Presentation on theme: "Biosonar/Echolocation Odontocetes –Toothed whales Dolphins, porpoises, sperm whales Bats Cave swiftlets Used for navigation, hunting, predator detection,"— Presentation transcript:
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)
non-whistling odontocete Phocoena phocoena SL pp ~ dB s Typical echolocation signals Smaller animals have amplitude limitations, so emit longer sounds?
Echolocation clicks Capable of whistling Non-whistling
Sending sound - melon
Sending and receiving sound
Dolphin phonic lips Endoscope view Ted Cranford 2 pairs One right, one left Can work independently
Bottlenose dolphin phonic lips Cranford et al. 1996
Sound reception No pinna! Norris (1968)’s Theory = Sound conveyed to middle and inner ear through acoustic fats in lower jaw. External opening = 3mm, plugged, no connection with tympanic bone
Receiving sound CT scan from Darlene Ketten “Acoustic fat” found ONLY here & melon
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 CT scan from Ted Cranford Clicks have 235 dB source level!
Funding science (an aside)
Sperm whale phonic lips Ted Cranford
Sperm whale click Mohl et al 2003
Sperm whale directionality
Sperm whale beam pattern
-30 dB -20 dB -10 dB 0 dB -30 dB -20 dB -10 dB 0 dB 0 ° 20 ° -40 ° 40 ° -20 ° -30 ° 10 ° 30 ° -10 ° 20 ° 40 ° -20 ° -30 ° 10 ° 30 ° -10 ° Dolphin Receive and Transmit Beams Transmit Au, W.W.L. and P.W.B. Moore, 1984
Source level and range – regular clicks
Click timing – regular clicks
Final approach to target “Terminal buzz” – dolphins “Creak” – sperm whales Function? Time (s) Freq (kHz)
Terminal buzz – beaked whales Recorded on a D-tag Madsen et al SearchApproachAttack?
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
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 Benoit-Bird et al 2006
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 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 Transducers Monofilament enclosure Calibration hydrophone
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 s s FREQUENCY (KHZ) s 0 SL = 203 dB EL = 212 dB SL = 200 dB EL = 208 dB SL = 187 dB EL = 193 dB Bottlenose dolphin Killer whale 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
Cod (Gadus morhua) Physoclist Most derived form
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?