Short Wave Podcast Episode Summary

Title: How Baby Bats Learn To Eavesdrop On Dinner
Host: Emily Kwong
Guest: Rachel Page, Behavioral Ecologist at the Smithsonian Tropical Research Institute
Release Date: May 14, 2025

Introduction: The Spectacle of the Congress Avenue Bridge

Emily Kwong opens the episode by painting a vivid picture of the annual emergence of Mexican free-tailed bats from Austin’s Congress Avenue Bridge. "An hour or so before sunset, hundreds of people gather at this one bridge to wait for the moment when bats take flight... Up to 1.5 million Mexican free-tailed bats take to the sky. This Exodus can last 45 minutes and it is hypnotizing" (00:16). This natural phenomenon not only attracts spectators but also serves as a backdrop for introducing the intricate behaviors and learning processes of bats.

Rachel Page’s Fascination with Bats

Rachel Page shares her serendipitous journey into bat research, sparked by Austin's vast urban bat colony. "I sort of fell into bats by chance. And really the reason I fell into them was because of Austin, because of that enormous urban colony of bats" (00:58). Her passion evolved during her graduate studies, leading her to specialize in the behavioral ecology of bats, particularly focusing on how they navigate and interact within their environments.

Navigational Marvels: Echolocation and Beyond

The episode delves into the complex navigation systems bats employ. Emily Kwong explains, "There are over 1400 different species of bats found throughout the world. And the way they navigate is hugely varied. Many use echolocation" (01:33). Rachel Page expands on this, highlighting that while echolocation is a primary tool, bats also utilize other senses. "But echolocation is not the only sense that they use" (01:49). This multifaceted approach allows bats to not only navigate but also communicate and hunt effectively.

Eavesdropping: A Sophisticated Hunting Strategy

A significant portion of the discussion centers on how fringe-lipped bats in Panama employ eavesdropping to locate and assess their prey—frogs. Rachel Page outlines this strategy: "These frog-eating bats... are actually listening in on the mating calls of frogs that are much, much lower in frequency. So they've had to evolve basically like another set of hearing sensitivity" (02:06). The bats' ability to discern between the calls of poisonous and non-poisonous frogs is critical for their survival.

Chemical and Acoustic Sensitivity in Prey Selection

Rachel Page explains the physiological adaptations that facilitate this selective hunting: "So they have enormous ears. This helps with their eavesdropping behavior as they listen in for frog calls and other prey sounds... they have this fringe on their chin and lips... to very quickly make chemosensory assessments of prey quality" (02:26). These adaptations enable bats to not only hear the frogs but also chemically assess whether the frog is safe to consume.

The Learning Conundrum: Innate vs. Acquired Behaviors

A pivotal question addressed is how juvenile bats develop the ability to distinguish between safe and toxic frogs. Rachel Page poses, "Was this through learning over time? Was it something that they were born with? Was it something in between?" (03:29). This inquiry sets the stage for discussing her research on whether these discriminatory behaviors are innate or learned.

Experimental Insights: Testing Juvenile Bats

To explore this, Rachel Page describes her experimental approach: "We captured a whole bunch of bats both Adults and juveniles this time. And we brought them into a flight cage... we just played the frog calls one by one and quantified what those reactions were" (11:14). The findings revealed that juvenile bats exhibit less discrimination between frog calls compared to adults, suggesting that experience and learning play crucial roles in developing this skill.

Behavioral Observations: Juveniles vs. Adults

During an engaging segment, Emily Kwong and Rachel Page conduct a playful experiment simulating the bats' decision-making process based on frog calls. For instance, when testing the tungra frog, Emily humorously predicts its toxicity, but Rachel Page corrects her: "That is the best frog of the forest... we call them the popcorn of the forest" (09:00). Conversely, the cane toad elicits a correct reluctance to approach due to its known toxicity. This interaction underscores the necessity for juvenile bats to learn through experience which calls signify safe prey.

Cognitive Flexibility and Learning Mechanisms

The conversation highlights the cognitive flexibility of bats, allowing them to adapt and correct mistakes when identifying prey. Rachel Page states, "If they do make a mistake at the eavesdropping level... they have a number of possibilities for correcting that mistake" (07:21). This adaptability is likened to humans learning to avoid spam calls after a bad experience, emphasizing the importance of learning in survival behaviors.

Implications for Broader Biological Understanding

Rachel Page emphasizes the broader significance of her research: "We're fascinated by eavesdropping behavior... you find it in nearly every taxonomic group that you look at. And I think that the ones that we haven't found it in is just because we haven't looked hard enough yet" (13:32). Her study is pioneering in elucidating how eavesdropping predators acquire their strategies, potentially inspiring similar research across various species.

Conclusion: The Importance of Learning in Predator-Prey Dynamics

The episode concludes by reaffirming the critical role of learning in the efficacy of predators like fringe-lipped bats. Rachel Page expresses hope that her findings will inspire further studies into eavesdropping behaviors, enhancing our understanding of complex ecological interactions. Emily Kwong wraps up by thanking the guest and producers, leaving listeners with a deeper appreciation of the sophisticated lives of bats.

Notable Quotes with Timestamps

• Rachel Page [00:58]: "I sort of fell into bats by chance. And really the reason I fell into them was because of Austin, because of that enormous urban colony of bats."

• Rachel Page [01:24]: "How on earth are they not bumping into each other? How can they recognize their own echolocation call? How are they also communicating socially with one another?"

• Emily Kwong [02:20]: "So they have enormous ears. This helps with their eavesdropping behavior as they listen in for frog calls and other prey sounds."

• Rachel Page [03:06]: "If they heard a particular frog call, they would expect, okay, this is palatable prey. I'm flying for it. Versus this is a poisonous frog. I'm gonna stay away."

• Rachel Page [07:02]: "So once they actually have the frog or toad in the mouth, if they've made a mistake, they will spit out that frog and toad."

• Emily Kwong [09:16]: "You're probably less likely to do that the next time. Like it's. It definitely is a learned behavior that over time you think?"

• Rachel Page [13:32]: "We're fascinated by eavesdropping behavior... you find it in nearly every taxonomic group that you look at."

Key Takeaways

• Eavesdropping as a Hunting Strategy: Fringe-lipped bats utilize auditory cues from frog calls to locate and assess prey, distinguishing between safe and toxic species.

• Learning Over Innate Behavior: Juvenile bats require experience and learning to develop the sophisticated ability to discriminate between different frog calls, highlighting the importance of environmental interaction in behavioral development.

• Cognitive Flexibility: Bats demonstrate the ability to correct mistakes in prey identification, akin to human learning processes, showcasing their adaptability and intelligence.

• Broader Implications: Understanding how bats and other predators learn to eavesdrop can shed light on complex ecological interactions and inform conservation strategies.

This episode of Short Wave offers an insightful exploration into the cognitive and behavioral ecology of bats, emphasizing the intricate interplay between innate abilities and learned experiences in shaping survival strategies. Through Rachel Page’s research, listeners gain a deeper appreciation for the nuanced ways in which animals interact with their environment and each other.