Dawn Hagel said she was driving Tuesday when she spotted the 16-month-old Australian cattle dog cringing beneath a parked pickup truck at the side of the road and two coyotes circling it.
Hagel, who owns two dogs herself, told the Calgary Sun she pulled alongside and opened the door.
"He was in the bus in a heartbeat -- he knew it was a much better fate," she said. "That dog was breakfast."
The dog was bleeding from two bite marks on its rear right leg, and passengers comforted it. Its owner, Hugh Magill, was tracked down by tags on its collar, the Sun said.
Magill said he was walking the dog named Duke without a leash when the dog saw a coyote and ran away. He said he searched and called the dog, but gave up and went home.
He told the newspaper Duke was found near where he bolted away.
The dog is expected to make a full recovery, the report said.