We have a lab/pit bull mix, a Chihuahua and a cat. There have been times when the hens escape their pen area and roam the yard. The lab/pit mix is oblivious to them - more interested in stalking squirrels. The Chihuahua usually mingles with the hens, but has nipped at one's rear end one time. That happened when I was trying to get her back into the pen. Not sure why she did that. The cat stays away. Both dogs have been in the pen with me on occasion when feeding and showed no aggression. I hope there continues to be peace and harmony.