Yes, it doesn't take long once they start. We had 3 taken by a fox in one day. They are quite brazen and come close to the house and I did a face to face with a fox, but was able to scare it away. Within the week, it met it's demise. Makes me a bit nervous when they get so bold.
We have a ton of rabbits and chipmunks here as well. I just think my birds are easier and when they hear the flock, it's like a dinner bell ringing for the buffet to begin.
At this point, I'm carrying double the amount of guineas I need or want and a two to one ratio of females to males for breeding. Now watch - I won't lose any and I'll have hundreds next year. I wish that were true, but somehow I don't think it will be the ending to this story.
Sorry to hear that your friend lost her 8.