In the murky waters of the Amazon, pink river dolphins exhibit a surprising behavior. Jets of urine sprayed into the air may play a key role in their social interactions.
These cetaceans, known as botos, navigate an environment where visibility is limited. Their already complex mode of communication appears to include unexpected chemical signals. A recent study, published in
Behavioural Processes, documents this rare phenomenon, opening new perspectives on the sociability of these animals.
Excerpt from the video (see below). An unprecedented behavior in cetaceans
During four years of observation, researchers recorded 36 instances of aerial urine jets. Males, lying on their backs, spray their urine to a height of over one meter (3.3 feet). This behavior, never observed in other dolphins, intrigues due to its frequency and precision.
In two-thirds of the cases, another male positions itself near the jet, seemingly observing or following it. This reaction suggests that urine could convey social or physiological information, although its exact role remains to be determined.
Adapted chemical communication
Amazon river dolphins possess sensory whiskers on their rostrum (snout), which could capture chemical signals. These structures, absent in marine dolphins, might allow them to detect hormones or other markers in urine.
A previous study on bottlenose dolphins showed that they use their tongues to taste urine and identify their peers. Botos might thus combine chemical and acoustic signals, with the impact of urine on water serving as a sound cue.
A scientific mystery to unravel
Researchers propose several hypotheses about the function of these urine jets. They could indicate an individual's social status or health condition, or even play a role in reproduction. However, the lack of a developed sense of smell in dolphins complicates the interpretation of this behavior.
This discovery highlights the adaptability of river dolphins to their environment. It also opens new avenues for studying chemical communication in cetaceans, a field still largely unexplored.
In brief: Why do Amazon river dolphins use urine to communicate?
Amazon river dolphins live in murky waters where visibility is limited. Unlike marine dolphins, they seem to exploit chemical signals to interact. Urine sprayed into the air might contain information about an individual's identity, social status, or physiological state.
Observations show that some dolphins actively approach urine jets and appear to analyze them. This reaction suggests a novel mode of communication, combining chemical and acoustic perception, particularly through the sensory whiskers on their rostrum.
This behavior raises new questions about cetacean communication. It could play a key role in social group structuring and reproduction, offering a new angle for studying the adaptation of dolphins to their unique environment.
Article author: Cédric DEPOND