I have no idea
apparently it happens everytime the Sheperds have finished their training, they get puss to do her thing infront of them, just to make sure they have been properly trained
I have had 7 Shepherds before my 2 Purring Panthers now, and I try & guess which Shepherd will be likely to break ranks, I could only pick 2
cats are harder to train I have worked out, but they all respond to being talked to, a lot, & pats & cuddles