After 4 months of watching my chickens my dog killed my favorite rooster. I've had the German Shepherd female for 10 years and I've only had the chickens 4 months. I just don't understand why she waited 4 months before deciding to kill one. Anyway I have reintroduced her to my tri-tronics sport 60 dog collar for some remedial chicken training. So far I think electricity is more powerful than her urge to kill chickens.