Bred in captivity, pygmy rabbits go back to the wild

Published 9:00 pm Friday, April 6, 2007

For tens of thousands of years, Columbia Basin pygmy rabbits munched on olive-drab sagebrush, dug burrows in the deep volcanic soil and did what rabbits do best.

But in recent decades, the animals have declined to the brink of extinction, prompting federal and state wildlife agencies to start a captive breeding program they hoped would restore the numbers of the tiny burrowing rabbits. The rabbit was listed for protection under the federal Endangered Species Act in 2003. Surveys in 2004 found none left in traditional areas.

Recently, wildlife officials released the first 20 rabbits raised in captivity, setting them free in a remote wildlife reserve near Ephrata in Douglas County in central Washington.

The effort is similar to the captive breeding programs that brought back the California condor, said Ren Lohoefener, Pacific regional director of the U.S. Fish and Wildlife Service in Portland, Ore.

“Any time you can bring something back from zero and re-establish it, it’s cause to celebrate,” he said. “This may be harder to do than with condors, because a lot more things eat bunnies than condors.”

The reasons the Columbia Basin rabbits declined are not precisely known, although scientists suspect inbreeding among such a small population was a major factor. Range fires, farming, disease and predators also are thought to have taken their toll, said Madonna Luers of the Washington state Department of Fish and Wildlife, which is cooperating with its federal counterparts in the program.

The Columbia Basin pygmy rabbit – not much bigger than a man’s hand – is the country’s smallest native rabbit and the only one in the United States to dig its own burrows.

The rabbits just released were born and raised at Washington State University and at the Portland Zoo in Oregon. They are descendants of the last known wild rabbits, caught in 2002 for the captive breeding program.

The rabbits were released in the Sagebrush Flats area about 18 miles northwest of Ephrata, part of a five-county range that was the rabbits’ original habitat.

Pygmy rabbits are still found in the West’s Great Basin, but the isolated Columbia Basin group is considered to be an evolutionary distinct population, said Rod Sayler, a Washington State University associate professor of natural resource sciences who leads the captive breeding project.

The Northwest Trek Wildlife Park south of Tacoma also participates in the captive breeding program, which has produced about 90 pygmy rabbits in all.

Only three purebred descendants of the original wild rabbits remain at the captive breeding sites, Sayler said.

The Columbia Basin rabbits were mated with more genetically diverse Idaho pygmy rabbits and their offspring carry at least 75 percent of the Columbia pygmy bloodlines, Sayler said.

An immediate result was that the crossbred rabbits became better breeders and more of their young survived, he noted.

“We found out they were suffering from severe inbreeding depression,” Sayler said. “No matter what we did, they just weren’t reproducing well. Believe me, we tried everything.

“That population had been isolated for thousands of years,” he said. “We added just enough to help them along and reproduction picked back up.”

The dozen males and eight females were placed in artificial burrows made of 20-foot-long perforated plastic irrigation pipes until they get used to the place and dig their own.

Each wears a tiny radio transmitter the size of a watch battery to help scientists track its movements.

The rabbits were released on public lands that are part of about 10,000 acres that state and federal wildlife agencies, the Nature Conservancy and state Department of Natural Resources have set aside for the rabbits.

But nearby private land owners also are important to the rabbit recovery effort, Washington Fish and Wildlife Director Jeff Koenigs said.

Rancher Dave Billingsley is one of three property owners who signed “safe harbor” agreements with federal agencies should the rabbits choose to make their homes on private land.

Fish and Wildlife’s Tom Buckley said the 20-year agreements hold landowners harmless for any “incidental takings” from normal use of land. Landowners are asked to tell federal agencies when pygmies are spotted so the rabbits can be moved elsewhere.

Areas providing both good soil and sagebrush are “pretty limited,” Buckley said. “With the cooperation of landowners, it allows us to expand the rabbits’ habitat.”