Female frogs eat male frogs trying to mate

John Gould, an ecologist at the University of Newcastle, heard the terrifying noise while conducting postdoctoral research on the dwindling population of the golden-green bell frog. In a pond Gould was surveying on Kooragang Island north of Sydney, he saw a large female frog chewing on a male frog’s hind leg as she slowly dragged him into a hole. “The male was doing his best to stop this from happening,” Gould said.

Cannibalism between adults was first documented in green and gold bell frogs, prompting Gould to investigate further. He eventually came to the conclusion that when female green and gold bell frogs are dissatisfied with a male’s song, they may turn him into a meal. According to Gould, females are almost the ultimate predators of males because their ears are perfectly designed to hear the calls of potential mates.

Cannibalism is common among amphibians. But usually only the smallest frogs, toads, or salamanders are eaten. Many species of tadpoles also eat smaller tadpoles to grow. In some cases, males eat eggs or larvae; for example, male hellbender salamanders may eat their young when faced with water shortages.

But researchers rarely observe adult cannibalism in amphibians. In a study published in the journal Ecology and Evolution, Gould combed the literature and found only two examples of adult frogs eating other adults in the lab, with the females being larger than the males. In the green and gold bell frog, females can grow to about 7 centimeters (2.9 inches) in length, while males max out at less than 5 centimeters (2.9 inches). Gould suggests that females may be able to determine which males are more suitable for mating or eating based on their calls. This means that males face greater risks when trying to attract mates.

David Pfennig, a biology professor at the University of North Carolina at Chapel Hill, wants to find more evidence of adult female frogs eating males before confirming that it is a common phenomenon. While the female frog may benefit from eating the male, it may come at a cost. The male may fight back or choke the female by taking a bite that is too large. Cannibalism can also spread disease in an infected population. After some struggle, the female frog pulls the male deeper into the hole, Gould says. The male squeals again, then successfully wrenches his hind legs out of the female’s mouth and flees.