What kind of critter is digging in the mulch below my trees

Crows do that here too. Skunks do it looking for June bug grubs. My cat uses the mulch for litter, but covers the hole with a pile of mulch that reminds me of Close Encounters of the Third Kind…

Might not be what you have there, but one time last summer I I was on my knees doing some weeding under an apple tree that had wood mulch, and the weeds were starting to come in at the edges some. I got tired of being on my knees and sat down - 20 seconds later a snake came barreling out like it had been shot out of a cannon.