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CORVALLIS - An Oregon State University professor is part of an international team planning how to do away with feral goats that are turning an island where Charles Darwin did some of the field work for his theory of evolution into a "dust bowl."

"Isla Isabela is rugged and has as much land mass as the rest of the islands in the Galapagos archipelago combined, and it's not going to be easy," said OSU wildlife biologist Bruce Coblentz, who has studied feral animals, or domestic animals gone wild, on islands in several parts of the world.

"People have always thought of the northern part of Isabela as being pretty much like it was when Darwin saw it - pristine," said the OSU scientist. "It won't be for long with these (non-native) goats there."

The Galapagos island chain, part of Ecuador, is in the Pacific Ocean about 600 miles west of the South American mainland.

In the early 1980s, Coblentz and two of his graduate students studied and killed feral pigs on another Galapagos island. In September the private Charles Darwin Foundation and the Galapagos National Park Service, operated by the government of Ecuador, invited him to a two-week workshop to help plan the eradication of feral goats on Isla Isabela.

The planning team included other scientists with expertise in eradicating various kinds of animals from areas where they are not native, and hunters from New Zealand who specialize in eliminating feral goats in that country.

"The idea was to design the perfect eradication program, or as close to that as possible," said Coblentz.

Isabela is about 85 miles long and 50 miles at its widest. It has five active volcanoes. The wider southern end is round. The rest is a narrower strip stretching north. The narrowest point, a stark lava field called Perry Isthmus, is only about seven-and-a-half miles wide.

Humans live on the southern end of Isabela, along with animals including wild pigs, goats, cattle, dogs, donkeys, cats and rats. But the rugged Perry Isthmus is a natural barrier for many creatures. Until the late 1970s and early 1980s, few had ventured across it.

Now "there may be 100,000 feral goats beyond Perry Isthmus," said Coblentz.

Some years, the OSU scientist said, the island receives more precipitation from marine fog than from rain. Feral goats, grazing in an ecosystem that did not evolve with them, kill low-lying trees filled with lichens, mosses, orchids, ferns and other plants that extract moisture from the fog.

When the trees disappear, the land dries up and becomes a "dust bowl," Coblentz said. "The vegetative communities on the northern end of the island have been hit hard in the last decade," he added.

The OSU scientist said the planning team has developed a three-stage eradication plan: Phase one, shooting feral goats on the north end of Isabela from a helicopter, with the hope of exterminating up to 75 percent of them. Phase two, hunting on the ground with trained dogs imported from New Zealand. Phase three, using "Judas goats."

"Judas goats" are goats captured and fitted with a radio collar. When released, "they want to be with other goats," Coblentz said. This will help Galapagos National Park Service rangers locate and kill remaining goats.

"They're hoping to get started in 1998. The estimate is that it will take 18 to 24 months," said Coblentz. "If I can get the funding I'd like to send a graduate student there to learn more about the dynamics of using Judas goats."

The researcher and his graduate students used Judas goats in projects with feral goats on San Clemente Island off the coast of southern California and on Aldabra Atoll in the Indian Ocean.

Why not trap the goats on Isabela live and remove them?

"It would be impossible," said Coblentz. "You simply couldn't round up all the goats, except for in the easy areas. It's been tried on other islands unsuccessfully, at an expense of millions of dollars. On San Clemente Island it prolonged ecological damage for 20 years."