The following is from a park publication:
Yellowstone's coyotes (Canis latrans) are among the largest coyotes in the United States; adults average about 30 lbs. and some weigh around 40 lbs. This canid (member of the dog family) stands less than two feet tall and varies in color from gray to tan with sometimes a reddish tint to its coat. Coyotes live an average of about 6 years, although one Yellowstone coyote lived to be more than 13 before she was killed and eaten by a cougar. 

Coyote-Human Interactions
Coyotes occasionally lose their wariness of humans and frequent roadsides or developed areas, becoming conditioned to human food by receiving handouts or picking up food scraps. They can quickly learn bad habits like roadside begging behavior. This leads to potential danger for humans and coyotes. Several instances of coyote aggression toward humans have occurred in the park, including one that involved an actual attack. Habituation most likely played a role in this unusual coyote behavior.

Beginning in 1988, park staff increased monitoring of coyotes along park roadsides. We experimented with scaring unwary coyotes from visitor use areas with cracker shell rounds, bear repellent spray, or other negative stimuli, but there is little indication that such techniques caused long-term term changes in individual coyote behavior. Those animals that continue to pose a threat to themselves or to humans may be translocated to other areas of the park, or even removed from the park ecosystem. Signs, interpretive brochures, and park staff continue to remind visitors that coyotes and other park wildlife are wild and potentially dangerous. They should never be fed or approached too closely, for the protection of humans and the animals.