Columbia Basin Pygmy Rabbit
(Brachylagus idahoensis)
In 2007, my tour took me to Washington State University (WSU) in Pullman for a lecture. It was there that I heard about the Columbia Basin pygmy rabbit, and the efforts being made to save it from extinction. Once you have seen one, you fall in love—a perfect little rabbit, the smallest in North America. An adult fit easily onto the palm of my hand. Childhood images of Peter Rabbit and his siblings, Flopsy, Mopsy, and Cottontail, thronged my mind. I was hooked!
The Columbia Basin population has been isolated from other pygmy rabbits for thousands of years, and is genetically differentiated from those found in Idaho, Oregon, Montana, Nevada, and California. They are specialist feeders, able to live on sagebrush in arid western US rangelands. They need tall, dense sagebrush plants for protection as well as food, and soils that are deep enough for the construction of a burrow system. They are one of only two North American rabbits that actually dig their own burrows.
Starting in the early 1990s, numbers of pygmy rabbits in Washington State declined following loss of habitat and fragmentation of the remaining sagebrush ecosystems as ever more land was taken over by farms, ranches, and urban development. In 1999, the Washington Department of Fish and Wildlife asked Dr. Rod Sayler and his colleague, Dr. Lisa Shipley, if they would help them conduct studies on the declining populations. At the time, Rod and Lisa were working on assessing the influence of cattle grazing in sagebrush habitats known to be important to pygmy rabbits. These studies had barely started when it was discovered that the largest remaining pygmy rabbit population had just suffered a major crash—possibly due to disease. Probably fewer than thirty individuals remained. USFWS gave these rabbits a temporary emergency endangered listing in 2001 with a final ruling to cement the listing in March 2003. At this time, it was decided to start a captive breeding program with the goal of subsequently releasing them back into the wild.
Sixteen rabbits were captured and sent to three facilities for captive breeding. If any were left in the wild, they soon vanished. Oregon Zoo had already started breeding the non-endangered Idaho pygmy rabbits in order to experiment on the best procedures before trying with the precious remnants of the Columbia Basin population. Rod and Lisa, heading the captive breeding program at Washington State University, found that it was necessary to house the rabbits alone, except for mating, because of high levels of aggression. Much was learned from observing the rabbits at night through remote cameras and infrared lights.
It soon became apparent that, unlike Idaho rabbits, the Washington individuals had much lower reproductive success—fewer kits per female, lower kit growth rates, and some bone deformities. And all three sites struggled with disease and parasites. Eventually it was concluded that this was partly caused by inbreeding depression resulting from reduced genetic diversity in the small captive population. Every time a genetically important rabbit died, it meant that more diversity was lost and the chances for long-term viability of the tiny remaining population were reduced. Eventually in 2003, the USFWS Recovery Team regretfully came to the conclusion that the only way to improve the reproductive fitness and thus save the last Columbia Basin pygmy rabbits was to allow some of them to mate with Idaho rabbits. This, as had been hoped, considerably boosted the breeding success and the health of the hybrid offspring.
Eventually, after six years, it seemed realistic to make plans to reintroduce some of the Washington rabbits into the wild, and once again Idaho rabbits paved the way. Forty-two captive-bred Idahos, equipped with radio collars, were released into the wild in Idaho. They did well, and following the release at least two surviving females gave birth.
The Story of Grasshopper
My visit to WSU happened to be just before the first twenty captive-bred Columbia Basin pygmy rabbits were due to be released in eastern Washington, a hundred miles from the university, on March 13, 2007. Each was fitted with a little radio collar so that its movements could be monitored. Everyone was excited and hopeful, but everyone knew there was no guarantee of success. I met Len Zeoli, a mature PhD student, who would be studying the rabbits’ adaptation to the wild. And I met Grasshopper, one of the male rabbits due to be released. What an utterly adorable little rabbit he was—I was saddened that he would have to carry a radio collar. Tiny though it was, he was tiny, too.
Of course, I was eager to hear how the release went. The report came back from Len that things had gone well, and the rabbits had been “very rabbit-like.” But there were unexpected problems—almost half the rabbits dispersed from the release area, traveling off presumably in search of new homes or mates. That did not happen in the test reintroduction in Idaho. In addition, losses to predators (coyotes, raptors) were high.
I asked specifically about Grasshopper. I was told that he, together with his brother Ant, were among the eight males who moved beyond the range of the telemetry equipment, which covers three-quarters of a mile. Eventually they were both located—just a few hundred yards from the field station where Len was staying. They had somehow made it across three and a half miles of inhospitable and sometimes rocky terrain. Knowing that they would not be able to last very long, Len captured both Grasshopper and Ant, and they were returned to captivity.
“Throughout the whole reintroduction program, everyone was pretty discouraged,” Rod told me, “but then something amazing happened that restored a little bit of hope.” One day when Len was keeping watch, a pygmy rabbit kit suddenly popped out of one of the artificial burrows they had installed. It sat there looking at him and he was able to get close-up photos. “We saw the kit periodically throughout the remainder of the summer,” said Len, “and it became famous in a photo widely published in a news release.”
The photo proved that captive-bred pygmy rabbits would breed in the wild in their first breeding season—if they could escape predators long enough and readapt to the arid sagebrush habitat. “By the end of summer,” Len said, “the remaining two released rabbits were taken by predators, and we terminated the field study for 2007. Everyone had hoped for greater success, but at least they have learned a lot that will help them plan better in the future.”
Rod and Len, I hear, have completed population modeling studies and concluded that the captive breeding population needs to be at least doubled so that more can be released to the wild. Since the first litters of the year usually die, perhaps because of cold wet soil, research associate Becky Elias is setting up breeding pens in a greenhouse. They are building much larger, more natural pens so that the rabbits will be better adapted to a natural environment. There are plans to release the next batch of young rabbits into a temporary enclosure at the release site to protect them from predators while they adjust to living in the wild. Sadly, I heard, both Grasshopper and Ant died before they could be released again, with a better chance of making it—but a new batch of young kits has been produced in captivity for future reintroductions.
Rod Sayler summed it all up: “We’re definitely not over the hump in terms of restoring this endangered species back on the landscape—there are big challenges ahead for this little rabbit. But we still have hope! We learned a lot from last year’s release, and we’re not giving up.”
My best wishes are with you all, the humans involved and all of the enchanting little rabbits.