Transcript Toothed whales

Bellwork: 04/03/2012
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Acoustics and Biology
Acoustics
• loudness (amplitude or pressure level)
• pitch (frequency)
Use of sound by marine animals
• Predation/defense
• Communication and social interaction
Same frequency,
Different amplitude
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Same amplitude,
Different frequency
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Amplitude determines sound level pressure or loudness
Frequency determines “pitch”
Loudness
(Amplitude, sound level)
Chart shows loudness in
dB of some things we are
familiar with
Sound levels in air and
water have different
reference levels, so
0 dB (air) ≈ 26 dB (water)
Marine animal sounds can
be made up of multiple
frequencies
The sound spectrum gives
the pressure level at each
frequency
Intensity  pressure2
dB = 10 Log10(intensity)
Spectrogram shows how sound spectrum
changes over time
An invertebrate example:
snapping shrimp
claw
Snapping shrimp make noise to stun their prey.
They create a cavitation bubble that “snaps” as it collapses.
http://www.dosits.org/resources/
all/featuresounds/snappingshri
mp/
http://stilton.tnw.utwente.nl/shrimp/
crab
Some fish use sound for
courting and as a fright
response
A fish example:
Atlantic Croaker
Toothed whales
Baleen whales
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Smaller (1.5 to 17 m long)
Social
Most are not migratory
Chase and capture individual fish,
squid, crabs
Use sound to echolocate, communicate
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Larger (15 to 30 m long)
Often solitary
Long annual migrations
Feed on aggregations of krill,
copepods, small fish
Use sound only to communicate
Baleen
(mysticete)
whales
Toothed
(odonticete)
whales
http://ww
w.dosits.o
rg/audio/i
nteractive/
#/46
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Larger whales produce lower-frequency sound
Larger whales can dive deeper
Toothed whales forage deeper than baleen whales
What happens to sound in deeper water?
Data from polaris.nipr.ac.jp/~penguin/penguiness/
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” (auditory
bulla).
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.
Frequency (Hz)
Social calls
http://www.seaworl
d.org/animalinfo/soundlibrary/audio/dolphi
ns.wav
Time (s)
Toothed
Baleen
Communication frequencies
Thick bars: most common vocalizations
Thin lines: extremes of frequency
Echolocation using echoes from sound pulses or
clicks
Whale can determine distance, angle,
size, shape, etc. from sound echoes
Echolocation frequencies
Mellinger 2007
Toothed whale
prey
Squid and large fish are:
•More likely to be solitary
•Good acoustic targets
(squid pens and fish swim
bladders have density
different from water)
Baleen whale
prey
Plankton are:
•More likely to aggregate
•Poorer acoustic targets
(density similar to water)
A good invention for listening to whales:
acoustic whale tag (D-Tag)
-Acoustic sensors (hydrophones) and 3D
accelerometers in a waterproof, pressureresistant case, mounted on suction cups
-Carefully sneak up on whale, attach D-Tag
-Record audio, pitch, roll, heading and depth
Mark Johnson with D-Tag
-Tag pops off, floats to surface 18 hours later
Long-Term Geotags:
Toothed whale foraging:
Beaked whales dive deep to find prey
Natacha Aguilar de Soto
(Yellow indicates echolocation)
Peter Tyack et al.
Baleen whale foraging: 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
Marine mammal sound levels are generally between 100
and 200 dB
Baleen whales
Toothed whales
Seals, sea lions, and walruses
Manatees and dugongs
Echolocation (toothed whales)
Worcester & Spindel 2005
Blue whales migrate and communicate over long distances
Man-made noise in the ocean
Outboard engine
6,300 Hz
These add constant
background noise
Commercial Ship
10 to 20,000 Hz
Low-Frequency
Active Sonar
100 to 500 Hz
230 to 240 dB
Airgun
10 to 500 Hz
Up to 232 dB
These are loud enough
to damage tissues and
cause hearing loss
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
Since the invention of propeller-driven motors (~150 years ago),
• Background noise level in the ocean has increased by ~45 dB
• Lowest background noise f has dropped from ~100 Hz to ~7 Hz
After motors
~7 Hz
Before motors
~100 Hz
After motors
~75 dB
Before motors
~30 dB
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
e.g. San Diego to Seattle
(area 10,000,000 km2 )
Current noise level
75 dB
Whale song stays
above ambient noise
level for ~60 km
e.g. New Brunswick to NYC
(area 10,000 km2)
Blue
whale
Range of effective communication for blue whale
singing at 20 Hz and 155 dB
Range before
mid-1800s
Current range
Noise-induced mass strandings
Mass strandings associated with Navy sonar activity
The Bahamas (2000):
14 beaked whales, 1 spotted dolphin, 2 minke whales
Cranial Bleeding
Naval Training Exercise: SONAR
The Canary Islands (2002):
14 beaked whales
Gas bubbles and bleeding in multiple organs, likely from
surfacing too quickly
Noise-induced mass strandings
Mass strandings associated with air guns
Tasmania and New Zealand (2004):
208 whales and dolphins
Mass Stranding: ExxonMobile Seismic Testing
Senegal and Madagascar (2008):
200 pilot whales and melon-head whales
Mass Stranging: Dolphins & Seismic Testing
Northern Peru (February 2012)
900+ dolphins stranded or washed ashore dead
• Middle Ear Bleeding
• Cracked bones in ear
• Hemorrhage in mandibular fat
• Air bubbles in liver, kidneys, bladder, and blood vessels
• Pulmonary emphysema
* The last two are associated with acute decompression
syndrome