's legislative representative in Washington.

Westbrook said native plants and animals also cause problems for the military. "But there is no natural control for the nonnatives," she said. "They are exploding in numbers, taking over huge swaths, because there are no natural predators."

Hirsh called invasive species a "silent invasion" moving across the country. "Usually it's too late by the time they're noticed," she said. "In many cases, we don't have the technology to remove them."

The report calls on military installations to draft plans, with a focus on prevention, rapid response, identification and a plan of attack.

-- Associated Press

On Guam, brown tree snakes damage electrical systems and bite hundreds of residents each year.

Feral hogs descended from European wild boars are a nuisance at Avon Park Air Force Range in central Florida.