That's true, LH -- and Ivor, thanks for the hypothesis. I haven't found any info online about why yawning is contagious, other than that scientists don't really know. In fact, it tseems they're not even sure why we (or animals) yawn. Another hypothesis is to give the message "look I'm tired, but don't bother attacking me ... see the size of my teeth?!?"

And a good question too, Ivor. But it's really not allthat puzzling ...