Thanks to the fact that a few survived the great slaughter of the 19th century, today we can see herds of bison majestically crossing a few streams in North America. Ecologist Dwayne W. Meadows wondered what effect the trampling of thousands of hooves can have on snails and other small animals that live in these streams. And he not only asked, but went to find out on an island in the Great Salt Lake, Utah.