Washington Department of Fish and Wildlife (WDFW) biologists are capturing pygmy rabbits in northcentral Washington for captive rearing to help recover the state endangered species.
Last week biologists captured four rabbits from burrows on WDFW's Sagebrush Flats Wildlife Area. The two pairs of rabbits are now in man-made burrows at Washington State University (WSU) in Pullman where scientists hope they will produce young that can be released in suitable habitat to boost declining populations. Another capture effort will be made on May 14 at the same site, just north of Ephrata in Douglas County.
The pygmy rabbit (Brachylagus idahoensis) is the smallest rabbit in North America; an adult rabbit can fit in the palm of a hand. It is patchily distributed in sagebrush-dominated areas of Oregon, California, Nevada, Utah, Idaho, Montana, Wyoming, and Washington. It is uniquely dependent on sagebrush for food and shelter, digging burrows in the deep, loose soil in which dense stands of sagebrush thrive.
Washington populations are separate from the core of the species' range, historically found in sagebrush habitat in Benton, Adams, Grant, Lincoln, and Douglas counties. Currently, fewer than 250 pygmy rabbits are known to survive in isolated fragments of suitable habitat in Douglas County. Loss of sagebrush habitat to agricultural conversion has been the primary factor in the decline.
The pygmy rabbit was listed as a state threatened species in 1990, upgraded to state endangered status in 1993. It is listed as a candidate species by the U.S. Fish and Wildlife Service (USFWS), which was recently petitioned to list it as federally endangered.
Recovery strategies have included protection of existing habitat, identification and management of lands for creation of new habitat, and research to better understand the effects of land use actions. Continued declines, however, suggested that Washington's isolated pygmy rabbit population was "genetically challenged."
"We figured we needed new blood," WDFW biologist John Musser explained, "so last year we worked with Idaho to bring some of their rabbits here."
Unfortunately, the Idaho rabbits proved to be too genetically different from the Washington rabbits. Instead of an inter-state relocation, two pairs captured in Idaho ended up in the Portland Zoo for captive rearing. Both produced litters, but only one litter survived.
The effort launched this year's new recovery strategy to capture Washington rabbits for captive reproduction and release -- a strategy agreed upon by a team of scientists from WDFW, USFWS, the Bureau of Land Management (BLM), and WSU. We're learning a lot about this species from the captive rearing project," Musser said. "For example, the adult female rabbit digs a special chamber in the burrow just for the babies. She covers her hairless, helpless young with dirt every day when she leaves the burrow to feed, then uncovers and cleans them when she returns to nurse them. You wouldn't even know there were baby rabbits in the burrow when she's gone."
Musser is hoping to capture four more rabbits next week for the rearing project at WSU. When young are produced and grown enough to be independent, they will be released back where their parents came from, hopefully in greater numbers and with a greater chance of survival.