More then likely they are in search of either under ground bee nests grubs or both.
It is very hard to control grubs in gardens without killing the beneficial insects as well.
You may want to put some of that black plastic mesh netting over some stakes to protect your
plants. It is pretty flimsy stuff but the animals do not see it, and it freaks them out when their faces touch it, and it generally scares them away. If it is an underground bees nest you may want to be careful of doing any work near by.
