Fish communicate in sign language

It turns out that there is some kind of fish sign language understood by the representatives of various species and invertebrates. Biologists from the UK figured this out by observing the behavior of coral grouper and salmon. Using an interesting alarm, fish predators informed their neighbors about the location of prey they could not reach.

Animated film The Reef 2: High Tide tells how all the inhabitants of a coral reef combined their efforts to protect their native home of sharks. In the movie, fish of various species were able to achieve a common goal negotiating not only with each other but even with invertebrate inhabitants of the coral ecological community. 

Recent research of the biologists from the University of Cambridge (UK) have proved that it is possible in real life. The only difference is that it was observed not in the case of protection of homes, but the example of collective hunting.

Scientists have long known about cases where during the hunt, many predators belonging to different species would join forces. Let's take a typical situation in the savannah where lions, cheetahs and leopards often form a "union" with the birds that feed on carrion. They hear their call signs and understand that in the area where the birds are circling there is a likelihood of a sick or injured animal. After killing prey, these hunters do not eat all of it, so those who have discovered the prey get "payment" for their work.

Sometimes there are ways of closer interaction. For example, hyenas, jackals and bat-eared foxes often direct their prey to lionesses. Once they successfully sacrificed the victim, they wait until the lions are full so they can start their meal. 

Of course, hyenas and jackals can kill some animals on their own, but why take the risk if this dangerous work can be done by someone else, someone stronger and more agile. In fact, many anthropologists believe that similar interaction of ancient people with wolves led to their domestication and later appearance of dogs.  

Collective defense techniques are also common. Everyone saw swarms of tiny birds desperately chasing a crow or a hawk. Looking at them with binoculars, one can see that these brave birds are members of different species - tits, finches and sparrows concerned with the appearance of a predator. While in "peaceful" life the birds do not get along with each other, in the face of a common threat they act in harmony.

Until recently, scientists did not anticipate that such communication during hunting was possible between such seemingly irrational creatures like fish. However, the work of the zoologists from the UK dispels this misconception. It all started with the fact that ichthyologist Alexander Vail and his colleagues studied the behavior of coral grouper and salmon. Shortly after the commencement of the research, the scientists noticed an interesting behavioral element. These predators at the detection of prey would always stand in the upright position on their head and shake it at the same time. What could this atypical behavior of a hunter mean?

At a closer look, scientists found that grouper and salmon assumed this position only in cases where they could not get to the prey (for example, if it was hidden among the rocks). And, most interestingly, after the hunters performed their trick (sometimes repeated several times) other fish - eels, wrasses, and other lovers of fresh fish would immediately rush to that area. They would drive the prey out of its hiding place, and then begin a collective hunt. Once, an octopus participated in such collective hunt, which begs a conclusion that even invertebrates understand the sign language of predators.    

As the biologists wrote in a paper published in Nature Communications, headstand met all the criteria of a hunting gesture - pointing to an object of a hunt, intended for a partner, and causing an immediate reaction. However, the latter does not always happen. Sometimes moray eels that have a reputation of slow thinkers did not immediately pay attention to this signal and grouper had to repeat it several times.  

It was also noted that in some cases the hunter slightly altered the repeated call - apparently for greater clarity. In some cases, it even had to literally push the slow moray eels towards the place where the prey was hiding. In one situation groupers had to wait for 25 minutes before moray eels realized that it was invited to take part in the pursuit of prey.

It appears that even fish that does not have a developed nervous system know what a goal of action is and are able to talk about it to get help. That is, they possess cognitive skills similar to those of mammals and birds.    

Anton Evseev

Pravda.Ru 

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