New federal rules proposed Tuesday would severely restrict medical and behavioral research on chimpanzees and send nearly all of the government’s remaining 450 research chimps into retirement, an unfunded project that could cost $25 million.

The recommendations, which set high hurdles for new studies using chimps, arrive even as research with the apes has grown increasingly rare.

“There is no compelling scientific reason to maintain a large research population,” said Daniel Geschwind, a researcher at the University of California at Los Angeles who co-chaired the working group that made the recommendations to an advisory panel for the National Institutes of Health. “The majority of NIH-owned chimps should be designated for retirement.”

The United States is the only country that keeps chimpanzees for research.

Just two of the 30 current federally funded chimpanzee projects would meet the proposed criteria. Both projects involve infectious diseases or immunology. Seventeen other projects would be allowed if the chimps’ housing conditions were upgraded.

Ginger, a 42-year-old chimpanzee, holds her new female baby on Aug.15, 2012, at Chimp Haven, the national sanctuary for retired research chimpanzees in Keithville, in northwest Louisiana. (Uncredited/AP)

Under the recommendations, researchers would have to meet the proposed rules to receive federal funding. Only studies that could not be done with people or other animals — such as rats, mice or monkeys — would be approved. Ongoing projects would be allowed to finish.

“It’s almost a stranglehold” on new research with chimpanzees, said John Pippin, medical director of the Physicians Committee for Responsible Medicine, an animal rights group.

The rules would require large outdoor habitats so the animals could live in social groups, as they would in the wild, with trees or climbing platforms, hay or leaves to build sleeping nests, and plenty of foraging options. No chimpanzee could be isolated in a cage or enclosure without a compelling medical need.

Animal rights groups largely applauded the proposal. “These recommendations reinforce what the public has been asking for, which is a move away from invasive research and getting chimps to sanctuaries,” said Kathleen Conlee, vice president of the Humane Society of the United States.

Although most research chimps would be retired under the plan, 50 should be kept for research, the group recommended. These animals would be housed in open habitats, with at least 1,000 square feet per animal, the equivalent of a roomy one-bedroom apartment. The NIH’s 451 research chimps now live at three laboratories in Texas and New Mexico.

But Alice Raanan of the American Physiological Society, which promotes medical research, said it’s unclear whether 50 research chimps would be enough for scientists seeking vaccines for hepatitis C, one of the last remaining research areas using chimps.

The NIH bred hundreds of chimpanzees in the 1990s for research on HIV and AIDS, but the animals proved poor subjects for that work, leaving a surplus of them in laboratories.

Yet to be decided is how to pay for the retired chimps, each of which costs $20,000 per year in upkeep.

In 2000, Congress funded a chimpanzee sanctuary in Louisiana but limited spending to $30 million. The NIH has since spent more than $29 million on Chimp Haven, which houses 109 apes and is raising $5 million in private donations to shelter 110 more animals due to arrive this year.

“If we were to expand [the sanctuary] it would take funds, and we don’t have the funds to do that,” said James Anderson, the NIH’s deputy director. “It is a concern for us and something we would have to have addressed at the congressional level.”

The recommendations cap about two years of public debate, triggered after the NIH shifted 14 previously retired chimps back into active research. The move brought outcries from activists and a congressional directive for the NIH to study the issue.

The NIH’s director, Francis Collins, has 60 days to accept or reject the proposal. He has publicly favored retiring the agency’s chimps. In September, he announced the retirement of 110 of them by saying, “It’s appropriate to move in the direction of getting many of those animals out of the research arena.”