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Human beings are social animals, and so are our close relatives monkeys. But many of the monkeys used in medical research live alone in cages. Some researchers are working to increase the number of lab monkeys that get to live with buddies. NPR's Nell Greenfieldboyce reports.
NELL GREENFIELDBOYCE, BYLINE: It's a beautiful day, and I'm standing under some trees outside a big enclosure the size of a basketball court. Inside the wire fence are about 60 monkeys, rhesus macaques.
MARIA CRANE: See the little baby right here with the mom sitting right underneath that blue climbing structure? That baby was probably born in the last two weeks.
GREENFIELDBOYCE: Maria Crane is the lead veterinarian here at Yerkes National Primate Research Center in Georgia. We watch as the monkeys groom each other and leap around on old playground equipment.
CRANE: They are extremely acrobatic. It's amazing when you watch them run around and play within these areas how agile they are.
GREENFIELDBOYCE: This is a breeding colony to produce monkeys for use in research. Over a hundred thousand non-human primates live in research facilities across the United States. Their lives usually start in a big social group like this one, but eventually most get taken to labs for use in studies, everything from testing new vaccines or drugs to studying cancer, diabetes or addiction. I ask Crane when monkeys get taken away from here.
CRANE: It depends on the project needs. But most of the animals remain in their natal group until about the age of 3.
GREENFIELDBOYCE: For a monkey, going to live in a small cage in a lab is a huge, stressful change. And it's even worse if they suddenly have to live alone. Kathleen Conlee is with The Humane Society of the United States.
KATHLEEN CONLEE: Social housing is the most important thing to a primate. No doubt.
GREENFIELDBOYCE: She says isolated monkeys can sometimes become emotionally disturbed.
CONLEE: They go crazy, I guess is the way you could put it, where they can self-mutilate to the point of breaking their skin, tears on their arms. So you've seen animals have tears on their arms and legs from self-biting, pulling all their hair out to the point where they're bald.
GREENFIELDBOYCE: She says for decades, regulations have required labs to care for the psychological well-being of primates, which includes housing them together whenever possible.
CONLEE: Unfortunately, when they wrote the standards, a lot of the standards have to do with how you can exempt yourself from social housing. So while there's an emphasis on it, it's just not happening to the degree that it should.
GREENFIELDBOYCE: In recent years, though, there's been increased pressure from regulators. And it comes as scientists are figuring out what it takes to pair monkeys together for life in a cage because just like people, not all monkeys will get along. If you put two of them in a confined space and they start to fight, there's nowhere to run. Injuries can be serious, even fatal.
That's why a couple dozen vets and lab workers recently gathered for a workshop held at Yerkes to learn about best practices for monkey matchmaking. Kris Coleman is one of the instructors. She's with the Oregon National Primate Research Center. She's been exploring temperament testing for monkeys.
KRIS COLEMAN: Temperament or personality is really just an individual's - how they handle environmental stress and how they handle change. So we can use this information to help make better, more compatible pairs.
GREENFIELDBOYCE: Researchers are also learning how to introduce monkeys slowly, watching for any signs of tension. Kate Baker is a primate expert at Tulane University.
KATE BAKER: The Holy Grail is give me an early sign of how this introduction is going to go so if it's going badly we can terminate the introduction attempt before anyone gets injured.
GREENFIELDBOYCE: Baker says lab workers care about the monkeys and do understand the importance of social housing. She's done a couple of surveys of labs back in 2003 and again in 2014. She found an increase in the percentage of monkeys in research studies that have a cage mate.
BAKER: It's gone up from 41 percent to 65 percent. So there has been a lot of progress now in the past - what is it? - 11 years.
GREENFIELDBOYCE: Some of that progress is because labs have started rethinking their assumptions about what's necessary for the science. To learn more about that, I visited Johns Hopkins University in Baltimore. I put on a disposable mask and a white lab coat. A veterinarian named Bob Adams shows me into a room. Inside there's nothing but metal cages and monkeys, pigtail macaques. They're infected with the monkey form of HIV. They reach out between the metal bars to accept pieces of apricot with their long fingers. One monkey cowers in the corner of its cage.
Now, this guy's down here by himself?
BOB ADAMS: No, he's got a friend. There's two.
GREENFIELDBOYCE: Oh. Hi, guys. Are you hiding back there?
His buddy is behind him, clutching his back. Every cage has two monkeys. Adam shows me a barrier he can use to separate them temporarily.
ADAMS: So they're tattooed so we know who they are. So we can give him his medication. And then as soon as that's done and they get their treat, we can just open the cage back up.
GREENFIELDBOYCE: And the two pals are back together again. This is a big change. It used to be that researchers would immediately put monkeys in separate cages as soon as they were experimentally infected because they worried that the monkeys might pass the viruses to each other and somehow mess up the science. That's how it was for two decades. Then a few years ago, Adam said, let's try letting them live with a cage mate. And it's worked out great. Researcher Kelly Metcalf Pate says it hasn't been an issue.
KELLY METCALF PATE: Part of the realization that people are coming to is not just that it's not a problem, but that it actually helps to improve the science.
GREENFIELDBOYCE: She uses these monkeys to study how HIV can evade treatment and says isolation can suppress the immune system. It's not what infected humans would experience.
PATE: The majority of patients, regardless of disease that we're looking at, aren't living in isolation.
GREENFIELDBOYCE: But thousands and thousands of lab monkeys do still live in isolation. And it seems clear at least some of these could be paired up. Eric Hutchinson is a vet who cares for the monkeys in the Johns Hopkins lab.
ERIC HUTCHINSON: There are lots of people doing almost exactly the same research that are still not housing their animals together because it's - I mean, it's not that hard to come up with a reasonable-sounding justification for keeping animals apart.
GREENFIELDBOYCE: Until you hear about somebody else that's doing the same kind of science but keeping the monkeys together. Nell Greenfieldboyce, NPR News.
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