Moth Mimicry: Using Ultrasound to Avoid Bats | HHMI BioInteractive Video

Summary

Jesse Barber's research in Gorongosa explores the intricate bat-moth interactions, a co-evolutionary battle spanning over 60 million years. Utilizing ultraviolet lamps to attract moths, Barber and his team study their anti-bat strategies, particularly the production of ultrasound to either jam bat sonar or signal unpalatability. Experiments with tethered moths and high-speed cameras reveal the moths' deceptive tactics, including Batesian mimicry, where some moths bluff their bad taste. The findings enhance our understanding of evolutionary adaptations in predator-prey relationships.

Takeaways

• 🦇 Jesse Barber studies bat-moth interactions in Gorongosa, Africa, focusing on their co-evolutionary battle.
• 🌍 This research fills in gaps in data, as Barber has previously worked in tropical regions but never in Africa.
• 🔊 Bats use echolocation to hunt, emitting high-frequency sounds to detect their prey in the dark.
• 🦋 Moths have evolved defenses, like ultrasound production, to avoid being eaten by bats.
• 🔦 To study moths, researchers attract them with UV light and record their ultrasound responses to simulated bat attacks.
• 🛠 Moths use different physical structures to produce sounds, including their thorax and modified genitals.
• 💡 Some moths use ultrasound to warn bats of their bad taste, while others jam the bat's sonar.
• 🎥 In experiments, synchronized ultrasound and video footage help analyze the moths' defense strategies during bat attacks.
• 😋 Moths that bluff by mimicking toxic species can still be eaten by bats if they do not genuinely taste bad.
• 🔄 The study adds to knowledge about evolution, showing how bats and moths are locked in an ongoing co-evolutionary arms race.

Q & A

Why did Jesse Barber come to Gorongosa?

Jesse Barber came to Gorongosa to study bat-moth interactions and to fill in important gaps in the data sets, as he had never worked in Africa before.

What is the significance of bats being nocturnal hunters?

Bats being nocturnal hunters is significant because it highlights their reliance on echolocation to navigate in the darkness, which is a key aspect of the bat-moth interaction.

How do bats use sound to find their prey?

Bats use echolocation to find prey by producing high-frequency calls and listening to the echoes from their targets to determine their position.

What strategies have moths evolved to avoid being eaten by bats?

Moths have evolved various anti-bat strategies, including the production of ultrasound above the level of human hearing to either signal their unpalatability or to jam the bat's sonar.

How do researchers attract moths for study?

Researchers attract moths by setting up lamps that emit ultraviolet light, which moths are drawn to.

What method do researchers use to determine which moths produce ultrasound as an anti-bat defense?

Researchers play recorded echolocation attacks to tethered moths and use a speaker and microphone setup to record the moths' responses.

What are the different structures moths use to produce sound?

Some moths have sound-producing structures on their thorax, while others use modified genitals at the tip of their abdomen to produce sounds.

How do moths use ultrasound to avoid being eaten by bats?

Moths use ultrasound either to signal to bats that they taste bad, acting as a warning, or to disguise their location by jamming the bat's sonar.

What experiment is set up to distinguish between moths signaling bad taste and those jamming sonar?

Researchers track wild bats hunting different moth species while recording their sounds and use high-speed cameras and ultrasonic microphones to document the interactions.

What is the role of Batesian mimics in the bat-moth interaction?

Batesian mimics are moths that imitate the sound of toxic moths to fool bats into thinking they taste bad, even though they are not.

How do researchers determine if a moth's signal of bad taste is honest or a bluff?

Researchers feed the moths to hungry wild bats and observe the bats' reactions to see if they spit out the moth, indicating it truly tastes bad, or if they consume it, suggesting the moth was bluffing.

How does the discovery of anti-bat strategies in African moths contribute to our understanding of evolution?

The discovery of these strategies adds to our knowledge of evolution by showing how random mutations and natural selection have led to the diversity of sound production strategies in moths over 60 million years of co-evolution with bats.

Outlines

00:00

🦇 Studying Bat-Moth Interactions in Gorongosa

Jesse Barber, a researcher, visits Gorongosa to study the interactions between bats and moths, focusing on their nocturnal behaviors and the use of sound in their evolutionary battle. Bats use echolocation to hunt, emitting high-frequency calls and listening for echoes to locate their prey. Moths, in response, have evolved various anti-bat strategies, including the production of ultrasound to either jam the bat's sonar or signal their unpalatability. The team captures moths using ultraviolet lamps and tests their defensive ultrasound production by playing back recorded bat echolocation calls. They also examine the physical structures moths use to produce these sounds. The research aims to understand how moths use ultrasound to avoid predation and the diversity of strategies employed in this co-evolutionary arms race.

05:01

🔊 Investigating Moth Defenses Against Bats

The research team sets up an experiment to understand how moths use ultrasound to protect themselves from bats. They use ultrasonic microphones and high-speed cameras to record the interactions between wild bats and different moth species, including a control moth that does not produce sound and an experimental moth that does. The team observes whether the moth's sound production is a signal of bad taste or a jamming mechanism to confuse the bat's sonar. They find that many moths in Gorongosa seem to send signals to bats, warning them of their unpalatability. However, some moths are Batesian mimics, bluffing with sounds similar to toxic moths without actually being toxic. To verify the moths' true nature, the team feeds them to hungry bats, noting the bats' reactions to determine if the moth's signal is honest or a bluff. This research contributes to the understanding of evolutionary strategies in predator-prey relationships and the ongoing co-evolutionary battle between bats and moths.

Keywords

💡Echolocation

Echolocation is a biological sonar system used by certain animals to navigate and find food in the dark. It involves emitting high-frequency sounds that bounce off objects and return as echoes, allowing the animal to determine the location and distance of these objects. In the video, bats use echolocation to locate their prey, the moths, by producing high-frequency calls and listening to the echoes from their targets.

💡Co-evolutionary battle

A co-evolutionary battle refers to an ongoing process where two or more species reciprocally affect each other's evolution through reciprocal adaptations. In the context of the video, this concept is used to describe the evolutionary arms race between bats and moths, where moths have evolved strategies to avoid being eaten by bats, and bats have evolved ways to overcome these defenses.

💡Ultrasound

Ultrasound refers to sound waves with frequencies higher than the upper audible limit of human hearing. In the video, moths have evolved to produce ultrasound as a defense mechanism against bats. They use this sound to either signal their unpalatability to bats or to jam the bats' echolocation, making it difficult for the bats to locate them.

💡Trophic interactions

Trophic interactions describe the relationships between different species in a food chain, particularly predator-prey dynamics. The video focuses on the trophic interaction between bats and moths, highlighting how these interactions have driven the evolution of unique adaptations in both species.

💡Nocturnal hunters

Nocturnal hunters are animals that are active during the night and hunt for food during this time. Bats, as mentioned in the video, are nocturnal hunters that rely on echolocation to navigate and find their prey in the dark.

💡Anti-bat strategies

Anti-bat strategies refer to the various tactics that moths have evolved to avoid predation by bats. The video discusses different strategies such as producing ultrasound to jam bat sonar or to signal unpalatability. These strategies are part of the co-evolutionary battle between moths and bats.

💡Batesian mimics

Batesian mimics are organisms that have evolved to imitate the appearance or signals of a harmful or unpalatable species to deter predators. In the video, it is mentioned that some moths imitate the ultrasound signals of toxic moths to deceive bats into thinking they are unpalatable, even though they may not be.

💡Sonar jamming

Sonar jamming is a defense mechanism where an organism interferes with the sonar signals of a predator to avoid detection. In the context of the video, some moths use ultrasound to jam the echolocation of bats, making it difficult for the bats to locate them during the hunt.

💡Signaling

Signaling in biology refers to the act of conveying information through a specific behavior, appearance, or sound. In the video, moths use ultrasound signaling to communicate with bats, either to warn them of their unpalatability or to disguise their location.

💡Natural selection

Natural selection is the process by which organisms with traits that are better suited to their environment are more likely to survive and reproduce. The video discusses how natural selection has driven the evolution of various anti-bat strategies in moths over millions of years, as those that could better evade bats were more likely to survive and pass on their genes.

💡Scientific method

The scientific method is a systematic approach to acquiring knowledge through observation, experimentation, and the formulation of hypotheses. The video emphasizes the importance of the scientific method in uncovering the complex interactions between bats and moths, and how each discovery leads to new questions and further understanding.

Highlights

Jesse Barber's research focuses on bat-moth interactions in Gorongosa, aiming to fill gaps in global data sets.

Bats use echolocation, a sonar-like ability, to navigate and hunt in darkness.

Moths have evolved various anti-bat strategies, including the production of ultrasound to deter bats.

The study in Gorongosa is significant due to the high diversity of bats and moths, offering a rich ground for research.

Researchers use ultraviolet lamps to attract moths for study.

Graduate students Eli Cinto Mejia and Nick Homziak assist in the research, contributing to the project's multifaceted approach.

Tethered moths are used in experiments to study their responses to recorded bat echolocation calls.

Moths produce sound using various structures, including their thorax and modified genitals.

The term 'Acoustic warrior' is used to describe moths that use sound as a defense mechanism.

Experiments are designed to differentiate between moth strategies of signaling toxicity versus jamming bat sonar.

Ultrasonic microphones and high-speed cameras are used to document bat-moth interactions in the wild.

Control moths that do not produce sound are used to compare with experimental moths that do.

Some moths are found to send signals warning of bad taste, while others may bluff, mimicking the sounds of toxic moths.

Batesian mimicry in the acoustic realm is discussed, where some moths imitate the sounds of toxic moths to deceive bats.

Moths are fed to wild bats to determine if their signals of bad taste are genuine or a bluff.

The research contributes to the understanding of co-evolutionary battles between predators and prey over 60 million years.

Natural selection and random mutations have led to the diversity of sound production strategies in moths.

The scientific method is praised for its ability to continually uncover new questions and advance knowledge.

Transcripts

JESSE BARBER: This looks like perfect bat habitat.

I came to Gorongosa to study bat-moth interactions.

And I've done work in the tropics all around the world,

but never in Africa.

And so we're here to try and fill

in some really important holes in our data sets.

Bats are nocturnal hunters.

And I was really fascinated by sonar, this ability

to use sound to navigate in the darkness.

And as I learned more about bats,

I started being interested in the prey of bats and insects.

And that led into studying bat-moth interactions, which

is an arms race, a co-evolutionary battle that's

been going on for more than 60 million years.

An amazing aspect of the dynamic battle between bats and moths

is that they use sound in the hunt.

To find prey, bats rely on echolocation.

They produce high frequency calls and listen to the echoes

from their targets to find their position.

Having long been on the bat menu,

moths have evolved strategies to avoid being eaten.

There's a lot of different anti bat strategies.

And the one we're studying here is sound production,

ultrasound production above the level of human hearing.

They have ears to hear bats coming.

And then producing their own ultrasound back at the bats.

The diversity of bats and moths in Gorongosa

makes it a great place to study these moth defenses.

The first thing we have to do is catch the moths.

So we put up lamps that emit a lot of ultraviolet light.

And those attract the moths to the sheet.

So I have two graduate students with me here in Gorongosa.

Eli Cinto Mejia is my master's student.

And then there's another graduate student here,

Nick Homziak.

And he's a PhD student in Dr. Akito Kawahara's lab

at the University of Florida.

NICK: Here's a little tiger moth.

Well, we've got around a little more than a dozen.

JESSE BARBER: After capturing the moths,

we determine which ones produce ultrasound

as an anti bat defense.

We play recorded echolocation attacks back to tethered moths.

So we have a speaker that's playing back these recorded

attacks.

And then we have a microphone near the moth

to record the sounds they make.

This gives us a very controlled way

of assaying their response to bat attack.

I'm ready for playback when you are, Eli.

ELI: OK, there we go.

JESSE BARBER: Yep, it's making sound.

Awesome.

A very large number of moth species

make sound back at bats.

And they use lots of different structures to do so.

Some have these sound-producing structures on their thorax.

Some use modified genitals at the tip

of their abdomen to make these sounds back at bats.

NICK: Acoustic warrior.

JESSE BARBER: Acoustic warrior.

The next question is, how do the moths use ultrasound

to avoid being eaten?

Butterflies and amphibians use striking colors

to signal to potential predators that they are toxic.

Some moths use the same strategy by signaling with ultrasound.

Other moth species use ultrasound

to disguise their location by jamming the bat sonar.

We set up an experiment to distinguish

between these strategies.

We track wild bats hunting different moth species

as we record their sounds.

I'm plugging in a bunch of ultrasonic microphones

so that we can record those sounds that moths make

when they're attacked by bats.

And then this is a high speed camera.

So behind me, you can see a lot of these infrared lights.

And we have the whole scene around us

illuminating the hunt.

The bats flying through this corridor.

We will lure bats with tethered moths.

This way we can document their interactions.

This is a control moth.

It does not make sound.

So I predict that it will be caught by the bats.

And these bats are echolocating well outside of our area range.

They're screaming into the night.

This is an experimental moth.

It's a noctuid.

It's a moth that we discovered makes sound.

And now let's see if its sound production protects it

from bats.

In this situation, we can't tell if the bats aren't trying

to catch it because they know it's chemically protected

or because it's jamming their sonar.

But it does seem that its sound production is protecting it.

In the lab, I synchronize the ultrasound with the video

so that I can analyze what happens at the exact moment

the moth makes sound.

If the bat is not able to locate the moth,

it suggests the sound from the moth is jamming the sonar.

If the bat is going for the moth but breaks away

at the last second, that suggests

the bat is picking up a sound that

tells it the moth tastes bad.

Most of the moths we've discovered here in Gorongosa

appear to be sending a signal to the bats,

as opposed to jamming their sonar.

And warning of bad taste is his primary signal.

But not all of these moths are honest.

Some are trying to bluff.

They're trying to fool the bat that they taste bad.

And they make it sound very similar to the ones that

are sending this honest signal of bad taste.

And these are called Batesian mimics.

In the visual world, Batesian mimics copy the appearance

of a species that taste bad.

Here some of the moths we have studied

are doing the same by imitating the sound of toxic moths.

To determine which moths really taste bad

and which are just bluffing, we feed them to hungry wild bats.

We lightly crush the moths' thorax

so they're not capable of producing ultrasound.

Because we don't want the bat rejecting

the moth because it knows those sounds

might indicate bad taste.

And I'm going to feed it this geometrid.

And now we want to see, is it palatable to this bat?

Is it sending a signal of bad taste or is it bluffing?

And the answer is, it's trying to fool the bat.

When a moth truly tastes bad, the bat

tries it and then spits it out, no matter how hungry it is.

The discovery of these anti bat strategies among African moth

species adds to our knowledge of how evolution works.

During the 60 million years that moths and bats have

been sharing the planet, random mutations

have arisen in different moss species.

And over the course of generations,

the ability to escape bat predation

has given rise to the diversity of sound production

strategies we see today.

Natural selection, in turn, favors new adaptations in bats,

locking predator and prey in a co-evolutionary battle.

Each new discovery builds on the one before it.

And that's the beauty of the scientific method

is itself advancing.

Because that question opens up new questions.

We'll never run out of questions about anything

on this planet, most likely.

We'll just continue to unfold it.

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