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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
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
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)
slide4

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
Echolocation clicks

Capable of whistling

Non-whistling

dolphin phonic lips
Dolphin phonic lips

2 pairs

One right, one left

Can work independently

Endoscope view

Ted Cranford

bottlenose dolphin phonic lips
Bottlenose dolphin phonic lips

Cranford et al. 1996

sound reception
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
Receiving sound

“Acoustic fat” found ONLY here & melon

CT scan from Darlene Ketten

evidence brill et al 1988
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
Sperm whale morphology

Clicks have 235 dB source level!

CT scan from Ted Cranford

sperm whale click
Sperm whale click

Mohl et al 2003

dolphin receive and transmit beams

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

final approach to target
Final approach to target
  • “Terminal buzz” – dolphins
  • “Creak” – sperm whales
  • Function?

Freq (kHz)

Time (s)

terminal buzz beaked whales
Terminal buzz – beaked whales

Search

Approach

Attack?

Recorded on a D-tag

Madsen et al. 2005

track of beaked whale
Track of beaked whale

Coloration is roll of animal

discrimination capabilities
Discrimination capabilities

Cylindrical targets with 0.2 mm wall thickness difference

Au, 1993

summary of echolocation clicks
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
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
Herring feeding rate

Control

Click train

Regular clicks

fish polarization
Fish polarization

Control

Click train

Regular clicks

conclusions
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
prey stunning by sonar signals

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
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, TNT 229-234 dB
      • Black powder 234-244 dB
    • Spark discharges230-242 dB

Dolphin click levels 225 dB

slide40
Problem
    • Odontocete signals of intensities observed to affect fish not observed in nature
  • Question
    • Can odontocete click trains or bursts debilitate fish?
slide41

Video camera

Calibration hydrophone

Monofilament enclosure

Video camera

Transducers

fish responses
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
signals

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
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
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
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
Sea Bass (Dicentrarchus labrax)

Euphysoclist

- Physostome juvenile

- Physoclist adult

Intermediate form

cod gadus morhua
Cod (Gadus morhua)

Physoclist

Most derived form

results50
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
conclusions51
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?