I have a Jack Russel\Chihuahua mix street dog rescued from Puerto Rico that hangs out with the chickens. The biggest threat she is is she competes for the treats, even the over grown pole beans that I shuck and throw at them in the yard! She and one of the BSL's were having a stand-off well one peck n the snout and the pup was out of there! So there are exceptions to the ankle biters being aggressive.