| MadSci Network: Zoology |
All mammals, including the hippopotamus pass gas. The two forms of passing gas are burping (belching) which occurs through the mouth and farting (flatulence), which occurs through the rectum. The gases are formed by swallowing air, eating too fast, or undigested foods. Normal, harmless bacteria in the intestine break down food and produce gas. Any excess gas production or accumulation will cause the passing of gas to occur through the mouth or rectum. Therefore, your friend was partially correct, hippos do pass gas through their mouths. It is called "burping."
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