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#Science

Brain size matters when it comes to survival, researchers say

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Researchers have revealed through a new study that size of the brain is an important factor that governs survival rate with bigger the brain implies better cognitive performance, which logically offers a higher survival potential. Therefore bigger the brain, the researchers say, win out over smaller ones.

Though previous studies have compared intelligence and survival potential of species with large brains versus species with smaller brains, they haven’t been able to show a causal relationship that larger brains do appear to have a survival advantage.

Looking for a causal relationship, four researchers from the Konrad Lorenz Institute of Ethology at the Vetmeduni Vienna studied fish to answer why investing in a larger brain might provide an evolutionary advantage to compensate for the fact that brain mass is very expensive to develop and maintain.

For their research, Alexander Kotrschal, Sarah Zala, Séverine Büchel and Dustin Penn form the institute carried out research on guppies with large and small brains in semi-natural streams. For their study, they aimed to test whether brain size influences survival. Therefore, they released 4,800 guppies from these selection lines into large semi-natural streams, which also contained a natural predator, the pike cichlid.

About half a year later, significantly more guppies with large brains had survived. The researchers suggest that large-brained fish have an advantage that allows them to better evade predation. “We have provided the first experimental proof that a large brain offers an evolutionary advantage,” explains first author Kotrschal, who has since moved on to Stockholm University.

Females with large brains better off

Large-brained females, whose brains were about 12 percent larger than that of the small-brained females, evaded their predators more often and so had a higher rate of survival. Larger brains did not provide any survival benefit for males. Ethologist Sarah Zala explains: “Male guppies are more colourful and more conspicuous than females and are therefore more easily caught by a predator. A larger brain does not appear to compensate this disadvantage.”

“Our findings support the hypothesis that large brains provide a survival benefit under predation pressure,” says co-author Dustin Penn.

The first results also suggest that groups of fish with large or small brains behave differently in the presence of the predatory cichlid. This behaviour merits further study. The researchers also want to know whether surviving fish produce more offspring. Genetic analysis should help provide clarity in this regard.