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Biosonar/Echolocation

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

  2. 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)

  3. 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?

  4. Echolocation clicks Capable of whistling Non-whistling

  5. Sending sound - melon

  6. Click variability

  7. Sending and receiving sound

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

  9. Bottlenose dolphin phonic lips Cranford et al. 1996

  10. 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.

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

  12. 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!

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

  14. Funding science (an aside)

  15. Sperm whale phonic lips Ted Cranford

  16. Sperm whale click Mohl et al 2003

  17. Sperm whale directionality

  18. Sperm whale beam pattern

  19. 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

  20. Click trains

  21. Source level and range – regular clicks

  22. Click timing – regular clicks

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

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

  25. Click timing

  26. Click intensity

  27. Track of beaked whale Coloration is roll of animal

  28. Buzz before impact

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

  30. 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

  31. 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?

  32. Herring feeding rate Control Click train Regular clicks

  33. Fish polarization Control Click train Regular clicks

  34. Herring swimming depth

  35. 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

  36. 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

  37. 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

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

  39. Video camera Calibration hydrophone Monofilament enclosure Video camera Transducers

  40. 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

  41. 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

  42. 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

  43. 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

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

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

  46. Cod (Gadus morhua) Physoclist Most derived form

  47. Results

  48. 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