Endangered Pygmy Rabbits Return to the Wild
WSU’s department of natural resource sciences has been the lead research institution in an effort to reintroduce the Columbia Basin pygmy rabbit to their natural habitat. Eleven of about two dozen pygmy rabbits scheduled for a March 13 reintroduction into their native sagebrush habitat in Douglas County come from Washington State University, one of three sites where the animals have been bred in captivity since 2000.
“It has been one of our biggest efforts in endangered species research,” said Rod Sayler, associate professor of natural resource sciences.
The releases are expected to become an annual affair over the next four to six years until the rabbit population can once again become re-established in the wild.
The Columbia Basin pygmy rabbit is a long-isolated, genetically unique population of small rabbits. Similar pygmy rabbits are found in Idaho, Oregon, Montana, Nevada and California. The Washington rabbits were on the verge of extinction when they were listed as a federal endangered species in 2003.
The animals’ decline followed a loss of habitat, habitat degradation and fragmentation of remaining sagebrush ecosystems as the land was converted into farms, ranches and urban development over the past 50 years.
When the wild population of Columbia Basin rabbits plummeted to less than 40 in 2001, the last rabbits were captured and sent to three facilities to begin a captive breeding program.
While no one knows exactly why the crash happened, inbreeding depression — the negative impact of decreased genetic diversity — was believed to be a contributing factor.
“The state gave us the first Columbia Basin rabbits to breed in 2001,” said Lisa Shipley, associate professor of natural resource sciences. ”That gave us the opportunity to conduct research on a number of topics, including nutritional ecology, breeding behavior and population dynamics.”
The Oregon Zoo and the Northwest Trek Wildlife Park near Eatonville got small populations as well. Spreading the small population of rabbits among the three facilities was a measure taken to make certain that the entire rabbit population would not be wiped out by disease or other catastrophe.
While many might assume that breeding rabbits might be easy, that’s not been the case. In the neighborhood of 250 of rabbits have been born at WSU since the captive breeding program began in 2002, but few have survived.
“The Columbia Basin pygmy rabbits had lower reproductive success, fewer kits per female, lower earlier kit growth rates and occasional bone deformities,” Sayler said. In addition, all of the breeding sites have struggled with disease problems and parasites.
Faced with possible loss of the entire population, an emergency genetic rescue was undertaken in 2003. Columbia Basin pygmy rabbits were mated with more genetically diverse Idaho pygmy rabbits. The resulting intercross kits were mated in a breeding scheme to maintain genetic diversity within the founding population and produce pygmies with about 75 percent Washington genes and 25 percent Idaho genes. Higher reproductive rates are evidence of the success of this effort, according to Sayler.
All of the rabbits which will be released on March 13 will be equipped with radio collars to enable researchers to monitor them.
Population models developed at WSU suggest that it will take years for the rabbit population to become safely established in the wild. A WSU doctoral student will conduct field studies of the radio-collared pygmies to find out what ecological factors influence their micro-habitat use and potential survival.
There is no guarantee of success. “They live in really harsh conditions,” Shipley said. “They have a very difficult life.”
“We are going to be doing very well to keep them surviving in Washington, but we are hopeful,” Sayler said.
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