2 Biosonar/Echolocation OdontocetesToothed whalesDolphins, porpoises, sperm whalesBatsCave swiftletsUsed 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 dolphinBelugaFalse killer whaleOdontocetes 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)
9 Dolphin phonic lips 2 pairs One right, one left Can work independently Endoscope viewTed Cranford
10 Bottlenose dolphin phonic lips Cranford et al. 1996
11 Sound reception No pinna! External opening = 3mm, plugged, no connection with tympanic boneNo 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 & melonCT scan from Darlene Ketten
13 Evidence: Brill et al. (1988) Behavioral ApproachBlindfolded dolphin discriminates between aluminum cylinder & sand-filled ringTwo hoods worn on lower jawGasless neoprene: doesn’t block soundsClosed cell neoprene: blocks soundsPerformanceNo hood vs. Gasless hood = no significant differenceNo hood vs. Closed cell hood = significant!
14 Sperm whale morphology Clicks have 235 dB source level!CT scan from Ted Cranford
31 Discrimination capabilities Cylindrical targets with 0.2 mm wall thickness differenceAu, 1993
32 Summary of echolocation clicks Short, loud, broadband signalsHigh resolutionOutstanding Discrimination capabilitiesHighly directionalEmitted in trainsSpacing 2 way transit time + processingVariable by speciesPorpoises longer and narrower bandwidthDelphinids shorter and wide bandwidthSperm whales much lower frequencyVariable in individualBy task/targetWith rangeDeformations of melon
33 The other side – fish hearing Clupeoid fishHerring, shad, menhaden, sardine, anchovySwimbladder morphology facilitates broad frequency hearing range2 ‘fingers’ of swimbladder surround auditory bullaeCan they hear (and respond to) the acoustic signals of a primary predator?
37 Conclusions Respond to echolocation clicks Stop feedingSchoolSwim downSwim fasterDo not respond to other signals in same frequency rangeCan hear and appropriately respond to predator cue
38 Prey stunning by sonar signals Benoit-Bird et al 2006Prey stunning by sonar signalsHypothesisOdontocetes use acoustic signals to capture preyStun, disorient, debilitate preyExisting supportSperm whales – rapid swimming prey in stomachs intactFish school depolarization while under attack in captivityFish lethargy while under attack in wildSome acoustic signals can injure/kill fish
39 Some acoustic signals can affect fish Observed effectsLoss of buoyancy controlAbdominal hemorrhageDeathSound characteristicsFast rise timesHigh pressuresExamplesExplosivesDynamite, TNT dBBlack powder dBSpark discharges dBDolphin click levels dB
40 ProblemOdontocete signals of intensities observed to affect fish not observed in natureQuestionCan odontocete click trains or bursts debilitate fish?
41 Video cameraCalibration hydrophoneMonofilament enclosureVideo cameraTransducers
42 Fish responses 15 minutes pre-exposure observation 15 minutes post-exposure observationFish behavior observedChanges in activity levelChanges in pitch/rollPost-experiment survival
44 Pulse rates Static pulse rate Modulated pulse “sweeps” 100, 200, 300, 400, 500, 600, & 700 pulses/secondExposure times of 7 seconds – 1 minute6 individuals of 2 species (sea bass, cod)Groups of 4 individuals of each speciesModulated pulse “sweeps”From 100 to 700 pulses/second in 1.1, 2.2, 3.2 secondsSimilar to a “terminal buzz”6 individuals of 2 species (cod, herring)
45 Subject selectionProposed “stunning” mechanism: Acoustic interaction with air-filled cavitiesSwim bladderPhysostomous“Open” - Air comes from gulping at surfacePhysoclistous“Closed” - Air is produced biochemically“Stunning” proposed from field observationsSalmon PhysostomousAnchovy Physostomous with extensions to lateral line & labyrinthMahi mahi No swim bladder3 species commonly preyed upon by OdontocetesVariety of swimbladder types
46 Herring (Clupea harengus) Physostome with air bladder extensions to labyrinth & lateral line- Increased sensitivity to sound- Respond to echolocation signalsModified primitive form
50 Results No measurable change in behavior No mortality Swimming activityBalance/buoyancy controlOrientationNo mortalityVariables exploredFrequency of signalPulse rate“Terminal buzz” simulationLong exposure timesMultiple individuals, different sizes, different species
51 Conclusions No response to stimuli Signals near maximums recorded for odontocete clicksStimulation with odontocete-like clicks alone is not enough to induce fish stunningAdditional stress?Other sensory inputs?Odontocete behavior?