From the perspective of author Wallace Stegner, who once wrote that "it is a better world with some buffalo left in it," the National Zoo has just gotten a whole lot better.

Today the zoo opens a 46,000-square-foot exhibit that pays homage to the once-grand American Prairie and features a colony of 14 burrowing prairie dogs, dozens of varieties of native prairie grasses and plants waving in the hot breeze, and a pair of majestic young bison--Ten Bears, the male, and Kicking Bird, the female.

Located on the main Olmstead Walk, next door to the Panda House, the multimillion-dollar exhibit is designed to educate visitors about the prairie that once covered 420 million acres in America but now has been reduced by development to 1 percent of that, or 4.2 million acres.

"It is important that we understand the interaction of people, plants and animals, how human interaction has affected our environment," said Mike Morgan, a zoo spokesman. "That's the idea behind the exhibit."

The "American Prairie" exhibit, which took four years to plan and build, is part of a $4 million zoo renovation that includes a new restaurant, gift shop and plaza. Instead of tall wooden boards decorated with animal pictures, the typical view during construction, visitors on their way to the giraffes and elephants will now see the bison and prairie dogs, 110 species of grass and plants--as many as 50 of them native to the prairie--and scores of interactive displays.

The misnamed prairie dogs--rodents that that make a high-pitched sound resembling a bark--have been fixtures at the zoo for years but have now been incorporated into the new exhibit. The animals, which burrow underground and have divided themselves into two separate groups that sometimes compete for space, quickly consumed the grass planted to supply them with food, leaving only dried brown remnants. They are now fed kale and other foods by zookeepers.

The American Prairie is a place where grass is stronger than trees, where devastating fires are vital for the land's survival, where temperatures can climb into the 100s on a summer day and plummet to 35 degrees below zero on a winter night. It is also where bison, the largest land animals native to North America, once numbered more than 30 million before they were hunted to near extinction a century ago.

Now, with conservation efforts continuing, there are about 200,000 bison, more commonly called buffalo, in the United States.

The bison, which covered parts of the country so densely in 1806 that explorers Lewis and Clark spoke of a "moving multitude" that "darkened the whole plains," have special meaning at the National Zoo. The facility's founder, conservationist William Temple Hornaday, began a campaign in the late 1800s to save them, and when the zoo opened on the Mall more than 110 years ago, bison were among the first animals displayed.

The zoo's previous bison residents were removed two years ago. The new prairie exhibit showcases Ten Bears, who at only 14 months already weighs about 600 pounds and will reach 1,800 pounds, and the smaller, 13-month-old Kicking Bird, who is still shedding the winter fur coat that bison grow to keep warm.

An electrified wire ensures that the bison, which move fast for their size and are dangerous to humans, stay in their enclosure. There is also a small house where the bison will be fed plants in addition to what they eat roaming their own little prairie.

Yesterday, the bison strolled leisurely through their new home, munching on what zoo assistant curator Stuart Wells said is probably their favorite treat--big bluestem, appropriately named because its thin stalks grow to more than six feet and have a decidedly blue cast. The plants are so numerous and high that when the bison lie down and lounge, the animals are hard to spot. But when they stand, they are impossible to miss.

"We're not sure we will breed them, or allow them to breed," Wells said. If the zoo decides against offspring, "we would take precautions."

Precautions? "Yes, preventive measures. On the male."

Translation: Ten Bears would get a bison vasectomy.

CAPTION: Ten Bears, left, and Kicking Bird, two yearling bison, roam through tall grass at the National Zoo's new 46,000-square-foot American Prairie exhibit.

CAPTION: A couple of curious prairie dogs poke their heads up from a hollow in the prairie run at the zoo's new exhibit. They are part of a colony of 14.