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Dropping dead: The new tactic female frogs employ to avoid male sexual advances

It appears that female frogs are not up for sexual activity at all times, and no self-respecting male frog wants to mate with a dead partner. Female frogs seem to have realized this and are now faking their death as a means to avoid unwanted advances from their male counterparts.

An extensive assessment of the mate avoidance behavior among European common frogs (Rana temporaria) has led to some interesting findings. A team of scientists recently discovered that female frogs have developed a few distinct methods to escape pushy males. These include rolling, grunting, special calls, and even appearing dead.

Mating behavior of frogs

Breeding among European common frogs is quite unique. For instance, their breeding season is relatively short. They also mate simultaneously in large numbers, usually in ponds.

The mating population is such that there are more males than females in the ponds. This scenario means there are several male frogs to a single female frog. This mating behavior often endangers the lives of the female frogs, and can actually lead to their death.

Rejecting unwanted advances

Before now, little was known about if and how female frogs could avoid this life-threatening situation. This research has now uncovered a number of avoidance tactics.

“We observed three female avoidance behaviors, namely ‘rotation,’ ‘release calls,’ and tonic immobility (death feigning),” the scientists wrote in their study.

Studying frog mating habits

The study was focused on male and female European common frogs collected from a pond during the breeding season. 

This population was separated into different tanks filled with water. There were two females and one male in each tank after the separation.

What was learned about female frogs

The researchers observed that a total of 54 female frogs were grasped by the males. Eighty percent of the grasped female frog population rolled onto their backs to prevent intercourse. 

The clinging males were also pushed back underwater, forcing them to leave the female frog.

For the females that the males mounted, 50 percent of them employed grunts and squeaks to avoid copulation. 

The researchers also observed that about one-third of the females adopted tonic immobility. This group of females layed motionless on their backs and stretched their limbs for two minutes – an appearance that suggests they are dead.

Age and experience 

These behaviors were also more common among the smaller females, with the older ones less likely to appear dead. “The smaller females also showed the full repertoire of behaviors more often than the larger females,” the researchers noted.

“Our observations suggest that female common frogs are not as passive as is usually assumed and that age and experience may play a key role in the performance of these behaviors.”

Unanswered questions about female frogs

Interestingly, the researchers could not determine why the female frogs adopted this method to escape mating. It may be a conscious behavior or a natural response to stress from the mating process.

Resolving this uncertainty may require a larger sample size, considering the males were only presented with two females during this experiment.

The study’s implications 

This is not the first time we have seen species feigning deaths to escape predators. However, it is not common, and this is the first time it has been observed among frogs.

A better understanding of the mating behavior among European common frogs can contribute significantly to conservation efforts. It may also serve as a strong foundation for advanced inquiries into the mating behaviors among amphibians.

Researchers from the Leibniz Institute for Evolution and Biodiversity Science carried out the study. Their findings are published in the journal Royal Society Open Science.

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