Mosquitofish are small, freshwater fish that have earned their moniker by happily feeding on mosquito larvae. They’re common to many parts of the world and their appetites have served them in good stead, as they’ve been deliberately introduced, for good or ill, into many different ecosystems from India to California as a way of lowering mosquito populations.

But it’s not just their diet that makes them notable - researchers have discovered that they’re also surprisingly numerate, and in some cases their numerical skills were even on a par with those of university students. The secret behind their amazing ability could lie in the fact that, like many small fish, they’re highly social. This means that when a mosquitofish finds itself all alone, its top priority becomes finding others and it can count how many other fish are around it. Under lab conditions, it can not only tell the difference between small numbers such as 4 and 8, but can also differentiate between quantities as large as 100 and 200.

Where the fish has some trouble, however, is in differentiating between ratios. Keen to see how the numerical skills of the fish compared to those of humans, the researchers asked a group of 25 undergraduate students to engage in a test that presented them with the same types of challenges, and the test showed that the students had the same difficulty in judging differences when it came to ratios.

According to the scientists, the results provide fascinating evidence that humans, fish, and other vertebrates all share the same abilities for processing numbers as a distant but common ancestor. While this paints the clever mosquitofish in a positive light, it also suggests that students’ numerical skills may have suffered as the result of one too many pub crawls.

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