Mac, the miniature donkey, can be kind of a jerk. He bats his eyelashes, angles his long furred ears toward you, flatteringly, like TV antennas, and pushes his belly up against your thighs. Then, just as you’ve grown comfortable with his small, stocky presence, his burro smell of sagebrush and sweet alfalfa, something dark and confusing stirs within him. He stiffens, whips his head back, and bites down hard on the bony part of your shin and doesn’t let go. Or he rears to stamp his...