Aug 19, 2022
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Conspicuous frogs have large brains to evade predators

Conspicuous frogs have large brains to evade predators

Frogs have developed a wide variety of strategies to evade predators. Some of the defense mechanisms used by frogs are quite bizarre, such as pretending to be dead, screaming, urinating, or puffing up their bodies.

In a new study led by evolutionary biologist Stefan Leupold of the University of Zurich, scientists set out to find out how frogs choose between two specific predator defense strategies: fleeing the scene and avoiding detection by using camouflage. The findings suggest that frogs have evolved to have either small or large brains, depending on which of these defense strategies they use.

While effective, both running and disguising come with potential costs. For example, it takes a lot of energy to physically run away from a predator. But while camouflage can save energy, it can be detrimental to successful mating and greatly limits where animals can live safely.

The study examined anti-predator adaptations in 102 species of Chinese frogs. The analysis showed that the frogs, which had fewer predators, had bodies adapted for flight, including large brains and muscular hind legs.

On the other hand, when frogs are faced with a lot of predators, running away is no longer the best option. “In such adverse conditions, the cognitive costs required for this strategy outweigh its benefits,” Leupold explained. “Here, evolution has led to a gradual shift from cognitive predator evasion to camouflage – and therefore smaller brains.”

According to the researchers, this study is the first to establish a direct link between brain evolution and various predator evasion strategies.

“Our study highlights the need to consider metabolic costs as much as cognitive benefits when studying brain evolution,” says Leupold.

“In particular, our phylogenetic pathway analysis revealed an indirect relationship between predation risk and crypsis that is mediated by brain size,” the study authors write. “This result suggests that at low predation risk, frogs can afford to be conspicuous and use their large brains for cognitive predator evasion. This strategy may become less efficient or energetically costly at higher predation pressure, leading to brain shrinkage and increased crypsis.” “

The study is published in the journal Science Advances.

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