She is a 6 yr old aussie mix and I guess she is doing it out of anxiety, as we don't have a lot of people over very often. My daughter thinks she's getting grumpy in her old age (6!) and has less tolerance for people and other dogs, other than my husband and myself, and our one other dog. I'll keep her on a short leash when others are over. Thanks for your comments.

We've had her since she was 8 weeks old. She's know my daughter (who is grown and lives a few miles away) since then. So it was out-f-the-blue when she snapped. It was so fast I hardly saw it. She didn't actually bite. And then she slinked away! No changes in her lifestyle. So odd. She does bark at strangers, noises, etc, but never was aggressive.

She snaps one time and walks away. Started with my adult daughter wearing flip flops (August) then my adult grandson wearing tennis shoes (December). We interviewed a house sitter yesterday and she did it to that young lady, too! My husband thinks it is because I am home and she is protective of me. Yet it is a new behavior this year; very random. Doesn't do it when the human first enters the house, either.