His name is Clay. He's a happy, creative 24-year-old male who prefers to live in solitude. Although most of the time he is peaceful, he has been known to become aggressive and violent in a manner that can terrify the people who love him.

If Clay were human, he would probably have been diagnosed with post-traumatic stress disorder (PTSD). But Clay is a chimpanzee, a survivor of years of invasive medical experiments, and a resident of the Save the Chimps sanctuary in Fort Pierce, Fla.

"Clay's a fabulous guy," says Sanctuary Director Jen Feuerstein. "He's really engaging with humans and loves to play. But he does not tolerate other chimpanzees at all. He gets very aggressive around them." Several attempts have been made to introduce him to other chimps, but none have been successful. "He lives on his own and it's going to stay that way."

To help Clay and chimpanzees like him, Save the Chimps is converting an old building on its 60-hectare sanctuary into a "special needs" facility that will house traumatized animals and others with medical conditions that prevent them from being around others of their species. The project has already raised around $230,000 of its $835,000 construction budget, says Feuerstein, which has enabled the organization to renovate the interior and move in its first few residents. The remainder will be used to fund outdoor yards and playgrounds so the apes living in the building have access to nature and fresh air.

"Right now, I've got about eight chimps that we consider 'special needs,'" Feuerstein says. "Hopefully the building will be able to accommodate about a dozen."

Several studies—for example, see research published in a 2008 issue of the Journal of Trauma & Dissociation and in a June 16, 2011, issue of PLoS One—have shown how traumatized chimpanzees can suffer from PTSD, especially after living in captivity. "We see all sorts of behaviors that I would characterize as PTSD," Feuerstein says. "We have chimps that self-mutilate or who scream for no apparent reason. We've had chimps that wouldn't go outside or chimps that rock back and forth—a lot of stress-related behaviors like that. I'm usually surprised that I don't see more of it."

Many chimps suffering from emotional trauma can ultimately be integrated back into groups and recover after what Feuerstein characterizes as a "challenging adjustment." But a small number, such as Clay—who was separated from his mother 10 hours after his birth and grew up apart from all other chimpanzees—cannot be integrated and end up living on their own. "But one thing Clay has is a very positive attitude," she says. "He's friendly and loves to play. He doesn't have any other stress behaviors or abnormal behaviors."

The revamped building will also house chimps with medical problems such heart conditions and epilepsy. "If a chimp has a seizure, other chimps will be afraid and hit them, jump on them or drag them around," Feuerstein says. Epileptic chimps are treated with the same drugs that humans receive, but success rates vary. The building will also serve as a potential home for chimps who become ill, develop heart troubles or who get kicked out of their social groups on one of the sanctuary's 12 1.2-hectare islands for some reason.

Feuerstein says that chimps in captivity suffer from a variety of health problems, including heart conditions, kidney disease, liver disease and diabetes, but the causes of these conditions—especially for the chimps at the sanctuary—remain unclear. "We don't know how much of this was from the research they endured because we don't have a record of what they went through."

The way the chimps were bred could also be a factor in their health. All of the apes at the Save the Chimps facility are common chimpanzees (Pan troglodytes), but they are likely crossbreeds of different subspecies because breeding at medical-testing facilities was "indiscriminate," Feuerstein says.

Despite their history of trauma and invasive medical experiments, Feuerstein says, most of the 266 chimps at their sanctuary are amazingly well-adjusted and forgiving to humans. "They're able to separate who treats them well and who doesn't. They don't hold a grudge."

Photos of Clay courtesy of Save the Chimps