One time Coyote was hunting for food for his children. He was trying to fool the animals, pretending he was in trouble and crying. Porcupine heard him and came to help him. Coyote noticed that he could not bite him without getting quills in his mouth so he convinced porcupine that what he needed to do was to sit on him, thinking he could crush porcupine. That didn't work. Porcupine knew he was in danger and raised his quills up and stuck Coyote in the rear.   That is why when Coyote is running sometimes his back end is raised high in the air.