Anthropogenic noise in the world's oceans is known to impede many species' ability to perceive acoustic signals, but little research has addressed how this noise affects the perception of bioacoustic signals used for communication in marine mammals. Bottlenose dolphins (Tursiops truncatus) use signature whistles containing identification information. Past studies have used human participants to gain insight into dolphin perception, but most previous research investigated echolocation. In Experiment 1, human participants were tested on their ability to discriminate among signature whistles from three dolphins. Participants' performance was nearly errorless. In Experiment 2, participants identified signature whistles masked by five different samples of boat noise utilizing different signal-to-noise ratios. Lower signal-to-noise ratio and proximity in frequency between the whistle and noise both significantly decreased performance. Like dolphins, human participants primarily identified whistles using frequency contour. Participants reported greater use of amplitude in noise-present vs noise-absent trials, but otherwise did not vary cue usage. These findings can be used to generate hypotheses about dolphins' performance and auditory cue use for future research. This study may provide insight into how specific characteristics of boat noise affect dolphin whistle perception and may have implications for conservation and regulations.

1.
Albuquerque
,
N. d. S.
, and
Souto
,
A.
(
2013
). “
Motorboat noise can potentially mask the whistle sound of estuarine dolphins (Sotalia guianensis)
,”
Ethnobiol. Conserv.
2
,
1
15
.
2.
Arbogast
,
T. L.
,
Mason
,
C. R.
, and
Kidd
,
G.
(
2002
). “
The effect of spatial separation on informational and energetic masking of speech
,”
J. Acoust. Soc. Am.
112
(
5
),
2086
2098
.
3.
Au
,
W. W. L.
(
1993
).
The Sonar of Dolphins
(
Springer-Verlag
,
Berlin
).
4.
Au
,
W. W. L.
, and
Martin
,
D. W.
(
1989
). “
Insights into dolphin sonar discrimination capabilities from human listening experiments
,”
J. Acoust. Soc. Am.
86
(
5
),
1662
1670
.
5.
Au
,
W. W. L.
,
Moore
,
P. W. B.
, and
Pawloski
,
D. A.
(
1988
). “
Detection of complex echoes in noise by an echolocating dolphin
,”
J. Acoust. Soc. Am.
83
(
2
),
662
668
.
6.
Au
,
W. W. L.
, and
Penner
,
R. H.
(
1981
). “
Target detection in noise by echolocating Atlantic bottlenose dolphins
,”
J. Acoust. Soc. Am.
70
(
3
),
687
693
.
7.
Bee
,
M. A.
(
2007
). “
Sound source segregation in grey treefrogs: Spatial release from masking by the sound of a chorus
,”
Anim. Behav.
74
,
549
558
.
8.
Bee
,
M. A.
, and
Riemersma
,
K. K.
(
2008
). “
Does common spatial origin promote the auditory grouping of temporally separated signal elements in grey treefrogs?
,”
Anim. Behav.
76
(
3
),
831
843
.
9.
Branstetter
,
B. K.
,
Bakhtiari
,
K.
,
Black
,
A.
,
Trickey
,
J. S.
,
Finneran
,
J. J.
, and
Aihara
,
H.
(
2016a
). “
Energetic and informational masking of complex sounds by a bottlenose dolphin (Tursiops truncatus
),”
J. Acoust. Soc. Am.
140
(
3
),
1904
1917
.
10.
Branstetter
,
B. K.
,
DeLong
,
C. M.
,
Dziedzic
,
B.
,
Black
,
A.
, and
Bakhtiari
,
K.
(
2016b
). “
Recognition of frequency modulated whistle-like sounds by a bottlenose dolphin (Tursiops truncatus) and humans with transformations in amplitude, duration and frequency
,”
PloS One
11
(
2
),
e0147512
.
11.
Branstetter
,
B. K.
,
Trickey
,
J. S.
,
Aihara
,
H.
,
Finneran
,
J. J.
, and
Liberman
,
T. R.
(
2013a
). “
Time and frequency metrics related to auditory masking of a 10 kHz tone in bottlenose dolphins (Tursiops truncatus
),”
J. Acoust. Soc. Am.
134
(
6
),
4556
4565
.
12.
Branstetter
,
B. K.
,
Trickey
,
J. S.
,
Bakhtiari
,
K.
,
Black
,
A.
,
Aihara
,
H.
, and
Finneran
,
J. J.
(
2013b
). “
Auditory masking patterns in bottlenose dolphins (Tursiops truncatus) with natural, anthropogenic, and synthesized noise
,”
J. Acoust. Soc. Am.
133
(
3
),
1811
1818
.
13.
Buckstaff
,
K. C.
(
2004
). “
Effects of watercraft noise on the acoustic behavior of bottlenose dolphins, Tursiops truncatus, in Sarasota Bay, Florida
,”
Mar. Mammal Sci.
20
(
4
),
709
725
.
14.
Caldwell
,
M.
, and
Caldwell
,
D.
(
1965
). “
Individualized whistle contours in bottle-nosed dolphins (Tursiops trancatus
),”
Nature
207
,
434
435
.
15.
Cook
,
M. L. H.
,
Sayigh
,
L. S.
,
Blum
,
J. E.
, and
Wells
,
R. S.
(
2004
). “
Signature-whistle production in undisturbed free-ranging bottlenose dolphins (Tursiops truncatus
),”
Proc. Royal Soc. B
271
,
1043
1049
.
16.
Darwin
,
C. J.
(
1997
). “
Auditory grouping
,”
Trends Cog. Sci.
1
(
9
),
327
333
.
17.
David
,
J. A.
(
2006
). “
Likely sensitivity of bottlenose dolphins to pile-driving noise
,”
Water Environ. J.
20
(
1
),
48
54
.
18.
DeLong
,
C. M.
(
2017
). “
Human listening experiments provide insight into cetacean auditory perception
,”
Proc. Mtgs. Acoust.
29
(
1
),
010001
.
19.
DeLong
,
C. M.
,
Au
,
W. W. L.
,
Harley
,
H. E.
,
Roitblat
,
H. L.
, and
Pytka
,
L.
(
2007a
). “
Human listeners provide insights into echo features used by dolphins (Tursiops truncatus) to discriminate among objects
,”
J. Comp. Psychol.
121
(
3
),
306
319
.
20.
DeLong
,
C. M.
,
Au
,
W. W. L.
, and
Stamper
,
S. A.
(
2007b
). “
Echo features used by human listeners to discriminate among objects that vary in material or wall thickness: Implications for echolocating dolphins
,”
J. Acoust. Soc. Am.
121
(
1
),
605
617
.
21.
DeLong
,
C. M.
,
Heberle
,
A. L.
,
Wisniewski
,
M. G.
, and
Mercado
,
E.
(
2014
). “
The ability to recognize objects from bottlenose dolphin (Tursiops truncatus) echoes generalizes across multiple orientations in humans and neural networks
,”
Anim. Cogn.
17
(
3
),
543
557
.
22.
Egan
,
J. P.
, and
Hake
,
H. W.
(
1950
). “
On the masking pattern of a simple auditory stimulus
,”
J. Acoust. Soc. Am.
22
(
5
),
622
630
.
23.
Fish
,
J. F.
,
Johnson
,
C. S.
, and
Ljungblad
,
D. K.
(
1976
). “
Sonar target discrimination by instrumented human divers
,”
J. Acoust. Soc. Am.
59
(
3
),
602
606
.
24.
Gorman
,
R. P.
, and
Sawatari
,
T.
(
1985
). “
The use of multidimensional perceptual models in the selection of sonar echo features
,”
J. Acoust. Soc. Am.
77
(
3
),
1178
1184
.
25.
Green
,
D. M.
(
1960
). “
Psychoacoustics and detection theory
,”
J. Acoust. Soc. Am.
32
(
10
),
1189
1203
.
26.
Green
,
D. M.
(
1993
). “
Auditory intensity discrimination
,” in
Human Psychophysics
, edited by
W. A.
Yost
,
A. N.
Popper
, and
R. R.
Fay
(
Springer
,
New York
), pp.
13
55
.
27.
Gridley
,
T.
,
Cockcroft
,
V.
,
Hawkins
,
E. R.
,
Lemon Blewitt
,
M.
,
Morisaka
,
T.
, and
Janik
,
V. M.
(
2014
). “
Signature whistles in free ranging populations of Indo-Pacific bottlenose dolphins, Tursiops aduncus
,”
Mar. Mammal Sci.
30
(
2
),
512
527
.
28.
Harley
,
H. E.
(
2008
). “
Whistle discrimination and categorization by the Atlantic bottlenose dolphin (Tursiops truncatus): A review of the signature whistle framework and a perceptual test
,”
Behav. Process.
77
(
2
),
243
268
.
29.
Helweg
,
D. A.
,
Roitblat
,
H. L.
,
Nachtigall
,
P. E.
,
Au
,
W. W. L.
, and
Irwin
,
R. J.
(
1995
). “
Discrimination of echoes from aspect-dependent targets by a bottlenose dolphin and human listeners
,” in
Sensory Systems of Aquatic Mammals
, edited by
R. A.
Kastelein
,
J. A.
Thomas
, and
P. E.
Nachtigall
(
De Spil Publishers
,
Woerden
), pp.
129
136
.
30.
Herman
,
L. M.
, and
Arbeit
,
W. R.
(
1972
). “
Frequency difference limens in the bottlenose dolphin: 1–70 kc/s
,”
J. Aud. Res.
2
,
109
120
.
31.
Herzing
,
D. L.
(
1996
). “
Vocalizations and associated underwater behavior of free-ranging Atlantic spotted dolphins, Stenella frontalis and bottlenose dolphins, Tursiops truncatus
,”
Aquat. Mamm.
22
,
61
80
.
32.
Holm
,
S.
(
1979
). “
A simple sequentially rejective multiple test procedure
,”
Scand. J. Stat.
6
(
2
),
65
70
.
33.
Holt
,
M. M.
, and
Schusterman
,
R. J.
(
2007
). “
Spatial release from masking of aerial tones in pinnipeds
,”
J. Acoust. Soc. Am.
121
(
2
),
1219
1225
.
34.
Janik
,
V. M.
(
1999
). “
Pitfalls in the categorization of behaviour: A comparison of dolphin whistle classification methods
,”
Anim. Behav.
57
(
1
),
133
143
.
35.
Janik
,
V. M.
,
Dehnhardt
,
G.
, and
Todt
,
D.
(
1994
). “
Signature whistle variations in a bottlenosed dolphin, Tursiops truncatus
,”
Behav. Ecol. Sociobiol.
35
,
243
248
.
36.
Janik
,
V. M.
,
King
,
S. L.
,
Sayigh
,
L. S.
, and
Wells
,
R. S.
(
2013
). “
Identifying signature whistles from recordings of groups of unrestrained bottlenose dolphins (Tursiops truncatus)
,”
Mar. Mammal Sci.
29
(
1
),
109
122
.
37.
Janik
,
V. M.
, and
Sayigh
,
L. S.
(
2013
). “
Communication in bottlenose dolphins: 50 years of signature whistle research
,”
J. Compar. Physl. A
199
,
479
489
.
38.
Janik
,
V. M.
,
Sayigh
,
L. S.
, and
Wells
,
R. S.
(
2006
). “
Signature whistle shape conveys identity information to bottlenose dolphins
,”
P. Natl. A. Sci. USA
103
(
21
),
8293
8297
.
39.
Janik
,
V. M.
, and
Slater
,
P. J.
(
1998
). “
Context-specific use suggests that bottlenose dolphin signature whistles are cohesion calls
,”
Anim. Behav.
56
(
4
),
829
838
.
40.
Johnson
,
C. S.
(
1968
). “
Masked tonal thresholds in the bottlenosed porpoise
,”
J. Acoust. Soc. Am.
44
(
4
),
965
967
.
41.
Kaplan
,
M. B.
, and
Mooney
,
T. A.
(
2015
). “
Ambient noise and temporal patterns of boat activity in the US Virgin Islands National Park
,”
Mar. Pollut. Bull.
98
(
1
),
221
228
.
42.
Kashino
,
M.
(
2006
). “
Phonemic restoration: The brain creates missing speech sounds
,”
Acoust. Sci Technol.
27
(
6
),
318
321
.
43.
Kershenbaum
,
A.
,
Sayigh
,
L. S.
, and
Janik
,
V. M.
(
2013
). “
The encoding of individual identity in dolphin signature whistles: How much information is needed?
,”
PloS One
8
(
10
),
e77671
.
44.
Kidd
,
G.
,
Mason
,
C. R.
,
Swaminathan
,
J.
,
Roverud
,
E.
,
Clayton
,
K. K.
, and
Best
,
V.
(
2016
). “
Determining the energetic and informational components of speech-on-speech masking
,”
J. Acoust. Soc. Am.
140
(
1
),
132
144
.
45.
King
,
S. L.
, and
Janik
,
V. M.
(
2013
). “
Bottlenose dolphins can use learned vocal labels to address each other
,”
P. Natl. A. Sci. USA
110
(
32
),
13216
13221
.
46.
Lemonds
,
D. W.
,
Au
,
W. W. L.
,
Vlachos
,
S. A.
, and
Nachtigall
,
P. E.
(
2012
). “
High-frequency auditory filter shape for the Atlantic bottlenose dolphin
,”
J. Acoust. Soc. Am.
132
(
2
),
1222
1228
.
47.
Lemonds
,
D. W.
,
Kloepper
,
L. N.
,
Nachtigal.
P. E.
,
Au
,
W. W. L.
,
Vlachos
,
S. A.
, and
Branstetter
,
B. K.
(
2011
). “
A re-evaluation of auditory filter shape in delphinid odontocetes: Evidence of constant-bandwidth filters
,”
J. Acoust. Soc. Am.
130
(
5
),
3107
3114
.
48.
Lusseau
,
D.
(
2003
). “
Effects of tour boats on the behavior of bottlenose dolphins: Using Markov chains to model anthropogenic impacts
,”
Conserv. Biol.
17
(
6
),
1785
1793
.
49.
Marshall
,
L.
, and
Jesteadt
,
W.
(
1986
). “
Comparison of pure-tone audibility thresholds obtained with audiological and two-interval forced-choice procedures
,”
J. Speech Lang. Hear. R.
29
(
1
),
82
91
.
50.
Marine Mammal Protection Act
, 16 USC §§ 1361 et seq. (
1972
).
51.
McCambridge
,
J.
,
de Bruin
,
M.
, and
Witton
,
J.
(
2012
). “
The effects of demand characteristics on research participant behaviours in non-laboratory settings: A systematic review
,”
PloS One
7
(
6
),
e39116
.
52.
Mercado
,
E.
 III.
, and
DeLong
,
C. M.
(
2010
). “
Dolphin cognition: Representations and processes in perception and memory
,”
Int. J. Comp. Psychol.
23
,
344
378
.
53.
Muller-Gass
,
A.
,
Marcoux
,
A.
,
Logan
,
J.
, and
Campbell
,
K. B.
(
2001
). “
The intensity of masking noise affects the mismatch negativity to speech sounds in human subjects
,”
Neurosci. Lett.
299
(
3
),
197
200
.
54.
Nelken
,
I.
,
Rotman
,
Y.
, and
Yosef
,
O. B.
(
1999
). “
Responses of auditory-cortex neurons to structural features of natural sounds
,”
Nature
397
,
154
157
.
55.
Petkov
,
C. I.
,
O'Connor
,
K. N.
, and
Sutter
,
M. L.
(
2003
). “
Illusory sound perception in macaque monkeys
,”
J. Neurosci.
23
(
27
),
9155
9161
.
56.
Pirotta
,
E.
,
Merchant
,
N. D.
,
Thompson
,
P. M.
,
Barton
,
T. R.
, and
Lusseau
,
D.
(
2015
). “
Quantifying the effect of boat disturbance on bottlenose dolphin foraging activity
,”
Biol. Conserv.
181
,
82
89
.
57.
Popov
,
V. V.
,
Supin
,
A. Ya.
,
Gvozdeva
,
A. P.
,
Nechaev
,
D. I.
,
Tarakanov
,
M. B.
, and
Sysueva
,
E. V.
(
2020
). “
Spatial release from masking in a bottlenose dolphin Tursiops truncatus
,”
J. Acoust. Soc. Am.
147
(
3
),
1719
1726
.
58.
Quick
,
N. J.
, and
Janik
,
V. M.
(
2008
). “
Whistle rates of wild bottlenose dolphins (Tursiops truncatus): Influences of group size and behavior
,”
J. Comp. Psychol.
122
(
3
),
305
311
.
59.
Quick
,
N. J.
, and
Janik
,
V. M.
(
2012
). “
Bottlenose dolphins exchange signature whistles when meeting at sea
,”
P. Roy. Soc. B-Biol. Sci.
279
(
1738
),
2539
2545
.
60.
Raudenbush
,
S. W.
, and
Bryk
,
A. S.
(
2002
).
Hierarchical Linear Models: Applications and Data Analysis Methods
(
Sage
,
California
).
61.
Ross
,
D.
(
2005
). “
Ship sources of ambient noise
,”
IEEE J. Oceanic Eng.
30
(
2
),
257
261
.
62.
Sayigh
,
L. S.
,
Esch
,
H. C.
,
Wells
,
R. S.
, and
Janik
,
V. M.
(
2007
). “
Facts about signature whistles of bottlenose dolphins, Tursiops truncatus
,”
Anim. Behav.
74
(
6
),
1631
1642
.
63.
Sayigh
,
L. S.
, and
Janik
,
V. M.
(
2010
). “
Dolphin signature whistles
,” in
Encyclopedia of Animal Behavior
, edited by
M. D.
Breed
and
J.
Moore
(
Academic Press
,
Oxford
), pp.
553
561
.
64.
Sayigh
,
L. S.
,
Tyack
,
P. L.
,
Wells
,
R. S.
, and
Scott
,
M. D.
(
1990
). “
Signature whistles of free-ranging bottlenose dolphins, Tursiops truncatus: Stability and mother-offspring comparisons
,”
Behav. Ecol. Sociobiol.
26
(
4
),
247
260
.
65.
Sayigh
,
L. S.
,
Tyack
,
P. L.
,
Wells
,
R. S.
,
Solow
,
A. R.
,
Scott
,
M. D.
, and
Irvine
,
A. B.
(
1999
). “
Individual recognition in wild bottlenose dolphins: A field test using playback experiments
,”
Anim. Behav.
57
(
1
),
41
50
.
66.
Sayigh
,
L. S.
,
Wells
,
R. S.
, and
Janik
,
V. M.
(
2017
). “
What's in a voice? Dolphins do not use voice cues for individual recognition
,”
Anim. Cogn.
20
(
6
),
1067
1079
.
67.
Seeba
,
F.
, and
Klump
,
G. M.
(
2009
). “
Stimulus familiarity affects perceptual restoration in the European starling (Sturnus vulgaris)
,”
PloS One
4
(
6
),
e5974
.
68.
Seeba
,
F.
,
Schwartz
,
J. J.
, and
Bee
,
M. A.
(
2010
). “
Testing an auditory illusion in frogs: Perceptual restoration or sensory bias?
,”
Anim. Behav.
79
,
1317
1328
.
69.
Shah
,
N. J.
,
Jäncke
,
L.
,
Grosse-Ruyken
,
M. L.
, and
Müller-Gärtner
,
H. W.
(
1999
). “
Influence of Acoustic masking noise in fMRI of the auditory cortex during phonetic discrimination
,”
J. Magn. Reson. Imaging
9
(
1
),
19
25
.
70.
Speltz
,
M. L.
, and
Bernstein
,
D. A.
(
1976
). “
Sex differences in fearfulness: Verbal report, overt avoidance and demand characteristics
,”
J. Behav. Ther. Exp. Psy.
7
(
2
),
117
122
.
71.
Sugita
,
Y.
(
1997
). “
Neuronal correlates of auditory induction in the cat cortex
,”
Neuroreport
8
(
5
),
1155
1159
.
72.
Thompson
,
R. K. R.
, and
Herman
,
L. M.
(
1975
). “
Underwater frequency discrimination in the bottlenosed dolphin (1–140 kHz) and the human (1–8 kHz)
,”
J. Acoust. Soc. Am.
57
(
4
),
943
948
.
73.
Tukey
,
J.
(
1949
). “
Comparing individual means in the analysis of variance
,”
Biometrics
5
(
2
),
99
114
.
74.
Vasconcelos
,
R. O.
,
Amorim
,
M. C. P.
, and
Ladich
,
F.
(
2007
). “
Effects of ship noise on the detectability of communication signals in the Lusitanian toadfish
,”
J. Exp. Biol.
210
(
12
),
2104
2112
.
75.
Warren
,
R. M.
(
1984
). “
Perceptual restoration of obliterated sounds
,”
Psychol. Rev.
96
,
2016
2022
.
76.
Warren
,
R. M.
, and
Obusek
,
C. J.
(
1971
). “
Speech perception and phonemic restoration
,”
Percept. Psychophys.
9
,
358
362
.
77.
Watwood
,
S. L.
,
Tyack
,
P. L.
, and
Wells
,
R. S.
(
2004
). “
Whistle sharing in paired male bottlenose dolphins, Tursiops truncatus
,”
Behav. Ecol. Sociobiol.
55
(
6
),
531
543
.
78.
Wier
,
C. C.
,
Jesteadt
,
W.
, and
Green
,
D. M.
(
1977
). “
Frequency discrimination as a function of frequency and sensation level
,”
J. Acoust. Soc. Am.
61
(
1
),
178
184
.
79.
Würsig
,
B.
, and
Richardson
,
W. J.
(
2009
). “
Noise, Effects of
,” in
Encyclopedia of Marine Mammals
, 2nd ed. (
Academic Press
,
London
), pp.
765
773
.
You do not currently have access to this content.