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

3. 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)

4. Typical echolocation signals
non-whistling odontocete
Phocoena phocoena
SLpp ~ dB
200 s 50
100
150
200
FREQUENCY (KHZ)
0.2
0.4
0.6
0.8 1
Tursiops
Phocoena
RELATIVE AMPLITUDE
whistling dolphin
Tursiops truncatus
SLpp ~ dB
200 s
Smaller animals have amplitude limitations, so emit longer sounds?

5. Echolocation clicks
Capable of whistling
Non-whistling

6. Sending sound - melon

7. Click variability

8. Sending and receiving sound

9. Dolphin phonic lips 2 pairs One right, one left Can work independently
Endoscope view
Ted Cranford

10. Bottlenose dolphin phonic lips
Cranford et al. 1996

11. Sound reception No pinna!
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.

12. “Acoustic fat” found ONLY here & melon
Receiving sound
“Acoustic fat” found ONLY here & melon
CT scan from Darlene Ketten

13. 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!

14. Sperm whale morphology
Clicks have 235 dB source level!
CT scan from Ted Cranford

15. Funding science (an aside)

17. Sperm whale phonic lips
Ted Cranford

18. Sperm whale click
Mohl et al 2003

19. Sperm whale directionality

20. Sperm whale beam pattern

21. Dolphin Receive and Transmit Beams
-30 dB
-20 dB
-10 dB
0 dB
0 °
20 °
-40 °
40 °
-20 °
-30 °
10 °
30 °
-10 °
Transmit
Au, W.W.L. and P.W.B. Moore, 1984

22. Click trains

23. Source level and range – regular clicks

24. Click timing – regular clicks

25. Final approach to target
“Terminal buzz” – dolphins
“Creak” – sperm whales
Function?
Freq (kHz)
Time (s)

26. Terminal buzz – beaked whales
Search
Approach
Attack?
Recorded on a D-tag
Madsen et al. 2005

27. Click timing

28. Click intensity

29. Track of beaked whale
Coloration is roll of animal

30. Buzz before impact

31. Discrimination capabilities
Cylindrical targets with 0.2 mm wall thickness difference
Au, 1993

32. 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

33. 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?

34. Herring feeding rate
Control
Click train
Regular clicks

35. Fish polarization
Control
Click train
Regular clicks

36. Herring swimming depth

37. 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

38. 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

39. 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 dB
Black powder dB
Spark discharges dB
Dolphin click levels dB

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

41. Video camera
Calibration hydrophone
Monofilament enclosure
Video camera
Transducers

42. 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

43. Signals Bottlenose dolphin Killer whale Sperm whale SL = 203 dB
EL = 212 dB 50
100
150
200
-60
-50
-40
-30
-20
-10
250  s
Bottlenose dolphin 50
100
150
200
-60
-50
-40
-30
-20
-10
250  s
SL = 200 dB
EL = 208 dB
Killer whale
SL = 187 dB
EL = 193 dB 50
100
150
200
FREQUENCY (KHZ)
-60
-50
-40
-30
-20
-10
500  s
Sperm whale

44. Pulse rates Static pulse rate Modulated pulse “sweeps”
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)

45. 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

46. Herring (Clupea harengus)
Physostome with air bladder extensions to labyrinth & lateral line
- Increased sensitivity to sound
- Respond to echolocation signals
Modified primitive form

47. Sea Bass (Dicentrarchus labrax)
Euphysoclist
- Physostome juvenile
- Physoclist adult
Intermediate form

48. Cod (Gadus morhua)
Physoclist
Most derived form

49. Results

50. Results No measurable change in behavior No mortality
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

51. 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?