Rose does that too.....she'll do it with her milk bones. She'll toss them up in the air, wait for them to land, then she'll roll on them. I think it is just their way of saying, this is mine and I like it! lol I don't know for sure though......If she is eating a steak bone or she just caught a rabbit or what not, and she is eating it, she'll rip up the grass around where she is eating the thing. I can't figure out why she does that either....