Dani Rabaiotti is the co-author of a book that passes the smell test. It’s titled “Does It Fart? The Definitive Guide to Animal Flatulence.” A zoologist at London’s Zoological Society, Rabaiotti got interested in the stinky subject after her brother asked her a question: Do snakes fart? She didn’t know. So she sniffed out the answer and kept tooting along until she became an animal fart expert. We rang her up to learn how animals like manatees and sloths pass gas. The process isn’t as simple as you might think.