I hear guineas going crazy outside the door today. Open the front door & the dog is on the porch & 15 guineas yelling at him from the bottom of the stairs. My Australian Shepard quickly entered the house. All the guineas them went on their way to wonder the yard. So guineas might be small but they can scare a dog that spends his evenings hearding cattle & chasing coyotes! I imagine the shrill noise is enough to scare many animals.