Natural Inquiries

The Case of the Missing Hare

06-01-2009 // Les Line

The jackrabbit seems to have disappeared from Wyoming’s Grand Teton National Park, an absence that may disrupt the park’s predator-prey relationships

“Not much can be said of the usefulness to man of these creatures,” Ernest Thompson Seton wrote more than 100 years ago in a paean to the animal he called the prairie hare. “But as to their beauty, there can be no argument. The hare is an ornament to the plains, a delight to behold. I would preserve it even as I would preserve a beautiful picture or view.”

A popular naturalist, author and artist early in the 20th century and cofounder of the Boy Scout movement, Seton lived on the Manitoba prairie and was intimately acquainted with a mammal that we know today as the white-tailed jackrabbit. Beauty, of course, is in the eye of the beholder, and while jackrabbits are absolutely fascinating animals, they’re seldom counted among North America’s glamorous wildlife species. Seton, however, was right on the first account. Many ranchers and farmers loathe jackrabbits because they may compete for forage with livestock and eat crops. Their fur has little value, and their meat is scarcely palatable.

But usefulness can be measured in other ways. Jackrabbits are important prey animals for many predators in our western states and provinces, from cougars to great horned owls to rattlesnakes. For some species a shortage of jacks can have serious consequences. One example: Coyote predation on young deer, elk and pronghorn increases when jackrabbits are scarce or absent, as may attacks on young livestock (suggesting that ranchers may be better off with jackrabbits than without them).

This effect of rabbit declines on predation seems to be occurring in Grand Teton National Park in Wyoming, where the white-tailed jackrabbit, which inhabits a vast sweep of western grasslands from the Canadian prairies to alpine meadows in the southern Rockies, is apparently extinct. There have been just three confirmed sightings since 1978, the coyote predation rate on pronghorn fawns is exceptionally high, and wildlife biologists are talking about reintroducing Seton’s beloved prairie hare to help restore order in the park’s sagebrush ecosystem.

Jackrabbits are members of a group of mammals called lagomorphs, meaning “harelike.” Front teeth that are chisel-edged for grazing and browsing distinguish these herbivores, most of which have big ears for detecting and long hind legs for fleeing danger. Their ranks include rabbits, such as the assorted cottontails that hop across the contiguous 48 states, and the squat little pikas that whistle while they work, building haystacks that enable them to survive harsh winters on stony western mountaintops.

Then there are the hares, among them the celebrated snowshoe hares of boreal forests. They’re called hares because their young are born fully furred (or haired) and quickly leave the natal nest, which is typically a shallow scrape in the dirt under some kind of protective cover. Baby rabbits, in contrast, are born naked, blind and helpless in a dish-shaped hollow that the mother lines with grass and her soft fur. What confuses matters is that four of North America’s seven native hares are instead called jackrabbits, or jackass rabbits in earlier times. The name derives from their exceptionally long ears, which rival those of the male or jack donkey (a female donkey is called a jenny).

There are a number of traits that all jackrabbits share. They are big lagomorphs, ranging from 5 to 9 pounds. For comparison, a large eastern cottontail might tip the scales at 2.5 pounds, a snowshoe hare at 3.5 pounds. Their eyesight is sharp, and their ears, which serve as heat exchangers that help keep the animals cool in hot climates, are keenly tuned to capture the faintest sounds. Jacks will forage all night if the sky is clear and the moon bright, then take an all-day siesta in “forms” scratched out under a bush. Heavily traveled trails connect those daytime beds with favorite feeding sites. Jackrabbits rarely go to streams or pools for water. Instead, they get moisture from the vegetation they consume, including spiny mesquite and cactus in desert habitats. Females produce several litters a year.

The largest ears—around 6.5 inches long—belong to the antelope jackrabbit, found from southern Arizona into Mexico. The hare is named for the white rump patches, like those of pronghorn “antelope,” that flash from side to side during zigzag flights, confusing pursuers. The dazzling flanks of another largely Mexican hare, the white-sided jackrabbit, serve the same purpose. This species’ range in the lower 48 states is restricted to 180 square miles of grassy plains in the southwest corner of New Mexico, and it is considered endangered both there and south of the border because of livestock overgrazing and the ensuing invasion of its habitat by shrubs that choke out native grasses.

Black-tailed jackrabbits are most commonly found on arid range and agricultural lands in the West and often congregate near preferred food sources. Their populations fluctuate dramatically, peaking every 6 to 10 years. A 1958 study in California estimated that jackrabbit populations can run as high as 400 animals per square mile, extending across several hundred square miles. Such a number of rabbits represents a copious and sometimes essential food supply for predatory animals. Biologists have found that the nesting success of ferruginous hawks on Utah’s Great Basin Desert, for instance, is synchronized with black-tail abundance. At the peak of their population cycle, jacks made up 90 percent of this large hawk’s diet. But when hare numbers hit bottom, few young hawks fledged.

White-tailed jackrabbits, for the most part, have a negligible impact on agriculture. Unlike the gregarious blacktails, they lead a solitary lifestyle except during the long breeding season, when several bucks will congregate to fight over potential mates, striking one another with those powerful hind feet. (Antelope jackrabbits stand on their hind feet and box like humans.) Whitetails typically feed on succulent grasses and green forbs and, in winter, on the buds, twigs and bark of shrubs that stick above the snow. This species is the only jackrabbit that molts from brown to white in winter as does the snowshoe hare—but only in the colder and higher parts of its range, up to 14,000 feet, where the hares dig snow caves with connecting tunnels to survive the cold.

So how did Grand Teton National Park, smack dab in the middle of white-tailed jackrabbit country, lose a species that can still be found not far away in the Gros Ventre River drainage? “It could have been disease, predation, extreme weather, human persecution or other factors,” says Wildlife Conservation Society biologist Joel Berger. “There’s no way to know. They simply slipped away without notice.” That’s not too surprising. Despite its importance as prey, the animal has never been more than a dim blip on the biological radar, with only one study, now more than 40 years old, about its life history. And in the western national parks, where big, awesome critters like bears, wolves, moose and elk command the attention of budget-strapped biologists, the white-tailed jackrabbit has been taken for granted. “We really don’t know how common white-tailed jackrabbits were in the park historically,” says Grand Teton biologist Steve Cain. (Contrary to a widely published report announcing the extinction of white-tailed jackrabbits in Yellowstone National Park to the north, some whitetails still roam there.)

Could and should they be reintroduced? “The National Park Service might consider it, especially if we come up with evidence that the species’ decline was related to human influences,” Cain says. Of course, North America’s top wild dog, the gray wolf, was successfully returned to the Teton area and Yellowstone National Park not long ago. But the concept of reintroducing small- to medium-size mammals to provide food for predators is something new. There is one precedent, however. Conservationists in Spain are restocking European rabbits, their population ravaged by disease, in a last-ditch effort to save the Iberian lynx and Spanish imperial eagle from extinction.

For now, as Berger stresses, studies to understand the biology and community-level dynamics of this little-known, unusual and ecologically important lagomorph are desperately needed.

There are no jackrabbits in New York’s Taconic Hills, where Field Editor Les Line resides. But the Cape hare, an Old World relative twice the size of local cottontails, was introduced there in the 1890s. They occasionally race his car uphill—and win.


Escape Routes
Well camouflaged, jackrabbits freeze if a predator approaches, bursting from cover at the last instant and hitting 30 to 35 miles an hour, possibly up to 45. They also are Olympic-caliber broad and high jumpers, bounding in excess of 21 feet in a single leap and capable of jumping 6 feet into the air to check on the whereabouts of enemies during getaway maneuvers.


A Taste for Hares
The coyote has a strong preference for jackrabbits. In one study in the Great Basin, blacktails comprised 75 percent of the prairie wolf’s larder, with the coyote population rising and falling with changes in jackrabbit abundance. In general terms, rabbits of all kinds make up one-third of the coyote’s diet across 17 western states.

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