Lightning never aroooed until I got Stomps, who is a natural singer. Even now, Lightning will usually only sing at night, and Stomps has to start it. I can get Stomps to aroo if I sing a song off-key (luckily that's the only way I CAN sing). He'll happily join in, and sometimes Lightning will too. It's the funniest thing in the world. Our next door neighbors have a dog who howls, and he'll often come over in the middle of the night and get my two going. That's not so funny, but I have to say they make a good trio.