Glad you asked...
Rat poison will kill them dead. It is written that they do have a liking for it so I am sure that it will kill them if they eat it. There are other ways.
Then again, this answer might help you...
There is a very simple way to poison a skunk. You can use a leftover food or anything that could attract the skunk. Put a small amount of pesticides on it and leave it near the place where the skunk lives.

