I returned from a long vacation to find that a fox had burrowed beneath my shed and had five or six half grown babies (kits?) living there. They are very cute and come out every early morning and evening but my neighbor thinks they may be a threat to his cats and generally not a good idea to have around. Is there a health and safety risk. Will they leave on their own when the kits are big enough? Do I need to intervene and how?

The neighbor does need to watch out for his cats. But (soap-box alert) the cats shouldn't be outside anyway as cats (even well-fed ones) kill millions of birds, voles, and other native wildlife each year (not to mention that cats that stay indoors tend to live longer). As long as people give the foxes space, there aren't health or safety risks to people. The foxes will only stick around till the end of summer and then the kits will head out to find new territories. You'll be able to fill in the den site when they are done. The only thing you need to do now is just pick up the foxes' "leftovers" if they bother you. They tend to be pretty messy around the den site. Try to clean up while they aren't around. What you pick up can go in the garbage. If you have other questions, please let me know.