Domesticated critters most certainly have different dialects & languages. I recall that the page a day kitty calendar once mentioned how kitties in Japan have more (& different) vowels than USA kitties, & other stuff about how kitty language differs from place to place. The interesting part is how critters from different countries have a bit trouble understand each other.
Seems like I heard on a tv show the other day that whales, dolphins, & other big fishies have differing dialects from one pod to another.