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Echolocation

A bat closing on a moth fires up to two hundred calls a second. Range has stopped mattering; knowing exactly where it is has started to.

Making a sound and building a picture from what comes back. Bats and toothed whales both do it, evolved it separately, and solve the same underlying trade-off in opposite directions depending on whether they need to detect something far away or place something close by.

Echolocation is an active sense: the animal supplies the energy, which means it can operate in total darkness and at whatever rate it chooses, and also means it is announcing itself constantly to anything that can hear. What makes it worth understanding in detail is that there is no single design. Every echolocating animal sits somewhere on a trade-off that comes straight out of the physics. A long call puts more energy into the air and so detects targets further away; a long call also overlaps with its own returning echo at close range, which blinds the animal exactly when it most needs to know where something is. A short broadband sweep does the reverse: it places a target precisely and does not reach far. So a bat hunting over open water uses long narrow calls, a bat hunting among leaves uses short broad ones, and unrelated species that share a habitat converge on similar designs — which is how you can tell the design is a response to the problem rather than an inheritance. Within a single attack the same trade-off plays out in seconds: as a bat closes on a moth, the calls get shorter and crowd together into the terminal buzz, up to two hundred a second, because range has stopped mattering and precision has started to. Toothed whales solve the same problem in water with different hardware — clicks made in the nasal passages, focused by a fatty organ in the forehead, and received through fat in the lower jaw — and reach discriminations fine enough to tell one metal from another by the echo.

Developed coverage · 71% complete · reviewed 2026-09-02

What this page covers

Laryngeal echolocation in most bats, click-based biosonar in toothed whales, and simpler forms in oilbirds, some swiftlets and a few shrews and tenrecs. Fruit bats mostly do not echolocate at all.

Often confused with: Social calls, which bats and dolphins also make constantly and which are not echolocation; Sonar, which is a reasonable analogy for bats and a poor one for electric fish

Quick facts

Independently evolved
At least twice — bats and toothed whales — plus simpler forms in birds
The trade-off
Reach against precision, and every species sits somewhere on it
A dolphin’s hardware
Clicks from the nose, focused by the forehead, received through the jaw
Doppler compensation
Some bats retune their voice in flight to hold the echo steady

Where this appears

Every organism below has been linked to this page because the evidence links them. Each one carries its own evidence, and its own limits.

The result that waited a century and a half for a microphone

How we know

The bat experiment that needed a microphone from the future

How does a bat avoid obstacles in complete darkness?

The design is old and the answer is not. In the 1790s Spallanzani released bats in a darkened room strung with wires and compared how they flew when blinded against how they flew with their ears plugged. Blinded bats flew normally. Deafened bats collided. The conclusion — that bats navigate by hearing — was rejected, ridiculed, and forgotten, because to every person who listened there was no sound. It was recovered in the 1930s when microphones capable of recording above the range of human hearing were pointed at a flying bat, and the calls turned out to have been there the whole time.

What happened

A bat that cannot see flies cleanly. A bat that cannot hear does not. And the animal is producing an intense stream of sound above the range of human hearing, shortening its pulses sharply as it closes on a target.

What it shows

That bats orient by listening to the echoes of their own calls, and — more usefully — that a correct result can be discarded for a century because the instrument needed to confirm it does not exist. What was missing in 1794 was not the idea or the experiment. It was a microphone.

What it does not show

It does not tell you what the bat extracts from an echo — distance, size, texture and movement were worked out much later, species by species. It also does not generalise across bats: several groups do not echolocate at all, and the large fruit bats navigate mainly by sight.

The controls — what makes this evidence rather than a story
  • Blinding and deafening as separate manipulations, so the two senses are distinguished rather than confounded.
  • A wire obstacle course as an objective measure — collisions can be counted.
  • The ultrasonic recordings as the independent confirmation, arriving from a completely different method a century and a half later.

From Listening in the Dark: The Acoustic Orientation of Bats and Men

It is worth sitting with what went wrong there. Spallanzani had the right experiment and the right answer in the 1790s, and it was rejected — because when careful people listened to a flying bat, they heard nothing, and a silent animal cannot be navigating by sound. The calls were above the range of human hearing. What was missing was not the idea, the design, or the rigour. It was an instrument, and it arrived in the 1930s.

There is no such thing as "the" bat call

Call design tracks the problem the animal is solving, not the family it belongs to.

Diagram

There is no such thing as the bat call

There is no such thing as the bat callOpen air — reachLong, one narrow frequency. Detects faraway. Poor at placing anything close.In clutter — precisionShort sweeps across many frequencies.Places things precisely, and not far.Closing on a mothCalls crowd together as the target nears — the terminal buzz. Range stopsmattering; knowing exactly where it is starts to.
The same explanation in words

Two spectrogram panels. The left, headed "Open air — reach", shows two long horizontal lines: calls held at one narrow frequency for a long time. The caption says they detect far away and are poor at placing anything close. The right, headed "In clutter — precision", shows five short steep strokes sweeping downward through many frequencies. The caption says they place things precisely and not far. Below, a row of vertical marks starts widely spaced on the left and crowds together towards the right, illustrating the terminal buzz as a bat closes on a moth: the calls crowd together because range has stopped mattering and knowing exactly where the target is has started to.

There is no such thing as "the" bat call. A bat hunting in open air uses long narrow calls that reach a long way; a bat hunting among leaves uses short broad ones that place things precisely and not far.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Echolocation call structure covaries with foraging habitat rather than with phylogeny: open-space foragers use long narrowband signals maximising detection range, while clutter foragers use short broadband signals maximising localisation accuracy and minimising overlap between call and echo. Unrelated species sharing a niche converge on similar designs.

Who this applies to
Insectivorous echolocating bats; fruit and nectar bats face different problems and some do not echolocate.
Studied in
Chiroptera
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A large comparative literature, an explicit physical trade-off that predicts the pattern, and convergence between unrelated lineages sharing a niche.

How far it can be extended

The habitat–call relationship holds across many species in unrelated families, which is what makes it convergence rather than inheritance.

Caveats

  • Habitat categories are convenient rather than sharp, and many species move between them within a night.
  • Call design also reflects prey type and the risk of being overheard by prey with ultrasound-sensitive ears.
  • Says nothing about how echo information is processed once it arrives.

Still unanswered

  • How much of the variation within a species reflects moment-to-moment adjustment rather than fixed design.

Last reviewed 2026-09-02

The evidence (2 studies)

How we know

Swinging a bat on a pendulum to see if it retunes its own voice

A flying bat’s own speed shifts the pitch of its returning echo. Does the bat correct for that?

Horseshoe bats have hearing sharply tuned to one narrow band of frequencies, which is a problem: flying towards a wall raises the pitch of the returning echo, and flying fast raises it out of the band the bat hears best. The bats were recorded while flying at different speeds, and then — the decisive part — swung towards and away from a wall on a pendulum. A pendulum changes the animal’s speed relative to the wall, and therefore the Doppler shift in the echo, without the bat choosing to do anything at all.

What happened

The bats lowered the frequency of their outgoing call by very nearly exactly the amount their own motion would raise the echo — holding the returning frequency almost constant however fast they were moving.

What it shows

A continuous, automatic correction: the animal adjusts its voice in flight to keep the echo landing where its ear is sharpest. It is a control loop of the kind engineers build deliberately, running in a bat, and the pendulum is what shows the bat is responding to the shift rather than to its own effort.

What it does not show

Only some bats do this. Doppler compensation belongs to the constant-frequency species, which hunt by listening for the flutter of insect wings against a steady tone; the many bats that use short sweeping calls face a different problem and do not compensate. Generalising this to "bats" would be wrong.

The controls — what makes this evidence rather than a story
  • The pendulum changes the physics without changing the bat’s behaviour, which separates the two.
  • Both directions of swing, so the correction can be shown to reverse with the shift.
  • A range of flight speeds in free flight, giving an independent measurement of the same relationship.

From Die Ultraschall-Ortungslaute der Hufeisen-Fledermäuse in verschiedenen Orientierungssituationen

A horseshoe bat’s hearing is tuned to one narrow band, and its own flight speed would shift the echo out of it. So the bat lowers the pitch of its call in flight by exactly the right amount.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Constant-frequency echolocating bats exhibit Doppler-shift compensation: they lower the emitted frequency in proportion to their velocity relative to a reflecting surface, stabilising the returning echo within the narrow band of the auditory fovea.

Who this applies to
Constant-frequency bats; the majority of echolocating bats use frequency-modulated calls and do not compensate.Do not extend this beyond the taxa listed — the popular version over-reaches.
Studied in
Rhinolophus ferrumequinum, Rhinolophidae
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

The pendulum manipulation changes the Doppler shift without changing the animal’s behaviour, which isolates the compensation from effort or intention.

How far it can be extended

Doppler compensation is a feature of a particular echolocation strategy and is absent in most bats.

Caveats

  • A 1968 study with the sample sizes and instrumentation of its period, though the result has been reproduced since.
  • Compensation is not perfect and breaks down at high closing speeds.
  • The narrow tuning that makes compensation necessary is itself a specialisation for detecting fluttering wings.

Still unanswered

  • How the motor control achieves the correction as quickly as it does.

Last reviewed 2026-09-02

The evidence (2 studies)
Words used here
Terminal buzz
The burst of very short, very rapid calls a bat produces in the last moments of an attack — up to about two hundred a second.
Constant-frequency call
A call held at one narrow frequency for a relatively long time. Good for detecting the flutter of insect wings; used by horseshoe bats and their relatives.
Clutter
Echoes from everything that is not the target — leaves, branches, the ground. The main problem for a bat hunting anywhere other than open air.

The same problem, solved in water with different hardware

Diagram

A dolphin speaks through its forehead and listens with its chin

Schematic. Anatomy is indicative and not to scale.

A dolphin speaks through its forehead and listens with its chin1 · clicks made here, in the nose2 · focused by the melon3 · a narrow beam4 · echoes return through fat in the lower jawNo mouth, no outer ear. Trained animals tell a hollow cylinder from a solidone by a fraction of a millimetre of wall thickness.Schematic. Anatomy is indicative and not to scale.
The same explanation in words

A dolphin head in profile with four numbered stages. First, clicks are produced at a point high in the nasal passages, marked with a dot — not in the mouth. Second, the sound passes forward through the melon, the fatty organ in the forehead, which focuses it. Third, three arrows leave the front of the head in a narrow forward beam. Fourth, a thickened path along the lower jaw marks the fat body through which returning echoes are conducted to the ear. A closing note says there is no mouth and no outer ear involved, and that trained animals can distinguish a hollow cylinder from a solid one by a fraction of a millimetre of wall thickness.

A toothed whale makes its clicks in its nasal passages, focuses them through a fatty organ in its forehead, and receives the echoes through fat in its lower jaw. Nothing about it works the way a mouth and an ear do.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Odontocete biosonar clicks are generated at the phonic lips in the nasal passages, beamed forward by the acoustically graded lipids of the melon, and received principally through the fat body of the mandible, which conducts sound to the auditory bulla.

Who this applies to
Toothed whales; baleen whales do not echolocate.
Studied in
Odontoceti
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

Established by anatomy, by acoustic measurement of the emitted beam, and by experiments that alter reception at the jaw.

How far it can be extended

The anatomy is shared across odontocetes, with the sperm whale representing an extreme elaboration of the same plan.

Caveats

  • Discrimination figures come from a small number of intensively trained captive bottlenose dolphins.
  • Performance in a quiet test pool is not performance in a noisy sea.
  • Not every click a toothed whale makes is echolocation; some are social, and telling them apart requires context.

Still unanswered

  • How much beam steering is achieved actively, and how it is controlled.

Last reviewed 2026-09-02

The evidence (2 studies)

  • Supports · primary

    The Sonar of Dolphins

    Au, 1993 · Springer

    The standard synthesis of production, beam formation and reception.

  • Supports · supporting

    The monopulsed nature of sperm whale clicks

    Møhl et al., 2003 · The Journal of the Acoustical Society of America

    The sperm whale as the extreme case, where the same apparatus produces the loudest biological sound measured.

A dolphin hears through its jaw, and its sonar reports what a thing is made of, not just where it is

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Dolphins generate broadband clicks in the nasal passages, focus them through the fatty melon into a directional forward beam, and receive returning echoes through fat channels in the lower jaw conducting to the middle ear. Trained animals discriminate targets differing in wall thickness, internal contents or material at ranges of tens of metres.

Who this applies to
bottlenose dolphins, principally trained animals in controlled discrimination tasks
Studied in
Tursiops truncatus
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

Decades of controlled discrimination testing with measured acoustics, supported by anatomical and acoustic modelling of the sound path.

How far it can be extended

The anatomical apparatus — melon, fat-filled jaw, nasal click generation — is shared across odontocetes, though click structure varies considerably by species.

Caveats

  • Performance figures come from trained captive animals on artificial tasks.
  • What wild dolphins actually attend to is far less characterised.
  • Echolocation is not vision with sound — the information returned is about material and structure, not colour or fine shape at distance.

Still unanswered

  • How much of a wild dolphin’s foraging depends on echolocation versus passive listening?
  • How do dolphins avoid being deafened by their own clicks?

Last reviewed 2026-08-10

The evidence (2 studies)

One caution that applies across this whole family: not every click a toothed whale makes is echolocation. Sperm whales produce codas that are used socially and are not obviously about locating anything, and dolphins whistle constantly alongside their clicking. Describing all of it as sonar collapses two systems that the animals themselves keep apart.

Where that distinction is drawn

What happens when the prey can hear you coming

An active sense broadcasts. Many moths have ears sensitive to precisely the frequencies bats use, and dive or spiral when they hear one — which is a defence that only exists because the bat has to announce itself in order to see. A few go further and answer back.

One tiger moth defends itself by producing clicks that disrupt a bat’s sonar

Well supported

Good evidence backs this, though some details remain open.

The tiger moth Bertholdia trigona produces high-rate ultrasonic clicks when attacked. Naive big brown bats capture silenced moths readily but repeatedly fail against clicking ones, and — unlike responses to warning or startle signals — do not improve with experience over successive nights.

Who this applies to
one tiger moth species tested against one bat species
Studied in
Bertholdia trigona
Why we rate it this way, and what the caveats are
Well supportedModerate confidence

The learning-curve design distinguishes jamming from the two competing explanations cleanly. Confidence is moderate rather than high because it rests on one moth species and one bat species in a flight room.

Caveats

  • Many tiger moths click; most are thought to be warning of toxicity rather than jamming.
  • One bat species, in captivity, naive to the moth.
  • The precise acoustic mechanism of the interference is not fully characterised.

Still unanswered

  • How many of the roughly 11,000 tiger moth species jam rather than warn?
  • Have any bats evolved counter-measures?

Last reviewed 2026-08-09

The evidence (1 study)

  • Supports · primary

    Tiger moth jams bat sonar

    Corcoran et al., 2009 · Science

    Bats failed against clicking moths and never learned to overcome them, ruling out aposematic warning and startle.

How we know

The moth that bats never learned to catch

A tiger moth clicks when a bat attacks. Is it warning that it tastes bad, startling the bat, or interfering with the sonar itself?

The three hypotheses are hard to separate from a single encounter and easy to separate over many, because they predict different learning curves. A warning is learned — a bat should stop attacking once it associates the click with a bad meal. A startle habituates — the bat should stop being surprised. Jamming keeps working regardless. Naive big brown bats were flown against tiger moths that were either able to click or had been silenced, over successive nights, with every encounter recorded acoustically and on high-speed video.

What happened

Bats captured silenced moths readily. Against clicking moths they failed repeatedly — and, over successive nights, never improved.

What it shows

The clicks interfere with echolocation rather than warning or startling. The flat learning curve is the discriminating evidence: a bat can learn around a warning and habituate to a startle, but it cannot learn its way out of a jammed signal.

What it does not show

One moth species against one bat species in a flight room. Most clicking tiger moths — of roughly 11,000 species — are thought to be warning of toxicity rather than jamming, so this is a demonstration that jamming exists, not that it is common.

The controls — what makes this evidence rather than a story
  • Silenced moths of the same species isolated the clicks as the variable, holding taste, appearance and flight behaviour constant.
  • Bats naive to the moth ensured no prior learning.
  • Repeating encounters across nights is the actual experiment: the shape of the curve discriminates the hypotheses.

From Tiger moth jams bat sonar

What is still unsettled

  • How much do echolocating animals steer their beam actively?

    Why it matters: A dolphin’s beam is narrow, and where it points determines what the animal can perceive. Whether that aiming is deliberate and how it is controlled is largely unknown.

    What would settle it: Simultaneous beam measurement and head tracking in freely behaving animals, which is technically difficult and rarely attempted.

  • What does an echo actually give an animal beyond distance?

    Why it matters: Discrimination experiments show bats and dolphins distinguishing texture, material and shape. How those properties are extracted from an echo is not well understood.

    What would settle it: Recording from the auditory pathway during discrimination, rather than measuring only the behavioural outcome.

  • How do bats hunting in dense groups avoid being jammed by each other?

    Why it matters: Thousands of animals calling in the same airspace should be a catastrophe of interference, and mostly is not.

    What would settle it: On-board recording from multiple individuals flying together, which has only recently become possible.

The research behind this page

9 studies, newest first. Each one has a page explaining what it found and what it could not show.

2015Molecular Biology and Evolution

Determining the null model for detecting adaptive convergence from genomic data: a case study using echolocating mammals

Convergent substitutions between echolocating lineages were not clearly in excess of the number expected between comparable non-echolocating lineage pairs, once an appropriate null expectation was applied.

2013Nature

Genome-wide signatures of convergent evolution in echolocating mammals

Convergent amino-acid substitutions between echolocating bats and cetaceans were reported at many loci across the genome, including but not limited to genes with known hearing functions.

2009Science

Tiger moth jams bat sonar

Bats captured silenced moths readily but failed repeatedly against clicking moths, and — critically — did not learn to overcome the clicks with experience, a pattern consistent with interference with echo processing rather than with a warning signal or a startle.

2003The Journal of the Acoustical Society of America

The monopulsed nature of sperm whale clicks

On-axis clicks are highly directional and reach source levels around 230 decibels re 1 micropascal at 1 metre, among the loudest sounds produced by any animal.

2001BioScience

Echolocation by insect-eating bats

Call structure tracks foraging habitat closely.

1993Springer

The Sonar of Dolphins

Dolphins produce short broadband clicks in the nasal passages, focus them through the fatty melon into a narrow forward beam, and receive returning echoes through fat channels in the lower jaw.

1968Zeitschrift für vergleichende Physiologie

Die Ultraschall-Ortungslaute der Hufeisen-Fledermäuse in verschiedenen Orientierungssituationen

Flying bats lowered the frequency of their outgoing call by almost exactly the amount their own motion would raise the echo, holding the returning echo within a narrow frequency band regardless of flight speed.

1958Yale University Press

Listening in the Dark: The Acoustic Orientation of Bats and Men

Bats emit ultrasonic pulses and orient by their echoes: deafened bats collide with obstacles that blinded bats avoid, and the pulses are produced in the larynx and shortened dramatically as a target is approached.

1941Journal of Experimental Zoology

The sensory basis of obstacle avoidance by flying bats

Blinded bats avoided the wires as well as sighted ones.

This page is a stop on a longer route

A guided journey reads several subjects in a deliberate order, with an argument for why one follows another. You can join in the middle.

Where to go from here

Each of these follows from something on this page — a relationship in the evidence, a claim people ask about, or the next mechanism along.

How complete this page is, and what it is still missing

NatureHQ publishes its own gaps. This page is at 71% completeness against what we would call a finished subject, and was last reviewed on 2026-09-02. It carries 6 claims and answers 23 mapped search questions.

  • 11 high-priority search intent(s) not yet covered
  • no research from the last few years is attached — check for newer work
  • no popular claim about this subject has been checked yet
  • Oilbirds, swiftlets and echolocating shrews are named and not described; all three are simpler systems worth a comparison.
  • Human echolocation is deliberately absent — it is real and it is a different literature.
  • How echo information is processed in the brain is largely deferred, because it is where the field is least settled.