I've had my chickens out in their newly finished coop for just over a week now and yesterday two black labradors got into my backyard while I was at work. My wife chased them out and no harm was done but I could see lots of big pawprints all around the coop. I never had problems with dogs getting into my yard before so I'm guessing that they can smell chickens from a long way off and just follow the scent. Judging from the stuff I've read on this forum, I'll bet that this is just the beginning and they'll be back.