City frogs sing more appealing love songs


WASHINGTON (Reuters) – City frogs and tropical forest frogs do not sing the same tune, the researchers found.

A study released Monday examined why Panama's tiny tetanus frogs adapt their mating mating in urban areas – an unexpected example of how animals change communications strategies when cities invade forests.

These frogs take advantage of the relative absence of predators spying on the cities to distribute longer love songs, which are more appealing to female frogs.

Tungara frogs do not croak like American frogs. For human ears, their distinctive call sounds like a low-frequency video game beep. For female frogs, it sounds like pillow talk.

Every afternoon, at sunset, the 1-inch brown toads crawl into puddles to serenade potential partners. The frog lady selects a partner largely based on her love song.

Researchers have found that urban frogs call faster, more frequently and add more ornaments – a series of staccato "mandrels" at the end of the initial lament – compared to those in the forest.

These sophisticated urban love songs are three times more likely to attract women, as scientists have learned by reproducing recordings of city and forest toad calls to a female frog audience in a laboratory. Thirty of 40 female toads jumped to the speaker tapping the calls of urban frogs, the researchers report in the journal Nature Ecology & Evolution.

Whether female frogs left the city or the forest, they showed the same preference for complex and accelerated chrome that combines high and low tones in fast arrangements.

Study co-author Michael J. Ryan, a biologist at the University of Texas who has studied frogs for more than 30 years, said that high and low grades are likely to stimulate the inner and outer auditory chambers of female toads pleasantly or interestingly. way.

So why do not the rainforest frogs sing the same way?

The scientists set out to confirm their hypothesis that frogs that added extra-strong "chucks" attracted not only more partners, but also more problems caused by frogs and parasitic mosquitoes. With the help of photographic traps and sticky paper, researchers have shown that extended toad calls have significantly increased the risk of attracting predators.

In the rainforest, frogs need to balance two goals: to attract a partner and stay safe.

In the city, there are no frog-eating bats, let alone snakes and mosquitoes. Male toads are freer to gird their hearts.

"An urban man can take greater risks," said lead author Wouter Halfwerk, an ecologist at Vrije University in Amsterdam.

A city frog also has to try harder to find a mate because the lady frogs are rarer in town. "Competition for women increases," Halfwerk said. "The best adaptation is to be the most attractive, with an elaborate love song."

Corinne Lee Zawacki, a University of Pittsburgh biologist who was not involved in the study, said the researchers' methodology confirmed that urbanization is the reason for the changes in the call.

"I love the choice of study system," she said. "A lot of background research has already been done on this frog, so we can see clearly how urbanization changes the interaction of natural and sexual selection" – or the trade-offs between survival and cutting goals.

But not all amphibians have the same fate as the tungara frogs of Panama.

"Amphibian populations are dwindling around the world, mainly due to habitat destruction," said Andrew Blaustein, an ecologist at Oregon State University, who did not participate in the study. "This is a rare case – and a very interesting case – of an animal adapting rapidly, in evolutionary terms, to new circumstances."


Follow Christina Larson on Twitter at @larsonchristina.


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