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Echolocation


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Echolocation

Definition: emission of sound pulses and use of

returning echoes to gain information about

surrounding environment

Functions: navigation and prey detection,

notsocial communication


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Frequency: pitch of sound measured in Hz or kHz; thenumber of cycles per unit time

Wavelength: distance from peak to peak of a soundwave

Bandwidth: frequency rangeNarrowband/constant frequency (CF): frequency range

10 kHz

Shallow FM: small change in frequency/time

Steep FM: large change in frequency/time

Describing sound

Vaughan et al. 2011 Mammalogy


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Bandwidth: frequency range

Broadband/frequency modulated (FM): frequency range>10 kHz

Steep FM: large change in frequency/timeShallow FM: small change in frequency/time

Describing sound



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Describing sound


Pipistrellus hesperus Tadarida brasiliensis


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Narrowband/constant frequency (CF): pure tone

Describing sound

Rhinolophus

ferrumequinum


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~ 18% of mammals echolocate:most bats,odontocete cetaceans, some shrews(Soricomorpha), some tenrecs (Afrosoricida)

Three basic types

Nasal: Odontocete cetaceans; Chiroptera:Nycteridae, Megadermatidae, Rhinolophidae,Hipposideridae, Phyllostomidae

Tongue clicks: one genus of Old World fruit bats(Rousettus)

Laryngeal: all other echolocating bats,echolocating shrews and tenrecs

Echolocation


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~ 18% of mammals echolocate: most bats,odontocete cetaceans, some shrews(Soricomorpha), some tenrecs (Afrosoricida)

Three basic types

Nasal: Odontocete cetaceans; Chiroptera:Nycteridae, Megadermatidae, Rhinolophidae,Hipposideridae, Phyllostomidae

Tongue clicks: one genus of Old World fruit bats(Rousettus)

Laryngeal: all other echolocating bats,echolocating shrews and tenrecs

Echolocation

Euderma maculatum

Hemicentetes semispinosus

Tursiops truncatus

Crocidura russala


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~ 18% of mammals echolocate:most bats,odontocete cetaceans, some shrews(Soricomorpha), some tenrecs (Afrosoricida)

Three basic types

Nasal: odontocete cetaceans; Chiroptera:Nycteridae, Megadermatidae, Rhinolophidae,Hipposideridae, Phyllostomidae

Lingual (tongue clicks): one genus of Old Worldfruit bats (Rousettus)

Laryngeal: all other echolocating bats;echolocating shrews and tenrecs

Echolocation


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Echolocation in ondontocete cetaceans

Physeter macrocephalus

Tursiops truncatusSmall odontocetes:

dolphins, porpoises,

orcas etc.

Largeodontocetes:

sperm whales

All use low frequency broadband

clicks for echolocation


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Tursiops truncatusSmall odontocetes:

dolphins, porpoises,

orcas etc.

Largeodontocetes:

sperm whales

All use low frequency broadband

clicks for echolocation

Why use echolocation?


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Echolocation in water vs. air


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Echolocation in water vs. airEcholocation in water takes less energy, pulses travelfurther, reach target faster, echoes return faster

Sound travels ~4x faster in water vs. air Intensity of a given frequency is higher in water vs. air

Sound attenuates (loses intensity) more slowly in water

Echolocation in water provides long range information Sperm whale >1,500 m

Bats: ~2.5 - 62 m


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Tursiops truncatus

Functional morphology


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Tursiops truncatus

Functional morphology: small odontocetesPhonic lips

Air forced through lips;

lips close producing

vibrations

Vibrations transmitted through

fluid-filled sacs around lips,

reflect off cranium, propagated

through oil-filled melon

Melon acts as acoustic lens:

beam of sound focused

forwards



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Tursiops truncatus

Functional morphology: small odontocetes

Sound vibrations transmitted via oil-

filled sinus in dentary to auditory bullae

Auditory bullae not fused to cranium;

surrounded by connective tissue and

mucous/air-filled sinuses

Lower mandible receives

sound vibrations


Phonic lips


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Echolocation in shrews

Are they really echolocating?


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Sorex araneus

Crocidura russala


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Sorex araneus

Crocidura russala

Do shrews increase call rate in cluttered environment?

Is call rate influenced by presentation of conspecific odor?


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Sorex araneus

Crocidura russala

Shrews increase call rate in cluttered environment

Call rate w/conspecific odor = call rate w/out conspecific odor


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Echolocation in Chiroptera

Haeckel, 1904 Kunstformen der Natur(Artforms of nature)


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Echolocation + flight are keyinnovations that are uniqueto Chiroptera

Echolocation + flight allows

bats to occupy competitor-free aerial nocturnal niche

Echolocation systems highly

variable within Chiroptera:optimized to specificrequirements of habitatstructure and feedingecology



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Major types of echolocation

Challenges of echolocation

and how bats solve them

Bat-moth coevolutionBarber and Conner 2007

Corcoran et al. 2009

Evolution of echolocationand flight



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Three basic types of echolocation

1) Lingual: one genus in PteropodidaeRousettus

Rousettus

aegyptiacus


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2) Nasal: five familiesRhinolophidae, Hipposideridae, Phyllostomidae, Nycteridae, Megadermatidae

Rhinolophus trifoliatus Choeronycteris mexicana Megaderma spasma

Hipposideros ridleyi

Artibeus jamaicensis


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3) Laryngeal: 12 familiesVespertilionidae, Molossidae, + 10 others

Euderma maculatum

Myotis myotis

Eumops perotis


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Laryngeal vs. nasal emission

Laryngeal echolocators:

Skull orientation similar to

most terrestrial animals

Nasal echolocators:

Rostral part of skull rotated

ventrally below level of

braincaseNasal cavity instead of

mouth aligned in direction

of flight

Myotis myotis

Artibeus jamaicensis


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Basic types of echolocation pulses

Frequency modulated (FM)

Short range detection and navigation

Target localization

Foraging in cluttered environments

Long range detection and navigation

Foraging in open environments

FM steep FM shallow


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Frequency modulated (FM)

Constant frequency (CF)

Long range detection and navigation

Foraging in open environments

FM steep FM shallow

Target detection


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High duty cycle vs. low duty cycle

High duty cycle

Pulse emission >60% of time

Most of pulse is pure CF tone;

All CF bats use high duty cycle

Fig. 1 Fenton and Ratcliffe 2004 Nature

Low duty cycle

Pulse emission


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Major types of echolocation


and how bats solve them

Bat-moth coevolutionBarber and Conner 2007

Corcoran et al. 2009

Evolution of echolocation



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1) Lingual 2) Nasal 3) Laryngeal

Myotis myotisRousettus aegyptiacus Rhinolophus paradoxolophus


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Basic requirements for echolocation system

Navigation among stationary obstacles Range: how far away? Direction: where is it?

Orientation: where am I?

Detection, localization and identification of food item Range

Direction

Shape/texture: what is it?

Detection, localization and identification of aerial prey Range

Direction

Shape/texture

Velocity of a moving target: how fast?


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Lasionycteris noctivagans


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Need to attend to returning echoes rather thanoutgoing pulse

Returning echoes always lower intensity

Many species emit at very high intensities

n

Lasionycteris noctivagans


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Need to attend to returning echoes rather thanoutgoing pulse

n


SolutionsI. Self-deafeningII. Neural attenuation

III. Low duty cycle

IV. Doppler shift


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Solution I: self-deafening


Sound dampening muscles

Tensor tympani controls

tension of tympanicmembrane

Stapedius controls contact

between stapes and oval

window

Both highly developed in

echolocating bats


Incoming sound waves


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Solution II: neural attenuation


Nerve impulses from inner

ear (cochlea) reduced inlower auditory relay nuclei in

brain (lateral lemniscus)


Incoming sound wavesSound waves translated

to nerve impulses

Lateral

lemniscus

Transmission to higher

auditory nuclei


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Self-deafening +neural attenuationReduce perceived outgoing pulse by ~40%

Incoming sound wavesSound waves translated

to nerve impulses

Lateral

lemniscus

Transmission to higher

auditory nuclei




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Solution III: low duty cycle separates pulse andecho in time


Pipistrellus:

low duty cycle


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Solution III: low duty cycleseparates pulse andecho in time

but

Low duty cycle pulses dont provide enough information

on small nearby targets

Low duty cycle aerial insectivorescombine higher

repetition rate with shorter pulse in attack phase



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Detection, localization and capture of aerialprey using low duty cycle

Vaughan et al. 2011 Mammalogy; modified from Kalko et al.1998. Behav. Ecol. Sociobiol.


Noctilio albiventris


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Detection, localization and capture of aerialprey using high duty cycle CF pulses Good target detection: more sound out = more

echoes returned

Good target discrimination: discriminate differentsized insects by rate of wing beats

but

CF signals dont provide precise information on

direction and velocity of flying insect High duty cycle: pulses and echoes overlap in time


Rhinolophus

ferrumequinum


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echoes returned


but

High duty cycle: pulses and echoes overlap in time

CF pulses dont provide precise information ondirection and velocity of flying insect



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echoes returned


but

High duty cycle: pulses and echoes overlap in time

CF pulses dont provide precise information ondirection and velocity of flying insect

Both problems solved using Doppler shift



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Doppler shift: perceived change in frequency ofa sound source caused by movement of sound

source and/or receiver


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High duty cycle CF echolocators use Dopplershift to obtain precise information on their own

direction and velocity relative to that of flying

insect



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High duty cycle CF echolocators use Dopplershift to solve problem of pulse/echo interference

Solution IV: separate pulse and echo in

frequency

Pulse frequency adjusted relative to echo frequency Shifted echo returned at frequency bat hears best


Rhinolophus

ferrumequinum


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n


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BAC > 0.3%: not a problem!


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Evolutionary arms race: bats vs. moths

E l i b h


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Bats:Ancestors of modern bats evolve echolocation;

some species feed on nocturnal moths


Photo: Jesse Barber

E l ti b t th


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Moths: Ears evolve in five families of nocturnal moths

Ears allow moths to detect echolocation pulses: moth

hearing is tuned to range of frequencies used by co-

distributed moth-eating batsSome species take evasive action: erratic flight or drop to

ground when bat is detected


Photo: Jesse Barber

E l ti b t th


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Moths: Ears evolve in five families of nocturnal moths

Ears allow moths to detect echolocation pulses: moth

hearing is tuned to range of frequencies used by co-

distributed moth-eating batsSome species take evasive action: erratic flight or drop to

ground when bat is detected

Bats: Some moth-eating bat species echolocate at

exceptionally high or low frequencies out of auditoryrange of nocturnal moths

Others use stealth: low intensity echolocation or no

echolocation at close range


Photo: Jesse Barber

Euderma maculatum

E l ti b t th


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Moths: Some eared moths evolve a noise-making organ,

produce high intensity ultrasonic pulses when underattack by a bat


tymbal

bat moth

Barber and Conner 2007 PNAS

E l ti b t th


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produce high intensity ultrasonic pulses when underattack by a bat

Bats:Avoid noise-making moths

Why?


tymbal

bat moth


E l ti b t th


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produce high intensity ultrasonic pulses when underattack by at bat

Bats:Avoid noise-making moths

Why?

Warning: sound-producing moths are noxious or

are acoustic mimics of noxious species

Jamming: moth pulses interfere w/bat

echolocationStartle: high intensity moth pulses startle

attacking bats


tymbal

bat moth


E l ti b t th


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Test of warning hypothesis

Mllerian mimicry: mutual resemblance between

two or more conspicuous unpalatable species to

enhance predator avoidance

Batesian mimicry: resemblance of an edible

species to an unpalatable species to deceive

predators


tymbal

bat moth


Lasiurus borealis

Eptesicus fuscus

E l ti b t th


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Test of warning hypothesis

Mllerian mimicry: mutual resemblance between

two or more conspicuous noxious species to

enhance predator avoidance

Batesian mimicry: resemblance of an edible

species to a noxious species to deceive

predators


tymbal

bat moth


Lasiurus borealis

Eptesicus fuscus

E l ti b t th


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Evidence for Mllerian mimicry Nave bats learn to avoid noxious sound-

producing moths

Experienced bats still attack noxious muted

moths

Evidence for Batesian mimicry Bats exposed to noxious moths avoid

palatable sound-producing moths

But


tymbal

bat moth


Lasiurus borealis

Eptesicus fuscus

Evolutionary arms race: bats vs moths


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producing moths


moths

Evidence for Batesian mimicry Bats exposed to noxious sound-producing

moths avoid palatable sound-producing

moths But


tymbal

bat moth


Lasiurus borealis

Eptesicus fuscus



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producing moths


moths

Evidence for Batesian mimicry Bats exposed to noxious sound-producing

moths avoid palatable sound-producing

moths But


tymbal

bat moth


Lasiurus borealis

Eptesicus fuscus



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tymbal

bat moth


Corcoran et al. 2009 Science

bat moth


Eptesicus fuscus



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tymbal

bat moth



bat moth


Eptesicus fuscus

Evidence for jamming hypothesis Nave and experienced bats attempt but fail

to capture high duty cycle sound-producing

moth

Evidence against startle hypothesis Bats dont habituate to high duty cycle moth:

capture rate doesnt improve with experience



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tymbal

bat moth



bat moth


Eptesicus fuscus

Evidence for jamming hypothesis Nave and experienced bats attempt but fail

to capture high duty cycle sound-producing

moth

Evidence against startle hypothesis Bats dont habituate to high duty cycle moth:

capture rate doesnt improve with experience


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Did echolocation evolve more than once in

the ancestors of modern bats?



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Chiroptera?

Fig 1b; Jones and Teeling 2006 TREE

Morphology

No echolocation*

Echolocation



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Chiroptera?

Fig 1a; Jones and Teeling 2006 TREE

Molecules

No echolocation*

Echolocation


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Simmons and Geisler 1998 Bul Am Mus Nat Hist

Fossils

Did Icaronycteris echolocate?Based on:

Size of cochlea (inner ear)

Shape of malleus (middle ear)

Shape of stylohyal bone (connects larynx totympanic bone)

Icaronycteris: ~53 MYA

Chiroptera?



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Fossils

Did Icaronycteris echolocate?Based on:



Shape of stylohyal bone (connects larynx totympanic bone)

YES!


Chiroptera?


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Fossils


Chiroptera?

Simmons et al. 2008 Nature


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Tursiops truncatus

How do dolphins and other odontocete cetaceansecholocate when blowhole is submerged?

Phonic lips

1) Air is taken in through

blowhole

2) Blowhole is closed

3) Air used to produceecholocation pulses is returned

from lungs to nasal sacs


Did echolocation or flight evolve first?


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Fig 1; Simmons et al. 2008 Nature

Fossils

Onychonycteris: ~52.5 MYA



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Fossils


Did Onychonycteris echolocate?



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malleus

stylohyal



Fossils


Did Onychonycteris echolocate?Based on:



Shape of stylohyal bone (hyoid apparatus)



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malleus

stylohyal



Fossils


Did Onychonycteris echolocate?Based on:



Shape of stylohyal bone (hyoid apparatus)

Probably not



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malleus

Stylohyal



Fossils


Did Onychonycteris echolocate?

echolocation?



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Fossils


Did Onychonycteris fly?



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Fossils



Artibeus literatus



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Fossils



YES!

echolocation?

flight

How did flight evolve?


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Fossils




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Fossils


Hypothesized sequence ofevolution

Arboreal/scansorial

Arboreal/gliding

Powered flight



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Fossils


Pre-flight characters retained inOnychonycteris

Claws on all digits

Relative limb lengths intermediate to

fully arboreal mammals and other bats

CynocephalidaeBradypodidae

Symphalangus

Chiroptera

Scandentia


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?

few million years



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?

Is evolutionarily rapid change in digit length possible from

a developmental perspective?

few million years



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Compared rates of proliferation and differentiation of cartilage cellsin digits of mouse and bat at various embryonic stages

Compared expression of bone morphogenesis protein (bmp2) inembryonic mouse vs. bat

Do embryonic bat digits elongate further if exposed to more bmp2protein?

?

few million years





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o d d g t e o e

Mouse and bat rates of proliferation and differentiation of cartilagecells are very similar at early embryonic stages





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g


Digit elongation in bats occurs during final stages ofembryogenesis, coupled with high expression of bmp2





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g



Addition of bmp2 protein results in longer metacarpals in embryonicbat cells; inhibition of bmp2 has opposite effect





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g



Addition of bmp2 protein results in longer metacarpals in embryonicbat cells; inhibition of bmp2 has opposite effect

?

few million years



YES



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How they do it: sperm whales

Air forced through single

pair of phonic lips;

lips close producing

vibrations

Vibrations transmitted through

spermaceti organ, reflect off frontal

air sac, propagated through junk

Spermaceti organ

homologous to right

posterior bursa;

junk homologous to melon

Physeter macrocephalusVaughan et al. 2011 Mammalogy



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Tursiops truncatus

All odontocetes uselow frequency

broadband clicks for

echolocation

Megaderma spasma Hipposideros diadema Coelops robinsoni


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Euderma maculatum

Rhinolophus

ferrumequinum

Rhinolophus trifoliatus

Rhinolophus ferrumequinum


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