BiosonarEcholocation Odontocetes Toothed whales Dolphins porpoises sperm whales

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)

Typical echolocation signals non-whistling odontocete Phocoena phocoena 0 200 s whistling dolphin Tursiops truncatus SLpp ~ 190 - 225 d. B 0 200 s RELATIVE AMPLITUDE SLpp ~ 150 - 170 d. B 1 0. 8 Tursiops Phocoena 0. 6 0. 4 0. 2 0 0 50 100 150 FREQUENCY (KHZ) Smaller animals have amplitude limitations, so emit longer sounds? 200

Echolocation clicks Capable of whistling Non-whistling

Sending sound - melon

Click variability

Sending and receiving sound

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

Bottlenose dolphin phonic lips Cranford et al. 1996

Sound reception No pinna! External opening = 3 mm, plugged, no connection with tympanic bone Norris (1968)’s Theory = Sound conveyed to middle and inner ear through acoustic fats in lower jaw.

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

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 Clicks have 235 d. B source level! CT scan from Ted Cranford

Funding science (an aside)

Sperm whale phonic lips Ted Cranford

Sperm whale click Mohl et al 2003

Sperm whale directionality

Sperm whale beam pattern

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

Click trains

Source level and range – regular clicks

Click timing – regular clicks

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

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

Click timing

Click intensity

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

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 • Observed effects – Loss of buoyancy control – Abdominal hemorrhage – Death • Sound characteristics – Fast rise times – High pressures • Examples – Explosives • Dynamite, TNT • Black powder – Spark discharges Dolphin click levels 229 -234 d. B 234 -244 d. B 230 -242 d. B 225 d. B

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

Video camera Monofilament enclosure Transducers Calibration hydrophone Video camera

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

SL = 203 d. B EL = 212 d. B Signals 0 -10 -20 -30 -40 0 250 s Bottlenose dolphin -50 -60 0 SL = 200 d. B EL = 208 d. B 50 100 150 200 0 -10 -20 -30 -40 0 250 s Killer whale -50 -60 SL = 187 d. B EL = 193 d. B 0 50 100 150 200 0 -10 -20 -30 -40 Sperm whale -50 0 500 s -60 0 50 100 FREQUENCY (KHZ) 150 200

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

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

Cod (Gadus morhua) Physoclist Most derived form

Results

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

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?