Aquatic Mammals
a publication of the European Association for Aquatic Mammals
Vol. 31, No. 2
2005
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submissions, please contact
Dr. Jeanette Thomas
Editor, Aquatic Mammals
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Wiggins, S.M.*, E.M. Oleson, M.A. McDonald, and J.A. Hildebrand.
2005. Blue whale (Balaenoptera musculus) diel call patterns offshore
of southern California. Aquatic Mammals 31(2):161-168.
*Scripps Institution of Oceanography, University of California, San
Diego, 9500 Gilman Drive, La Jolla, CA 92093-0205, USA
Diel and seasonal calling patterns for blue whales (Balaenoptera
musculus) were observed in coastal waters off southern California
using seafloor-mounted autonomous acoustic recording packages
(ARPs). Automated call counting from spectrogram cross-correlation
showed peak seasonal calling in late summer/early fall. When call
counts were organized by daily time intervals, calling peaks were
observed during twilight periods, just after sunset and before
sunrise. Nighttime calling was grater than daytime calling, but also
showed a minimum between the dusk and dawn calling peaks. These peaks
correlate with the vertical migration times of krill, the blue whales'
primary prey. One hypothesis to explain these diel variations is that
blue whale calling and foraging may be mutually exclusive activities.
Fewer calls are produced during the day while prey are aggregated at
depth and foraging is efficient. More calls are produced during the
twilight time periods when prey are vertically migrating and at night
when prey are dispersed near the sea surface and foraging is less
efficient.
Mello, I.*, and M. Amundin. 2005. Whistle production pre- and
post-partum in bottlenose dolphins (Tursiops truncatus) in human
care. Aquatic Mammals 31(2):169-175.
*Kolmården Djurpark, Research and Education Centre, Kolmarden, Sweden
The bottlenose dolphin (Tursiops truncatus) has a highly variable
acoustic repertoire of whistles, clicks, and pulse burst
sounds. Whistles are used to express individuality (signature whistle)
and emotional state, and to initiate and maintain contact within a
group. This study investigated the whistle production type pre- and
post-partum of three female bottlenose dolphins and their calves at
the Kolmården Djurpark, Sweden. Gestation lasts approximately 12
months, and with the approach of delivery, the behaviour of the female
changed in several ways. Observations of the behaviour and sound
production were done for up to seven months prior to birth and for up
to the first 22 months of the calves' lives. The results showed that
whistle production increased significantly for all three females in
the seven months pre-partum, with an accelerating increase in the days
prior to birth. The whistles, therefore, might be used as an indicator
that delivery is imminent. After birth, the mother-calf pair whistled
more often when separated (66%) than when together (34%), and
significantly more often when the calf returned to its mother than
when she retrieved the calf.
Blomqvist, C.*, I. Mello, and M. Amundin. 2005. An acoustic play-fight
signal in bottlenose dolphins (Tursiops truncatus) in human
care. Aquatic Mammals 31(2):187-194.
*Department of Research and Education, Kolmårdens Djurpark, Kolmården,
Sweden
Play-fighting is common in many mammals, especially among juveniles
and subadults, providing a safe opportunity to practice behaviours
important in adult life. To prevent escalation into a potentially
dangerous real fight, play-fighting often is accompanied by acoustic
and/or visual appeasement behaviours. We studied aggressive and
play-fight behaviours in bottlenose dolphins (Tursiops truncatus) at
the Kolmården Djurpark. The results showed that play-fighting subadult
dolphins emitted a characteristic sound, which was never observed in
aggressive interactions. This was a short pulse burst followed by an
FM-whistle. By plotting pulse repetition rate (PRR) vs. duration of
the bursts, two main clusters were found. The bottom cluster had a
mean PRR of 59 pulses per second (pps), and a mean duration of 154
msec. The top cluster had a mean PRR of 502 pps and a mean duration
of 149 msec. These play-fight clusters were compared separately to
corresponding adult aggressive pulse burst clusters. Taking both PRR
and duration into consideration, no significant difference was found
between the top clusters, or between the bottom clusters, in the two
age groups. The trailing whistles were divided into five different
frequency contour categories. These did not resemble the signature
whistles of any of the play-fighting dolphins. The average start and
end frequencies were 13.0 kHz and 10.1 kHz, respectively, and the
maximum and minimum frequencies were 13.7 kHz and 7.0 kHz,
respectively. The mean duration was 410 msec. Based on the fact that
this sound occurred only in play-fights, we propose that it helps
prevent a play-fight from escalating into a real fight and, hence, is
analogous to the "laugh" and "chuckle" seen in apes.
Morisaka, T.*, M. Shinohara, and M. Taki. 2005. Underwater sounds
produced by neonatal bottlenose dolphins (Tursiops truncatus):
I. Acoustic characteristics. Aquatic Mammals 31(2):248-257.
*Department of Zoology, Graduate School of Science, Kyoto University,
Kitashirakawa-oiwake, Sakyo, Kyoto, 606-8502, Japan
Bottlenose dolphins (Tursiops truncatus) communicate using various
acoustic signals, including whistles and pulsed sounds. Many studies
have been conducted on dolphin whistle development over a long span,
but little research has been done on sounds produced by neonatal
dolphins just after birth. For this reason, we studied the acoustic
characteristics of underwater sounds produced by two neonatal
dolphins. Both whistles and burst-pulses were identified as neonatal
sounds at 1.5 h after birth. Whistles became longer by the
hour. Whistle durations were highly correlated with respiration
intervals. The neonate randomly produced various types of whistles,
but no dominant whistles were documented. There were significant
differences between neonates in the proportion of whistles to
burst-pulses used, and also in the acoustic characteristics of their
whistles. Acoustic characteristics that are unique to each individual
neonate might help a mother dolphin to recognize her neonate.
Morisaka, T.*, M. Shinohara, and M. Taki. 2005. Underwater sounds
produced by neonatal bottlenose dolphins (Tursiops truncatus):
II. Potential function. Aquatic Mammals 31(2):248-257.
*Department of Zoology, Graduate School of Science, Kyoto University,
Kitashirakawa-oiwake, Sakyo, Kyoto, 606-8502, Japan
Neonatal bottlenose dolphins (Tursiops truncatus) produce many sounds
just after birth, including whistles and pulsed sounds. Herein, we
report the possible function of the sounds produced by two
captive-born, neonatal bottlenose dolphin as revealed by behavioural
observations. Typical sucking sounds were observed during 71 to 81% of
all suckling bouts. Since the neonates produced more sounds at the
beginning of the suckling sequence than expected, it appeared that
they might use the sounds as care-solicitation signals or begging
signals. These sounds contained a higher proportion of whistles than
sounds in other contexts, which implied that the proportions of sound
types, especially whistles, were important for neonatal dolphins and
their mothers to initiate the nursing sequence.
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