Mom coyote and a year-and-a-half old pup were headed up a path when, up ahead, what came into view was that same enthusiastic dog from a previous posting, running after tossed pinecones. Note her extreme alertness in the first slide when she first sees what is going on. Although the dog owner stopped his activity immediately upon seeing her, the dog continued to bounce around enthusiastically in anticipation of the next pinecone being tossed. Coyotes often get upset around very active dogs. Neither the dog nor the coyote could have predicted that the other was going to suddenly appear where it did, so the situation could not have been prevented.
Because of the dog’s activity level, Mom coyote felt a need to warn the dog to keep away, so she went into her warning display mode. It lasted only a few seconds. Her messaging was very clear. When she saw that she was not going to be pursued, she stopped her display, calmed down, and walked on with her pup. Then, the owner and dog continued their fun. Note that the pup just stood and watched before moving on with his mother.
I have only seen an alpha coyote react in this manner. Younger coyotes would probably have just watched the dog activity out of curiosity and then run off. And note that no coyote in our San Francisco area parks has ever given this message to just a human. With just a human there, all coyotes are likely to run off the path or take a very wide berth around the human. Still, your best preventative recourse against your dog and a coyote engaging is to leash the minute you see a coyote and keep moving on, away from the coyote. Please keep your eyes open always in a coyote area — even if you don’t see one right off, know that they are around and could pop out any minute.
Coyote Yipps 
