. >> reporter: veterinarian jocelyn bezner checks her charges. >> now i want to check over each one,e sure they're healthy. >> reporter: bart was born here, he turned 20 in january 14. his records are sketchy at best, like most of theirs. >> we don't know what the study was for. we just know that he was in a study. >> reporter: experts say every chimp has its own personality. bart's spitting vinegar. he interrupts my conversation with bezner. >> that's the testosterone. >> reporter: he was getting a kick out of his antics. the concrete and steel enclosures have been modified with pass-throughs. the chimps can visit each other, play, roughhouse. it wasn't that way before save the chimps took over. so this is the infamous -- >> this is the dungeon. this is the dungeon. and this a small cage that they lived in. >> wow. >> reporter: like a prison, one cell after another, chimps lived this way sitting day after day, year after year, until needed for a research project. what do you feel like when you walk in here? >> it's almost like it's haunted. it's a really dismal place. there's not re