Photo: Uryadnikov Sergei/Getty Images/iStockphoto

As a baby orangutan, Pony was kidnapped from the forest in Borneo and sold into sex slavery. For the first several years of her life, she was kept chained to the wall of a brothel in a remote village, shaved daily, and pimped out alongside human prostitutes. When she was finally rescued — at that point, she was around six or seven years old, right before orangutans typically enter puberty — she was found lying on top of a mattress covered in sores and would gyrate whenever a human male walked past.

Now 17, Pony is still recovering from the trauma of her early life. Since her rescue in 2003, Pony has been living at the Nyaru Menteng Orangutan Reintroduction Center in Kalimantan, Borneo, which rescues and rehabilitates captured orangutans with the aim of gradually releasing them into the wild. Pony has progressed socially since she first arrived — she is now a dominant female, although “most of her friends are much younger and smaller than her,” says Fransiska Sulistyo, the animal welfare coordinator at the Borneo Orangutan Society, who is currently in charge of Pony’s care. Still, she is completely dependent on BOS staff, having gone through two failed attempts to release her; in each case, Pony refused to explore or forage for food, and instead sat in the same spot all day, waiting to be fed.

Although Pony is an extreme case, most of the orangutans at the center “have some level of trauma,” Sulistyo says. They have been rescued from zoos or circuses, or kept as pets. Many of them show behavioral signs of trauma when they arrive: They rock back and forth, they pace. That kissy thing orangutans do that humans find so cute? It’s actually a sign of distress, according to Sulistyo, who estimated that about 10 to 20 percent of the orangutans at the center are unlikely to be able to return to the wild ever again.

To put it another way: Pony and other orangutans at Nyaru Menteng suffer from post-traumatic stress disorder. Scientists have known for a while that animals can develop PTSD just like humans can; what they still don’t know, though, is the best way to treat it. While some symptoms are species specific, others are universal. “Monkeys might bite themselves, birds might pull their feathers out, dogs and cats can compulsively lick their fur off. And people will sometimes cut themselves or burn themselves,” says Kristine Coleman, a scientist at the Oregon National Primate Research Center. For people with PTSD, talk therapy is a crucial part of treatment. For other species, that’s obviously not an option, leaving the people who work with traumatized animals struggling to help them.

Not surprisingly, given what we know about mental illness in humans, mental-health issues in animals can frequently be traced back to trauma and poor conditions in early life. “There are certain behavioral indicators of past stress. We know a lot about outcomes of having poor maternal history, for instance,” says Stephen Ross, a primatologist in charge of chimpanzee welfare at the Lincoln Park Zoo in Chicago. Chimpanzees separated from their mothers early “will often show behavior throughout their life that is indicative of this past stress, such as rocking and pacing.” Social skills are also impacted. “Early stressful experiences result in a lack of social skills and difficulty fitting in, which leads to further isolation and stress,” often exacerbating other problems, Ross says.

Aside from medication, which can be tricky to get right, and adjusting the animal’s environment to be more socially and cognitively stimulating, one of the main methods of treating animals with psychological problems is a type of conditioning called Positive Reinforcement Training. In PRT, food treats and other rewards are used to reinforce desirable behavior, such as engaging socially, being active, and not cowering.

PRT can be quite successful in certain contexts. For example, it’s been shown to be effective in reducing stereotypic behaviors (repetitive motions like rocking, touching, or tapping), which are thought to result from boredom or loss of control. But it’s much less successful for animals with more serious, intractable problems, including self-injury. There’s even evidence that it can backfire for some animals: A 2010 study, for example, found that anxious chimps were more likely to become agitated when they got a wrong answer during PRT training. “Thus, for these anxious animals,” wrote the authors of a 2014 review, PRT may not “provide the same psychologic well-being benefits afforded to other individuals. Instead, training may actually increase stress for these animals.”

For animals with more severe problem behaviors like persistent self-injury, essentially the only option is carefully monitored medication with drugs originally developed for humans, including the antidepressant Prozac and the antipsychotic Haldol. Naloxone, the medication given to revive people who have overdosed on opioids, has also been found to be moderately effective for treating self-injury in animals. As with humans, however, medication only goes so far.

“One thing we are doing more and more in the laboratory environment is trying to provide individualized medicine, so really identifying the causes of behavior to find a more effective treatment,” Coleman says. Often this goes back to an animal’s history, but it can also involve looking at individual temperament or personality. “Not every animal that has self-injury grew up in a suboptimal environment. It’s really only a risk factor,” Coleman says, and “we know there’s a link between temperament and behavioral issues in humans.”

Still, although animal personality is attracting researchers’ attention more than it used to, “personality assessment is not widely used within the animal-care field,” Coleman says. “The research is very new.”

One of the earliest clues into the role of temperament in trauma recovery in animals came from Harry Harlow, whose experiments rearing monkeys formed the basis of what we know about the link between maternal attachment and later mental health. In the 1960s, following those early experiments, Harlow conducted another series of far more disturbing and less well-known studies in which he essentially tortured baby monkeys, imprisoning them shortly after birth for 3, 6, 12, or 24 months without any social interaction or environmental stimulation in enclosures he macabrely insisted on calling “the pit of despair.” When released, the monkeys were naturally incredibly disturbed. Harlow and his team observed their behavior and attempted to rehabilitate them.

Unsurprisingly, the longer the monkeys were confined, the worse off the monkeys fared, but there were also individual differences between monkeys held for the same amount of time. Some recovered socially faster than others, which Harlow attributed to monkeys’ varying personalities, as all had been exposed to the same level of trauma.

Harlow’s contemporaries rightly condemned the experiments, eventually establishing a set of ethical guidelines for experimenting on animals. It’s only in recent years — decades after Harlow’s work — that investigations into animal temperament and trauma are becoming more common again. Conducted ethically, these studies could provide a path to better treatment for abused animals, which is currently takes a one-size-fits-all approach.

“Knowing an individual’s temperament can help animal behaviorists determine the right course of treatment,” Coleman says. It can also be used to identify those at risk for developing behavioral problems down the line, paving the way for early interventions to prevent those behaviors from occurring in the first place.

Back in Borneo, Sulistyo and her staff do their best with what they have. Most of the orangutans that come to them are intensely scared of humans when they arrive, which can affect their treatment. “Some of those who are afraid show aggressiveness, while others are more submissive — they are not happy with human contact but they will submit to it,” Sulistyo says. Other factors, such as the age at which the animals were rescued, also influence their reaction and recovery. “It’s difficult when dealing with older orangutans,” Sulistyo says. “If we receive them when they are still very young, it’s easier. We have babysitters who sleep and cuddle with them.”

For orangutans who are either too old or aggressive toward humans when they are rescued, or whose trauma is extreme, like Pony, the main thing is “giving routine activities, showing her that these kinds of human are not harmful to her,” Sulistyo says. “Gradually, she starts to trust humans again.”