A flock of fish makes a "wave" to protect themselves from predators

At a sports stadium, spectators sometimes make a "wave" by consistently standing up with their hands raised. Scientists have discovered that a small freshwater fish known as sulfur molly (Lat. Poecilia sulphuraria), does the same thing, only with a different purpose.

It is estimated that up to 4,000 fish are collected per square meter. In some cases, hundreds of thousands of fish can take part in one wave. The waves can be repeated up to 2 minutes with an interval of 3-4 seconds.

At first, scientists did not understand what exactly the fish was doing and why. Then they noticed a lot of fish-eating birds nearby and thought that this behavior could be a defensive maneuver. Studies have confirmed that surface fish waves significantly reduced the frequency of bird attacks.

Sulfur mollies are so named because they live in sulfur springs, which are toxic to most other fish. In the presence of a person, they also feel danger and start their "flash mob". When you're around, it's hard not to notice, the scientists said.

The study is published in Current Biology.