The nose knows...
Coyotes have both a keen sense of smell and an insatiable curiosity. Coyotes use their noses to find prey and smell approaching predators. A coyote's nose also lets it know when it has reached the boundary of another coyote's home range. They have such a good sense of smell that they can recognize other coyotes by the markings they leave behind.
Coyotes mark their home ranges (areas in which they hunt) by defecating and urinating along the boundaries. This marks the boundaries with scents from their musk glands. They will also sometimes mark boundaries by scratching the ground (called "ground scratching"), leaving behind scent from glands in the pads of their feet. Within a home range coyotes will maintain a territory that they patrol and defend from other coyotes. The closer you are to the coyotes' core area, the area in which they spend most of their time (areas with the best sleeping spots, watering holes, food sources, or denning sites), the greater the number of scent markings there are.