These animals can hear everything - Jakob Christensen-Dalsgaard

Summary

The video script explores the remarkable auditory adaptations of various animals, revealing how they perceive sounds beyond human capabilities. From owls using their asymmetrical ears to pinpoint prey to the long-eared jerboa's heat-radiating ears that detect low-frequency noises, the script highlights the diversity of hearing mechanisms. It also delves into high-frequency sound detection in toothed whales and bats, and the unique hearing organs of insects like the greater wax moth. The script concludes with baleen whales and snakes, emphasizing the vast range of frequencies animals can perceive.

Takeaways

• 👂 Humans have limitations in hearing certain sounds, while other species have adaptations that allow them to perceive sonic extremes.
• 🦉 Owls use their entire face to funnel sounds, with large and sensitive eardrums, and asymmetrical positioning to determine the direction of sounds.
• 🦉 Great grey owls can hear prey under snow due to their adaptations, including thick wing coatings to reduce flight sounds.
• 🐦 Long-eared jerboas have the largest ears relative to body length, which help them detect low-frequency noises and radiate heat.
• 🦊 Fennec and bat-eared foxes use their large, swiveling ears to detect sounds in their respective habitats, such as activity beneath the sand or savanna sounds.
• 🕷 Ogre-faced spiders lack traditional ears but have leg receptors that are sensitive to soft sound waves, allowing them to catch prey even when blindfolded.
• 🐳 Toothed whales like dolphins and sperm whales have stiff middle ear bones that efficiently propagate high-frequency vibrations, enabling them to emit and listen to high-frequency sound pulses.
• 🦇 Bats and some toothed whales use high-frequency sound pulses to detect small insects, with wavelengths small enough to generate strong reflections.
• 🐛 Insects like the greater wax moth can register extremely high frequencies, thanks to their vibration-sensitive membranes, and hearing organs have evolved independently multiple times among insects.
• 🐋 Baleen whales emit some of the lowest frequency sounds among mammals, which can travel vast distances and be detected by other baleen whales, possibly through their skull conduction.
• 🐍 Snakes and Namib Desert golden moles can sense ground vibrations through their jawbones and large middle ear bones, respectively, allowing them to detect low-frequency activity.

Q & A

What is the basic principle behind how animals hear sounds?

The basic principle of hearing involves structures that vibrate in response to sound waves, exciting sensory cells which then generate signals transmitted to the brain by nerves for processing.

How do owls adapt to hear sounds that are too quiet for humans?

Owls use their whole faces to funnel sounds inward, with larger and more sensitive eardrums than humans, and their asymmetrical ear positioning allows them to determine the direction of a sound's source due to the slight delay in sound wave arrival.

What special adaptations do great grey owls have to reduce their flight sounds?

Great grey owls have thick velvety coatings on their wings and long feather combs and fringes, which are thought to help reduce their flight sounds, allowing them to hover undetected while hunting.

How do long-eared jerboas utilize their large ears?

Long-eared jerboas use their large ears to sense low-frequency noises and to radiate heat, helping them stay cool.

What role do the large ears of Fennec foxes play in their hunting behavior?

Fennec foxes use their large, swiveling ears to rapidly home in on activity beneath the Sahara sands, aiding in their hunting.

How do bat-eared foxes use their ears to detect subtle sounds in their environment?

Bat-eared foxes can pick up savanna sounds as slight as termites crawling and munching on grasses, thanks to their large ears.

What unique adaptation do ogre-faced spiders have to detect sound?

Ogre-faced spiders have receptors on their legs sensitive to sound waves, allowing them to catch airborne prey even after being blindfolded.

What feature allows toothed whales like dolphins to hear high-frequency sounds?

Toothed whales have extra hard, stiff middle ear bones that efficiently propagate high-frequency vibrations, enabling them to hear and emit sound pulses around 200,000 hertz.

What is the highest frequency sound recorded from an animal?

The greater wax moth can register the highest frequencies of any animal recorded, up to 300,000 hertz, thanks to thin, vibration-sensitive, eardrum-like membranes on their abdomens.

How do baleen whales communicate using low-frequency sounds?

Baleen whales emit sounds around 14 hertz, the deepest among mammals, which can travel thousands of kilometers and are possibly picked up by other baleen whales via their skulls conducting the vibrations to their ear bones.

How do Namib Desert golden moles use their large middle ear bones to sense low-frequency activity?

Namib Desert golden moles likely use their large, club-like middle ear bones to sense low-frequency activity in mounds more than 20 meters away, possibly by sticking their heads into the sand.

Outlines

00:00

👂 The Acoustic World of Animals

This paragraph introduces the concept of sound in the natural world, highlighting the limitations of human hearing and the extraordinary adaptations of other species that allow them to perceive sonic extremes. It explains the basic principles of hearing, which involves vibrations and sensory cells, and how certain animals, like owls, have evolved unique ways to capture and interpret sounds. Owls use their large, asymmetrically placed eardrums to determine the direction of sounds, while their wings' special features help them hunt silently. The paragraph also touches on other animals with remarkable hearing abilities, such as the long-eared jerboa and various species of foxes, and ends with the intriguing fact that some spiders can detect sounds through their legs.

Keywords

💡sonic extremes

The term 'sonic extremes' refers to the highest and lowest frequencies of sound that can be heard. In the context of the video, it highlights the range of sound that certain animals can perceive, which is far beyond human capabilities. For instance, the script mentions that some animals can detect sounds that are too quiet for humans, while others can hear extremely high frequencies, like the greater wax moth up to 300,000 hertz.

💡vibrations

Vibrations are oscillations or fluctuations in a medium, such as air or water, caused by a moving object. They are fundamental to the concept of sound, as they are the physical waves that trigger the hearing process. The video script explains that these vibrations are detected by structures that vibrate in response, exciting sensory cells and leading to the perception of sound. An example from the script is the Namib Desert golden moles using their large middle ear bones to sense low-frequency vibrations in the sand.

💡eardrums

Eardrums, also known as tympanic membranes, are thin layers of tissue that vibrate in response to sound waves. They are a crucial part of the hearing mechanism in many animals, including humans. The script mentions that owls have proportionally much larger and more sensitive eardrums than humans, allowing them to detect faint sounds, such as a vole tunneling under snow.

💡asymmetrical positioning

Asymmetrical positioning refers to the arrangement of body parts in a non-symmetrical manner. In the context of the video, it describes the positioning of an owl's ears, which are not aligned on the same plane. This positioning allows the owl to perceive sound waves at different times, aiding in the determination of the sound's direction, as illustrated by the script.

💡sound-absorbing and -amplifying structures

Sound-absorbing and -amplifying structures are parts of the ear designed to either capture or enhance sound waves. The script points out that despite having these structures, human ears cannot detect many noises that are too quiet. In contrast, animals like owls and jerboas have adaptations that allow them to hear sounds beyond the human range, such as the owl's large eardrums and the jerboa's oversized ears.

💡velvety coatings

Velvety coatings refer to the soft, thick coverings on certain surfaces, like the wings of the great grey owl mentioned in the script. These coatings are believed to help reduce the sound of the owl's flight, allowing it to approach its prey silently and undetected.

💡low frequency noises

Low frequency noises are sounds with a lower pitch or slower oscillation rate. The script explains that the long-eared jerboa uses its large ears to sense these low frequency noises, which helps it detect subtle movements in its environment, such as the vibrations caused by insects.

💡receptors

Receptors are specialized cells or sensory organs that respond to specific stimuli. In the video script, ogre-faced spiders are described as having receptors on their legs that are sensitive to sound waves, enabling them to detect the soft sounds of mosquito flight and catch their prey.

💡high-frequency vibrations

High-frequency vibrations refer to rapid oscillations or waves that occur at a high pitch. The script discusses how toothed whales, such as dolphins and sperm whales, have adaptations that allow them to propagate and perceive these high-frequency vibrations efficiently, which is essential for echolocation and hunting.

💡ultrasonic onslaughts

Ultrasonic onslaughts describe the high-frequency sounds that some animals, like bats, emit and that other insects, like the greater wax moth, must detect and respond to. The script notes that these sounds are at frequencies above the human hearing range and are used for communication, navigation, and hunting.

💡ground vibrations

Ground vibrations are the tremors or oscillations that can be felt through the earth. The script mentions that snakes use their jawbones to pick up these vibrations, which helps them to sense the movement of prey or predators in their vicinity.

Highlights

Many sounds in the world are inaudible to human ears, but other species have extraordinary adaptations to access sonic extremes.

Animals like owls have larger and more sensitive eardrums than humans, with asymmetrical positioning to help determine the direction of sound sources.

Great grey owls can detect the subtle sounds of prey, like a vole tunneling under 18 inches of snow, due to their specialized hearing adaptations.

Long-eared jerboas have the largest ears in proportion to body length, helping them sense low-frequency noises and radiate heat.

Fennec foxes use their large, swiveling ears to locate activity beneath the Sahara sands, while bat-eared foxes can pick up faint savanna sounds.

Ogre-faced spiders, lacking traditional ears, have leg receptors sensitive to soft sound waves, enabling them to catch airborne prey even when blindfolded.

Toothed whales like dolphins and sperm whales have stiff middle ear bones that efficiently propagate high-frequency vibrations.

Some toothed whales and bats emit sound pulses around 200,000 hertz to detect tiny insects through strong reflections.

The greater wax moth can register frequencies up to 300,000 hertz, the highest of any animal, thanks to vibration-sensitive membranes on their abdomen.

Hearing organs in insects have evolved independently more than 20 times, with various body parts used for detecting sound.

Katydids can sense ultrasonic sounds with their front legs, while certain hawkmoths can hear with their mouthparts.

A parasitic fly registers cricket chirps from organs behind its head, and the praying mantis has a single hearing organ in its thorax.

Baleen whales emit sounds around 14 hertz, the deepest among mammals, with vibrations traveling thousands of kilometers.

Baleen whales may pick up these deep vibrations through their skulls, which conduct them to their ear bones.

Snakes detect ground vibrations through their jawbones, which are directly connected to their middle ear bones.

Namib Desert golden moles use their large middle ear bones to sense low-frequency activity in mounds more than 20 meters away by sticking their heads into the sand.

The variety of hearing adaptations in the animal kingdom ensures that even the faintest sounds in nature are likely to be detected by some species.

Transcripts

The world is always abuzz with sounds,

many of which human ears simply can't hear.

However, other species have extraordinary adaptations

that grant them access to realms of sonic extremes.

And some of them don’t even have ears— at least, not like we typically imagine.

To understand how the animal kingdom’s best listeners do it,

we need to know the rules of their game.

When an object in a medium like air or water moves,

it sends out physical waves.

The basics of hearing involve structures that vibrate in response to these waves

and excite sensory cells,

generating signals that nerves transmit to the brain,

where they’re processed.

But despite the assemblage of sound-absorbing and -amplifying

structures in our ears,

many noises are too quiet for us to detect.

Owls, however, have some workarounds.

Our external ears funnel sounds inward—

but many owls use their whole faces to do this.

Their ears, hidden beneath a flap of feathers,

have eardrums proportionally much larger and more sensitive than humans’.

And because many owls ears are positioned asymmetrically,

sound waves reach them at different times.

This slight delay helps their brains determine the direction

of the sound’s source.

And great grey owl wings have especially thick velvety coatings

and long feather combs and fringes,

which are thought to help reduce their flight sounds.

So, while hovering, they can go undetected

and concentrate on the subtle sounds of their prey.

All these adaptations enable a great grey owl to hear a vole

tunneling under 18 inches of snow—

and make a fatal strike.

Other animals are almost all ears,

like the aptly named long-eared jerboa,

which is the animal kingdom’s largest ears in proportion to body length.

These sizable sound-collectors help the jerboas sense low frequency noises—

and keep cool by radiating heat.

Fennec foxes use their large, swiveling ears

to rapidly home in on activity beneath Sahara sands,

while bat-eared foxes can pick up savanna sounds

as slight as termites crawling and munching on grasses.

Ogre-faced spiders, meanwhile,

might not have ears in the traditional vertebrate sense,

but their legs are covered by receptors sensitive to sound waves

as soft as those generated by mosquito flight.

This allows them to catch airborne prey—

even after being blindfolded by scientists.

Lots of different features also help animal ears hit especially high notes,

like the extra hard, stiff middle ear bones of toothed whales;

like dolphins and sperm whales,

which efficiently propagate high-frequency vibrations.

Indeed, some toothed whales and bats emit sound pulses around 200,000 hertz

and listen for the reflections.

These high-frequency wavelengths—

more than 10 times higher than what we can hear—

are small enough to generate strong reflections from objects

as tiny as the insects many bats are after,

which would be missed altogether by lower ones.

But many insects are also in on the conversation—

and vigilant to ultrasonic onslaughts.

The greater wax moth can register the highest frequencies

of any animal recorded— up to 300,000 hertz,

thanks to thin, vibration-sensitive, eardrum-like membranes on their abdomens.

In fact, hearing organs have evolved independently

more than 20 times among insects.

Katydids sense ultrasonic sounds with their front legs;

certain hawkmoths can hear with their mouthparts;

a parasitic fly registers cricket chirps from organs behind its head;

and the praying mantis has just one hearing organ,

which sits smack in the midline of its thorax.

But how low can animals go?

Well, baleen whales emit sounds around 14 hertz,

the deepest among mammals.

These vibrations can travel thousands of kilometers.

And they get picked up by other baleen whales—

possibly via their skulls,

which conduct the vibrations along to their ear bones.

Snakes pick up ground vibrations by way of their jawbones,

which connect directly to their middle ear bones.

And Namib Desert golden moles regularly stick their heads into the sand,

which likely helps them use their large, club-like middle ear bones

to sense low frequency activity in mounds more than 20 meters away.

So, odds are: if a tree falls in a forest, someone’s bound to hear it.