Just got in from taking my 9 month old puppy out for a walk. While we were out there, he decided to take off after a possum. He got off into the tall grass and harassed the possum as it tried to flee. Most possums around here don't actually play possum. They either run like they're on fire, or they hiss, growl, and sling attitude all over the place.
This one tried to run, but with the pup on his heels, he was having trouble. He evidently got a nip in, too, since I heard my pup yelp. No blood or other damage on the pup, so I think he was just spooked. Had he just picked up the possum by the back of the neck/head and taken a few steps (and I've seen him do it), the possum probably would have lived up to its name. As it was, he was trying to herd the marsupial instead (he's a quarter blue heeler and a quarter German Shepard), so he'd run in, nip at it, and jump back.
He's treed quite a few possums and raccoons over the past few months, but he doesn't seem to be able to follow a scent trail. He's pretty good at sighting what he wants to go after, though.