Male Amazon river dolphins swim to the surface, roll over, and pee straight up into the air, and they don’t do it to show off to the ladies. In fact, they usually only practice this bizarre behavior when they’re in the presence of other males, which swim right up to the pee stream as it lands back in the water. Scientists call this party trick “aerial urination,” and a new research study suggests it might just be a form of scent marking.
On land, terrestrial animals use scent marking through urine spraying as a way to claim territory and communicate with potential mates. For aquatic mammals, though, urine spraying doesn’t seem like it’d make as much sense, but Amazon river dolphins make a show of it. Why?
Researchers published a study in which they observed these dolphins in the wild for about four years and paid particular attention to aerial urination. Interestingly, after a male dolphin sprays, researchers say the “receiver” male (if there’s one present, and there usually is) “either approaches the urine stream with its rostrum (sometimes pursuing it) or stays where the stream contacts the water.”
The scientists hypothesize that this is a form of communication between males and not just a weird quirk. As for what exactly they’re communicating by doing this, it’s still a mystery.
See “aerial urination” in action here: