The angels know how to count

The most popular tropical ornamental fish species not only possesses good appearance, but also has the ability to estimate and distinguish between one and three numbers.

Belonging to tilapia, angelfish (or fairy fish) is one of the smartest and most beautiful fish in the world, but scientists do not know if they are capable of counting or distinguishing numbers.

Robert Gerlai, a psychology professor at the University of Toronto in Canada, decided to explore the counting ability of angelfish, Discovery News reported. He and Luis Gomez-Laplaza, a researcher at Oviedo University in Spain, exploited a behavior of angelfish: They often join the largest herd when they enter strange environments. In order to eliminate the possibility of fish entering large herds to increase the chance of mating, the two researchers only used adult fish.

They put the fish into closed tanks, each with two different fish stocks in different numbers. Fish always choose larger flocks to join if the herd is two or more times larger than the small flock. But if the number of fish in the herd is less than twice that of the small herd, their choice no longer follows the rule. This shows that the fish's estimation capacity only occurs under certain conditions.

After the study results were published in Animal Cognition , the two researchers found that the angelfish can differentiate the difference between numbers 2 and 3. Specifically, if a group has three children and a herd have two children, they always join the larger herd.

" This ability is similar to the fact that people count objects, not estimating behaviors. However, the angels' counting ability does not exceed the number 3 ," he said.

Accurate counting does not bring many benefits to angelfish. Therefore, perhaps their counting skills do not grow beyond the number 3. But estimating the size of the herds allows angels to receive greater protection (the larger the flock they join, the greater the level of safety). higher). In addition, the larger the number of fish in the herd, the more the number of eyes to look for. Therefore, the ability to distinguish large and small herds is vital for angelfish.

Recently, Angelo Bisazza, a professor of psychology at Pavoda University, conducted a number of experiments to prove that mosquito fish are also capable of estimating. He and his colleagues even trained mosquito fish so that they were able to distinguish the fish from different proportions.

Nicola Clayton, a leading expert in animal thinking at Cambridge University in the UK, said, lions and salamanders are also capable of estimating numbers. She speculated that the fish that live in the herd also have the same estimation as angelfish.