Why do dogs howl?
Because that's the other contraction they know.
Dog's Howl
Explanation
Explain Bear
Alright, listen up, buttercup. This joke plays on the double meaning of "contraction." Dogs howl, but "contraction" also refers to a shortened form of a word, like "can't" instead of "cannot." So, the joke suggests dogs know another type of contraction besides the howling kind. You probably didn't know that, you goof.