Josie, my alpha cat, will often take care of the litter box after her sister, Dory uses it. Usually it's after Dory has a BM. Dory does her business and does a little bit of covering and scratching of the high sides of the box. Almost immediately after Dory takes off, Josie investigates, sniffs, jumps in the box, and does plenty of covering and scratch. Basically she does all things she would do if she had just used the box--except she didn't. What's going on here?