Friday, February 1, 2008

Pygmy rabbits try to hold on

Diminutive rodent species considered for federal ESA listing

Express Staff Writer

Photo courtesy Wendy Zumpf, University of Idaho An adult pygmy rabbit sits at the entrance to its underground burrow. Pygmy rabbits are one of the few species of rabbit that dig their own burrows.

The West's iconic sagebrush-steppe habitat covers millions of acres of rolling uplands. It's a superlative landscape of wide-open vistas and seemingly endless expanse.

Now imagine trying to find a secretive species of animal small enough to fit in the palm of your hand that inhabits this sagebrush-dotted land.

Lost in the immensity of the sagebrush steppe is the diminutive Brachylagus idahoensis, more commonly known as the pygmy rabbit, North America's smallest species of rabbit. Not much is known about these cuddly little creatures, which is why state and federal agencies are working to document both the health and range of the species.

And while a tall order for sure, it's a job the Idaho Department of Fish and Game's Beth Waterbury is passionate about. Waterbury is the Fish and Game's regional nongame biologist for the Salmon Region and is taking part in an ongoing project to document where and in what numbers pygmy rabbits exist in Idaho.

The fieldwork being done by Waterbury and others comes at the same time as officials with the U.S. Fish and Wildlife Service are considering listing the pygmy rabbit under the federal Endangered Species Act. To help in the listing decision, the FWS is accepting scientific information from governmental and private entities until March 7.

The agency is expected to decide whether to list the pygmy rabbit within a year.

The consideration of the pygmy rabbit for federal protection is the result of a lawsuit filed by several Western conservation groups, including the Hailey-based Western Watersheds Project.

A separate subspecies of pygmy rabbit inhabiting central Washington is already protected under the ESA. Biologists are attempting to rebuild that population through a captive-breeding-and-release program, although high levels of predation is hurting the success of the program.

Locally, pygmy rabbits are known to live in places like the Thousand Springs Valley northwest of Mackay in the upper Big Lost River valley and south of the Wood River Valley near Magic and Mormon reservoirs.

Waterbury said the Thousand Springs Valley population of pygmy rabbits is one of the most healthy in the region. She said the area's expanse of continuous sagebrush is exemplary of good pygmy rabbit habitat.

It's also just a major mountain range away from the Lost River Mountains to the east, where in the late 1800s a research expedition first documented the existence of Brachylagus idahoensis in the upper Pahsimeroi River Valley.

Waterbury said she and others have witnessed a decrease in the upper Pahsimeroi population in recent years.

Still, she said there are other spots in this remote corner of Idaho that contain high-quality sagebrush habitat full of pygmy rabbits. She said the valleys of the Big Lost River, Little Lost River, Birch Creek and Lemhi River are among those.

"You have sagebrush habitat that is still very intact on a large scale," she said.

Studying the pygmy rabbit

Pygmy rabbits reside in sagebrush ecosystems supporting tall, dense stands of sagebrush and deep, friable soils suitable for excavating burrow systems, University of Idaho Ph.D. student Wendy Estes-Zumpf writes in the summer 2005 issue of "Windows to Wildlife," an Idaho Department of Fish and Game publication.

A member of the lagomorph family of rabbits, hares and pikas, pygmy rabbits occupy harsh, dry expanses of sagebrush in the Great Basin desert and surrounding intermountain region covering seven Western states, Estes-Zumpf states.

Sporting a very small tail matching the gray tinge of their body, pygmy rabbits are 9 to 12 inches long and generally weigh no more than a pound.

Estes-Zumpf writes that the rabbits are uniquely adapted to their sagebrush habitats, being one of just a few species that consume large quantities of sagebrush, which contain monoturpenoids, chemicals toxic to most animals if eaten in large amounts.

One of a suite of sagebrush-obligate species that includes greater sage grouse, pygmy rabbits are particularly vulnerable to loss and alteration of sagebrush-steppe habitats due to their specialized habitat needs and limited dispersal capabilities. Population declines apparently linked to habitat loss and fragmentation have elevated concerns over the conservation status of this species.

In the Salmon region, Waterbury and other biologists with the Fish and Game and the U.S. Bureau of Land Management are conducting inventories to identify the distributional limits and population centers of pygmy rabbits in the east-central basins of Idaho. Fish and Game biologists are also providing logistical support to University of Idaho researchers investigating pygmy rabbit ecology and population dynamics. These researchers, operating under UI Associate Professor Janet Rachlow, are also considering the movement and gene flow of pygmy rabbits.

Waterbury said the work has already led to several surprises.

She said the conventional wisdom regarding pygmy rabbits suggested that juveniles only dispersed about 100 meters from their natal burrows. She said this now appears to be off by a good bit.

Waterbury said biologists now think young pygmy rabbits will establish new home ranges of their own as far away as one to 12 kilometers from their birthplace.

"Much greater than we thought," she said. "That's good news."

She said the research has also proven that dispersing pygmy rabbits can get across smaller obstacles in the landscape such as small creeks.

"They do make pretty good movements if the habitat is there," she said.

It's this last factor that is apparently the most critical and generates the greatest challenges to conserving pygmy rabbits in the longterm. It all comes down to habitat fragmentation, Waterbury and others say.

She said that in areas without continuous sagebrush, whether due to wildfires, livestock grazing or oil and gas development, pygmy rabbits dispersing to other suitable areas become highly prone to predation both from the air by raptors and from the ground by coyotes, long-tailed weasels and badgers.

While freely admitting that some populations of pygmy rabbits are in decline, Waterbury doesn't necessarily believe that an ESA listing is the answer. She said that by working with federal land managers and continuing to monitor the species, pygmy rabbits can be preserved.

And key to this is continued study, which is shedding light on these rare animals, she said.

"We're filling in the blanks," she said.

Protecting pygmy rabbits

Habitat fragmentation is the single most pressing issue, contributing to a decline in pygmy rabbits in the states of Idaho, California, Oregon, Nevada, Montana, Wyoming, Utah and Washington, said Katie Fite, biodiversity director for Western Watersheds Project.

Fite contended that oil and gas development, wildfires and range improvements for livestock grazing are causing this fragmentation. She said that in Idaho, range improvements are being justified under the guise of protecting sage grouse.

While projects like building new watering areas do spread out livestock grazing, she said, they also contribute to the spread of noxious weeds into pristine expanses of sagebrush where grazing was light in the past. She said these projects further fragment the remaining sagebrush habitat because of new roads and allow invasive species like cheatgrass to spread.

In turn, the cheatgrass, which dries out earlier in the spring, leads to hotter and more widespread wildfires, she said. She said the wildfires in turn further fragment the habitat, to the pygmy rabbit's detriment.

"Distribution (of livestock) equals disturbance," she said.

Fite said the answer is to reduce or remove livestock-grazing pressure on federal lands where pygmy rabbits live. She said this is especially true for the largest, most intact expanses of sagebrush steppe that remain.

These remaining reservoirs of big sagebrush habitat need to be preserved if the pygmy rabbit is to survive longterm, she said.

"Instead of chipping them into more little pieces," she said.

Fite said that in a sense, today's pygmy rabbits are found in islands with large areas of unsuitable habitat created in between. She said this fragmentation threatens the longterm survival of pygmy rabbit populations, many of whom are simply disappearing.

"What we have now is isolated populations," she said. "What you have to do is look where they aren't."

Fite said a great example of this is central Washington's lone population.

"That population went away," she said.

Why protect pygmy rabbits?

The pygmy rabbit isn't the gray wolf or the grizzly bear. It's not the silvery salmon racing upstream from the Pacific Ocean to its clear-water birthplace. And it's certainly not the majestic bald eagle.

Caring about the survival of those charismatic species is easy. Caring about a species like the little-known pygmy rabbit, no matter how adorable they may be, is another matter.

Still, those who love them aren't deterred.

The significance of declining pygmy rabbits goes beyond just the single species, Waterbury said.

"The canary in the coal mine analogy is good. You're losing a piece of the puzzle out there," she said.

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