Although identifying an animal’s track and sign is enormously satisfying, our feelings are obviously not reciprocated. The wild animals who leave their tracks do not care about us, except for the desire to be invisible. They want to wind secretly past my house while I am sleeping, past your house while you are sleeping. They want to be unseen, unnoticed, unloved.

A glorious exception is scat. More on that later.

The wild animals on this Earth do not want us seeing into their secret lives, and we know why. We’ve killed so many of them already. It’s not just extinction. It’s the loss of abundance. In the past fifty years, the populations of more than five thousand species of fish, reptiles, amphibians, birds, and mammals have dropped by almost 70 percent. Humans and our domesticated livestock now account for 96 percent of the weight of mammals worldwide. Wild mammals add up to 4 percent. The scientific term is defaunation. At first that word feels awkward, stilted, like marbles in the mouth. Defaunation. Then it becomes exactly right.

What Walks This Way: Discovering the Wildlife Around Us Through Their Tracks and Signs