Pets

We hang plastic bags on doorknobs to collect our recyclables. Whenever TB would walk by one, she would start vibrating her butt and tail really fast. I thought it was static electricity from the bag rubbing against her fur that set it off, but I had never seen another cat do that. She was a gray tabby with black 'skis' and a tiny patch of red on her withers. Her "sister" -- at least we think she was -- had more calico in her tabby coat and a flat face that suggested Persian ancestry. So we knew they were mixes, and looked like different genes dominated in each one, but had no idea the "ultrasonic butt wiggle" was some kind of diagnostic trait. Thanks for the info, and the story about Ember !