A raccoon or muskrat midden at Van Tassel Access on the Maumee River.

A midden is like a garbage heap, except without all the plastic, paper, etc and with the food usually completely eaten :) In this case, the "packaging" on the meal were the valves (shells) of the live mussels.

Mussels are an important food source for muskrats and the state endangered river otter. They are also the most critically imperilled family of organisms on the North American Continent.