We have two cats and pondered about this long time ago. The best resource we found was the BBC documentary: <a href="http:&#x2F;&#x2F;www.bbc.co.uk&#x2F;programmes&#x2F;b04lcqvq" rel="nofollow">http:&#x2F;&#x2F;www.bbc.co.uk&#x2F;programmes&#x2F;b04lcqvq</a> also has an e-book <a href="http:&#x2F;&#x2F;www.bbc.co.uk&#x2F;programmes&#x2F;articles&#x2F;4Hbdn6T21hKDH6bfVBkj4Wm&#x2F;a-guide-to-your-cat-interactive-ebook" rel="nofollow">http:&#x2F;&#x2F;www.bbc.co.uk&#x2F;programmes&#x2F;articles&#x2F;4Hbdn6T21hKDH6bfVBk...</a>