As a survival strategy, female frogs play dead during sex

No, not a sex game, but a survival strategy: Researchers from Berlin’s Natural History Museum have discovered something fascinating about our native grass frogs. To avoid the enormous flow of males wanting to mate, female frogs have developed various defense strategies.

These go so far that the females sometimes simply play dead to avoid the male sex drive, according to researchers Carolin Dittrich and Mark-Oliver Rödel.

How does this rush against women come about? According to the Berlin frog experts, frogs or toads with a very short reproductive period are called “explosive” spawning species, with reproduction usually limited to a few days to two weeks in early spring. During this time, thousands of animals gather at the pond – and they only want one thing: to reproduce.

“The males are not picky and grab everything that moves with great force,” the researchers write. It is not uncommon for many males to latch onto a female, “and a ‘mating ball’ is formed,” the article goes on to say. “The female often dies in this.”

The females have developed effective strategies to protect their own lives. The most common behavior to escape the male’s grasp is for the female to rotate around her own body axis. The frog ladies basically wriggle out of the situation.

According to their own statements, the researchers also noted that the females make two different calls. A deeper, low-frequency growling sound imitates the male’s ‘release’ call. A trick to beat him at his own game and make him quit. The frog experts also recorded a higher frequency ‘squeak’, the effect of which has yet to be investigated.

“The final and most astonishing behavior was a tonic immobility, commonly called dead play, in which the females extend their arms and legs stiffly from their bodies and remain motionless until the male lets go,” Dittrich and Rödel write.

This dead play in connection with mating is exceptional and very rarely observed. «I know of only a few studies in which tonic immobility was found in connection with mating, for example in spiders or dragonflies. It is generally believed that this strategy is used last to avoid being eaten by predators,” says Dittrich.

Rödel adds: “We therefore suspect that this defensive behavior evolved to protect the female from the formation of mating balls, which often lead to the death of the female. By calling, females can show that they are not ready to mate, and if this does not work, stressed females can fall into tonic immobility.”

The study by the Berlin researchers was published on October 11 in the open access journal “Royal Society Open Science”.

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