Is there a way to delete all the wild foxes in the game?

I don't know what you're doing to see them, but simmerLella is right. The foxes are not in manage worlds by default, otherwise I would have just deleted them from that menu instead of asking for help here. 

Speaking of which, simmerLella, did you ever find a solution? I did my fair share of Googling but nothing is coming up, that's why I'm asking. No worries if not!