I have raised and kept several differnt Rat terrier's with my birds over the last 21 years. They need to be worked with alot around the chickens. But once broken off the birds I have had several that I could trust with my birds all the time. Rat terriers range from 10 to 40 pounds most of mine are 14 to 18 pounds. They are the best dogs that I have ever had around my chickens. They are tuff and not afraid of much.