Old McDonald is moving the farm.

The Reston Animal Park, a fixture in western Fairfax County for more than 20 years as a place to take children on weekends to groom the goats and ape the monkeys, has a new home in Loudoun County.

This month, owner Bob Johnson began moving his menagerie to Sunshine Farms, an 18-acre spread just south of Leesburg on Route 15. Like Noah with his ark, the move couldn't be accomplished in just a day or two; Johnson says it will be mid-November before all his animals are relocated.

"Not everyone is here yet," said Johnson, a Washington environmental policy wonk-turned-Dr. Doolittle who has taken over a portion of the Leesburg farm and produce stand and created new digs for three dozen of his animals, including goats, deer, Yorkshire pigs, ornamental turkeys, horses, donkeys, emus and llamas.

In coming weeks, he will build or renovate barns and stalls for the rest, among them a red-tailed hawk, an African steer with a four-foot horn span, a Himalayan bear cub, a camel, a half-dozen gibbons and squirrel monkeys, a boa and a python, two Aldabra tortoises and handfuls of tarantulas and hissing Madagascar cockroaches.

Johnson and his wife, Shirley, have a six-year lease on three acres at Sunshine Farms, a produce stand that this time of year has pumpkins and gourds, a straw maze and hayrides.

The Johnsons hope to expand their animal park, which is open almost year-round, to five acres, one-sixth the size it was at its Reston site on Hunter Mill Road near Baron Cameron Avenue.

The move follows several years of legal sparring between Johnson and his Reston landlord over the terms of Johnson's lease.

"This just feels more like the country," Johnson said recently as he stacked bales of hay at his new site. "There just wasn't space in Reston. If an animal got out, they'd get in the middle of a parking lot and they'd panic, and people would, too. It was getting too crowded."

He may have spoken too soon, though. A former cornfield adjacent to Sunshine Farms sprouts three-acre lots for 30 large homes--the kind of development that drove him from Fairfax.

"I can't seem to get away" from development, Johnson said over the din of trucks and backhoes moving dirt to prepare for driveways for the mini-mansions. "It keeps following me."

Johnson was forced to cut back the size of his herds in Reston as some of the rented fields where his bison, deer and zebras had grazed were sold to developers. Now he keeps only a few deer and one bison. The population growth closing in on him had another downside: Teenagers would sometimes steal his turkeys and sheep as a prank.

Five years ago, the Johnsons became embroiled in a legal battle with their landlord, Mack S. "Jack" Crippen Jr. Crippen had sold a portion of his family's 300-acre farm to a developer and ordered the Johnsons to move, but the couple argued that they had an agreement to rent for 15 more years.

The two sides reached a compromise that allowed the Johnsons to stay on the land at least five years, at an annual rent of less than $30,000, Johnson said. When the lease expired this year, the Johnsons and the Crippens--Jack and his wife, Sandra--parted company.

"It was time to move on," said Johnson, 57. "We had been looking around in Leesburg for the last five years and finally got a spot."

The Crippens started the park in 1975 and ran it for four years before selling the animals to the Johnsons. Sandra Crippen said the family has hired a couple from southern Virginia to take over the Reston facility, which will reopen in January as Reston Zoological Park.

Johnson, who plans to keep the name Reston Animal Park even though he's in Loudoun, said he had 100,000 visitors annually in Reston. Sunshine Farms' manager, Michelle Marovelli, said 200 children come through her "Pumpkinville" every 20 or 30 minutes on some autumn weekdays.

"There's apples and cider and now animals to pet," she said. "It's a perfect fit."

Visitors pay $9.50 on weekends and $6 on weekdays, with children younger than 2 free.

On a recent sunny morning, an excited group of Douglass Community Center preschoolers bolted from the hay ride to the gates of the animal farm, as Johnson tried to maintain order.

"Don't chase it!" he shouted at one toddler who was in determined pursuit of a fluffly black sheep. The animal made a narrow escape by leaping over a second small child, who had bent over to tie his shoe.

After a few minutes, the boy and the sheep called a truce from opposite corners of a pen decorated with these warning signs: Be careful. Emus like to peck at shiny things. Don't feed them fingers.

Johnson, whose own fingers and hands bear scars from snakebites over the years, shook his head and smiled. "Kids and animals together. What could be better?"

What indeed? For most suburbanites, an afternoon at the petting farm is a hands-on lesson.

"We've never petted a llama before," said Aber Abdin, 39, as the woolly beast pecked at the gray and yellow pellets of food in her hand. "All I can think of now is that I can't wait to wash my hand."

Nearby, Jeremy Schlegel, 4, was making his own discovery.

"Mom! Mom! Come pet the cow," Jeremy shouted as he and a playmate, Tommy Stogoski, also 4, rushed toward the animal.

Trailing behind, his mother gently corrected him. "Honey, that's a donkey."

Jeremy wrapped his arms around the donkey's furry neck. "Okay. Okay," he said. "Whatever it is, let's touch it and take it home."

CAPTION: Krysta Meredith joins a flock of ducks at the Reston Animal Park.

CAPTION: Children pet a white deer at the Reston Animal Park, which will keep its name at its new home in Loudoun County. The petting zoo is moving to three acres at Sunshine Farms on Route 15, south of Leesburg. Above, a llama takes a close look at a visitor who is taking a close look at it.