Bats show a huge variation in the foods they consume to survive. Some species specialize in fruits, others in insects and others in flower nectar. There are even species that catch fish with the legs.
At the Smithsonian Institute for Tropical Research in Panama, they took decades studying a species: the lip bat with fringes (trachops cirrhosus). This bat is a carnivore specialized in feeding on frogs.
The male frogs of many species emit sounds to attract females. Ranivorous bats listen to those sounds to find their next dam. But how do sounds and prey associate?
Scientists were interested in understanding how predators who listen to their prey acquire the ability to distinguish between tasty and dangerous dams. Combining our experience in animal behavior, cognition of bats and frog communication to investigate.
How do bats recognize the sound of a tasty meal?
There are almost 8,000 species of frogs and toads in the world, and each one has a unique sound. For example, the first metallic sound reproduced by scientists on a speaker came from a large and toxic cane toxic. The second, “squeak” came from the Tungal frog, a preferred dam for these bats. Just as herpestologists can identify a kind of frog for their sound, rank bats can use these sounds to identify the best food.
Over the years, the research team learned a lot from bats that feed on frogs on how they use sound and echolocation to find dams, as well as the role of learning and memory in the success of the search for food. In the newly published study, they focused on how associations between the sounds that a bat hey and the quality of the dam he expects throughout his life.
They considered whether the associations between sound and a delicious meal are an evolutionary specialty with which bats are born. However, this possibility seemed unlikely because the species of bat they studied has a wide geographical distribution in Central and South America, and frog species found in this area vary greatly.
Instead, they raised the hypothesis that bats learn to associate different sounds with food as they grow. But this idea had to be checked.
First, scientists and collaborators spent time in the forest and in ponds to register the mating songs of 15 of the most common frog species in our study area in Panama.
Then, they installed fog networks along the streams of the Sovereignty National Park to capture wild bats for the study.
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This is how frog songs determine what the bat will eat
For the test, each bat lodged individually in a large outdoor flight camera. From a speaker on the ground, in the center, the songs of a kind of loop frog for 30 seconds were reproduced and the bat behavior was measured, which hung from a cloth coincidence. As expected, adult bats were generally not interested in the sounds of unpleasant species, such as those with toxins or those too large so that the bat can load them.
But the story was different for young bats. The youth responded with significantly more predators behaviors to the songs of toxic toxic comparison compared to adults. They also responded with less intensity than adults to the sounds of the Tungal frogs, an abundant and appetizing dam that adult bats prefer.
Therefore, it seems that young bats must learn associations between sounds and food throughout their lives. As they grow, they learn to ignore the songs of frogs that are not worth concentrating on the songs of frogs that will be a good dam.
To better understand how the sounds drive associations with dams, the acoustic properties of the different songs were measured. It was discovered that some of the most notable characteristics of the songs were correlated with body size: larger frogs produce smaller songs, that is, their voices are more serious. Both adult bats and young people responded more intensely to the largest species, which would provide them with more abundant meals.
However, there was a clear exception in adult responses: toxic toxic toxic and frogs caused much weaker responses than expected for their body size. This finding led to the hypothesis that bats have an early bias to pay attention to the sounds associated with a larger body size.
Then, they must learn through experience that the quality of food not only depends on size. Some abundant meals are toxic or impossible to transport, which makes them unpleasant to the palate.
After the bats spent a few days with scientists, they were released in their original capture. They left, taking with them a small RFID label, such as those used by pet owners to identify their dogs and cats, to find them in the future study.
As bats continue with their lives in nature, the understanding of the subtleties of information discrimination continues to be deepened. How do people filter information overload to make decisions that make sense and benefit them? That is the same challenge that bats face daily.
*Logan S. James is a researcher associated in animal behavior by the University of Texas in Austin; Rachel Page is part of the Science Staff of the Smithsonian Institute for Tropical Research and Ximena Bernal is a professor of biological sciences from the University of Purdue.
This text was originally published in The Conversation
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