Smart and persistent competitor
Coyotes are resourceful and intelligent predators. Though closely related, coyotes and wolves are highly competitive. Because coyotes are so much smaller than wolves, a single coyote is not a threat to a healthy adult wolf — but they will kill unprotected wolf pups. When they have the advantage of numbers, coyotes may harass wolves.
Wolves will kill coyotes whenever they can to eliminate competition. In fact, with the reintroduction of wolves to Yellowstone, coyote numbers decreased by half. Coyotes soon learned to start denning closer to roads (which wolves avoid) and have become less vocal in the park (probably to reduce detection by wolves).