The National Institutes of Health own 518 research chimpanzees. But since the late nineties, long before biomedical research on chimpanzees was actually banned in 2015, the use of our closest animal relative in science has been declining. And the NIH is still trying to figure out what to do with its aging community of ex-lab chimps.​ Over 200 research chimps are still being housed in labs, instead of sanctuaries. The research chimpanzees and their ancestors, contributed to the eradication of diseases like Hepatitis A and B and polio in many parts of the world. They’ve helped us better understand the human body and mind. Any other lab animal would be euthanized -- but not chimpanzees. It’s a decision that acknowledges just how similar they are to humans, and the CHIMP act, signed by President Clinton in the year 2000, makes it official: The Federal Government guarantees that all research chimps will live out their lives in a federally approved sanctuary. That sanctuary is Chimp Haven in Louisiana. This month, ten years after the first chimps arrived there and some of them experienced trees and open space for the first time, Chimp Haven is celebrating a milestone. More than half the NIH chimps have made it into the sanctuary system. But to accept more transfers, Chimp Haven will need to expand, and it’s struggling to find the funding it needs. VICE News Tonight visited Chimp Haven to see what retirement looks like for the lucky half of America’s research chimps. Subscribe to VICE News here: http://bit.ly/Subscribe-to-VICE-News Check out VICE News for more: http://vicenews.com/ Follow VICE News here: Facebook: https://www.facebook.com/vicenews Twitter: https://twitter.com/vicenews Tumblr: http://vicenews.tumblr.com/ Instagram: http://instagram.com/vicenews More videos from the VICE network: https://www.fb.com/vicevideo