What sound rabbits?

I told a Japanese woman who I just met that she should feel free to call or email any time she felt like practising her English. Late yesterday evening I got an email from her saying that birds chirp, lions roar, dogs bark, but what sound do rabbits make? This stumped me so a few minutes later I'm at www.ask.com typing in 'what sound do rabbits make' to see what Jeeves has to say about the whole thing. Turns out most rabbits sometimes make soft grunts and that's about it. I informed my new friend of this.