Adult Male Dolphins Are Peeing into the Air — Scientists Think They're Trying to Send a Message

Using his powerful tail flukes, a male dolphin propels himself upwards to reach the surface. He rolls on his back and flips his body upside down, exposing his penis out of the water. Then, ejects a stream of pee into the air that arcs through the sky like a watery jet shimmering iridescent under bright sunlight. This queer sighting is frequently observed in the wild Tocantins River, where pink river dolphins like to participate in what the scientists called “aerial urination” in a paper published in Behavioural Processes.

When the Canadian researcher & co-author of the paper, Claryana Araújo-Wang, and her colleagues first noticed this bizarre behavior among Amazonian dolphins, it left them stunned. “We were really shocked, as it was something we had never seen before,” Araújo-Wan told New Scientist. According to Amazonian folklore, the river dolphins are shapeshifters that transform themselves into handsome men at night and seduce young human women. This myth stems from the fact that dolphins have human-like genitalia. But it wasn’t known to scientists that these otherwise intelligent dolphins are likely to pee like humans. However, as it turns out, this behavior is a way for them to regulate certain functions- scent marking, for instance.

Scent marking through urine spraying is an important behavior in the animal kingdom. Animals spray urine to aid mate selection, territory marking, predator defense and chemical communication, according to the paper. National Geographic explains that animals like lions, tigers, bears, coyotes, mice, and wolves spray urine to mark their territory. Porcupines spray urine to signal their partners that they’re ready for mating whereas male tilapias use urine to prove their sexual prowess. Monkeys even bathe in urine to attract their mates through scent. While this behavior was known to be typical in terrestrial animals, it wasn’t quite observed in aquatic animals. Researchers found that these dolphins, also called “botos,” used “quasi-olfaction” to mark their scent. 

“An individual will start to slowly flip belly-up and expose the penis and urinate. When another male is present, he may sometimes chase the urine stream with his rostrum,” Araújo-Wang described what she saw on the scene, to National Geographic. Her study documented 36 instances of “aerial urination” by botos between 2014 and 2018 and recorded the sequence, duration, and social context of their behavior.

Two-thirds of the documented cases involve the presence of receiver dolphins. “When a ‘receiver’ male is present, it either approaches the urine stream with its rostrum, sometimes pursuing it, or stays where the stream contacts the water,” the researchers noted in the paper. They found that when the arc of a dolphin’s urine landed in the water, another male dolphin nearby would stick his snout into the urine stream, sometimes even chasing it. Scientists think that this could be a form of communication in which they transfer information to fellow dolphins through the chemicals in their urine. Or, the peeing dolphin could simply be attracting his mate.

“It is possible that aerial urination is another behavior of the males’ social-sexual repertoire,” Araújo-Wang told National Geographic, adding that she suspects this “aerial urination helps in advertising male quality in terms of social position or physical condition.” If not sexual agendas, then this urine-spraying behavior could be a form of communication. However, since the urination researchers observed in dolphins had a very short duration, they hypothesized that it couldn’t be triggered by a desire to eliminate waste.

“Aerial urination, often occurring in the presence of other males, serves social or communicative functions beyond the physiological need for waste elimination,” the team noted. Even though scientists are still confused about what exactly triggers this unusual behavior in dolphins, they propose that this could either serve as a social function or an aid for attracting mates. Or, it could be just another funny thing that male dolphins like to do.