Yes, but be advised that not all animals are mailable:
The following are examples of other live, warm–blooded animals that are nonmailable:
Cats or kittens.
Dogs or puppies.
Squirrels and flying squirrels.
edit: I think it's funny that they had to put "flying squirrels" in there in addition to squirrels. This means that someone attempted to mail a flying squirrel and when they weren't allowed they said, "but it aint says nuffin' about no flyin' squirrels, just terrestrial squirrels and thems differnt."