
A scientific study unleashed on the world last week found that male Amazon river dolphins (botos) engage in a novel behavior called “aerial urination” where they flip onto their backs and shoot a jet of urine into the air while other dolphins hold their heads above water to let their friend’s urine wash over their rostrums (beaks). Here’s a photo montage of this behavior in action:

Some interesting facts about this behavior:
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It’s only males that engage in this behavior, both on the urine production and urine reception end of things.
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One of the dolphins observed in this study produced a steady stream lasting for 41 seconds – twice as long as the average urination session for a terrestrial mammal
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The urination sessions happened in social contexts, which means it wasn’t about “waste elimination”
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The dolphins being peed on appeared to seek out the urine stream to let the urine run over the sensitive hairs/bristles on their rostrums.
So what does it all mean – why are they doing this? The authors (Claryana Araújo-Wang, Mauricio Cantor, and John Y. Wang) suspect it’s a form of communication. We’ve seen in previous studies that some dolphin species have enough ability to taste that they can tell each other apart based on the chemical information in each other’s urine. But this aerial urination thing is odd because the dolphin getting peed on is probably already well aware of the identify of the dolphin peeing on them. So what information is being communicated through this form of delphinid watersports?
The answer is that the authors don’t really know. But their working hypothesis is that because botos live in a society where males are larger than females and tend to fight with each other for access to food and sex, they are learning something important about the social status of the males whose urine they are letting splash all over their faces. Probably something about how manly or dangerous or physically fit or free from disease and parasites these urine-ejecting other males might be. As an enterprising young male boto, you know not to pick a fight with another boto bro if his urine tastes extra manly. So it’s worth sticking your head into that urine stream to figure out what this other dude’s deal is.
This urine communication system is not unlike how dogs smell each other’s scent markings to learn information about each other, only botos appear to be peeing directly onto each other (as opposed to lamp posts) in order to convey this information.
So there you have it everyone! Surely it’s going to be a better day now that you’ve added “aerial urination in Amazon river dolphins” to your list of new stuff you’ve learned today?
~Justin
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This commentary originally appeared in Dr. Justin Gregg’s personal newsletter, The Narwhal Diaries. Check it out as a free or paid subscriber!