Pete is a cat. He, Mickey, and Minnie are all the same age if you count by animated short release dates because they were all in "Steamboat Willie."
With very few exceptions, WD Television Animation series shouldn't be used to establish a story canon, because many liberties were taken in favor of cheaper production or expanded storylines.
(Ducktales/Carl Barks' comic books; Goof Troop/the original animated shorts; New Adventures of Winnie the Pooh/the original theatrical releases and the books)
In Star Wars terminology, the newer, doglike Pete would be considered Expanded Universe, not true canon.
So yeah, he's a cat...:lookaroun :lol: