Pancho was walking funny after a woods patrol yesterday, and I figured he had some leaves or a stick caught in his fur. I checked out his belly, and found a mass of burs.
Ingenious, sticky burs. After much googling of bur removal technique, which include pulling the fur from the bur, not the other way around, I've gotten most out. (Pancho also like to work them out with his teeth, spit them on the ground, and attack them.)
I may have to shave his belly to prevent futuring burrings. Or dress in him some kind of form-fitting suit, like red jammies with snaps.