It is quite amazing that there are many more animal species that practice cannibalism than one would expect. There are over 1500 document species that partake in this behaviour. Although the reasons may vary, cannibalism always serves an evolutionary purpose.
In Kooragang Island located in New South Wales, Australia for the first time scientists have observed green and gold bell frogs engaging in cannibalistic behaviour.
Adult female green and golden bell frogs are likely to prey on male frogs during their mating season if they find their mating calls unfavourable.
The researchers became aware of this when they heard a shrill cry coming from one direction during their field survey. John Gould who was the principal investigator and postdoctoral researcher at University of Newcastle traced it down to a larger female frog that was eating a male frog.
The female frog grabbed the leg of her unsuspecting victim and began dragging him towards the burrow situated near the edge of the pond.
Gould said, “The male frog struggle as hard as he could against being drawn inside. He held onto anything near him including sticks in the ground”.
In the end, the male managed to flee. After the event, Gould and his group studied their observations over three breeding seasons and compared them with other cannibalism studies.
For instance, amphibians sometimes display cannibalistic behavior when tadpoles eat each other or adults prey on juveniles. People often observe this behavior in cramped areas or when a significant size disparity exists between the predator and its prey.
In different species of frogs adult females are bigger than their male counterparts. Consequently they can dominate males nutritionally and even consume them during the time of mating.
Researchers hypothesized that cannibalism could have arisen via natural selection. In this process, a male’s mating call greatly influences whether he will be chosen as a partner or become dinner.
Female frogs prefer larger mates with deeper calls and often see smaller ones as less attractive, sometimes even as food.
Bigger men are also subject to predation. Females may eat their partners after laying all their eggs.
Gould clarifies, “Male frogs looking for a mate take considerable chances. While they make loud calls in order to attract one; they risk becoming food for other animals.”
Researchers need to establish the frequency of cannibalism in green and golden bell frog populations. Its impact on these populations also requires investigation.
Ecology and Evolution is the journal that published the study.
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