European female frogs will play dead to avoid mating if several males climb onto their backs simultaneously during the breeding season.
The female frog plays dead in an experiment in a water tank. (Video: Live Science).
Researchers have discovered that female frogs have developed several strategies to avoid mating, including rolling over, making murmuring sounds, and even playing dead. They announced their research findings on October 11 in the journal Royal Society Open Science. European frogs (Rana temporaria) are known for their explosive breeding behavior, often gathering in large numbers to mate in ponds. Typically, the number of male frogs far exceeds that of females, meaning that six or more males can compete to climb onto a female’s back at any given time. In some cases, females can be inadvertently killed within these mating clusters, according to Carolin Dittrich, a researcher at the Natural History Museum in Berlin.
However, female frogs have developed several techniques to avoid pairing up. “Instead of being passive and helpless, we found that female frogs can use three key strategies to avoid unwanted males, either because they are not ready or do not want to mate,” Dittrich explained.
The researchers collected male and female European frogs from a pond during the breeding season and placed them into water-filled tanks, each containing two females and one male. They then filmed the frogs for several hours. Among the 54 female frogs approached by males, 83% reacted by rolling onto their backs. This position forced the males underwater, compelling them to release the female frog to avoid drowning.
The female frog plays dead.
The research team also found that 48% of the female frogs being climbed on by males emitted growling and high-pitched sounds. The growling mimics the calls that male frogs typically make to ward off other males. However, Dittrich and her colleagues are uncertain about the significance of the high-pitched sounds. They also observed that one-third of the female frogs remained motionless with their limbs spread for about two minutes after being captured by a male. They suspect that the female frogs are playing dead, although they cannot prove that this behavior is conscious. It may also be a reflexive response to pressure.
Younger and smaller female frogs are more likely to use all three strategies to repel males, while larger and older individuals seldom play dead. As a result, smaller females often escape approaching males more effectively. It is possible that younger females have experienced fewer breeding seasons and thus feel more stressed when a male approaches, prompting a stronger reaction.
Although the experiment may differ from real-world situations, similar strategies have been observed in nature. The tactic of playing dead to avoid unwanted males is seen in many other animal species, including dragonflies, spiders, and Spanish ribbed newts (Pleurodeles waltl). Understanding such behaviors could aid future conservation efforts.
