So last year, I had some problems with the Pyrenees eating hens. I couldn't figure out what was happening, so I hid in a patch of cedars and watched as two playful puppies followed the flock around and managed to catch a hen. They then laid down with the hen between their paws and proceeded to lick the hen, and then pull out feathers. What was happening was the pups were playing, and being affectionate (licking), but chickens are very delicate, so it didn't take much to kill the bird. Once dead, instinct kicks in and the pups eat the carcass. This is pretty common across the board for livestock guardian dogs - the guy that we're buying our goats from told me about how his Anatolian shephards quickly dispose of any stillborn goat kids. Dead animals attract predators, so the dogs are protecting their flocks/herds. Pretty neat.
But to stop inappropriate play, I came up with the idea demonstrated below. It's just a chicken wrapped in polywire fencing hooked up to a charger. The chicken is on a rubber mat, so it can't be shocked because there's no ground. A mischievous puppy, however, will complete the circuit and get popped on it's nose or mouth, and it will probably be a lesson that sticks for the rest of the pup's life.
In other news, I finally got the chickens back out to pasture yesterday. Finally!