A friend of mine, who owns many of those critters, told me once that when they "wave", it's actually because they wanna have sex. With you. Isn't that charming?
I know for a fact that I don't carry 0,14 gram of fecal matter. That's impossible. I am way too anal (pun not really intended) about wiping / washing for that. So, according to that research, if I don't carry that 0,14 gram of poop, then it means that someone else is carrying it FOR ME. Some people are really full of shit, I guess.