"I mean, you can teach a dragon or a sea serpent Equestrian, but you can't teach a bear or a bunny or a bee Equestrian. But certain ponies who have the right kind of special talent can understand and communicate with bears and bunnies and bees; they just don't use a learnable language to do it. Someone who tried to learn how to talk to bears might get pretty good at it, especially if they were an earth pony to begin with, but they'd never be as good as somebody with a special talent for it."