Female frogs have ways to avoid the attention of males
Carolin Dittrich
Male frogs commonly coerce female frogs into mating, but some females have come up with ways to avoid harassment – including playing dead.
Many frog species, including the European common frog (Rana temporaria), only have a short window of a few weeks each year to mate. This means that lots of males simultaneously compete for the attention of females, sometimes leading to deadly clashes as individuals are submerged under a competing group of males.
“It could be that there are several males clinging to one female, which often leads to the death of the female,” says Carolin Dittrich at the Natural History Museum in Berlin, Germany.
Now, Dittrich and her colleagues have found that female common frogs employ a few different tactics to evade males.
The team collected common frogs during the breeding season – 96 females and 48 males – and placed one male and two differently sized females in a box filled with 5 centimetres of water. The frogs were then allowed to move freely for 1 hour while the team recorded their behaviour.
Of the 54 female frogs that were embraced by a male as part of the mating process, 83 per cent rotated away, making it the most common escape tactic.
Many used more than one technique. Another popular avoidance measure was to make what is known as a release call, which was observed in 48 per cent of females.
“Males typically use release calls to signal other males that they are a male, so to let them go,” says Dittrich, and the females seem to mimic this call to convince males to let free them too.
The way male European common frogs pile onto females sometimes results in death by drowning
Carolin Dittrich
Thirty-three per cent of clasped females exhibited “tonic immobility”, otherwise known as playing dead.
In 46 per cent of the cases, the females evaded the male’s attention, with higher rates of success for smaller females, which are more easily able to escape from a male’s grip.
Although this study was done in a lab, Dittrich thinks female frogs would exhibit similar behaviour in the wild.
“Usually, it is seen that females are helpless,” she says. “But this study shows that they are not as passive as previously thought.”
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