It was nighttime on Kooragang Island, north of Sydney, Australia, when the high-pitched squeals began.
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John Gould, an ecologist at Newcastle University who does postdoctoral research on the declining population of golden green bell frogs, ran towards the chilling sounds.
At a pond, he saw a large female frog nibbling on the hind leg of a male as she slowly dragged him toward a hole.
“The male frog was going to great lengths to prevent this from happening,” Gould recalled.
The act of apparent cannibalism was the first recorded among adults in this species. Gould believes that when a female green-and-golden bell frog is unhappy with a male’s song, she may choose to make him her meal.
Cannibalism is well known among amphibians.s. But usually the younger frogs, toads or salamanders end up as dinner.
Cannibalism among adults has rarely been observed. For a study published in June in the journal Ecology and Evolution, Gould scoured the literature and found only a couple of examples, many in the lab, of adult frogs cannibalizing other adults. Almost all of these cases involved females that were larger than the males.
In green and golden bell frogs, for example, females can grow up to about 7 centimeters long, while males are typically less than 5 centimeters.
Gould believes that a female may be able to determine whether a male is better to mate with or eat based on the strength of his calls. This means that males risk their lives when trying to attract mates.
“There may be a reason they are not often found together in ponds,” Gould said.
David Pfennig, a biology professor at the University of North Carolina at Chapel Hill who was not involved in Gould’s research, has studied cannibalism among spade-footed toads. He said he would like to see more evidence that adult females cannibalize males before accepting that the phenomenon is more than occasional.
While females might benefit from cannibalizing males, there are costs, too. Males might fight back, or females might choke on more than they can chew. Cannibalism can also spread disease in infected populations. Gould would like to explore this idea further, too.
While stories of cannibalism don’t usually have a happy ending, the male frog in Gould’s study lived to tell the tale. After a struggle in which the female dragged him further into the hole, the male screamed once more and pulled his leg free from her mouth, leaping to freedom.
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