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Acoustics and Biology. Use of sound by marine animals Predation/defense Social interaction Navigation Man-made sounds and their effects on animals. An invertebrate example: snapping shrimp. claw crab . Snapping shrimp make noise to stun their prey.

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Acoustics and Biology

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Acoustics and biology l.jpg

Acoustics and Biology

Use of sound by marine animals

  • Predation/defense

  • Social interaction

  • Navigation

    Man-made sounds and their effects on animals


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An invertebrate example:

snapping shrimp

claw crab

Snapping shrimp make noise to stun their prey.

They create a cavitation bubble that “snaps” as it collapses.

http://stilton.tnw.utwente.nl/shrimp/


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A fish example: Atlantic Croaker

Some fish use sound for courting and as a fright response


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Toothed whales

Smaller (1.5 to 17 m long)

Social

Most are not migratory

Chase and capture individual fish, squid, crabs

Use sound to echolocate, communicate

Baleen whales

Larger (15 to 30 m long)

Often solitary

Long annual migrations

Feed on aggregations of krill, copepods, small fish

Use sound only to communicate


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Baleen

(mysticete)

whales

Toothed

(odonticete)

whales


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Data from polaris.nipr.ac.jp/~penguin/penguiness/


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Outgoing sound is generated by the vocal cords and projected through the melon.

Incoming sound is received through the jaw, which transmits sound waves through a fat channel to the ear.


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Social calls

Frequency (Hz)

Dolphins live in social groups that stay together 5-10 years. They have “signature whistles” that can be used to recognize individuals at distances of >500 m.

Time (s)


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Communication frequencies

Toothed Baleen

Mellinger 2007


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Echolocation using echoes from sound pulses or clicks

Whale can determine distance, angle, size, shape, etc. from sound echoes


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Beaked whale echolocation

Constant Frequency

(measure distance)

Frequency Modulation

(pinpoint location)

Intensity of sound echo

Sound level

Whale speed

Johnson et al. 2004


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Echolocation frequencies

Mellinger 2007


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Why don’t baleen whales echolocate?

  • Their prey (krill, copepods) are poor acoustic targets

  • They produce low-frequency sounds with long wavelengths. Wavelength gives the minimum detection distance.

Minimum

echolocation

frequency


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Toothed whale

prey

Squid and fish are good acoustic targets

(squid pens)

(fish swim bladders)

Plankton are poorer acoustic targets

(density similar to water)

Baleen whale

prey


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Baleen whales

Toothed whales

Seals, sea lions, and walruses

Manatees and dugongs

Echolocation (toothed whales)

earthquake

rainfall

Marine mammal sound levels are generally between 100 and 200 dB


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Acoustic receivers used to measure ocean temperature

also record whales and other noises

Worcester & Spindel 2005


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Worcester & Spindel 2005


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~2,250 km

migration

Burtenshaw et al. 2004


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Blue whales migrate and communicate over long distances


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High-frequency sounds are absorbed more quicklyAbsorption of sound in SOFAR channel

Because baleen whales have long migrations, they need to use low frequencies to stay in touch.

Because toothed whales move in groups, they can use high frequencies without losing touch.


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Transmission loss

Sound signal loses intensity due to:

-Cylindrical spreading

-Spherical spreading

-Absorption

Blue

whale

Dolphins


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A cool invention for listening to whales:

acoustic whale tag (D-Tag)

  • Acoustic sensors (hydrophones) and 3D accelerometers in a waterproof, pressure-resistant case, mounted on suction cups

  • Carefully sneak up on whale, attach D-Tag

  • Record audio, pitch, roll, heading and depth

  • Tag pops off, floats to surface 18 hours later

Mark Johnson with D-Tag


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Beaked whales are deep divers

Natacha Aguilar de Soto

Peter Tyack et al.


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Right whales dive to bottom of the mixed layer where plankton are most concentrated

Fig. 4. Eubalaena glacialis and Calanus finmarchicus. (a-d) Examples of diving and tracking observations during feeding behavior. Contoured C. finmarchicus C5 abundance estimated from the OPC casts is shown. Color scale shown in (d) applies to all plots. () Times of visual contacts.

() Times and locations at which a resurfacing occurred and a conductivity-temperature depth/optical plankton counter (CTD/OPC) cast was conducted. Solid and dashed lines indicate the sea floor and the top of the bottom mixed layer, respectively, measured at the location of each CTD/OPC cast.

Baumgartner and Mate 2003


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krill

Echo sounder image of vertically migrating zooplankton

www.oceanobservatory.com


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Dolphins have different day/night dive behavior because they can’t reach prey during daylight hours

plankton


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Large baleen whales can reach bottom of mixed layer even in daytime


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Man-made noise in the ocean

These add constant background noise

Outboard engine

6,300 Hz

Commercial Ship

10 to 20,000 Hz

Airgun

10 to 500 Hz

Up to 232 dB

Low-Frequency Active Sonar

100 to 500 Hz

230 to 240 dB

These are loud enough to damage tissues and cause hearing loss


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Humans add noise to the ocean

Potential effects of man-made sounds on marine mammals:

  • Temporary or permanent hearing loss or impairment

  • Disruption of feeding, breeding, nursing, acoustic communication and sensing

  • Death from lung hemorrhage or other tissue trauma

  • Psychological and physiological stress


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Toothed whalesSeals and walruses

Hearing threshold

Sound pressure that causes a temporary shift in the hearing threshold after an exposure

of 1 second


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(Bold, filled diamonds, mean of all six singers; other symbols, individual singers). The maximum received level of the sonar at the whale ranged from 130 to 150 dB re 1 Pa. Songs were grouped in the exposure condition if a sonar transmission occurred at any point during the song. The average number of songs per singer in the pre-exposure, exposure and post-exposure conditions was 3.2, 4.7 and 3.8, respectively. Differences were assessed using a mixed-model analysis of variance treating exposure condition as a fixed factor, whale identity as a random factor, and each song duration as an independent observation. The effect of exposure condition on song duration was statistically significant at P=0.047 (F2,10=4.200, power=0.50, n=6).

Miller et al. 2000

Humpback whale songs are several minutes longer in the

presence of low-frequency active sonar


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Signal-to-noise ratio (SNR)

Psignal = power of communication signal

Pnoise = power of background noise

For communication, need a minimum SNR of 3 to 5 dB.

A good SNR is 20 to 30 dB.


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Background noise level in the ocean has increased by ~45 dB since the invention of propeller-driven motors (~150 years ago)

After motors

~75 dB

Before motors

~30 dB


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Can use transmission-loss curves to calculate the effective communication range

Blue whale song

20 Hz, ~155 dB

Pre-motor noise level

30 dB

Whale song stays

above ambient noise

level for ~2,000 km

(area 10,000,000 km2 )

Current noise level

75 dB

Whale song stays

above ambient noise

level for ~60 km

(area 10,000 km2)

Blue

whale


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Range of effective communication for blue whale

singing at 20 Hz and 155 dB

Range before

mid-1800s

Current range

(yes, that tiny speck)


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Noise-induced mass strandings

Mass strandings associated with Navy sonar activity

The Bahamas (2000):

14 beaked whales, 1 spotted dolphin, 2 minke whales

Bleeding in ears

The Canary Islands (2002):

14 beaked whales

Gas bubbles and bleeding in multiple organs

Mass strandings associated with air guns

Tasmania and New Zealand (2004):

208 whales and dolphins

Senegal and Madagascar (2008):

> 200 pilot whales and melon-head whales


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Toothed whales

Smaller (1.5 to 17 m long)

Social

Most are not migratory

Chase and capture individual fish, squid, crabs

Use sound to echolocate, communicate

Baleen whales

Larger (15 to 30 m long)

Solitary

Long annual migrations

Feed on aggregations of krill, copepods, small fish

Use sound only to communicate


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A great source of information on sound in the ocean:

http://www.dosits.org/

Oceanus has many articles on sound in the ocean:

http://www.whoi.edu/oceanus/viewTopic.do?o=read&id=83&type=11


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