Scientists document rare urination behavior in Amazon river dolphins

Amazon River dolphins have been observed spraying urine into the air, but why does this happen? Scientists speculate that it may have a social or sexual function

Scientists have documented a bizarre behavior among Amazon river dolphins (Inia geoffrensis) or botos. Several male dolphins have been observed spraying streams of urine into the air, behavior that has puzzled scientists and prompted scientists to have reservations.

One study team led by Claryana Araújo-Wang observed the animals for over 218 hours and recorded 36 instances of what has been termed “aerial urination.” As the animal performs the act, a male dolphin turns over onto its back slowly, displays its penis, and fires a jet of urine that passes above the surface of the water. Even more interestingly, another male dolphin often comes near, following the stream of urine with its rostrum, as if it is attracted to it.

Many animals use urine to communicate

While the reason for this behavior is unknown, scientists suspect it could be sexual or social. A number of animals use urine for communication: lions and wolves use it to signal territories, and certain rodents and crustaceans use it to signal readiness to mate. In botos, it could be a bid to establish a dominance order among males or to signal health and social standing.

Pollution could interfere with these communications

Chemical communication is important in mammals but is unique in dolphins because they evolved to lose their sense of smell. Instead, they have learned to use taste to detect chemical cues. Previous studies on bottlenose dolphins (Tursiops truncatus) have shown that the cetaceans are capable of distinguishing between individuals by tasting urine, which could mean that botos have a similar method. However, without controlled experiments, it is still difficult to determine whether aerial urination is a communicative function or simply a fun activity.

In addition to the behavioral consequence, this discovery can have an importance in species conservation. If chemical cues are their mode of interaction, pollution of waters can disrupt these critical communication, endangering their survival and reproductive activities. Increased understanding of the role of chemistry in the social interaction of botos could be the way to conserve these fascinating Amazon River inhabitants.

Source: ScienceDirect