Costello (born in 2000) is the most quiet and shy macaque at the sanctuary. He and his best friend Rusty (both neutered males) can frequently be seen grooming one another from head to toe, or picking and eating grass that grows along their habitat. Costello endured the same surgical brain procedures that Rusty and Gary did, but he prefers to spend a lot of time in his climate-controlled indoor enclosure (complete with skylights) instead of people-, bird-,or squirrel-watching like Rusty and Gary do. The only thing Costello loves more than Rusty is food, and he's not picky! He will politely take any sweet fruit from his keeper's hands, then dart off to a high tree stump to devour it while happily vocalizing.