As a result of a banterly exchange on Twitter (the origins of which I'm uncertain), I dug up a kinda interesting piece on trying to understand fox language. There may be more useful stuff out there.
Wouldn't it be nice to be able to understand a little more of all these fox noises we hear.
Here are some weird fox with tortoise noises!:
and a bundle more fox noise stuff on YouTube here
Coincidentally, I also listed to an interesting piece on BBC WS considering whether monkey and apes have language.