Prof Paul White on ‘The Behaviour of Marine Mammals’, including how they communicate and hunt speaking to Isle of Wight Cafe Scientifique on 12 March 2018.

1. A Wail in the Ocean?
Paul White

2. The ISVR
• The Institute of Sound and Vibration Research (ISVR)
– Is a Unit (department if you prefer) in the Faculty of Engineering and
the Environment at UoS
– Just over 50 years old
– World famous research institute into a wide range of topics in sound
and vibration, including:
• Transport noise: aircraft, trains and cars
• 3D sound reproduction
• Active control of sound and vibration
• Hearing technologies: hearing aids, implants (e.g. cochlear implants)
– Runs a variety of taught courses.
• Degrees in Acoustical Engineering and Audiology

3. Outline
• Marine Fauna
• Marine mammals
• Cetaceans (whales and dolphins)
• How cetaceans use sound
• Ambient noise
• Impacts of anthropogenic noise
• Mid-Frequency Active Sonar (beaked whales)
• Noise from Shipping (blue whales)

4. Marine Fauna
• Invertebrates
– Zooplankton, Sponges, Cnidarians (corals, jellyfish,
sea anemones, etc), Worms, Lophophorates, Arthropods (e.g. crustaceans),
Molluscs (including Cephalopods), Echinoderms (e.g. starfish)
and Hemichordates.
• Vertebrates
– Fish (ca 30,000 species, including bony fish and the sharks and rays)
– Reptiles (sea turtles, sea snakes, etc)
– Marine birds (penguins, gannets, etc)
– Marine Mammals (ca 120 species)

5. Marine
Mammals
Pinnipeds Sirenians Carnivores
Sea Otters,
Polar bears
Dugongs,
Manatees
Seals,
Sea lions
Walruses
Whales,
Dolphins,
Porpoises
Cetaceans
(4 sp.) (2 sp.)
(83 sp.)
(35 sp.)

6. Belugas and
Narwhals
Beaked
Whales
Sperm
Whales
Porpoises
Rorqual
Whales Right and
Grey Whales
River
Dolphins Oceanic
Dolphins
Black
Fish
(Killer whales
and pilot whales)
Cetaceans:
Whales and Dolphins
Porpoises
Dolphins
Whales

7. Whale, Dolphin or Porpoise?
2.5 m long
1.5 m long
3 m long
3.5-4 m long
Pygmy Killer WhaleRisso’s Dolphin Hector’s DolphinRight Whale Dolphin
1.8 m long
Burmeister’s Porpoise

8. Belugas and
Narwhals
Beaked
Whales
Sperm
Whales
Porpoises
Rorqual
Whales
Right and
Grey Whales
River
Dolphins
Oceanic
Dolphins
Black
Fish
(Killer whales
and pilot whales)
Cetaceans:
Toothed and Baleen Whales
Baleen Whales (12 sp.)
Toothed Whales (71 sp.)

9. Baleen and Toothed Whales
• Baleen whale (Mysticetes)
– Feed on large prey aggregations
– Grazing-type behaviours
• Toothed whales (Odontocetes)
– Feed on individual large prey items
– Hunting-type behaviours

10. Baleen Vocalisations
• Baleen whales use social calls and some species “sing”.

11. Toothed Whale Vocalisations
• Toothed whales use sounds for 2 purposes:
– Sensing the environment – Echolocation
– Social calls.
• The types of sounds used tend to be different for the different
roles.
• Echolocation sounds tend to be clicks
• Social calls tend to be whistles, sequences of clicks or pulsed
sounds.

12. Example Vocalisations
• Echolocation
• Social calls

13. Ambient
Noise in the
Ocean and
Whale Calls
Baleen Whale
Vocalisations*
Toothed Whale
Vocalisations
* Excluding humpback whales

14. Summary of Ambient Noise Sources
• V. Low Frequency (1-10 Hz) several effects including: earth
quakes and internal waves.
• Low Frequency (10-100s Hz) the noise is a result of distant
ships.
– Frequencies used by baleen whales.
• Mid-frequency (100s-10,000s Hz) the noise is a result of
weather at the surface (wind).
• High frequencies (10 kHz – 100 kHz)
– Frequencies used by toothed whales.
• Very high frequencies (100 kHz upwards) the dominant noise
source is thermal noise.
– Some frequencies used by toothed whales.

15. Man-Made Sound Sources
• Man’s increasing exploitation of marine resources has led to
an increase of noise:
Acute Sources:
– Seismic Surveys
– Construction
– Military Sonar
Chronic Sources:
– Shipping
Very loud, short term (days/weeks/months)
sources
“Easy” to mitigate against – control each process
to minimise impact, clear lines of responsibility.
Less intense, but long-term noise.
“Hard” to mitigate against: not the “responsibility”
of a single source.

16. Possible Impacts
No detection
Detection
Masking
Reaction
Injury
Death
Source
Blues: Behavioural impacts
Reds: Clear physiological impacts

17. Mass Strandings
• Historically mass strandings of whales take place – some
species are much more prone to this phenomenon than others.
1577 1902
2017 (New Zealand)

18. Military Sonar
• The use of mid-frequency active sonar has, almost certainly,
caused the death of beaked whales.
• Several notorious instances:
– Mediterranean, 1996 (12).
– Bahamas, 2000 (15).
– Canary Islands, 2002 (14)
& 2004 (4)
http://www.nmfs.noaa.gov/prot_res/overview/Interim_Bahamas_Report.pdf

19. Beaked Whales (21 sp.)
• These are extraordinary creatures.
• Only recently been intensively studied
(not until their deaths were linked to
sonar).
• They are deep diving (0.5-2 km), with
dives typically lasting an hour.
– Dives are conducted to feed on squid.
• The deepest recorded average dives of
any marine mammal.
• Mass strandings have historically rarely
recorded.

20. Possible Causes of Death
• These animals have a regular pattern of deep
dives interspersed with sequences of shallow
dives.
• It is not believed that the sonar directly causes
physical trauma.
• Rather the sonar causes a behavioural reaction
which leads to death.

21. Seismic Surveys
• Exploration for oil deposits at sea involves the use of loud
sound sources.
• This would seem to disturb animals, e.g. causing displacement,
but no (little) evidence of injury.

22. Construction
• In particular, off-shore wind farm construction is a major
cause for concern.
• The UK is about to embark on phase II of wind farm
construction in the North Sea.
• Primary concern is during the construction phase – pile
driving.

23. Trends in Shipping Traffic
Increased commercial activity over
the last 40 years has lead to an
increase in the number of ships and
their gross tonnage.
Source – “Ocean Noise: Turn it down, A report on ocean
noise pollution” IFAW 2008.

24. Trends in Shipping Noise
• Various studies [1-3] (at a small number of sites) have
suggested that there has been an increase in the ambient noise
level in the low frequency band (10-100 Hz).
• This trend equates to an increase of approximately 3 dB per
decade.
• This increase has been attributed to an increase in ship traffic.
• Not at all clear this trend is continuing.
[1] R. K. Andrew, B. M. Howe, and J. A. Mercer, "Long-time trends in low-frequency traffic noise for four sites off the North
American west coast” (abstract) The Journal of the Acoustical Society of America, vol. 127, 1783, 2010.
[2] R. K. Andrew, B. M. Howe, J. A. Mercer, and M. A. Dzieciuch, "Ocean ambient sound: Comparing the 1960s with the
1990s for a receiver off the California coast," Acoustics Research Letters Online, vol. 3, 65-70, 2002.
[3] M. A. McDonald, J. Hildebrand, and S. M. Wiggins, "Increases in deep ocean ambient noise in the Northeast Pacific west
of San Nicolas Island, California," The Journal of the Acoustical Society of America, vol. 120, 711-718, 2006.

25. Blue Whales and Ship Noise
• Blues whales produce a regular pulsed call.
• A whale at 80 km range an ocean with noise
level equivalent to a 1960s level:
×20
×20
• A whale at 100 km range an ocean with
noise level equivalent to a 1960s level:
×20
• The increase in noise between 1960 and
2010 reduces the range that blue whale
calls can be detected to 10% of the orignal
range (reduction to 1% of the area).

26. The Converse Argument
• The number of whales was dramatically reduced due to
whaling in the 20th century.
• So in 1900 there were many more whales, but much less noise,
whereas in 2010 there are fewer whales and more noise.
2010 1900

27. Adaptations
• In response to high noise environments marine mammals have
been shown to be capable of adapting the vocal behaviour to a
limited extent.
• This includes changing the pitch of vocalisations and changes
in levels of the emitted sounds.
– The assumption is commonly made that animals have evolved to such
that their vocalisations are optimised in some way.
– By altering their vocalisations to compensate for increased noise the
assumption is that the vocalisations are in some sense less efficient.

28. Possible Effects of
Increased Ambient Noise Levels
• An increase in the level of ambient noise could cause the
masking of source, which may:
– Inhibit the ability of one animal to hear the calls of conspecifics.
– Calls of predators may be masked.
– Baleen whales may exploit ambient sounds in the ocean to orient
themselves and aid navigation.
• In humans increased background noise levels is associated
with increase stress levels, which have health impacts.
– Recent work on Northern Right Whales (population ca 300 individuals)
shows increased stress hormones in the proximity to shipping lanes.

29. Shipping Noise
“Impact” of 1 Ship on 1 Whale
N. Aguilar, M. Johnson, P. T. Madsen, P. Tyack, A. Bocconcelli, and J. F. Borsani, "Does intensive ship noise disrupt foraging
in deep-diving Cuvier's beaked whales (Ziphius cavirostris)?," Marine Mammal Science, vol. 22, pp. 690-699, 2006.
Passage of noisy ship
Cuvier’s beaked whale
(Ziphius cavirostris)

30. Conclusions
• Increases anthropogenic noise have the potential to cause harm
in the marine environment.
– There is very little definitive evidence of this, but much concern
(absence of evidence is not evidence of absence).
• Judging the impact is very difficult at the population level.
• There are many potential factors influencing the impact of
sound.
• There is little know about the impact of sound on the vast
majority of marine species.

33. Frequency Weightings
• In air-borne acoustics A-weightings are extensively used to
reflect the frequency selectivity of the human ear.
• A-weightings are based on equal-loudness contours.
– They are based around the 40 phon contour – relatively quiet.
• Other weightings for human perceptions are used.
• One approach to assessing impacts of sounds in marine
mammals is based on weighting sounds according to species
audiograms (Malme, et al., 1984), later dubbed the dBht.
• This approach has not been widely adopted, partly because of
uncertainties in the audiogram data.
Malme, C. I., et al., (1984). “Investigations of the potential effects of underwater noise from petroleum industry activities on
migrating gray whale behavior. Phase II: January 1984 migration” BBN Report No. 5586; NTIS PB86-218377.

34. M-Weightings
• A widely accepted approach is based on M-weightings.
• M-weightings consider cetaceans in 3 species groups based on
their hearing capabilities.
– There are also 2 further weightings for pinnipeds (seals and sea-lions)
one for in-water hearing and one for in-air hearing.
• These groupings are:
– Low frequency cetaceans
• The baleen whales
– Mid-frequency cetaceans
• Oceanic dolphins, sperm whales, beaked whales, blackfish, etc
– High-frequency cetaceans
• Porpoises and small dolphins
“Marine Mammal Noise Exposure Criteria: Initial Scientific Recommendations” Brandon L. Southall, Ann E. Bowles, William
T. Ellison, James J. Finneran, Roger L. Gentry, Charles R. Greene Jr., David Kastak, Darlene R. Ketten, James H. Miller, Paul E
Nachtigall, W. John Richardson, Jeanette A. Thomas & Peter L. Tyack, Special Issue Aquatic Mammals, 33(4), 2007.

35. M-Weighting Curves
• The weighting curves are 2nd order band-pass filters, defined
by 2 parameters:
– flow and fhigh which define the upper and lower hearing limits for the
species group, these roll-off at 12 dB/octave.
– The form is the same as human C-weighting curves.
• M-weighting curves have the following shapes
Low frequency
cetaceans
(baleen whales)
Mid-frequency
cetaceans
(e.g. dolphins)
High frequency
cetaceans
(e.g. porpoises)

36. Criteria Based on M-Weightings
• Alongside the M-weighting curves there are criteria proposed
to assess whether a sound has an impact: injury or behavioural
response.
• For injury the criteria is based on an M-weighted SEL (source
equivalent level) of 215 dB re 1 mPa2 s.
– This is based on measured levels that induce Temporary Threshold
Shifts (TTS) in marine mammals (195 dB re 1 mPa2 s).
– In humans PTS (Permanent Threshold Shifts) occurs 20 dB above the
inception of TTS, hence the 215 dB re 1 mPa2 s value.
• Behavioural responses, there are no clear criteria.

37. Observed Behavioural Reactions
• For low frequency cetaceans (baleen whales), field
observations suggest the following:
– Levels of 90 to 120 dB re 1 mPa induce no response.
– Between 120 and 160 dB re 1 mPa do induce responses
• The form and “strength” of the response varies with context
and the stimulus.
• Not just baleen whales may be affected by low frequency
sounds.
– Harbour porpoise, which are high frequency animals, react to and are
affected by low frequency sounds, e.g.
• TTS in porpoises has been shown to occur at SELs of 164 dB re 1 mPa2 s
for 4 kHz (Lucke et al., 2009).
Lucke K., Siebert, U., Lepper, P.A. and Blanchet M. “Temporary shift in masked hearing thresholds in a harbor porpoise
(Phocoena phocoena) after exposure to seismic airgun stimuli”, J. Acoust. Soc. Am., 125(6), (2009).

38. Comments on M-Weightings
• Suitable for assessing impacts of intense sounds (sonar, pile
driving, seismic surveys).
• Shipping noise is unlikely to induce injury, see later, it potential
induces a behavioural response: where the M-weighting criteria
are less certain.
• Defining a level which produces a significant behavioural
response is very difficult:
– What constitutes a “significant” impact?
– What species is involved?
– What is the context?
– What factors other than received level should be considered?
– ……….

39. Sources of Underwater
Noise from Ships
• Cavitation
– At high speeds (above the cavitation inception speed (CIS)) cavitation
is certainly the dominant noise source.
• Machinery Noise
– Mainly in the form of tonal lines primarily in the low frequency band.
• Flow noise
– Hydro-dynamic noise of the hull moving through the water, very low
frequency.
• Noisy ships may emit a wide range of frequency
– The ship that disturbed the beaked whale emitted noise in the ultrasonic
region (10s kHz).

40. Ship Noise Spectrum
Data supplied by TSI

41. M-Weightings to Assess Potential
Injury from Cruise Ship Noise
• The weighted noise
spectrum recorded
at 10 knots.
• The criterion for TTS, from non-pulsed sounds, is an SEL of
195 dB re 1 mPa-s.
• If an animal stays at within 100 m, it would take 3.5 days
before inducing a temporary threshold shift!

42. Definitions of SL
• Traditionally underwater acoustic sources have been measured
through their source level (SL).
• However the use of the SL can lead to misunderstandings and
confusion.
• The concept of SL has not been “well” standardised
IEC definition is:
“Sound pressure level on the axis of a sound projector at the
reference distance of 1 metre, unless otherwise specified, from
the effective acoustic centre of the projector.”
ANSI definition is:
“[the SPL] on the axis of the sound projector at a reference
distance of 1 meter from [a specified point associated with] the
projector”

43. A Fuller Definition of SL
• The source level is based on a far-field measurement which is
back-projected to 1 m, it is NOT the SPL at 1 m* from the
acoustic centre of the source.
– Practitioners understand this as being implied and one might reasonably
conjecture that the reason for the flaws in the ANSI and IEC standards.
• A fuller (imperfect) definition might be:
– The SL is the (hypothetical) SPL, measured at distance 1 m, from a
monopole source in a homogeneous medium whose character matches
the far-field character of the source under examination.
* 1 m is the almost universal reference distance, others can be used without significantly changing the discussion. Note
that the 1 m distance is often meaningless. For example machinery noise may have an acoustic centre which is within the
of the vessel and so in many circumstances the reference point, 1 m from the acoustic centre is also within the vessel.

44. Marine Mammal Hearing
• Marine mammal hearing is believed to share many features
with the hearing of terrestrial mammals.
• There are inherent difficulties in conducting hearing tests on
such animals.
• Many tests have been conducted on a few species/individuals,
e.g. bottlenose dolphins.
• These tests are either based:
– Behavioural responses, requiring trained (and hence captive) animals
– Electrophysiological, can be performed on captive or stranded animals.
• Many species hearing tests have not been possible so far, in
particular the hearing of baleen whales is poorly understood.
– May infer something regarding the range of hearing from the frequency
range of vocalisations in that species.

45. Audiograms of Marine Mammals
• The audiograms of
marine mammals have a
similar general shape to
those of other mammals (inc.
humans).
• These audiograms are subject to considerable uncertainty
– There are concerns about masking effects in some frequency bands.
– Normally very few individuals of a species have been measured – some
times in unnatural conditions, e.g. stranded animals.

46. Measurement of the SL
• If one can measure the source in free-field conditions then
computing the SL is trivial.
• Realistically in underwater acoustics this has been
approximated by making measurements in deep water away
from boundaries.
– For small source and high frequencies, this is feasible, for ships it is
generally not.
• Ship noise is always observed in the presence of a highly
reflective (pressure release) boundary: the sea surface.
• For ships is reasonable to measure a level for the dipole source
and not seek to compute the equivalent monopole level.

47. An Alternative to the
Source Level
• An alternative to the SL is to referred to the source product
and avoids some of the potential ambiguity.
• Numerically these two are the same (under the assumption of a
lossless spherical spreading model).
– It is a re-interpretation, not a different measure!
• The source product, S, in linear terms is
where r is the range and prms is the rms pressure, this can be
converted in dB in the usual way.
S=rprms

48. Measuring Ship Noise
• The problems with measuring ship noise have meant that
dedicated standards are appropriate.
• Recently several such standards/formal protocols have begun
to emerge.
– ICES Standard for Research Vessels (1995)
– ANSI “Quantities and Procedures for Description and Measurement of
Underwater Sound from Ships” S12.64 (2009)
– DNV “Silent Class Notation” (2010)
– ISO Standard Under-development
• These standards effectively compute the dipole SL assuming a
spherical spreading model (although they do not explicitly
state this).

49. Summary of
Measurement Standards
• Water depth:
– ANSI (Grade A: 300 m, B: 150 m, C: 75 m)
– DNV (30 m beneath the keel)
– ICES (Ideally 80-100 m)
• Hydrophone positioning
– ANSI (Suspended in the water column: A&B 3 ‘phones, C 1 ‘phone )
– DNV (Bottom mounted)
– ICES (Suspended or bottom mounted)
• Measurement position:
– ANSI (CPA should be > 100 m)
– DNV (CPA 150 m – 250 m)

50. Acoustic Problems
• Problems at low frequency, e.g. at 10 Hz, l ~ 150 m (note flow
for low frequency cetacean M-weighting curve is 7 Hz).
– Need to be at sufficient range to ensure you are in the far-field of a
source, usually the near-field boundary  d2/l (d is the dimension of
the source
– At longer ranges you need sufficient water depth to be above the modal
cut-on frequency, ~ 40 m (l/4).
• Source directivity:
– Horizontal directivity: In many cases the measurement protocols
specify measurements should be made at CPA: such measurements are
made broad-side to the ship. In some instances a source may have a
directivity such that the acoustic axis is not broadside to the vessel.
– Vertical directivity: Dipole radiation ensures that the sources will have
vertical directivity. This will most affect measurements made at a
single depth, with a single hydrophone.

51. Factors Affecting Ship Noise
• The noise from a vessel depends on a range of factors,
including:
– Weather, sea state, condition of the vessel (fouling/damage), speed,
loading of the vessel, …