My BP started drinking while soaking in a clear bin with his mouth against the side slightly. It is most definitely a slurping type of drinking although I am not sure exactly how it works. I mean we use air as the vacuum for drinking that way (through a straw) but when Monkey was drinking his nostrils were submerged and no air was visible (bubbles). I would venture to say that my theory is that they use some air in their lungs (deep breath) and then suck some water in initially. Then they use that water and air combination to create the vacuum to suck more water in much like if you swish water in and out of your mouth while under water. They then swallow a little and push the rest back out to create the vacuum to pull more water in...doing this until they are satisfied. I was going to video tape it but he never gives me enough time to get the camera and if I have the camera ready, he never does it. Little booger.