Marine Mammal Sensory & Sound Production

Systems

MARE 390Dr. Turner

Sound

Production, transmission, & reception of sounds produced by marine mammals unique – airborne & waterborne

Manner differs between taxa & media

Purposes: Communication within species to location of unseen targets with echolocation

Sound Propagation

Acoustic energy characterized by velocity, frequency, wavelength, & amplitude

Human hearing 18 Hz to 15kHzMarine mammal vocalizations above & below

< 18 Hz (infrasonic)> 20 kHz (ultrasonic)

Sound in Air & Water

Sound travels 5X faster in water (1550m/s) than air (340m/s) depending upon temperature & salinity (depth)

Why increased capacity for sound production?

Poor light transmission & vision in water

Functions of Sound

Dolphins – large variety of whistle-like sounds; can understand complex linguistics

Many sounds used for communicationSignature calls identify individuals

Loud impulse sounds – debilitation of prey, self-defense, intimidation of conspecifics

Echolocation – active detection & identification of a target with sound

Acoustic Signal

Frequency, duration, & energy level are portrayed as:Spectrogram (frequency with time)

Power spectrum (sound pressure levels with time)

Frequency spectrum (sound pressure levels with frequency)

Acoustic Signal

Spectrogram (frequency with time)

Power spectrogram(sound pressure levels with time)

Frequency spectrum (sound pressure levels with frequency)

Use of Sounds

Low frequency sounds – attenuate more slowly so good for long distance communication

High frequency sounds – attenuate more quickly but have the potential to provide more information on target resolution

Mammalian Ear

Evolved for detection of sound vibrations in air

Amplitude (loudness) determined by the number of hair cells stimulated

Frequency (pitch) depends upon the distribution pattern of stimulated hair cells

Pinniped Sounds

Sounds produced 1° with larynx

2° - teeth & pharyngeal pouches

Typical mammalian ear with modificationsamplify sound receptionengorged with blood during diving

Cetacean Sounds

Nasal sacs ventral to blowhole produce sounds including whistles & echolocation

Monkey-lips or Phonic lips – produce sounds as air is forced through them

tweaking end of air-filled balloon

Cetacean Sounds

Sperm Whale Head

Sound Propagation

Melon contains low-density lipids which serve as an acoustic lens to create focused directional sound beams

Mysticete Rhythms

Mysticete larynx possesses structures homologous to vocal folds - are capable of sound generation

Mysticete Rhythms

(U-fold) in the lumen of the larynx- vibration of edges may generate sounds- walls of the laryngeal sac can serve as a resonant space

Sound ReceptionAll cetaceans have good hearing

Auditory canal narrow in odontocetes; plugged in mysticetesGlove finger – projection of eardrum into ear canal

Odontocete Reception

Unique sound reception pathway – jaw

Pan Bones - Posterior portions of mandibles, flared, thin to transparency

Filled with low density lipid – similar to melon

Directly connects with the auditory bulla of the middle ear

Odontocete Reception

Other Marine Mammals

Sea Otters & Polar Bears – no special adaptations; similar to terrestrial mammals

Sirenians – have lipid filled zygomatic process (skull bone) connects to ear analogous to pan bone in odontocetes

Poor directionality and lack of high frequency sound reception reason for high number of boat strikes

Pinniped Sounds

In air vocalizations – classified by species, age, & sex

Otariids more vocal than phocids

Male calls – barks, roars, grunts

Mother-pup calls – used specifically for recognizing & locating each other

Underwater vocalizations – typically male “songs”

Pinniped SoundsWeddell seal

N. Elephant seal

California sea lion

Other Marine Mammal Sounds

Walruses – males produce a series of knocking sounds

Sirenians – chirp-squeaks; little geographic variation; key in keeping calves with mothers

Sea otters – above water low-frequency sounds; similar to sea lions

Polar bears – females – defensive growls; males - chuffs

Other Marine Mammal SoundsWalrus

Manatee

Sea Otter

Polar Bear

Cetacean Sounds

Echolocation – projecting short-duration sounds and listening for reflected echoes

Signature whistles – narrow band frequency modulated (FM) sound with harmonic structure; specific to individuals

Mysticete sounds – low-frequency sounds used for long distance communication

Prey stunning sounds – loud blasts of sound called “bangs” to debilitate prey

Echolocation

Used by about 20% of mammals (bats & odontocetes

Evolved independently in 5 mammalian lineages (bats, shrews, hamsters, lemurs)

Dolphins may use successive echolocation clicks followed by multiclick processing

Echolocation

Echolocation

Bottlenose dolphin

Risso’s dolphin

Beluga whale

Sperm whale

Signature Whistles

Hypothesized that whistle broadcasts identity of the animal & other information (state of arousal, fear, food, etc)

More social animals whistle more often

Often different dialects representing regional distributions

Vocal Clans

Killer whales & Sperm whales

Pods share calls including calls specific to individuals

Pods are loosely associated into clans; share clan specific calls as well – some but not all calls

Vocal Clans

Prey Stunning Sounds

Blasts of sounds called “bangs” used to stun or debilitate prey

First identified in sperm whales – jaw claps

Energetics of sperm whale feeding ecology

Evidence difficult to collect – 240-250 db of sound required for stunning

Empirical Evidence

Empirical studies suggest that sounds not enough to debilitate – playback experiments; conducted with live fish but not live dolphins/porpoises

Mysticete Sounds

Hypothesized to have some form of echolocation – never substantiated

Different equipment – form/function of sounds production in odontocetes

Most well known sound production from humpbacks- male songs

Mysticete Sounds

Broad system clicks & pulses

Low frequency whale tones with very long wavelengths

Humpbacks sing long complex songs

Humpback Songs

Mysticete Sounds

Blue whale

Humpback whale

Bowhead whale

Sound in the Ocean

Sound pollution thought to be as detrimental to marine mammals as chemical, thermal, physical

NATO & Navy Sonar war games

ATOC – Acoustic Thermometry of Ocean Climate – 260 watt low frequency sounds

Sound in the Ocean

Sound pollution thought to be as detrimental to marine mammals as chemical, thermal, physical

NATO & Navy Sonar war games

ATOC – Acoustic Thermometry of Ocean Climate – 260 watt low frequency sounds

Sound in the OceanSources of Human-Generated Ocean NoiseTransportation: Aircraft, ships and boats, icebreakers, hovercrafts and vehicles on iceDredging and Construction: Dredging, tunnel boring, other operations.Oil Drilling and Production: Drilling from islands and caissons, bottom-mounted platforms, and vessels; andoffshore oil and gas production.Geophysical Surveys: Air-guns, sleeve exploders, and gas guns.Sonars: Fish finders, depth sounders, and military systems.ExplosionsOcean Research: Seismology, acoustic propagation, acoustic tomography, acoustic thermometry

Sound in the Ocean

Ocean Acoustic Tomography (Acoustic Thermometry) - technique used to measure temperatures across large distances in the ocean

Sounds travel between transmitter and receiver of known distance (typically 100-5000km); time for sound to reach received depends upon temperature of water (and other variables)

Sound in the OceanATOC - Acoustic Thermometry of Ocean Climate

Most infamous regarding marine mammals

Public outrage and political reaction primarily caused by misinformation

Sound in the OceanAMODE (Acoustic Mid-Ocean Dynamics Experiment) & SYNOP (Synoptic Ocean Prediction) – most recent versions

Workshop: Navy Sonar and Cetaceans:Why Does RIMPAC have us on High Alert?

What Is RIMPACRim of the Pacific Exercise – since 1971

World's largest international maritime exercise

Hosted and administered by the US Navy, US Marine Corps, US Coast Guard & Hawaii National Guard

Held biennially in June and July in Hawaii

ParticipantsAlways: United States, Canada, and Australia,

Sometimes: United Kingdom, Japan, Republic of Korea, Chile, and Peru

Observers: France, Singapore, Malaysia, the Philippines, Thailand, Colombia, Mexico, India, Ecuador, Indonesia, China and Russia

PurposeEnhance coordination armed forces in Pacific

Key to military readiness; conflict "hot spots“China & Taiwan North Korea & South Korea, US, Japan

Conduct ship-sinking & torpedo exercises Test new naval vessels and technology

Exercises

Marine Mammals and Sound

Patterns of ConcernGreece, May 1996‘atypical’ mass stranding of 12 Cuvier’s beaked whales associated with acoustic trials by vessels from NATO

Bahamas, March 200016 whales (14 beaked, 2 minke) stranded over 2 daysUS Navy vessels were using active high intensity sonar

Madeira, May 20003 Cuvier’s beaked whales over 4 days NATO naval exercises involving multiple ships

Patterns of ConcernCanary Islands, September 200214 beaked whales (4 species) on same day as nearby International naval exercise (Neo-Tapon 2002)

Gulf of California, September 20022 Cuvier’s beaked whales near research vessel conducting seismic surveys

Canary Islands, July 20044 Cuvier’s beaked whales, coincided with the naval exercise ‘‘Majestic Eagle”, conducted 100 km to the north

Patterns of ConcernHonshu Japan, 1950s until 2004 11 reported mass strandings (total of 51 beaked whales ) Adjacent base for operations; US Navy’s Pacific 7th Fleet

Taiwan, February-March 2004 several cetacean strandings; including a beaked whaleCoincided with a joint US/Philippine military exercise

Almería, Spain 2006 ‘atypical” mass stranding of Cuvier’s beaked whalescoincident with a NATO naval exercise

Patterns of ConcernScotland, 2008Cuvier’s beaked whales, dying at sea and washing ashoreResearchers are investigating potential naval activities

Other species:Minke, pilot (long & short finned), pygmy sperm, pygmy killer, other smaller dolphins

During RIMPAC:Oahu, 2006: Pygmy Killer Whale

Molokai, 2008: Beaked Whale

In Hawaii3 species of beaked whales

Highest sightings – West side Hawaii Island

Why do we think they Strand?Gas and fat emboli

Acoustically mediated bubble growth

Dysbaric Osteotrauma (DOT)

Behavioural alterations

Resonance

Disseminated Intravascular Coagulation (DIC) -coagulopathy, bleeding diathesis

Why do we think they Strand?Gas and fat emboli - essentially “the bends” - gases forced out of solution during rapid ascent - causes clots, tissues damage, fractured bones

Acoustically mediated bubble growth - although marine mammals protected from “the bends” - sound waves cause gases to come out of solution - exaggerates nitrogen effects – especially in deep divers

Why do we think they Strand?Dysbaric Osteotrauma (DOT) - produces chronic lesions in bones - damage to marrow - long-term effects of gas bubbles in fat/blood

Behavioural alterations - acoustic exposure is not the primary cause - mechanism that causes a behavioural response that induces beaked whales to forgo natural diving protocols - animal with nitrogen in blood could be frightened by sonar - forced to alter its dive profile; ascend faster than normal

Why do we think they Strand?Resonance - Air-containing spaces in diving mammals resonate sound - energy reflected or absorbed – damaging tissues

Disseminated Intravascular Coagulation (DIC) -coagulopathy, bleeding diathesis - diathetic fragility, or the tendency to bleed - may occur in concert with resonance - bleeding becomes associated with the tissues of resonating structures or air spaces - may also result from a stress response initiated byacoustic exposure

Necropy FindingsEar damage - massive ear damage and blood clots along auditory nerve

Acute systemic haemorrhages - within the lungs, CNS, kidneys;

Fat & Gas emboli - in vessels from: brain, choroid plexus, visceral/parietal serosa, kidneys

Why do we think they Strand?

What is the Government’s RoleUS Navy and NOAA (Oceanic & Atmospheric Admin)

Working under – National Defense Exemption of the Marine Mammal Protection Act

Means Navy can “take” animals under MMPA for purposes of Military Readiness

- have to report after - must take steps to reduce take

How it worksUS Navy contacts NOAA – notifies about RIMPAC - when takes place (July 6-30, 2010) - where takes place – Main Hawaiian Islands - supports research before, during, & after - reports out afterwards: After Action Report

In ConclusionConclusive evidence is still lacking

Many scientists feel enough evidence to act

Public “Scientific” opinion – Government has evidence but afraid to act

Navy sonar and cetaceans: Just how much does the gun need to smoke beforewe act?

Marine Pollution Bulletin 56 (2008) 1248–1257