Do you know what to look for when trying to spot signs of river otter? Learn some sure signs that otter have been nearby and take a walk on our beautiful trails to see if you can spot signs for yourself. Along the way we will look for signs of other elusive mammals like bobcat, coyote, or mink. More information at grassriver.org. Grass River Natural Area is located at 6500 Alden Highway, Bellaire MI.