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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