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Biosonar/Echolocation Odontocetes Toothed whales Dolphins, porpoises, sperm whales Bats Cave swiftlets Used for navigation, hunting, predator detection, …. primary sense in these animals Signals from Different Species

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Biosonar/Echolocation

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Biosonar/Echolocation

  • Odontocetes

    • Toothed whales

      • Dolphins, porpoises, sperm whales

  • Bats

  • Cave swiftlets

  • Used for navigation, hunting, predator detection, …. primary sense in these animals


Signals from Different Species

  • Odontocetes that whistle (Type II – near & offshore, social, low object density)

    • Bottlenose dolphin

    • Beluga

    • False killer whale

  • Odontocetes that DO NOT whistle (Type I – near shore and riverine, dense complex environment)

    • Family Phocoenidae (Harbor porpoise, Finless porpoise, Dall’s porpoise)

    • Genus Cephalorhynchus (Commerson’s dolphin, Hector’s dolphin)


SLpp ~ 150 - 170 dB

1

0

200 s

0.8

Tursiops

Phocoena

0.6

non-whistling odontocete

RELATIVE AMPLITUDE

Phocoena phocoena

0.4

whistling dolphin

0.2

Tursiops truncatus

0

0

50

100

150

200

SLpp ~ 190 - 225 dB

FREQUENCY (KHZ)

0

200 s

Typical echolocation signals

Smaller animals have amplitude limitations, so emit longer sounds?


Echolocation clicks

Capable of whistling

Non-whistling


Sending sound - melon


Click variability


Sending and receiving sound


Dolphin phonic lips

2 pairs

One right, one left

Can work independently

Endoscope view

Ted Cranford


Bottlenose dolphin phonic lips

Cranford et al. 1996


Sound reception

External opening = 3mm, plugged, no connection with tympanic bone

No pinna!

Norris (1968)’s Theory = Sound conveyed to middle and inner ear through acoustic fats in lower jaw.


Receiving sound

“Acoustic fat” found ONLY here & melon

CT scan from Darlene Ketten


Evidence: Brill et al. (1988)

  • Behavioral Approach

    • Blindfolded dolphin discriminates between aluminum cylinder & sand-filled ring

    • Two hoods worn on lower jaw

      • Gasless neoprene: doesn’t block sounds

      • Closed cell neoprene: blocks sounds

    • Performance

      • No hood vs. Gasless hood = no significant difference

      • No hood vs. Closed cell hood = significant!


Sperm whale morphology

Clicks have 235 dB source level!

CT scan from Ted Cranford


Funding science (an aside)


Sperm whale phonic lips

Ted Cranford


Sperm whale click

Mohl et al 2003


Sperm whale directionality


Sperm whale beam pattern


0 dB

40 °

0 dB

40 °

-10 dB

30 °

-10 dB

30 °

-20 dB

20 °

-20 dB

20 °

-30 dB

10 °

-30 dB

10 °

0 °

0 °

-10 °

-10 °

-20 °

-20 °

-30 °

-30 °

Transmit

-40 °

Dolphin Receive andTransmitBeams

Au, W.W.L. and P.W.B. Moore, 1984


Click trains


Source level and range – regular clicks


Click timing – regular clicks


Final approach to target

  • “Terminal buzz” – dolphins

  • “Creak” – sperm whales

  • Function?

Freq (kHz)

Time (s)


Terminal buzz – beaked whales

Search

Approach

Attack?

Recorded on a D-tag

Madsen et al. 2005


Click timing


Click intensity


Track of beaked whale

Coloration is roll of animal


Buzz before impact


Discrimination capabilities

Cylindrical targets with 0.2 mm wall thickness difference

Au, 1993


Summary of echolocation clicks

  • Short, loud, broadband signals

    • High resolution

    • Outstanding Discrimination capabilities

  • Highly directional

  • Emitted in trains

    • Spacing 2 way transit time + processing

  • Variable by species

    • Porpoises longer and narrower bandwidth

    • Delphinids shorter and wide bandwidth

    • Sperm whales much lower frequency

  • Variable in individual

    • By task/target

    • With range

      • Deformations of melon


The other side – fish hearing

  • Clupeoid fish

    • Herring, shad, menhaden, sardine, anchovy

    • Swimbladder morphology facilitates broad frequency hearing range

      • 2 ‘fingers’ of swimbladder surround auditory bullae

  • Can they hear (and respond to) the acoustic signals of a primary predator?


Herring feeding rate

Control

Click train

Regular clicks


Fish polarization

Control

Click train

Regular clicks


Herring swimming depth


Conclusions

  • Respond to echolocation clicks

    • Stop feeding

    • School

    • Swim down

    • Swim faster

  • Do not respond to other signals in same frequency range

  • Can hear and appropriately respond to predator cue


Benoit-Bird et al 2006

Prey stunning by sonar signals

  • Hypothesis

    • Odontocetes use acoustic signals to capture prey

      • Stun, disorient, debilitate prey

  • Existing support

    • Sperm whales – rapid swimming prey in stomachs intact

    • Fish school depolarization while under attack in captivity

    • Fish lethargy while under attack in wild

    • Some acoustic signals can injure/kill fish


Some acoustic signals can affect fish

  • Observed effects

    • Loss of buoyancy control

    • Abdominal hemorrhage

    • Death

  • Sound characteristics

    • Fast rise times

    • High pressures

  • Examples

    • Explosives

      • Dynamite, TNT229-234 dB

      • Black powder234-244 dB

    • Spark discharges230-242 dB

      Dolphin click levels 225 dB


  • Problem

    • Odontocete signals of intensities observed to affect fish not observed in nature

  • Question

    • Can odontocete click trains or bursts debilitate fish?


Video camera

Calibration hydrophone

Monofilament enclosure

Video camera

Transducers


Fish responses

  • 15 minutes pre-exposure observation

  • 15 minutes post-exposure observation

  • Fish behavior observed

    • Changes in activity level

    • Changes in pitch/roll

    • Post-experiment survival


0

-10

-20

-30

-40

0

250  s

-50

-60

0

50

100

150

200

0

-10

-20

-30

-40

0

250  s

-50

-60

0

50

100

150

200

0

-10

-20

-30

-40

-50

0

500  s

-60

0

50

100

150

200

FREQUENCY (KHZ)

SL = 203 dB

EL = 212 dB

Signals

Bottlenose dolphin

SL = 200 dB

EL = 208 dB

Killer whale

SL = 187 dB

EL = 193 dB

Sperm whale


Pulse rates

  • Static pulse rate

    • 100, 200, 300, 400, 500, 600, & 700 pulses/second

    • Exposure times of 7 seconds – 1 minute

    • 6 individuals of 2 species (sea bass, cod)

    • Groups of 4 individuals of each species

  • Modulated pulse “sweeps”

    • From 100 to 700 pulses/second in 1.1, 2.2, 3.2 seconds

    • Similar to a “terminal buzz”

    • 6 individuals of 2 species (cod, herring)

    • Groups of 4 individuals of each species


Subject selection

  • Proposed “stunning” mechanism: Acoustic interaction with air-filled cavities

    • Swim bladder

      • Physostomous

        • “Open” - Air comes from gulping at surface

      • Physoclistous

        • “Closed” - Air is produced biochemically

  • “Stunning” proposed from field observations

    • Salmon Physostomous

    • Anchovy Physostomous with extensions to lateral line & labyrinth

    • Mahi mahi No swim bladder

  • 3 species commonly preyed upon by Odontocetes

    • Variety of swimbladder types


Herring (Clupea harengus)

Physostome with air bladder extensions to labyrinth & lateral line

- Increased sensitivity to sound

- Respond to echolocation signals

Modified primitive form


Sea Bass (Dicentrarchus labrax)

Euphysoclist

- Physostome juvenile

- Physoclist adult

Intermediate form


Cod (Gadus morhua)

Physoclist

Most derived form


Results


Results

  • No measurable change in behavior

    • Swimming activity

    • Balance/buoyancy control

    • Orientation

  • No mortality

  • Variables explored

    • Frequency of signal

    • Pulse rate

      • “Terminal buzz” simulation

    • Long exposure times

    • Multiple individuals, different sizes, different species


Conclusions

  • No response to stimuli

    • Signals near maximums recorded for odontocete clicks

  • Stimulation with odontocete-like clicks alone is not enough to induce fish stunning

    • Additional stress?

    • Other sensory inputs?

    • Odontocete behavior?


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