Bats learn which frogs are safe to eat by eavesdropping

Bats in the dense tropical forests stretching from Panama to Brazil don’t hunt by sight – they listen.

One species, the fringe-lipped bat, doesn’t fly aimlessly in search of food. Instead, it tunes into the love songs of frogs and toads. But here’s the twist: not every song leads to a safe or tasty meal.

Some frogs are too big. Others are toxic. So how do these bats know which calls are worth following? It turns out, they learn through experience.

Learning what’s edible takes time

Researchers at the Smithsonian Tropical Research Institute (STRI), together with scientists from Purdue University, found that fringe-lipped bats aren’t born knowing which calls to trust. Instead, they learn as they grow. This study offers the first clear evidence that predators who eavesdrop on other species’ signals sharpen their skills over time.

Fringe-lipped bats are among nature’s most skilled eavesdroppers. They key in on the mating calls of more than a dozen frog and toad species in their habitats.

As soon as they hear the right call, they swoop in within seconds. But not every call promises a safe bite. Some frogs defend themselves with toxins. Others are just too large to handle.

How bats avoid bad frogs

To avoid a bad meal, adult bats have developed a keen ability to filter out the wrong calls – like a spam filter for frog croaks. What scientists didn’t know was whether this ability was instinctual or learned. That question sparked this new study.

“It’s truly remarkable that these bats hunt using the calls of an entirely different group of animals in the first place, and we have wondered for a long time how these bats acquire this unusual skill,” said Logan James, STRI postdoctoral researcher and lead author of the study.

Wild bats face frog audio test

To figure it out, the research team captured both adult and juvenile fringe-lipped bats from the wild. They then played recordings of 15 different frog and toad mating calls – some from palatable species, others from toxic or oversized ones.

As expected, the adult bats were picky. They clearly responded more often to calls from edible frogs. The younger bats, however, weren’t as selective. On average, juveniles reacted similarly to all the calls, regardless of the frog’s palatability.

Danger detection takes practice

The one thing they could do was recognize larger prey by sound, just like the adults. But they hadn’t yet learned to identify which species were toxic. This finding suggests that young bats rely on size cues early on, while their ability to detect danger develops with time and experience.

“We knew from previous research that these bats are very clever and can learn during experiments, but we had not tested whether their aptitude for learning had a role in fine-tuning their responses to sound cues from their natural prey,” said James.

Juvenile bats still learning the ropes

This research is the first to compare how predators of different ages respond to the same eavesdropping cues. And the results are surprisingly relatable. Like many young animals – and even human kids – these juvenile bats need time to build up their decision-making skills.

“We have studied this fascinating species for years, and in many aspects, we understand its behavior very well,” said Rachel Page, staff scientist at STRI and one of the study’s senior authors.

“But this was the first time we had ever tested juvenile bats. It was so interesting to see that, like human children, young bats needed time and experience to hone their discrimination skills.”

A widespread predator pattern

The findings point to a much broader pattern in nature. Fringe-lipped bats may not be the only predators who learn this way. Many animals might be sharpening their hunting instincts through trial and error.

Ximena Bernal, a research associate at STRI and professor at Purdue University, is one of the study’s senior authors.

“This study highlights the power of development and learning to shape eavesdropping behavior, an insight that may extend far beyond bats to other predators also navigating complex sensory environments,” said Professor Bernal.

“We hope it will inspire other scientists to examine how early experience modulates predator-foraging decisions.”

The full study was published in the journal Proceedings of the Royal Society B: Biological Sciences.

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