Female frogs found to fake death to avoid unwanted advances from males

Nearly one-third of females in study laid motionless on their backs to get out of mating with male

Female frogs would sometimes go as far as faking their own deaths to avoid male attention, scientists have found.

Researchers assessed mate avoidance behaviour in European common frog and found that females use a number of methods, including special calls, grunting, rolling, and even feigning death to get rid of unwanted males.

European common frogs are known to be an “explosive” breeding species with a very short breeding season. They gather in ponds to mate in large numbers with a high risk of death among mating females.

Previous research found that during these mating events where males outnumber females, several males can cling on to a female frog, causing their deaths.

However, until now scientists have not found how the female frogs attempted to reject unwanted males.

“We observed three female avoidance behaviours, namely ‘rotation’, ‘release calls’ and tonic immobility (death feigning),” scientists, including those from the Leibniz Institute for Evolution and Biodiversity Science in Germany, wrote in the study published on Wednesday in the journal Royal Society Open Science. The new study may lead to better conservation efforts.

Scientists collected male and female European common frogs from a pond during the breeding season.

They divided the collected frogs into tanks filled with water such that each tank contained two females and one male.

Overall 54 female frogs were grasped by males in the study, of which over 80 per cent rolled onto their backs to avoid copulation.

This move, according to scientists, puts the males clinging on to the female’s back underwater, leading to them letting go of the female frog.

About half of the females that were mounted by males used grunts and squeaks to attempt to get away from sex.

Scientists also found nearly one-third of the females laid motionless on their backs with limbs stretched as if they were faking death for about two minutes after a male climbs onto them.

“The smaller females also showed the full repertoire of behaviours more often than the larger females,” researchers noted, adding that older females were less likely to feign death.

However, it remained unclear whether the female response appearing to faking death was a conscious behaviour or an involuntary response to stress.

Overall, scientists found that nearly half of the females mounted by a male successfully escaped using these strategies.

The tactic to avoid predators by faking death has until now only been observed in a handful of species.

With the latest findings, researchers hope to better understand mating behaviour in amphibians and broaden their conservation efforts.