Over-the-hill chimpanzees will soon spend their retirement years in a Louisiana old folks home.

Construction has begun on Chimp Haven, planned as the country's only preserve dedicated to chimps who have been retired as entertainers or as subjects of laboratory research. Up to 300 chimps will find themselves on 200 acres of grass and woods for foraging, climbing and monkeying around.

"A lot of young adult chimpanzees have been born in captivity, and a huge number have never walked on grass, climbed a tree or poked a stick in the mud," said Linda Brent, a behavioral primatologist and Chimp Haven's president. "They haven't had the stimulation they need to grow socially, and that will be part of what they'll need to learn at Chimp Haven."

About 1,600 chimps now live in the United States, most in drug and infectious disease research labs but without research value. Once the tests are done, a chimp's lab career is usually over.

Animal experts say it is only right to provide the primates -- whose genetic makeup varies less than 1 percent from man's -- with spacious grounds that have facilities to accommodate their high intelligence levels.

"These animals are powerful, intelligent, resourceful and long-lived, and that all adds up to an animal that requires special accommodations," said Dan Maloney, general curator at the Audubon Zoo in New Orleans, who also worked with chimps at the Philadelphia Zoo. "I applaud any facility that's going to take this on and do it in a responsible way."

At the labs, chimps are injected with drugs being tested or are infected with a disease. A career in the lab can be as short as three years. A chimp is rarely useful to scientists if it has already undergone medical tests or been injected with a disease or drug. Chimps can live into their sixties; those who outlive their research value typically spend the rest of their lives in small lab enclosures.

At least 260 of the chimps to be retired at Chimp Haven are the result of a breeding program in the 1980s that produced far more of the primates than researchers needed, Brent said.

Linda Koebner, Chimp Haven's executive director, led one of the first "chimp rescues" in 1974, when a research lab gave her permission to take 10 of its chimps to live on an island in a Loxahatchee, Fla., preserve.

While a number of preserves exist for exotic animals, Chimp Haven was founded in 1995 as a nonprofit with the goal of creating a preserve devoted to chimps. Its board of directors now includes primatologists, experimental scientists and veterinarians who care for chimps in research labs.

Funding for Chimp Haven comes from donations and from a federal contract after Congress passed the 1991 "Chimp Act," which dedicated as much as $30 million to care for chimps that were owned by the federal government or involved in federal research labs.

The government of Caddo Parish, in northwest Louisiana, donated land for a facility that will eventually include indoor areas for the chimps and an education center for visitors. Last month, workers began pulling down trees to begin construction of the walls and moats that will surround the preserve.

After lifetimes spent inside laboratories, some chimps might have difficulty adjusting to life at Chimp Haven, even though the northern Louisiana climate and landscape are similar to chimps' native areas of Africa.

"A lot of the old-timers, who were born wild, actually know how to be chimpanzees," said Koebner, who has a background in behavioral primatology. "Guys who were born in the lab don't have a clue."

Because of sketchy record-keeping, some of the chimps' histories are a mystery.

One is Janice, a female now about 40 years old, who has spent most of her life in breeding and biomedical research programs, and a number of years confined alone.

Janice used to be feisty, moving and thinking quickly. After years in captivity, she is now slow-witted and slow on her feet, Brent said.

"She's beaten down a little bit. She's not the same animal she used to be," said Brent, who works with the chimp at a lab in San Antonio.

He is confident that living in the outdoors at Chimp Haven will transform Janice into her former self. "I have no doubt that at Chimp Haven, she'll become a very dominant, capable individual."