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Twelve years of tracking 52-Hz whale calls from a unique source in the North Pacific


Abstract and Figures

A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones.
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Deep-Sea Research I 51 (2004) 1889–1901
Twelve years of tracking 52-Hz whale calls from a unique
source in the North Pacific
William A. Watkins, Mary Ann Daher
, Joseph E. George, David Rodriguez
Woods Hole Oceanographic Institution, MS 36, Woods Hole, MA 02543, USA
Received 2 March 2004; accepted 5 August 2004
Available online 12 October 2004
A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and
eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded
by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in
1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in
the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been
recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from
August to February with most in December and January. The species producing these calls is unknown. The tracks of
the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from
0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C)
mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other
whale species (blue, fin and humpback) monitored year-round with the same hydrophones.
r2004 Elsevier Ltd. All rights reserved.
Keywords: Acoustic tracking; 52-Hz whale calls; Underwater sounds; Whale tracking
1. Introduction
Biological sounds with emphasis near 50–52 Hz
were recorded over the last fifteen years from a
single source in the deep waters across the North
Pacific basin. These calls, referred to here as 52-Hz
calls, were identified during systematic monitoring
of whale sounds from US Navy Sound Surveil-
lance System (SOSUS) and other hydrophone
arrays (Watkins et al., 2000a, b, 2001). Studies of
the occurrence of calling whales in these waters
were conducted by the Navy beginning in the late
1980s, and a systematic monitoring program by
the Woods Hole Oceanographic Institution
(WHOI) has continued since 1995. The 52-Hz
calls were initially reported by Watkins et al.
0967-0637/$ - see front matter r2004 Elsevier Ltd. All rights reserved.
Corresponding author. Tel.: +1 508 289 3258; fax:
+1 508 457 2169.
E-mail address: (M.A. Daher).
(2000b), and were assumed to be produced by a
whale because of their somewhat similar charac-
teristics to known sounds from baleen whales.
These 52-Hz calls also have been noted on
geophysical hydrophones in the Gulf of Alaska
by NOAA Pacific Marine Environmental Labora-
tory’s Vents Program (2003) with sample calls
displayed on the Web. The calls have been
consistently distinctive and readily identifiable,
and their source has been tracked seasonally
during the last 12 years.
Low-frequency underwater sounds from indivi-
dual whales have been recorded and tracked since
the 1950s by means of US Navy SOSUS and other
hydrophone installations in the North Atlantic
(cf. Walker, 1963;Schevill et al., 1964;Patterson
and Hamilton, 1964;Watkins, 1981;Watkins
et al., 1987) and in the North Pacific
(cf. Kibblewhite et al., 1967;Northrop et al.,
1968;Thompson and Friedl, 1982). SOSUS
provided convenient, accurate, and well-tested
acoustic tracking, although over the next 40 years,
such classified Navy data usually were not avail-
able for biological study. Then in 1992, data from
US Navy Integrated Sound Surveillance Systems
including SOSUS were partially declassified, al-
lowing new, spectacular observations of calling
whales in deep water, such as the 43-day, 3200-km
track of a lone calling blue whale in the western
Atlantic (Clark, 1995).
Much of the earliest tracking of whale sounds
was from moored hydrophone systems, and was
focused on the low-frequency sounds from fin
whales (Walker, 1963;Schevill et al., 1964;North-
rop et al., 1968). Tracking of the movements of
other baleen whales in similar ways waited another
20–30 years, for example, bowhead whales (Clark
and Johnson, 1984;Clark, 1989) and blue whales
(Edds, 1982;McDonald et al., 1995;Moore et al.,
2002). Shipboard hydrophone systems and sono-
buoys also were used to track calling baleen whales
(Watkins and Schevill, 1972;Watkins, 1981;Clark
and Fristrup, 1997;McDonald et al., 2001), but
because of low-frequency ship and wave noise, this
has been less useful than passive moored systems
for longer-term tracking of low-frequency calls.
Coherent tracks longer than a few hours or days
have been rare.
The distinctiveness of the 52-Hz calls has
allowed unusually long-term, confident tracking.
Analysis of these calls and their variations
compared to the sounds of other whales will be
the subject of another report. Here, we describe
the seasonal movements of the 52-Hz whale over
twelve successive years.
2. Methods
The 52-Hz calls were recorded by hydrophones
of the US Navy SOSUS and other arrays during
monitoring to quantify the distribution and
seasonal occurrence of calling whales across the
North Pacific (Watkins et al., 2000a, b). The
acoustic data from 10 or more of these arrays
were monitored regularly by analysts experienced
in operation of the Navy signal processing systems
and trained in recognition of the sounds produced
by the different whale species.
The 52-Hz calls were easily distinguished from
sounds produced by the whale species regularly
monitored in detail in these same waters, particu-
larly blue whales (Balaenoptera musculus), fin
whales (Balaenoptera physalus), and humpback
whales (Megaptera novaeangliae). The 52-Hz
tracks were compared with locations and tracks
for these whales monitored in the same waters
during the same period by the same equipment
(Watkins et al., 2000a, b, 2001;Moore et al., 2002).
For the 52-Hz call tracking, systems at the US
Naval Ocean Processing Facility (NOPF), Whid-
bey Is., WA, were used without modification for
monitoring, acoustic source location, and signal
processing. These Navy facilities, hydrophone
arrays, their characteristics, and associated data
processing techniques have remained classified.
For source location, call sequences from multiple
arrays of hydrophones were analyzed and matched
in detail spectrographically. Call series that could
be exactly matched on three to five or more arrays
accounted for 70% of the source locations.
Acoustic positions were derived by triangulation
of beam-formed sound directional vectors from
the arrays, and refined by differences in sound
arrival-time measurements between receiving ele-
ments. Locations for the source of repeated groups
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–19011890
of calls provided consistent replication of posi-
tions. Source position accuracies were estimated to
be within 1–10 km, frequencies were specified to
0.25 Hz, and time to 1 s. Analysis of the 52-Hz calls
in Fig. 1 used a Kay Sonograph (C7029A, Kay
Elemetrics, Pinebrook, NJ).
Detailed tracking of the 52-Hz source used
Navy data prior to 1995, and since then, WHOI
used averaged source positions from repeated call
sequences within the previous 24 h, often from
long bouts of successive call series. Distances and
speeds were measured between each incremental
track position, including track positions before
and after gaps in calling during the same season.
Tracking was continued across the gaps in calling
(described below) because of the consistency of
source speed, direction, and distance of travel, as
well as the similarity and uniqueness of calls before
and after these periods. For calculated track
speeds and distance within any one season, it
was assumed that the same source was being
tracked when calling resumed. Likewise, similar
calls from a unique source that occurred in
successive seasons in the same regions of the
North Pacific were assumed to be from the same
The 52-Hz calling is described with specific
terms. ‘‘Calls’’ denote individual, discrete tones of
a few seconds duration that formed the basic unit
of seasonal calling. ‘‘Groups’’ refer to clusters of
2–20 or more calls with up to 30 s between calls
that constituted the usual calling sequence. ‘‘Ser-
ies’’ indicate multiple call groups separated by up
to 10 min. ‘‘Bouts’’ describe extended periods of
calling sometimes over many hours with successive
series of call groups. ‘‘Calling periods’’ refer to the
time in which successive bouts of calling contin-
ued, varying from days to months with relatively
consistent calling. ‘‘Gaps’’ in calling indicate
variable periods, sometimes of several days, with-
out calls during seasonal call tracking.
3. Results
Distinctive tonal calls with emphasis at 52-Hz
were detected in 1989, and for the next three years,
these calls were received for a few weeks annually
from a single source that remained generally in
waters near 461N 1261W. Although the deep
waters of the North Pacific basin were monitored
year-round via SOSUS and other hydrophone
arrays, these calls have been the only ones found
with similar characteristics. The 52-Hz calls have
only been detected in north-central and north-
eastern Pacific waters, and because they were
consistently so different, a special effort was made
to locate and monitor the source. These calls have
been recorded seasonally now for 15 years, and
their source has been tracked for 12. The calls were
attributed to a whale because they had features
that were typical of some of the repetitive low-
frequency tonal sounds produced by baleen whale
species (cf., Watkins and Wartzok, 1985;Watkins
et al., 1992;Stafford, 2003;Stafford et al., 2001;
Clark and Ellison, 2004).
The 52-Hz whale calls were characterized by (1)
high received levels, characteristically well re-
corded on multiple arrays, (2) dominant frequen-
cies of 50–52 Hz with sidebands of approximately
17 Hz, but with no energy at the fundamental
frequency, (3) tones of 3–10 s centered on the
dominant frequency, (4) downward sweeping tone
frequencies of as much as 2 Hz, depending on
duration, (5) grouped call sequences in repetitive
series, and (6) reception from only one source.
Fig. 1. Spectrogram of a group of 52-Hz whale calls from 3
February 1993, the second group of Fig. 2 and group B
of Table 1.
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–1901 1891
The 52-Hz whale calls were unique. A typical
group of these calls is illustrated in Fig. 1, with
calls at 51.75 Hz, measured at the midpoint of the
duration of the call. Sidebands were recorded at
69.25 and 34.5 Hz, but there was no fundamental
frequency at the sideband interval. Typically, there
was a variable mix of short (3–5 s) and long
(6–10 s) calls, with each one centered on the
dominant frequency. Intervals between calls in a
group varied from 3 to 30 s.
Call groups also were clustered in series of 2–20
or more, with intervals between groups in series
varying from 2 to 10 min (Fig. 2,Table 1). Series of
call groups lasted variably from about 30 min to
several hours. Such bouts of calling usually
included many series of call groups. Calling periods
contained many bouts of calling and lasted variably
over a few hours to many days. Calling occurred on
(87%) 55 of the 63-day calling period during the
92–93 track, illustrated by the total duration of
calling each day (Fig. 3). There was no consistent
pattern to the temporal succession of calls in
groups, to the temporal pattern of the sequence of
call groups within series, to the occurrence of
calling during bouts, or in the amount or timing of
calls during calling periods. Calling amounts during
each successive track were different.
The 52-Hz tonal calls have been variable with
short-term changes within groups and over longer
time periods. These variations included lowered
frequency components of particular calls and
slower, as well as, more rapidly changing frequen-
cies particularly at the end of calls. In addition,
there has been a long-term gradual downward
change in the dominant call frequency, so that
after 15 years, the center frequency of the calls has
become close to 50 Hz. In spite of such variation,
these calls have remained consistently recogniz-
able, never overlapping, well defined and distinct
from other ambient sounds.
Gaps in calling of 1–16 days occurred irregularly
during seasonal calling periods. There also were
occasional longer gaps of 33–78 days toward the
beginning of four of the seasons (93–94, 95–96,
01–02, and 03–04), as well as a gap of 42 days in
the middle of the 97–98 season. During each of
these gaps in calling, the whale’s speed and
direction of travel was maintained, and when calls
resumed, they were like those that occurred before
the gap. No other similar calls were recorded
during these gaps in calling, leading us to conclude
that when calling resumed, it was the same whale
producing these unique calls. The 52-Hz calls were
recorded during an average of 52% of the days
during calling periods, ranging from 17% (93–94)
to 87% and 86% (92–93 and 00–01) in different
The 52-Hz calls typically started and stopped
abruptly, with no gradual increase or decrease in
levels. These calls occupied a frequency band that
often had relatively low-noise, and they were
composed of distinctive call spectra that made
them readily recognizable. The 52-Hz calls were
consistently recorded well on multiple hydrophone
systems, allowing confident tracking.
3.1. Tracking
The 12 seasonal tracks of the 52-Hz whale
averaged 47 km/day, ranging from 31 to 69 km/
day. Tracks lasted variably from 2 to 5 months,
and each traversed different waters. Tracks varied
in length from the 92–93 track of 708 km to the
02–03 track of 11,062 km, with an average track
length of 5518 km. Tracks began variably between
August and December (3 in August, 4 in Septem-
ber, 3 in October, and 2 in December), but all
tracks ended within a period of a few weeks
in January or early February (9 in January, 3 in
early February). The tracks of the 52-Hz whale
Fig. 2. Temporal sequence for a series of 52-Hz call groups from 3 February 1993. The group of Fig. 1 is the second one here.
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–19011892
consistently were not related to the locations or
movements noted for other calling whale species
(blue, fin, and humpback) monitored closely year-
round in these same waters (cf., Watkins et al.,
2000b;Moore et al., 2002).
The first 2 tracks of the 52-Hz whale were less
consistent than the succeeding ones. The beginning
92–93 track of 47 days was only 708 km. After 10
days of calling in the same general area that it had
occupied for the previous three seasons, tracking
began when the whale started to move. The whale
stopped moving after 47 days, but continued to
call for the last 6 days of its 63-day calling period.
For all other calling periods during subsequent
years, tracking was initiated with the first identi-
fied call of this whale and continued until calling
stopped. The second 93–94 track was much longer
but was less coherent with intermittent calling
interspersed by long gaps in calling. Tracks in
succeeding seasons were more consistent.
The 52-Hz whale tracks varied widely each
season. To illustrate some general similarities
among particular tracks, they have been divided
arbitrarily into three categories (Table 2). The
meandering tracks (A) were over short ranges
(tracks 92–93, 96–97 and 00–01, Fig. 4). The west-
to-east tracks (B) had predominantly latitudinal
movements (tracks 93–94, 95–96, and 99–00, Fig.
5). The north-to-south tracks (C) had mostly long
longitudinal travel (tracks 94–95, 97–98, 98–99,
01–02, 03–04, and track 02–03 had both Aand C
movement, Fig. 6). The 12 tracks fell into this
category sequence: A, B, C, B, A, C, C, B, A, C, A/
C, C (Tables 2 and 3). The long 02–03 track of
11,062 km was divided with the first half mean-
dering (A) for 5849 km and the last half N–S (C)
for 5213 km.
There was an overall, though variable, trend
toward more consistency in the form, speeds and
distances of the 52-Hz whale tracks with successive
seasons. Of the first 5, 4 tracks had meandering
and W–E characteristics with little southerly
movement. Of the 12 tracks, 6 had N–S travel,
including the last 3, and 5 of the last 7 (Fig. 6). The
4 meandering tracks (including first-half of 02–03)
averaged 4218 km, the 3 W–E tracks averaged
4655 km, and the 6 N–S tracks (including last of
02–03) averaged 5897 km.
The tracks for the 52-Hz whale indicated relatively
slow, continuous movement. Speed for all the tracks
averaged 2.8 km/h (range 0.7–3.8 km/h). Meandering
Table 1
Times, durations, and intervals for calls and call groups
portrayed in Fig. 2, with each group identified in sequence by
letter and calls within groups by number (example, C4 is the
fourth call in the third group)
Group/call Time from
start (min)
calls (s)
A1 0:01 7 9
A2 0:17 6 7
A3 0:30 5 9
A4 0:44 5 4:23
B1 5:12 6 6
B2 5:24 5 11
B3 5:40 6 6
B4 5:52 5 12
B5 6:09 6 11
B6 6:26 5 4:19
C1 10:50 6 6
C2 11:02 5 8
C3 11:15 5 6
C4 11:26 5 9
C5 11:40 5 6:29
D1 18:14 7 8
D2 18:29 6 9
D3 18:44 6 10
D4 19:00 5 4:10
E1 23:15 6 6
E2 23:27 5 11
E3 23:43 6 9
E4 23:58 6 9
E5 24:13 5 5:56
F1 30:14 7 7
F2 30:28 5 2:13
G1 32:46 7 9
G2 33:02 6 7
G3 33:15 5 8
G4 33:28 5 4:10
H1 37:43 6 6
H2 37:55 5 6
H3 38:06 5 22
H4 38:33 6 7
H5 38:46 5 2:15
I1 41:06 7 7
I2 41:20 6 17
I3 41:43 6 6
I4 41:55 5
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–1901 1893
tracks averaged 1.9 km/h, W–E tracks averaged
2.5 km/h, and the N–S tracks were fastest, averaging
3.5 km/h (range 2.9–3.8). The 12 tracks are plotted in
Figs. 4–6, divided by the three categories: mean-
dering, W–E, and N–S. Details of each track are in
the Appendix. Track speeds and daily distances are
listed in Table 2,andforeachtrack,startandend
times are given with positions and percent of calling
days in Table 3.
3.2. Habitat
The 52-Hz whale roamed widely across the deep
waters of the central and eastern portion of the
North Pacific basin. Most of the tracks of this
whale originated in northern waters (8 above
501N, 1 below 451N) and variably between 125W
and 160W. As the tracks progressed, the whale
generally moved slowly toward the east, then often
turned a bit north and then south. The whale
tracks remained mostly north of 501N except for
those with long north-to-south components which
ended between 461N and 221N(Table 3,Figs.
4–6). Even during the meandering (A) tracks, the
whale did not concentrate its activity in any
particular locale. There were no apparent repeated
patterns to the whale’s travel.
The whale spent relatively little time in any
particular area, and did not repeatedly visit the
same location during any season, or in subsequent
seasons except during passages on somewhat
different tracks. The total amount of time spent
in the different areas by the 52-Hz whale as it
traversed these central and eastern waters of the
North Pacific waters is plotted in Fig. 7. For this,
the number of hours spent in each area during the
whale tracks were added for each of the three track
categories (A, B, C), and then the categories were
plotted separately within successive blocks of
approximately 550 550 km (between 101east–
west at these northern Latitudes and 51north–
south). This illustrates the generally random
character of the whale movements, as well as the
waters that were visited most. The area from 501N
to 551N and 1451W to 1551W was traversed during
tracks of all three categories, and was the area
Fig. 3. Duration of daily calling during the 63-day calling period of 92–93.
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–19011894
crossed the most. The N–S tracks each were
different, but when added together, they had the
most time in many areas partly because there were
twice as many tracks in this category. Otherwise,
there did not appear to be any localized habitat
4. Discussion
The recognition of the unique 52-Hz whale calls
recorded by US Navy SOSUS and other arrays
over a 15-year period (1989–2004) with tracking of
the source during the last 12 years has provided an
unusual opportunity to document the seasonal
activities of what we believe to be an individual
whale. This is an example of acoustic tracking at
its best, taking advantage of well-calibrated, well-
placed acoustic hydrophone systems, and highly
trained and experienced trackers. In contrast to
these long (up to 11,000-km and 176-day) acoustic
tracks of the 52-Hz whale, the usual acoustic
tracking opportunity for an individual whale lasts
hours at best (cf., Watkins and Schevill, 1977;
Clark, 1989;McDonald et al., 1995), and the
recognition of the individual being tracked often
relies on non-acoustic identifiers, such as visual
marks (Edds, 1982;Clark and Fristrup, 1997;
McDonald, et al., 2001). The exception has been
the tracking of recognizably distinct or relatively
isolated sources such as the Atlantic blue whale
tracked using SOSUS (Clark, 1995).
We do not know the species of this whale,
whether it was a hybrid or an anomalous whale
that we have been tracking. It is perhaps difficult
to accept that if this was a whale, that there could
have been only one of this kind in this large
oceanic expanse, yet in spite of comprehensive,
careful monitoring year-round, only one call with
Table 2
The 52-Hz track form, duration, total km distance, days heard calling, km/h speed, and average km distance per day traveled each
YEAR Form Days Distance Call days km/h km/day
92–93 Meander 47 708 55/63 0.7 15
93–94 W–E 127 4891 21 2.5 39
94–95 N–S 56 3868 26 3.8 69
95–96 W–E 101 3160 19 2.6 31
96–97 Meander 78 4295 26 3.0 55
97–98 N–S 136 8447 41 3.5 62
98–99 N–S 113 4770 55 2.9 42
99–00 W–E 135 5916 97 2.5 44
00–01 Meander 132 6019 114 2.0 46
01–02 N–S 144 7293 74 3.5 51
02–03 Meander/N–S 176 11,062 129 3.2 63
03–04 N–S 106 5789 59 3.8 53
Fig. 4. Meandering tracks (A) of the 52-Hz whale for 92–93,
96–97, and 00–01. Daily calling positions are marked. Stars
indicate the start of tracks.
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–1901 1895
these characteristics has been found any where,
and there has been only one source each season.
The 52-Hz calls have been distinct from those of
the other species monitored systematically in the
same waters by the same equipment during the
same time periods (cf., Watkins et al., 2001).
Although the calls had a repetitive, low- frequency
tonal character similar to many baleen whale
sounds, they were not particularly like any sounds
so far identified from those species (Watkins and
Wartzok, 1985;Watkins et al., 1992;Clark and
Ellison, 2004). In addition, the variable tracks of
the 52-Hz whale and the apparent lack of specific
habitat preferences also were different from those
of the other species monitored in the same waters
(Watkins et al., 2000a, b;Moore et al., 2002).
Although the 52-Hz calls did not match those from
any other species, they did not necessarily repre-
sent a different species, but perhaps some anom-
alous or hybrid individual with a modified call.
It is unusual to recognize the call of an
individual whale more than a few hours. Although
not recognized as individuals, sperm whales have
been followed for days by acoustic tracking of
sounds from groups as they moved together (cf.,
Whitehead and Weilgart, 1991), and during
particular behaviors individual sperm whales were
identified and tracked for short periods by their
sounds (Watkins and Schevill, 1977). Though not
tracked, calls during certain behaviors by different
dolphin species have allowed recognition of
individuals over long time periods (cf. Sayigh et
al., 1995). Also, a number of cetacean species have
been followed by tag signals for long periods while
their sounds have been monitored (cf., Watkins et
al., 1999). However, recognizable individual dis-
tinctions in sounds that could be followed by
acoustics alone to provide positive tracking of
individuals over significant periods have not been
The usual impediments to successful acoustic
tracking of underwater biological sources include
detectable level of calls above background noise
on all systems needed for tracking, the presence of
noise and other sounds with competing spectra,
and the inability to distinguish the calls of the
Fig. 5. West-east tracks (B) of the 52-Hz whale for 93–94,
95–96, and 99–00. Daily calling positions are marked. Stars
indicate the start of tracks.
Fig. 6. North–south tracks (C) of the 52-Hz whale for 94–95,
97–98, 98–99, 01–02, the meandering and north-south (A/C)
track of 02–03, and 03–04. Daily calling positions are marked.
Stars indicate the start of tracks.
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–19011896
individual being tracked. None of these impedi-
ments applied when tracking the 52-Hz whale: the
calls were well above background noise and were
received consistently on multiple hydrophone
arrays, they occurred in low-noise portions of the
ambient noise spectra so they were easily identi-
fied, and they were distinctly different from other
sounds in the region.
Changes by the 52-Hz whale in calling and in its
movements over the years perhaps were indicative
of a maturing individual (Tables 2 and 3). Calling
periods became more consistent with fewer gaps as
the seasons progressed, generally, becoming longer
with increased percentage of calling and fewer long
initial gaps during calling periods. There also was
a gradual 2 Hz decrease in the primary frequency
of the calls over the 15 years of monitoring. The
later tracks in each category were likely to be
longer and faster. As years passed, there were
more long treks to the south, with 5 of the last 7
tracks having this pattern, including all of the last
3, perhaps suggesting the beginning of a more
organized southward migratory pattern. Possibly
this also was indicated by the development of a
more regular seasonal calling pattern with increas-
ing southerly treks during the last weeks of each
The Navy hydrophone systems allowed con-
venient monitoring and tracking of the 52-Hz
whale calls. Using beam-formed processing of data
from large arrays deployed in deep water per-
mitted consistent detection of the sounds on
multiple arrays at long ranges. These systems
assured accurate, repeatable source positions
because of their well-tested calibrations. The lack
of calls before and after tracking periods appeared
to be because the whale was not producing calls,
and not due to the lack of the ability of the
monitoring equipment to detect the sounds. As the
tracks demonstrated, the monitoring system was
not limited geographically, and appeared to detect
these calls, usually on multiple arrays, whenever
calls were produced in these deep-water regions.
This series of long tracks of the 52-Hz whale
during 12 successive years demonstrates the
potential of such underwater sound systems to
Table 3
Start and end dates with positions and percent of calling days for each of the seasonal tracks of the 52-Hz whale
Track Start Lat. Long. Track/calling% End Lat. Long.
92–93 18 Dec. 46.3N 126W 47 days/87% 3 Feb. 43.8N 128.6W
93–94 12 Sept. 42.4N 160.6W 127/17% 16 Jan. 45.9N 143.9W
94–95 12 Dec. 48.5N 133.2W 57/47% 6 Feb. 22.2N 126.9W
95–96 9 Oct 51.5N 158.1W 101/19% 18 Jan. 43.2N 133.8W
96–97 28 Oct. 53.2N 143.5W 78/33% 14 Jan. 39.5N 135.9W
97–98 4 Sept. 47.5N 136.7W 136/30% 18 Jan. 26.8N 137.8W
98–99 22 Sept. 54.1N 158.3W 113/49% 13 Jan. 30.6N 131.6W
99–00 1 Sept. 53N 148.5W 135/72% 14 Jan. 46.6N 130.3W
00–01 24 Aug. 51.6N 150.1W 132/86% 3 Jan. 45.4N 138.4W
01–02 22 Aug. 53.5N 155.7W 144/51% 13 Jan. 26.5N 126.7W
02–03 12 Aug. 52N 157.0W 176/74% 3 Feb. 33.0N 132.0W
03–04 3 Oct. 55.8N 153.4W 106/56% 17 Jan. 29.5N 129.3W
Fig. 7. Time spent in blocks of 10151shows the variable
habitat of this whale. Blocks are approximately
550 km 550 km in these northern latitudes.
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–1901 1897
follow and describe acoustic behaviors of open
ocean whales—probably not possible any other
way. With the recognition of distinctive features in
sounds from individuals or groups, their normal
activity would be detailed by acoustic tracking,
with no disturbance.
The program of whale call monitoring in the
North Pacific has enjoyed consistent encourage-
ment and direct participation by US Navy
Commands and personnel throughout the years
of research and analysis at Whidbey Is. NOPF.
Their contribution has been thoroughly appre-
ciated. Support for this work has been from a wide
variety of sources, including the SERDP Council
through SPAWAR (Dennis Conlon), the Marine
Mammal Program of the Office of Naval Research
(Robert Gisiner, #N00014-96-1-1130), the Chief of
Naval Operations Environmental Program N45
(Frank Stone) and US Army Corps of Engineers
(#DCA87-00-H-0026) with additional funding
from the Department of Defense Legacy Resource
Management Program, SPAWAR and ONR
(#N00014-02-10238), the National Marine Fish-
eries Service (#AB133F-02SE0870). The Woods
Hole Oceanographic Institution maintained the
continuity of the program between increments of
formal support. Experienced analysts sharing in
the monitoring and tracking responsibilities have
been Darel Martin and Scott Haga. Sue Moore,
Katherine Stafford, John Hildebrand, Christopher
Clark, and three anonymous reviewers have
commented helpfully on these data and previous
versions of the manuscript. This is Contribution
Number 10687 from the Woods Hole Oceano-
graphic Institution.
Appendix. Track details
The 92–93 meandering track (A) spanned 47
days (within a 63-day calling period) and covered
708 km (Fig. 4). Although calling began on 7
December 1992 (46.31N, 1261W), the whale
remained in essentially the same waters for the
next 10 days. Then on 18 December, tracking
began as the whale started to move. Tracking
continued until 3 February, although significant
movement was recorded on only 6 days during this
period. Calling ended on 10 February 1993
(43.81N, 128.61W). Calls were recorded on (87%)
55 of the 63-day calling period, and the whale was
tracked for 47 days (Fig. 2). The track was
confined to an area of approximately 400 km
north-to-south by 300 km west-to-east. Speeds
during the 47-day period of tracking averaged
0.7 km/h (median 0.8, SD 0.33) for an average
daily distance of 15 km.
The 93–94 west–east track (B) spanned 127 days
and covered 4891 km, but had less than 480-km
north–south travel (Fig. 5). This was the second
season that this whale was observed to move, and
calling was sporadic although distinctive. Calling
began on 12 September (42.41N, 160.61W) and
stopped after only 6 days. Then 78 days later,
calling resumed on 7 December (46.41N, 127.51W)
and continued sporadically until 16 January
(45.91N, 143.91W) including sporadic gaps in
calling of 1–13 days. Calls were recorded on only
(17%) 21 of the 127-day calling period. The whale
had started calling near 1601W, traveled quietly
eastward to 1271W, the general area of its mean-
dering in 92–93, and then it returned halfway back
to its starting point. Speed averaged 2.5 km/h
(median 2.1, SD 1.56) for an average daily distance
of 39 km.
The 94–95 north–south track (C) spanned 56
days and covered 3868 km. The track included
north–south travel of more than 2800 km but
east–west movement of less than 800 km
overall (Fig. 6). The whale started calling on 12
December (48.51N, 133.21W), and went eastward
to the general area visited the previous 2 years
(46.51N, 126.51W). It turned on 8 January to
travel southward until 6 February (22.21N,
126.91W). Calls were recorded on (47%) 26 of
the 56-day calling period, interspersed by 1–5-day
gaps in calling. Speed averaged 3.8 km/h (median
3.1, SD 2.87) for an average daily distance of
69 km.
The 95–96 west–east track (B) spanned 101 days
and covered 3160 km within a broad north–south
range of 1400-km (Fig. 5). Calling started on 9
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–19011898
October (51.51N, 158.11W) and stopped after only
2 days. Calling resumed on 16 November after 33
days of silence with the whale meandering 470 km
to the northeast (55.81N, 146.81W). The whale
then traveled eastward and southward about
1400 km to end on 18 January (43.21N,
133.81W). Calls were recorded on (19%) 19 of
the 101-day calling period, interspersed by periods
of 1–14-day gaps in addition to the initial gap of 33
days. Speed averaged 2.6 km/h (median 1.3, SD
3.33) for an average daily distance of 31 km.
The 96–97 meandering track (A) spanned 78
days and covered 4295 km within an area of
approximately 1500 1700 km
, including a
southeastward component (Fig. 4). Calling began
on 28 October (53.21N, 143.51W), continued with
sporadic gaps of 1–10 days, and ended on 14
January (39.51N, 135.91W). Calls were recorded
on (33%) 26 of the 78-day calling period. Speed
averaged 3 km/h (median 2.3, SD 2.31) for an
average daily distance of 55 km.
The 97–98 north–south track (C) spanned 136
days and covered 8447 km in two separate areas
(Fig. 6). Calling began on 4 September (47.51N,
136.71W) with the whale moving northward
approximately 960 km (to 56.71N) and meandering
in that northern area until at least 27 November
(54.21N, 138.81W). Except for a few calls on 27
November, the whale was quiet for 42 days (2
Nov.–14 Dec.), then it resumed calling and mean-
dering again in a second area, 1700 km to the
south (391N, 146.61W). Over the last weeks of its
track, the whale moved steadily southward until 18
January (26.91N, 137.81W). Calls were recorded
on (30%) 41 of the 136-day calling period. Speed
over this entire second longest track averaged
3.4 km/h (median 2.3, SD 3.73) for an average
daily distance of 62 km.
The 98–99 north–south track (C) spanned 113
days and covered 4770 km. The track started as a
meander in northern waters, went farther north-
east into the Gulf of Alaska, and then turned for a
2900-km trek southward (Fig. 6). Calling began on
22 September (54.11N, 158.31W), and was inter-
mittent with sporadic gaps of up to 16 days
through November, then continued calling
through 13 January (30.61N, 131.61W). Calls were
recorded on (49%) 55 of the 113-day calling
period. Speed averaged 2.9 km/h (median 2.1, SD
2.49) for an average daily distance of 42 km.
The 99–00 west–east track (B) spanned 135 days
and covered 5916 km as it meandered slowly
eastward in northern waters (Fig. 5). Calling
started on 1 September (531N, 148.51W), and the
whale was tracked northeastward and then south-
eastward to end on 14 January (46.61N, 130.31W).
Calls were recorded on (72%) 97 of the 135-day
calling period, with 1–4 days of silence mainly
toward the end of the track. Speed averaged
2.4 km/h (median 1.5, SD 2.73) for an average
daily distance of 44 km.
The 00–01 meandering track (A) spanned 132
days and covered 6019 km. The track was confined
to waters more than 1000 km offshore and turned
slowly southeastward (Fig. 4). Calling started on
24 August (51.61N, 150.11W), continued regularly
during most of the track, and ended on 3 January
(45.41N, 138.41W). Calling was recorded on (86%)
114 of the 132-day calling period. Speed averaged
1.9 km/h (median 1.7, SD 1.23) for an average
daily distance of 46 km.
The 01–02 north–south track (C) spanned 144
days and covered 7293 km. The track began with
some meandering in northern waters, then it went
southward (Fig. 6). Calling started on 22 August
(53.51N, 155.71W) and stopped for 9 days until 30
August (53.61N, 153.51W). Calling resumed 53
days later on 23 October (551N, 149.31W) with the
whale meandering in more northerly waters until it
turned toward the south on 7 December (51.81N,
145.11W). The whale continued steadily south-
ward until 12 and 13 January when the track
turned toward the east, and calling ended (26.51N,
126.71W). Calling was recorded on (51%) 74 of the
144-day calling period. Speed averaged 3.5 km/h
(median 3.2, SD 2.31) for an average daily distance
of 51 km.
The 02–03 track had both meandering and
north-south (A/C) components. During the first
100-day meandering portion, the whale traveled
5849 km and averaged 58 km/day, and during the
last 76-day N–S portion, the whale traveled
5213 km and averaged 69 km/day. The full track
spanned 176 days and covered 11,062 km. This
combined track was the longest in both duration
and distance (Fig. 6). Calling started in northern
W.A. Watkins et al. / Deep-Sea Research I 51 (2004) 1889–1901 1899
waters on 12 August (521N, 1571W, and over the
next 3 months, the whale meandered slowly
northeastward and then southeastward. Then,
beginning on 19 November (521N, 1471W), the
whale turned southward and changed to the N–S
travel mode until calling stopped on 3 February
(331N, 1321W). During the full track, calling was
recorded on (74%) 129 of the 176-day calling
period. For the first meandering portion of the
track, speed averaged 3.0 km/h (median 2.1, SD
3.3), and during the N–S portion speed, speed
averaged 3.4 km/h (median 2.3, SD 4.5). For the
full track, speed averaged 3.2 km/h (median 2.2,
SD 3.8) for an average daily distance of 63 km.
The 03–04 north–south track (C) spanned 106
days and covered 5789 km, and started farther
offshore than previous north–south tracks (Fig. 6).
Calling began on 3 October in northern waters
(55.81N, 153.41W) and continued for a short
period with 1 day of silence and slow movement
only until 8 October. During the subsequent 39-
day gap and the next 20 days of calling which
resumed on 17 November (54.51N, 151.61W),
there was only continued slow movement. Then
on 6 December, the whale began traveling steadily
south-southeastward until calling stopped on 17
January (29.51N, 129.31W). Calling was recorded
on (56%) 59 of the106-day calling period. Speed
averaged 3.8 km/h (median 2.9, SD 3.6) for an
average daily distance of 55 km.
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... The vocal repertoire of most, if not all cetacean species, has been described in varying levels of detail. However, despite this there are a number of whale calls where we do not know the actual source (Stafford et al. 1999, Watkins et al. 2004, Sousa and Harris 2015, Brodie and Dunn 2015, Nieukirk et al. 2016, Leroy et al. 2017. These sounds are thought to be of biological origin due to their non-random repetition, seasonal patterns of detection, frequencies greater than 10 Hz and variation within signal types (Stafford et al. 1999, Sousa andHarris 2015). ...
... Perhaps the most well-known of these unknown calls is the "Watkins whale" sound, often referred to as the "52 Hz" call. The 52 Hz call is thought to be from a single whale, not known to follow the patterns of presence of other whale species such as the blue, fin and humpback whales, and therefore presumed to be a blue-fin whale hybrid (Watkins et al. 2004. In some instances the origin of these initially unknown calls has been confirmed, for example the Antarctic minke whale (Balaenoptera bonaerensis) "bio-duck" sounds (Risch et al. 2014), Northern minke whale (Balaenoptera acutorostrata) "boing" sounds (Rankin and Barlow 2005) and dwarf minke whale (B. ...
... To provide adequate data on the population dynamics and movements of a species of interest, PAM requires an understanding of a species' vocal repertoire(Parks et al. 2011b). However, monitoring of ocean noise can inadvertently result in the discovery of a "new" sound from an unknown source (e.g.Stafford et al. 1999, Watkins et al. 2004, Sousa and Harris 2015, Brodie and Dunn 2015, Nieukirk et al. 2016, Leroy et al. 2017. ...
... Hybridization in blue and fin whales appears to be largely unidirectional (male fin x female blue), and while it is an understudied phenomenon in baleen whales, it has been documented in multiple ocean basins, suggesting that its frequency might be underestimated (Pampoulie et al. 2021). If the acoustic features of hybrids are reliably intermediate between the parents, passive acoustic monitoring and tracking might offer a tool to study the frequency and behavioral ecology of living hybrids (e.g., Watkins et al. 2004). For example, it has been hypothesized that the 'Watkins' whale' (also known as the '52-Hz whale') may have been a bluefin hybrid based on the time frequency characteristics of its song, which are intermediate between the two species in the North Pacific (Watkins et al. 2004;Stafford et al. 2007). ...
... If the acoustic features of hybrids are reliably intermediate between the parents, passive acoustic monitoring and tracking might offer a tool to study the frequency and behavioral ecology of living hybrids (e.g., Watkins et al. 2004). For example, it has been hypothesized that the 'Watkins' whale' (also known as the '52-Hz whale') may have been a bluefin hybrid based on the time frequency characteristics of its song, which are intermediate between the two species in the North Pacific (Watkins et al. 2004;Stafford et al. 2007). ...
Baleen whale migrationMigration emerges as a foundational theme of cetacean behavioral ecology and the relationships that bind humans and whales together. From facilitating the culmination of the great human migrationMigration many centuries ago, to their roles as ecosystem service providers, baleen whales have influenced the path of human history. With a focus on modern technologically enabled insights, we provide an overview of what scientists currently know about the spatial and temporalTemporal distribution of baleen whales and their migratory behaviorsMigratory behavior. Although a coarse modelModel of seasonally paced north–south migrationMigration generally applies, a deeper analysis reveals the remarkable diversity of baleen whale migrationsMigration. Some species, including gray whalesGray whale(Eschrichtius robustus)Eschrichtius robustus, migrate relatively close to shore; others, including humpback whalesHumpback whale(Megaptera novaeangliaeMegaptera novaeangliae), tend to migrate across ocean basins. Some species, including Bryde’s whalesBryde’s whale(Balaenoptera edeni)Balaenoptera edeni, appear to largely reside in middle to low-latitude ecosystems, relatively removed from cold, high-latitude water. In contrast, bowhead whalesBowhead whale(Balaena mysticetus)Balaena mysticetus remain within Arctic ecosystems all year, and others, including Omura’s whalesOmura’s whale(Balaenoptera omurai)Balaenoptera omurai, may not migrate at all. The scientific focus to date has largely been on population-specific studies of where whales go, what their behaviors are, and when they undertake their migrationsMigration. Thus, there remains much to be learned, particularly regarding why baleen whales migrate and how they navigate during their long-distance migrationsMigration. Technological innovations such as satelliteSatellite tags and passive acousticsPassive acoustic have revolutionized our understanding of baleen whale behavioral ecology and ethology, and technologyTechnology will continue to play a critical role in advancing the science of baleen whale migrationMigration.
... [6][7][8] Acoustic monitoring targeted at specific species often leads to the discovery of sounds from unknown sources. [9][10][11][12][13] Based on sound characteristics, such as the duration, spectral shape, frequency, overtones, or repetition patterns, it is generally possible to identify the nature of their source (biological, geological, or anthropogenic). 14 In the case of biological sounds, hypotheses can be made about the type of animal that produce them (e.g., shell fish, fish, mysticeti, odontoceti). ...
... 14 In the case of biological sounds, hypotheses can be made about the type of animal that produce them (e.g., shell fish, fish, mysticeti, odontoceti). For instance, Watkins et al. 10,11 concluded that the so called "52-Hz call" or "Watkins' whale call" is emitted by a baleen whale, which may correspond to a blue-fin hybrid whale, based on the call characteristics and its seasonal and geographic occurrences. 15 Similarly, Sousa and Harris 12 described two new acoustic signals recorded near Diego Garcia Island, in the northern Indian Ocean, which have similar characteristics to blue whale calls. ...
Since passive acoustic monitoring is widely used, unidentified acoustic signals from marine mammals are commonly reported. The signal characteristics and emission patterns are the main clues to identify the possible sources. In this study, the authors describe two previously unidentified sounds, recorded at up to five widely-spaced sites (30 × 30 degree area) in the southern Indian Ocean, in 2007 and between 2010 and 2015. The first reported signal (M-call) consists of a single tonal unit near 22 Hz and lasting about 10 s, repeated with an interval longer than 2 min. This signal is only detected in 2007. The second signal (P-call) is also a tonal unit of 10 s, repeated every 160 s, but at a frequency near 27 Hz. Its yearly number increased greatly between 2007 and 2010, and moderately since then. Based on their characteristics and seasonal patterns, this study shows that both signals are clearly distinct from any known calls of blue whale subspecies and populations dwelling in the southern Indian Ocean. However, they display similarities with blue whale vocalizations. More particularly, the P-call can be mistaken for the first tonal unit of the Antarctic blue whale Z-call.
... Long-term passive acoustic data are currently being collected (EU INTERREG VA COMPASS project; and could be analysed to investigate the presence of unusual call types. For instance, the 52-Hz call (Watkins et al., 2004) is hypothesized to be transmitted by blue whale (Balaenoptera musculus)  fin whale (Balaenoptera physalus) hybrids (Stafford et al., 2007). If such hybrid-specific vocalizations exist, they may provide insights into the occurrence of bottlenose  Risso's dolphin hybrids. ...
Full-text available
Bottlenose dolphin photo‐identification data were compiled from western Scotland to identify individuals and ultimately investigate population size, demographic parameters, spatio‐temporal distribution, and movement patterns. Opportunistic citizen science photographs revealed what appeared to be an adult bottlenose × Risso’s dolphin hybrid along with an apparent second‐generation hybrid or back‐cross calf. Both had atypically short rostra and the dorsal fin of the adult was noticeably taller than is normal for bottlenose dolphins. Based on these characteristics, this case may represent a congenital rostral abnormality or the first intergeneric calf reported for this species combination, either in captivity or in the wild. The previously reported presence of several putative hybrids and mixed‐species sightings in the area, in combination with the tall dorsal fin, provide support for the second possibility, i.e. intergeneric hybrids. Although rare, hybridization may have disproportionate conservation consequences, with population‐level impacts in very small coastal populations of long‐lived, slow‐breeding animals.
... Medrano-González and colleagues (2001) are found in other mysticete species like blue and fin whales (Cummings and Thompson, 1971;Watkins et al., 1987;Rivers, 1997;Mellinger and Clark, 2003;Helbel et al., 2020). In previous research of unusual mysticete vocalizations like the 52-Hz calls (Watkins et al., 2004) it has been suggested that the sound source could be a hybrid whale. However, this not a parsimonious hypothesis because there is no clear reported case of hybridization between humpback whales and blue or fin whales (Crossman 78 Discussion et al., 2016;Árnason et al., 2018). ...
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Humpback whales (𝘔. 𝘯𝘰𝘷𝘢𝘦𝘢𝘯𝘨𝘭𝘪𝘢𝘦) are among the most vocally complex animals. Besides the stereotyped song produced by males mainly during the reproductive season, humpback whales have a diverse repertoire of non-song vocalizations, known as social calls (SCs). These are usually considered random displays, produced in all contexts, regardless of the whales' sex or age, but little is known about calling behavior or call function. Most research on SCs have focus on the Northeast and Southwest Pacific and Northwest Atlantic populations. The SC repertoire and the calling behavior of the humpback whales of the Southeast Pacific (Breeding Stock G) has only been partially documented in two studies. Here two different passive acoustic methodologies (over-the-sides hydrophones and DTAGs) were used to investigate diversity, associated behavior, and context of the Breeding Stock G humpback whales’ SCs in their breeding and feeding grounds. The Stock G catalogue is composed of 48 call types, from which a high percentage are blend and unknown calls. Call rates in the breeding ground of Colombia were higher than in the feeding ground of the Western Antarctic Peninsula. Some call types were frequently found in a competitive context, denoting a possible motivational feature (aggression) of such calls. In Antarctica, a third of the vocal activity was related to surfacing events, and calling behavior was influenced by the presence of conspecifics, the tag (individual), and the period of the day. The results showed that most calls were produced and combined in non-random patterns within bouts. Some of the bouts composed of pulses showed stable structures across time and space similar to bouts reported in allopatric populations. Finally, a new vocal display of repetitive series of cry-like calls, named Repetitive Tones (RTs), is reported in Colombia. Different scenarios about the origin and the function of these calls are discussed. The resemblance of RTs to feeding calls from Alaskan whales may support cross-equatorial displacement between North and Southeastern Pacific populations. The future use of DTAGs in the breeding ground to record SCs and the expanded database of different individuals from Antarctica will allow for deeper analyses of Stock G diversity and calling behavior, better facilitating comparisons between feeding and breeding areas. Community-wide agreements on definition and nomenclature of SCs are necessary for the refinement of the Social Call Global Catalogue and cross-population comparisons.
... W przypadku samych wali dziobogłowych dysponujemy bardzo skąpymi danymi o emitowanymi przez nie odgłosach. Są one generalnie znane dla wala Cuviera -Ziphius cavirostris, wala Gervaisa -Mesoplodon europaeus, Berardius arnuxii oraz wala Blainville'a -Mesoplodon densirostris [123,124]. W innych przypadkach nie dysponuje się wystarczającymi danymi. Wynika to z rzadkości spotkań z omawia-nymi tutaj zwierzętami i -w efekcie -utrudnieniom w rejestracji wyżej wspomnianych dźwięków. ...
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The article discusses selected geophysical and photogrammetric methods that are currently used for geological surveys. Their practical application for recognizing the geological and geomorphological structure of the Kraśnik area was presented. The digital analysis of stereoscopic aerial photos, the LPIS (Land Parcel Information Systems) digital terrain model and the ALS (Airborne Laser Scanning) digital terrain model were used. Photogrammetric methods were used to analyse the topography and geological structure. The directions and runs of faults and lithological outcrops of rock complexes were interpreted. Two methods were used for geophysical research. The first of them is ERT (Electrical Resistivity Tomography). Research using this method enabled interpretation of the lithological structure of rocks and tectonics. Thanks to it, the lithology of rock complexes was recognized and the fault was interpreted. The second method is the analysis of a semi-detailed gravimetric photo. Thanks to this method, folded structures in chalk formations and numerous faults were interpreted. The study provided new data on the geological and geomorphological structure of the Kraśnik area. Further photogrammetric studies will focus on the use of short-range photogrammetry, satellite interferometry and geophysical surveys in geological cartography. Keywords: digital terrain model, airborne laser scanning, electrical resistivity tomography, semi-detailed gravimetric photo, Lublin region
... Depuis l'essor du suivi par acoustique passive, le répertoire vocal des différentes espèces, sous-espèces ou populations de mammifères marins a puêtre décrit pasà pas en associant des observations visuelles et acoustiques. Il est aussi relativement courant que de nouveaux sons soient identifiés dans les enregistrements et décrits dans la littérature Watkins et al., 2000bWatkins et al., , 2004. L'acoustique passiveétant une méthode aveugle, il est possible, d'après les caractéristiques des signaux, de déterminer la nature de leur source (biologique, géologique, ou anthropique) ; l'identification définitive des sources biologiques requiert toutefois des observations conjointes visuelles, souvent difficilesà acquérir dans les zones inaccessibles telles que les mers polaires. ...
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La baleine bleue Antarctique, Balaenoptera musculus intermedia, est en danger critique d’extinction depuis la chasse baleinière intensive du 20e siècle. L’état de ses populations et leur écologie restent encore mal connus. En raison de l’inefficacité des observations visuelles, la surveillance par acoustique passive est privilégiée pour étudier cette espèce vocalement très active. Cette thèse porte sur l’analyse de 7 ans de surveillance acoustique passive dans l’océan Indien austral, région d’habitat et de migration particulièrement importante pour la baleine bleue Antarctique. Déployé depuis 2010 sur une aire de près de 9 000 000 km2, le réseau d’hydrophones OHASISBIO fournit une base de données acoustiques multi-site et pluri-annuelle. L’application d’un algorithme de détection automatique des vocalisations de baleines bleues Antarctique, préalablement testé et validé, a permis d’établir les patrons géographiques et saisonniers de présence de l’espèce au sein du réseau. L’analyse systématique de ces vocalisations a également permis de caractériser des variations intra- et inter-annuelles de leur fréquence, affectée par une décroissance long-terme et des modulations saisonnières. L’analyse préliminaire de signatures vocales d’autres espèces présentes dans le réseau - rorquals communs et trois populations de baleines bleues pygmées – a révélé des variations de fréquence similaires de leur vocalisation et permis d’esquisser leurs patrons géographiques et saisonniers. Enfin, deux vocalisations, jusqu’alors non décrites, aux caractéristiques semblables à celles de baleines bleues, ont été identifiées et caractérisées.
There has been enormous growth in technical mechanisms for collecting, analyzing, and visualizing baleen whale acoustic behaviors. Organizing and synthesizing the import of these behaviors remain a challenge, as is the placement of such efforts within the broader framework of adaptationAdaptation, selective advantageSelective advantage, and behavioral and evolutionary ecologyEvolutionary ecology. Synthesis based on bioacoustic behaviorBioacoustic behavior includes consideration of low-frequency, physical acoustic propagationAcoustic propagation in the marine environmentPhysical environment and the resultant potential beneficial opportunities for baleen whales to communicateCommunicate, forageForage, navigateNavigate, orient, and maintain social organization. Observations of baleen whale bioacoustic behaviorsBioacoustic behavior range from singing as a male reproductive advertisement display occurring over periods of many months within a potentially enormous communicationCommunication space to non-singing events associated with short duration social contexts involving both sexes and multiple age groups. Such observations are helpful as a starting framework but should be recognized as simplifications given the high levels of behavioral variabilityBehavioral variability and complexity inherent in these long-lived, large-brained species. A variety of observations, referred to as discrepant eventsDiscrepant event, suggest that present understandings of baleen whale behavioral ecologyBehavioral ecology are insufficient to explain the spatial and temporal scales over which baleen whales engage in bioacoustic behaviorsBioacoustic behavior. Such behaviors and behavioral variabilityBehavioral variability at ocean basin scales have promoted the concepts of acoustic environmentAcoustic environmentand acoustic habitatAcoustic habitat, and motivated concerns over the biological influences of anthropogenic sounds on species-specific habitats, behaviors, and survival.
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The article explores possible intersections between cultural disability studies and the blue humanities. It opens with a discussion of cultural representations of atypical aquatic mammals and fish. Yet, the main focus is placed on various contemporary literary texts (Mateusz Pakuła’s Wieloryb: The Globe, John Wilson’s From the Depths, and Kaite O’Reilly’s In Water I’m Weightless), which were written either by or for artists with disabilities. As will be shown, all of them allude to water or/and marine environment in order to comment on disability, its social constructedness and context dependence, and the conservation of biological and cultural diversity. In doing so, these texts challenge the fixedness of the disabled/non-disabled binary and subtly hint at a possibility of transgressing the traditional opposition between the human and the animal. This in turn points to the potential of applying the oceanic perspective, or what Philip Steinberg and Kimberley Peters call ‘wet’ and ‘more-than-wet’ ontologies, in disability studies.
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Bezvadu sensoru tīkli ir kļuvuši par neatņemamu daļu no visuresošās skaitļošanas (Ubiquitous Computing) un lietu interneta (Internet of Things). Darba ietvaros izstrādāta un aprakstīta vispārīgā metode iegulto sensoro iekārtu izveidei, kuru pielietojot, iespējams radīt rīkus objektu monitoringam un datu ievākšanai, kas, savukārt, izmanto zema enerģijas patēriņa iegultas sensorās iekārtas un heterogēnus bezvadu sensoru tīklus. Darba gaitā izstrādātā metode pielietota, lai radītu rīku kopumu, kas piemēroti savvaļas dzīvnieku, piemēram, Eirāzijas lūšu (Lynx lynx) vai Eirāzijas pelēko vilku (Canis lupus lupus) monitoringam un aktivitāšu noteikšanai. Darbā izvirzītā hipotēze arī aprobēta un iegūtie rezultāti apkopoti, pielietojot radītos rīkus auto orientēšanās pasākumu dalībnieku izsekošanai. Daļa no darba rezultātiem tiek pielietoti datu ieguvei un apmaiņai, veicot apvidus izpēti pirms saules un vēja enerģijas ieguves iekārtu uzstādīšanas. Darbā sasniegtie rezultāti, radot dažāda pielietojuma iegultās sensorās iekārtas balstoties uz piedāvāto vispārīgo metodi, pierāda, ka tā ir pielietojama.
A certain intense, underwater, transient sound has been observed over extended areas of the Atlantic and Pacific Oceans. The power spectrum for a single pulse of this sound is strongly peaked, energy being confined to a narrow band centered in the vicinity of 20 cps; the sounds accordingly have been named twenty‐cycle pulses. A single pulse typically lasts about one second; the pulses normally occur in trains, or groups, characterized by remarkably regular repetition rates. A common rate is one pulse approximately every 10 sec, although others are observed. A typical pulse train is of several minutes' duration; separated by silent periods two to three minutes in length, pulse trains often repeat for many hours. On the continental shelf south of New England, the positions of scores of sources of this sound have been determined by remote acoustic ranging; the sources are found to move. Speeds are typically a few knots. Radiated sound levels are so high that the sources are detectable tens of miles away. Source densities of only one in several hundred square miles are most common. Movements appear random, suggesting that the source is biological. The low areal density, the high source level, and speeds of a few knots that are sustained for hours suggest a large animal. Characteristics possibly correlated with the sounding cycles of whales are apparent. The hypothesis that the sounds originate from the heartbeats of whales appears credible on several counts.
Signals of 20 Hz were recorded at SOFAR depth hydrophones of the Pacific Missile Range at Midway, Wake, Oahu, and Eniwetok Islands in the North Pacific. The signal strength, source movement, and seasonal peak (in winter) suggest a biological source.
From time to time, strong underwater transient sounds have been detected in New Zealand waters. Much of this activity appears to be biological in origin, and some of it is obviously similar to underwater signals observed in other parts of the world. Other components are by no means so well known and provide further interesting examples of pulses in which the energy is confined to a narrow band of frequencies around 20 cps. These pulses are described.