We lived on 40 acres once upon a time ago and our neighbors had a flock of guinea. The birds took to ranging our property about half the time, and spent a lot of that time right out our front door. We had a pit bull who attacked and ate any small animal she came across. You can only imagine our shock the day she took off after those birds and they all, instead of running away, turned to run towards her, yelling and honking up an awful noise. Darcy tucked tail and ran back to stand by my husband with a terrified look on her face, totally taken aback at this unexpected response. Eventually, she got over her fear of them and found it great fun to run after them and make them holler, but she never did kill one of the birds, or even act like she really wanted to. All that just to say that, I bet if you had a good natured dog with a submissive personality, your guinea could establish themselves as not to be messed with. The birds did return to their owners property each night, but they wondered very far during the day.