‘It’s risky for male frogs’: Female frog hangs around and tries to eat screaming male

 

Breeding seasons can be dangerous for males frogs trying to impress a potential mate: They can quickly find themselves dragged away and eaten by an unimpressed female, the researchers found.

For the first time, scientists on Kooragang Island in New South Wales, Australia, have observed adult female green and golden frogs (Litoria aurea) preying on their male counterparts during the breeding season. They detailed their findings in a study published June 12 in the journal Ecology and evolution.

Researchers first observed this behavior during a survey when they heard a high-pitched scream.

“You sometimes hear it in the field, and it’s often a frog that’s being attacked,” said the study’s lead author. John Gouldpostdoctoral researcher in population ecology at the University of Newcastle, Australia, told Live Science.

After tracking the cries, Gould discovered that the distressed noises were coming from a male whose thigh had been almost entirely ingested by a larger female. She was dragging him into a hole at the edge of a pond.

“The male frog really tried to prevent this from happening, so he was grabbing onto everything around him, like sticks in the ground, to keep from being dragged down,” Gould said.

The male eventually managed to escape. This observation prompted Gould and his team to compare their nocturnal field observations over three consecutive breeding seasons with other studies that have reported cases of sexual cannibalism.

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A green frog bites the hind leg of a frog of the same species while it is on a log on the forest floor

Scientists spotted a female green frog (like the one on the right) biting the hind leg of a male of the same species. (Photo credit: John Gould and Chad T. Beranek)

Cannibalism East well documented in amphibiansBut most reported cases involve either adults cannibalizing juveniles that emerged from the water or tadpoles cannibalizing each other, Gould said.

Amphibious Cannibalism usually occurs when large numbers of animals congregate in the same area, such as when tadpoles emerge from eggs, and when there are noticeable size differences between predator and prey.

Many species of frogs exhibit sexual dimorphism: adult females are often significantly larger than males.

“There is a very good opportunity for females to exploit their male counterparts, not only as breeding partners, but potentially as prey,” Gould said.

Researchers have speculated that this cannibalism may act as a process of natural selection.

Females can differentiate between potential mates or prey based on the quality of their calls during the breeding season. Larger males with deeper calls may be considered better breeding partners, leaving smaller, lower-quality males as potential meals.

However, Gould suggests that superior mates cannot escape predation either. Instead, once females have laid all their eggs after mating, they may choose to eat their mate, much like female praying mantises, which decapitate and eat their mate during or after mating.

“It’s risky for male frogs. They’re working hard to find a mate, but they have to take that extra risk of maybe being used as prey,” Gould said.

Scientists still don’t know for sure what influences these cannibalistic behaviors. Observations of sexual cannibalism are rare because they happen quickly. However, that doesn’t mean they’re uncommon, Gould said.

Gould points out that field observations of amplexus – when a male frog mounts a female to fertilize her eggs – are also relatively rare, even though scientists know it is necessary for reproduction.

Further research is needed to establish the frequency of these cannibalistic events and their impact on local populations of green and golden frogs, the team said.