Mystery solved: the fish “wave” to scare the birds

In order to survive in the sulfur-rich waters around Teapa, poecilia sulfuraria Especially in the upper layer rich in oxygen. This makes the small fish, which are closely related to the guppies commonly found in aquariums, as easy prey for anglers as the kingfisher. But fish don’t give up easily, according to new research in the scientific journal current biology. They scare away birds with collective wave movements. The researchers discovered this behavior because the fish made waves as they passed them – and the fish seemed to sound the same alarm as the presence of a hungry fisherman.

This wave motion is similar to wave In football fields and concert halls. The same holds true for Mexican sulfur pools, the researchers wrote. When the kingfisher dives into the water to catch a fish, the fish in the immediate vicinity respond with a small dive. Their neighbors do the same, and so do their neighbors until the whole school of hundreds of thousands of fish joins. up to two minutes.

baffling effect

The researchers write that it works. Birds that attack against their better judgment during such a wave are unlikely to end up with a fish. They seem to learn to wait for the wave to pass, and as a result they attack less. Biologists attribute this to the confounding effect: The bird has difficulty orienting itself when the water is moving.

Behavioral biologist Charlotte Himmelrijk of the University of Groningen, who was not involved in this research herself, says the fish may be diving because they are startled. “If a kingfisher attacks in the middle of a school, the fish swimming nearby will be stunned. They dive in response.” It’s also a shocking response, she says, that all the other fish do the same. “They are worried about shooting neighbors and do the same. It has evolved into that mass wave with which they are now defending themselves against bird hunting.”

This phenomenon is more common in the animal kingdom. Honeybees also wave together when threatened. Himmelrijk also sees similarities with her own research on starlings. “When a bird of prey attacks a flock of starlings, they individually move away from the attacker in a zigzag motion. When they all do this, it looks from the ground like a black belt moving through the flock.” How long it lasts depends on how hungry the birds are from the raptors. “The same goes for fish,” she suspects, “the more stunned the fish by the attacker, the longer the wave moves.”