What is That Strange Mini Volcano in the Yard?

The crayfish (or crawdaddy if you live in the southern U.S.), is a small crustacean resembling a tiny lobster.  The crayfish spends most of its time in the chamber at the bottom of its burrow so is rarely seen. Only at night does it become active bringing soil to the surface. It feeds mostly on decaying roots and buried plant matter, but sometimes eats worms or insects. Some species live alone but others are more communal.