The **Amazon river dolphins** (*Inia geoffrensis*), known as botos, have left scientists perplexed by showing an **unusual behavior**: shooting jets of **urine out of the water**.
During over 200 hours of observation in Brazil, a group of researchers documented this practice, in which **males expel urine** that reaches up to one meter in height, **attracting the attention of other dolphins** that follow it with their snout or wait for it to fall into the water.
Although the reasons behind this behavior are still unclear, it is speculated that it **could be a method of social communication**. The findings were published in *Behavioural Processes*, generating new lines of research.
Urine as a social language
Claryana Araújo-Wang and her team from the CetAsia Research Group, based in Ontario, Canada, led the study that recorded 36 cases of **male boto aerial urination**. Researchers suspect that this act goes beyond a simple physiological function and serves a **social purpose**.
In other animal species, urine is commonly used as a communication tool. For example, African **cichlid fish** (*Astatotilapia burtoni*) use it to establish territorial dominance, while river crabs **use chemical signals** in their urine to show aggression.
In the case of botos, this practice could involve **complex signaling** based on chemical compounds present in the urine.
How do they detect urine signals?
The discovery has led researchers to propose several hypotheses. One suggests that the bristles on the botos’ snout could be key to **detecting the chemical signals** in the urine. These signals could contain information about the **physical, social, or reproductive status** of the dolphins.
The theory is supported by previous studies conducted with bottlenose dolphins (*Tursiops truncatus*), which demonstrated the ability to identify other individuals through the **taste of their urine**.
According to a 2022 study by Jason Bruck, a researcher at Stephen F. Austin State University in Texas, these dolphins use their tongue to analyze the chemical composition of urine underwater. However, Bruck questions whether the **hairs on the botos’ snout** are sufficient to process such complex signals.
Is sound an additional clue?
Another hypothesis suggests that the **sound of the urine falling** into the water could function as an **acoustic signal**. Since botos have limited vision, this noise could guide other dolphins to the sampling site.
Although there is no definitive conclusion yet, researchers believe that aerial urination could be a novel form of **communication in cetaceans**, opening new doors to understand their social behavior. According to Bruck, “chemical signaling remains a fascinating frontier in the study of dolphins.”
This finding adds a new dimension to the understanding of river dolphins and highlights the complexity of their **social interactions**, expanding perspectives on how cetaceans use the environment to communicate.
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