That's what I figure. Anything with a loud bang sound might work too, like firecrackers, or the high-pitched whistles that make them whine. There's Bear Spray (maybe, not sure of its effect on dogs,) pepper spray, set up noisy traps, whatever, something that stings but doesn't injure. I hear Guinea Fowl are excellent at raising the alarm whenever a strange animals ventures onto their turf, although they only fight back if they're defending a mate.