* ECOLOGY * AND EVOLUTION : MASTER GLOBAL ESSAY

CANNIBAL FROGS. A bad review ? She nearly ate him alive ? It was nightmare on Kooragang Island north of Sydney, Australia, when the high-pitched shrieking started.

John Gould, an Ecologist at the University of Newcastle conducting postdoctoral research on the declining population of green and golden bell frogs, raced toward the chilling sounds.

There, in a pond, he had been surveying, he spotted a scene that might have fit in an amphibian reboot of a Hannibal Lecter movie : A large female frog was chomping down on the hind leg of a male while pulling him into a hole.

The act of apparent cannibalism was the first between adults recorded in this species, and it gave Dr. Gould an appetite to learn more about the topic. Ultimately, he believes that when a female green and golden bell frog isn't pleased by the song of a male, she might opt to turn him into a meal.

The females '' are almost the ultimate predators  for males,'' Dr. Gould said, because their ears are perfectly in tune to the calling of their would-be-beaus.

Cannibalism is well known among amphibians. But usually it is the younger frogs, toads or salamanders that end up as dinner. The tadpoles of various species eat smaller tadpoles, for example, to get ahead in life.

In some cases, this happens regularly between siblings. In others, adults sometimes cannibalize eggs or larvae - researchers recently discovered that hellbender fathers may eat their young when faced with suboptimal water conditions.

But adult-on-adult cannibalism has seldom been witnessed. For a study published last month in the journal Ecology and Evolution, Dr. 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 occurred in cases where the females were bigger than the males. In green and golden bell frogs, for example, females can grow to about 2.75 inches [ about seven centimeters ] in length while males usually max out at less than two inches.

Dr. Gould believes that a female may be able to tell whether a male is better for mating or eating based on the strength of his calls, meaning males take a big risk when trying to attract females.

'' You've really got to give props to the male frogs out there, that they are putting their lives on the line to reproduce,'' Dr. Gould said.

'' Maybe there's a reason why males and females, you don't often find them next to each other in ponds.''

The World Students Society thanks Joshua Rapp Learn.