[♪ INTRO] You’ve probably seen people doing  the wave at sporting events.

It’s a fun little pastime where large groups  of people all stand up and then sit down in succession, like at the proper time, so  that from a distance it looks like a wave. Well, scientists have uncovered that  some fish do this as well, but for them, it’s not just a fun way to pass the time  while they’re bored between innings.

For sulphur mollies, it is  a matter of life or death. Sulphur mollies are small freshwater  fish found living in sulfur springs in a particular region of  Mexico, hence their name. The springs there have high  concentrations of hydrogen sulfide, which gives off that characteristic sulfur smell.

Hydrogen sulfide also reacts  with oxygen in the water, lowering the amount of oxygen  available for the fish to breathe. As a result, these little  fish spend a lot of their time hanging out at the water’s  surface to get enough oxygen. And there are often a lot of  these fish in one location.

As many as 4,000 fish per square meter. Unfortunately, hanging out in a large  group close to the surface means they are vulnerable to attack by  hungry creatures, like predatory birds. But, these little fish have  evolved a peculiar behavior, the ability to do the wave, which  helps them avoid becoming dinner.

German researchers have observed  that an attack or sometimes even just the approach of a predator  is enough for the sulphur mollies to start doing the repeated waves in the water. It all starts with the fish closest  to the predator diving down vertically into the water and splashing  the surface with their tail. Then, the fish closest to that one  mimics the behavior, and so on, forming a big splash at the surface that travels away from the predator in a wave-like motion.

Researchers think this running wave  on the surface confuses the predator, because it looks as though  the wave is moving away while the fish themselves are actually just  moving vertically down into the water. The fish could repeat this  behavior over and over again, with one wave occurring every three to four  seconds, for up to two minutes at a time. And the researchers have observed  that these waves are pretty effective!

Whenever they did the wave it doubled  the time that the birds waited to attack. And scientists also saw birds changing locations suggesting they might have  decided to attack something else! So doing the wave definitely keeps these  little ones alive longer and who knows, maybe it’ll also give the edge to your  favorite sports team in their next sports game.

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