Very, er, odd question. XD I'm actually kind of afraid to answer this, but I guess I will anyway since I've got nothing better to do.
Yes, they do. In "The otter Woman", Rico, Private, Kowalski, and Julien have a burping contest, plus the one from the Kids Choice Awards two years zamani that Rico entered. And Kowalski let one rip once underwater. XD
I'm pretty sure there are a few other examples too, but I can't think of any off-hand.
There was that one part in "Popcorn Panic" where the lemurs where sitting on a popcorn thingy (I forgot what its called XD) and Mort thought his popcorn piece was done, but then he farted on it. LOL