Female frogs play dead to escape males

Female European frogs will play dead to avoid mating if several males climb on their backs at the same time during breeding season.

Researchers have found that female frogs have developed a number of strategies to avoid mating, including rolling around, grunts, and even playing dead. They published their findings on October 11 in the journal Royal Society Open Science. European frogs ( Rana temporaria ) are known for their explosive breeding, often gathering dozens of them to mate in ponds. Typically, males far outnumber females, meaning six or more males may compete to climb onto a female's back at a time. In some cases, females can be killed inside these mating spheres, said Carolin Dittrich, a researcher at the Natural History Museum in Berlin.

However, female frogs have evolved several techniques to avoid mating. "Rather than being passive and helpless, we found that female frogs can use three key strategies to avoid males they don't want to mate with, either because they're not ready or because they don't want to mate," Dittrich said.

Researchers collected male and female European frogs from a pond during mating season and placed them in water-filled tanks, each containing two females and one male. They then filmed the frogs for several hours. Of the 54 female frogs approached by a male, 83% responded by rolling onto their backs. This kept the male underwater and forced him to release the female to avoid drowning.

The team also found that 48 percent of the female frogs mounted by the males made high-pitched growls and squeaks. The growls mimicked the calls that males make to ward off other males. But Dittrich and his colleagues weren’t sure what the higher-frequency squeaks meant. They also observed a third of the female frogs lying motionless with their limbs spread out for about two minutes after being grabbed by the males. They speculated that the females were playing dead, though they couldn’t prove it was conscious behavior. It could also be an automatic response to stress.

Younger and smaller females were more likely to use all three strategies to repel males, while older and larger individuals were less likely to play dead. As a result, younger females were better at escaping approaching males. It is possible that younger females, having had fewer mating seasons under their belts, were more stressed by the approach of males and reacted more strongly.

While experiments may differ from real-life situations, similar tactics are widely observed in nature. The tactic of feigning death to avoid unwanted males is found in many other animals, including dragonflies, spiders, and Spanish-ribbed newts ( Pleurodels waltl ). Understanding such behavior could inform future conservation efforts.

An Khang (According to Live Science )

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