Bunnies’ Bickering Gets In Way

Eighteen Columbia Basin pygmy rabbits, captured for breeding in hopes of saving them from extinction, have failed to reproduce at the rapid rate for which bunnies are famous.

The 15 offspring born in the first year of the program are not an unreasonable number, but they are hardly a population explosion.

“We have the potential to have many more than that,” said David Hays, an endangered species biologist for the state Department of Fish and Wildlife.

The sluggish birth rate, combined with an unexpected mortality rate, means that none of the rabbits will be released to the wild this summer.

Unlike domestic rabbits, the scrappy pygmies, when left alone, sometimes fight instead of making babies.

“We have to keep a close eye on them,” Hays said.

There are probably fewer than 30 Columbia Basin pygmy rabbits in the wild, all living on state land northwest of Ephrata. They are believed to be genetically unique among pygmy rabbits, which are found in eight Western states.

The tiny bunnies -- which weigh about two-thirds of a pound and measure 4 to 6 inches long -- are believed to be the smallest rabbits in the world.

Biologists had high hopes for the captive breeding program, placing one group at the Oregon Zoo in Portland and another at Washington State University in Pullman.

In the first year, the captive rabbits bore 15 young total, but seven adults and six of the babies have died. Eleven of the 13 succumbed to disease.

One disease, coccidiosis, is not uncommon among captive animals. But the other, avian tuberculosis, caused by a soil-borne bacteria, surprised veterinarians because many mammals are resistant.

Pygmy rabbits are considered imperiled in Oregon, Montana, Wyoming and Utah, and vulnerable in California, Nevada and Idaho, according to NatureServe, a nonprofit organization that develops and provides information on plants, animals and ecosystems.

The Washington population is in the biggest trouble and received an emergency federal protection order for endangered species in November 2001. The emergency listing expired last year, but a proposal to classify the rabbits as endangered is pending, and action is expected this year.

“They’re not doing too well,” said Chris Warren, a biologist for the U.S. Fish and Wildlife Service in Spokane. “They’re down to about nothing in the state.”

Spring breeding season is just around the corner for the little round-eared rabbits. Compatible captive bunnies will be left together longer and given some privacy in as natural a setting as possible, with the hopes that nature will take its course.

If the Columbia Basin bunnies don’t do what they’re supposed to, one option under consideration is inviting some captive Idaho pygmy rabbits over for a romantic getaway.

Ten captive Idaho pygmies produced 31 young last year -- at Northwest Trek wildlife park near Eatonville and at Washington State University -- and 20 of the group were released into the wild near the Energy Department’s Idaho National Engineering and Environmental Laboratory at Idaho Falls last summer. Three of the young died in captivity, a much lower mortality rate.

Scientists really know very little about the pygmies, the only burrowing rabbits in North America.

“It’s generally a concern. We’ve had more success with the Idaho than the Washington rabbits. It may be something’s going on there that we don’t know about affecting breeding,” Hays said.

And with so few rabbits left in the Columbia Basin, health problems caused by inbreeding can also be a problem.

Introducing the Idaho pygmies into the Columbia Basin population is not the first choice of biologists, but it might have to be done, Warren said.

“When you have so few animals, you really start worrying about the genetic consequences,” he said. “That’s the main reason we’re trying to get a captive breeding program in place.”

The isolated Washington population probably never was very large, and biologists believe that loss of habitat is the primary reason that there are so few in the Columbia Basin now.

The Washington pygmies and Washington farmers, it turns out, like exactly the same kind of rich soil.

“This area was grazed heavily during the turn of the century, and big irrigation projects were put in, converting the land to crops,” Warren said.”

A high mortality rate, as much as 80% to 90%, is expected in the wild, which is one of the reasons rabbits are prolific, Hays said. But if four to five new ones survive each year and breed successfully, the population could be reestablished, he said.