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Humans are known to carry a tune, but we're hardly the only animals that sing. In fact we've got five of nature's finest singers, and what makes them so unique.

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Whether alone in the shower or on stage at Carnegie Hall, humans have been known to carry a tune.

But we are hardly the only animals that sing, a number of different species sing as a form of communication. And no, not all of them are birds!

These animals might sing for a number of reasons, including to mark their territory, or warn off predators in the area, but when we talk about song in this video, we're mainly going to be talking about attracting a mate. And we're going to distinguish singing from other noise-making behaviors as something that involves organized patterns of sounds and rhythms. But technicalities aside, these songs are as different as the animals themselves.

Some of them are more appealing to human ears, some are less. So here are 5 of nature's finest singers, and what makes each one so unique. So let's start out with the obvious one, we all know that birds sing.

And though they are probably the sweetest songsters next to humans, they produce song in a totally different way. We humans sing from our larynx, a structure in our throats that contains our vocal folds, or vocal chords. These vocal folds vibrate to produce sound, and as the muscles in the larynx tighten and loosen around them, they can produce higher and lower notes.

Birds, on the other hand, use a unique specialized organ called a syrinx, generally located at the bottom of their trachea where the bronchial tubes from the lungs meet. While the structure of the syrinx varies from species to species, air from the lungs generally causes vibrations that produce sounds.  What's even cooler is that since the syrinx is associated with both lungs, its structure allows some species of birds to produce two sounds at once, something humans cannot do without extensive training. One songbird that employs this dual sound trick especially well is the wood thrush.

Native to the eastern US, wood thrushes can be heard serenading the woods with songs like this one. Such elaborate songs rely not just on the thrush's advanced singing organs, but on their brains as well! And the way they learn those songs can teach us something about how our brains work to acquire skills.

Songbirds have a whole brain region dedicated to song, known as the song system. It helps them learn the often complex rhythms and patterns that make up their species' songs. In fact, a 2017 study from the University of Pennsylvania found that birds teach themselves songs much like how humans learn a new skill.

Part of their brain acts as the tutor, and another part as the student.  Think about when you're learning a new dance move. One part of your brain works on imitating the move, while another part critiques each attempt until the imitation gets better. If the student part of the brain isn't getting it, the tutor part has to adapt its teaching methods.

If the connections between neurons in a bird's brain aren't strengthening while the bird is trying to learn the song, the tutor neurons need to change up their teaching signals so the student neurons are more receptive. And since human brains can work the same way, using songbirds as a model to understand how this works is giving scientists a clearer view of how we can adapt to acquire new skills. Bats' best-known use of sound is their ability to navigate in the dark using echolocation but some species can also sing!

Like humans, bats sing using their larynges. However, the muscles they use to vibrate their vocal folds are super strong, allowing them to produce especially high pitched sounds. Their songs, on the other hand, sound a lot like bird songs, with similarly complex patterns and rules for how different pieces can be put together.

Lesser short-tailed bats, for example, produce elaborate songs to convey information to females, like their size, which may indicate that they're a better mate than that other guy. This species of bats chooses a roost from which to serenade females, which they may have sole possession of or share with other bats. Then, they get their song on.

And here's a little bonus fact for you, the males also mark their roosts using urine so they can find it easily again and also so females can find their way over if they're interested in mating.  The lesser short-tailed bat's song is too high-pitched for humans to hear, but there are species of bats, like the Mexican free-tailed bat, that croon at a pitch that we can enjoy, at least some of the time. Like, check this one out *plays sound* If you went out for a walk late one night, you would be forgiven for thinking that was a bird. Research suggests that bats sing because it takes way less energy to belt out a song than it does to fly.

I mean it makes sense, if you could use sounds that carry over a long distance to relay your message to your best friend rather than traveling all that way, you probably would too. And bats don't have phones. Since singing can often be heard across long distances, bats can relay information about territory, migratory behavior, food availability, and their desire to mate all without having to leave their perch.  What do you picture when you think of singing bugs?

Crickets? The summertime drone of cicadas, maybe? Perhaps, but their melodies are outdone by fruit flies of the genus drosophila.

Just check this out *Plays sound* Drosophila typically produce these songs with vibrations from their wings. The vibrating wing creates two primary modes of song: sine and pulse. The pulse song sounds like a series of pulses, while the sine song ebbs and flows in a way that looks like a mathematical sine wave when recorded.

Right now, we know there are two distinct types of pulse songs and one sine song, but scientists believe there could be more. Males are the crooners in this species and they have a larger wing muscle to produce these musical vibrations. Fruit fly courtship songs are incredibly diverse and scientists aren't entirely sure why the variations have evolved as they have.

We do know that male flies produce different songs depending on the sensory cues they receive from females during courtship, though. In a 2018 paper, scientists showed that males will change up their pitch and song speed based on those cues, and that usually means they sing louder and faster. Females hear and process these songs via a collection of cells on their antennae called the Johnston's organ.

Since the fruit fly is one of our favorite model organisms for studying developmental biology, the neurobiology behind how they sing and respond to songs gives us a better sense of how animals hear and respond to auditory signals in general. Drosophila songs can teach us a thing or two about evolution as well. For example, the Hawaiian variety's song is pretty different from the continental varieties, likely because it creates vibrations using its abdomen instead of its wings.

While the reason for this difference isn't entirely clear, it seems to be a behavioral and anatomical adaptation to a different environment. So you know the idiom "quiet as a mouse?" Well, mice and rats actually have songs of their own we just can't hear them because they sing at frequencies that are way too high-pitched for the human ear to pick up. Unless someone shifts their recording to a frequency we can hear, which researchers at Duke did during a study published in 2015, and they sent us this. *plays sound* Thanks to new statistical tools that help scientists break down rodents' songs, they discovered that male mice sing rather complex songs to woo females just like songbirds. When male mice smell female urine, the researchers found the sing louder, more complex songs.

Sometimes, really complex. One species of mouse in Central America can communicate using 100 different notes. Sometimes, males even sing duets to woo females.

What's unclear is how they produce such high-pitched, complex tunes. They don't have beefed-up larynx muscles like bats, so scientists aren't sure how they're doing it. The way rodents' brains moderate this complex form of communication, however, can teach scientists a lot about rodent social interactions.

The neurons mice use to make vocalizations involve a neural pathway that's similar to what humans use to speak and sing, so researchers have used this knowledge to create rodents whose brains experience communication difficulties similar to human stuttering. And by learning more about how that plays out in their brains, that could ultimately help doctors treat speech disorders in the future.  Now, if whales and dolphins are the prima donnas of the underwater world, the toadfish is not that. These mud-colored, bug-eyed, reef-dwelling fish aren't so pretty to look at, but what they lack in looks they make up for in pure enthusiasm.

In 2016, when researchers were trying to record an ocean soundscape off the coast of Panama, the toadfish stole the show because their songs drowned out everything else. So, they created a separate study to learn more about this strange crooner by setting up underwater microphones near their burrows. Over six days, they ended up recorded 14 different toadfish, all with their own distinct song and style.

Listento this. *plays sound* Basically, the fish were engaged in a Pitch Perfect style riff-off, but instead of pop song covers they performed a series of grunts and boops. Toadfish do not give each other room to perform, either, the scientists often noted the males would interrupt and even sing over one another, trying to drown their competition out. Like most other animals on this list, the males are the ones most often doing the singing to attract females or, in the toadfish's case, to lure females back to their burrow for some private time.

However, unlike any other animals on this list, toadfish produce song using their gas-filled swim bladders, the organ that helps many fish control their buoyancy. The muscles attached to the toadfish swim bladders are the fastest known muscle in vertebrates, and they contract rapidly to create the pulse vibration that's the basis of this song. The faster these muscles move, the louder the toadfish's song is amplified.

And thanks to their penchant for vocal competition, toadfish singers are teaching scientists a lot about acoustic communication underwater and, in turn, that may help uncover social engagement behaviors in other aquatic animals. Their songs have also taught scientists about how vocal communication has evolved across species. For example, a 2008 study found that the circuitry of the brain that controls the sonic muscles in the toadfish's swim bladder look very much like the circuits that control song production in birds, amphibians, and mammals.

Obviously, each species system evolved differently over time, but the study's researchers suggest that the neural circuits that control singing in all vertebrates came from what you see in ancient fish, which toadfish resemble. Their music may be more beautiful to each other than it is to us, but every one of nature's singers sings for good reason, and those reasons can provide fascinating insight into why these communication patterns evolve in the first place. Thank you for watching this episode of scishow, which was brought to you with the help of our patrons!

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