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The Blue Whale, Balaenoptera musculus

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  • Blue Sea Research

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pers. They are members of the family Balaenopteridae, all of which have fringed baleen plates rather than teeth. Baleen whales graze through swarms of small crustaceans known as krill, and capture the krill in their baleen as water is filtered through. Like most balaenopterids, blue whales exhibit no well defined social or schooling structure, and in most of their range they are generally solitary or found in small groups (Tomilin, 1957). Distribution and Migration Blue whales are found in all oceans and undertake extensive north-south migrations each year, traveling from winter grounds in low latitudes to summer feeding grounds in the Arctic or Antarctic high latitudes. Since most whaling occurred on the high­ latitude feeding grounds, the distribu­ tion of these whales in these areas is fairly well known. In Antarctic waters, for example, blue whales and minke whales, Bal­ aenoptera acutorostrata, are found in the coldest waters closest to the ice edge, with fin, B. physalus, and sei whales, B. borealis, distributed, respectively, in somewhat lower latitudes (Mackintosh, 1965). A distinct subspecies called the pygmy
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The Blue Whale,
Balaenoptera musculus
SALLY
A.
MIZROCH, DALE
W.
RICE,
and JEFFREY
M.
BREIWICK
Introduction
The blue whale, Balaenoptera mus-
culus (Linnaeus, 1758),
is
not only the
largest
of
the whales,
it
is
also the
largest living animal, and may range
in size to over
30
m (100 feet) and
weigh up to
160
metric tons (t)
(Mackintosh, 1942). Blue whales are
entirely bluish-gray in color, except
for the white undersides
of
the flip-
The authors are
with
the
National Marine
Mammal Laboratory, Northwest and Alaska
Fisheries Center, National Marine Fisheries
Service, NOAA,
7600
Sand Point Way N.E.,
Bin
C15700, Seattle,
WA
98115.
pers. They are members
of
the family
Balaenopteridae, all
of
which have
fringed baleen plates rather than
teeth. Baleen whales graze through
swarms
of
small crustaceans known
as krill, and capture the krill in their
baleen as water
is
filtered through.
Like most balaenopterids, blue whales
exhibit no
well
defined social
or
schooling structure, and
in
most
of
their range they are generally solitary
or
found
in
small groups (Tomilin,
1957).
Distribution and Migration
Blue whales are found in all oceans
and undertake extensive north-south
migrations each year, traveling from
winter grounds in low latitudes to
summer feeding grounds in the Arctic
or
Antarctic high latitudes. Since
most whaling occurred on the high-
latitude feeding grounds, the distribu-
tion
of
these whales in these areas
is
fairly
well
known.
In Antarctic waters, for example,
blue whales and minke whales, Bal-
aenoptera acutorostrata, are found
in
the coldest waters closest to the
ice
edge, with fin, B. physalus, and
sei
whales, B. borealis, distributed,
respectively, in somewhat lower
latitudes (Mackintosh, 1965). A
distinct subspecies called the pygmy
Figure
I.
- Geographical distribution
of
the blue whale. Simple hatching indicates the
summer
feeding
grounds.
Stippling
indicates distribution
during
autumn,
winter,
and
spring; records
are
scarce
during
these seasons,
and
the distribution is,
to
a large extent, speculative.
46(4),1984
15
A
blue
whale
surfacing
in
the
North
Atlantic
off
Spain
reveals
its
mottled
back
and
small
step-like
dorsal
fin.
Photo
by
S.
Mizroch.
blue whale,
B.
m. brevicauda, in-
habits the southern Indian Ocean
south to lat. 55°S (Ichihara, 1966).
The Northern Hemisphere distribu-
tion
of
blue whales
is
not as clear-cut.
Jonsgard (1%6) reports blue whales
at
the edge
of
the pack
ice
in the North
Atlantic. Nishiwaki (I966), using
catch statistics,
fixes
the northern
limits in the North Pacific
at
the Aleu-
tian Islands, although Sleptsov (I
96
I)
saw blue whales
as
far north
as
the
Chukchi Sea.
The winter distribution
of
blue
whales remains something
of
a
mystery. Since blue whales migrate to
and from winter grounds in the open
ocean, away from coastlines where
they may be observed, scientists have
yet to delineate these areas in either
the Northern
or
Southern Hemi-
spheres (Jonsgard, 1966; Mackintosh,
1966). Summer and assumed winter
distributions are shown
in
Figure I.
Stock Identity
The stocks
of
blue whales can be
16
grouped into four large geographic
regions: The North Pacific, North
Atlantic, northern Indian Ocean, and
Southern Hemisphere. Within these
large areas there are further stock
separations.
North Pacific
Blue whales have been hunted
in
Japanese and Korean waters,
off
Kamchatka, in the Aleutian Islands,
and in smaller numbers
off
California
and British Columbia, but very little
is
known
of
movements and stock
boundaries
of
blue whales in the
North Pacific. They are found from
the Chukchi Sea south to the waters
off
Taiwan and Costa Rica (Rice,
1978;
Leatherwood, et aI., 1982), but
there
is
no speculation as to stock
units in this broad area, and the Inter-
national Whaling Commission (IWC)
has not set specific boundaries.
North Atlantic
Blue whales have been hunted
off
northern Norway, Svalbard (Spits-
bergen), Iceland, the British Isles
(primarily the Hebrides), and New-
foundland. The pattern
of
exploita-
tion generally was
of
high catches in
one location over a
10-
to 15-year
period, followed
by
a sharp decline
in
catches, after which time the industry
moved to another location and
repeated the pattern
(TIDnnessen
and
Johnsen, 1982). J
onsgiird (I955) con-
cluded that these localized depletions
in blue whale stocks were a result
of
excessive hunting, and assumed some
separation in stock units. No specific
studies have been conducted to test
this, however, and the IWC considers
the North Atlantic stock as one unit
for management purposes.
Northern Indian Ocean
Blue whales have been reported
year-round in the Gulf
of
Aden, Per-
sian Gulf, and Arabian Sea, eastward
across the Bay
of
Bengal to Burma
and the Strait
of
Malacca. Nothing
is
known
of
the seasonal movements
of
these animals. A temporarily stranded
female gave birth to a calf in Trin-
comalee Harbour, Sri Lanka, in
Marine
Fisheries
Review
Rear
view
of
a blue whale surfacing
off
Spain, showing the broad lunate tail flukes. Photo
by
S.
Mizroch.
December
1946.
The blue whales
in
this area probably constitute a
separate stock and have never been
hunted.
Southern Hemisphere
The main feeding areas in the
Antarctic were separated into five
(and later six) statistical areas by the
IWC. These areas were developed
based on distributions
of
humpback
whale,
Megaptera novaeangliae
(Mackintosh, 1966), and
mayor
may
not indicate stock differences
in
other
balaenopterids, such
as
blue whales.
Mark-recapture experiments are in-
conclusive,
and
although many
whales are recovered near where they
were marked, some are recovered one
or more areas away. Brown (1962)
hypothesized that blue and fin whales
disperse more on the feeding grounds
than do humpback whales, and con-
sequently there
is
overlap among
various breeding stocks. Since blue
whales, unlike humpbacks, have no
well
defined breeding areas,
it
is
im-
possible to delineate the Southern
46(4),1984
Hemisphere breeding stock units. For
management purposes, however, the
IWC considers the whales
in
each
of
the IWC statistical areas to be sep-
arate stock units.
Life History and Ecology
Feeding
Most blue whales spend the sum-
mer in high latitudes and the cold cur-
rents on the eastern sides
of
the
oceans, where food production
is
high. They often range offshore, but
less
so than
fin
whales, and tend to be
nomadic. The blue whale
is
virtually
monophagous, and feeds almost
ex-
clusively on euphausiids, or krill, that
congregate in dense shoals near the
surface-notably:
Euphausia super-
ba, E. crystallorophias, and E. vallen-
tini
in
the Antarctic; E. pacifica,
Thysanoessa inermis,
T.
longipes, and
T.
spinijera
in
the North Pacific; and
Meganyctiphanes norvegica and
T.
inermis in the
North
Atlantic
(Nemoto,
1959).
The only exception
appears to be
off
the coast
of
Baja
California, where they have been seen
feeding on shoals
of
the pelagic red
crab,
Pleuroncodes planipes (Rice,
1978).
Blue whales, like most other baleen
whales, migrate several thousand
miles toward equatorial waters in the
autumn. During the winter they fast
for several months, living
off
their fat
reserves.
Reproduction
The basic reproductive cycle
of
the
blue whale
is
biennial. Mating takes
place over a 5-month period during
the winter. Females appear to be
seasonally monoestrous, but if they
fail to conceive, they may ovulate two
or
three times during one estrous
cy-
cle. The single calf, born after a gesta-
tion period
of
about 1 year, measures
about 7 m
(23
feet) long. The calf
is
weaned late the following summer
when it
is
about 7 months old and
16
m
(53
feet) long. Both sexes attain
sexual maturity at an age
5-15
years.
17
Current
and Pre-exploitation
Stock Sizes
Gambell (1976) evaluated various
rough estimates
of
current
and
pre-
exploitation blue whale stock sizes
and
presented the following sum-
marized figures:
Management
There has been little new informa-
tion
on
blue whale abundance since
hunting ceased in 1967. While there
have been numerous sightings
of
blue
whales
off
Mexico (Baja California)
during the last several years, there are
little
or
no useful census
data
for
population assessment.
Blue whale populations have
not
been assessed by the
IWC
since the
mid-1970's.
Estimates
of
the
in
the Antarctic, enabling the industry
to
process whales wherever they were
found. Since catcher boats were no
longer limited
to
operating near land
stations
or
moored factory ships, blue
whale catches, which had ranged
from
about
2,000
to
6,000 per year
from 1914 through 1924, suddenly in-
creased from 12,734 in 1928-29 to
29,410
in
1930-31.
Although the scale was different,
the general pattern
of
exploitation
in
the Antarctic was the same as
everywhere else. By 1936-37, only
14,304 blue whales were taken,
and
by
1937-38 the fin whale catch (28,009)
was nearly double the blue whale
catch (14,923) (Fig. 2). Afterward, the
blue whale catch declined steadily un-
til it ceased with the
ban
on blue
whale catches in 1967.
Natural Mortality
Important
natural mortality factors
are unknown.
The
blue whale
is
rela-
tively free
of
ectoparasites and en-
do
parasites (Rice, 1978). They
do
not
even
harbor
the stomach worms,
Anisakis sp., which are nearly ubiq-
uitous in virtually all other cetacean
species; presumably this
is
because
blue whales
do
not
eat fish, which are
the host
of
the infective stage
of
the
worms. Predation
on
blue whales by
killer whales, Orcinus orca,
is
rare.
Natural mortality rates have
not
been
established, but may be considered to
be similar
to
those
of
the fin
whale-
about
4 percent per year in adults
(Allen, 1980).
Exploitation and Population Size
History
of
Exploitation
Large-scale exploitation
of
blue
whales did not begin until the in-
troduction
of
the explosive
harpoon
and
the steam-powered catcher
boat
in Norway
in
1864. This marked the
beginning
of
the modern phase
of
whaling, in which whalers had the
tools
to
hunt
the faster swimming, less
buoyant rorquals.
North Pacific
Although the Japanese did not
enter the era
of
modern whaling until
the turn
of
the century, they enjoyed
some success catching rorquals (most
likely other
than
blue whales) in
earlier times using a sophisticated net-
ting technique. Blue whale catches by
the Japanese, using modern techni-
ques, peaked in 1912 (236), declined
substantially the next year (58), in-
creased in 1914 (123),
and
declined
thereafter until they ceased entirely
when
IWC
regulations prohibited
their capture after
1965
(Tj1Innessen
and
Johnsen, 1982).
Modern whaling
off
the Pacific
coast
of
North America began in
1905
in Victoria, B.C., with a Norwegian
crew
contracted
by
Canadian
businessmen.
The
early catches were
mostly humpback whales,
but
some
numbers
of
blue whales were also
taken. According to
Tj1Innessen
and
Johnsen (1982), the peak catch
of
blue whales (239) in the northeastern
Pacific occurred
off
California in
1926.
The
catch
of
blue whales south
of
the Aleutians averaged
about
50 a
year until 1930. In these areas, as
in
the North Atlantic, catches rose,
peaked, and declined in a fairly short
period. During the late 1950's
and
ear-
ly
1960's,
Japan
caught
about
70 blue
whales per year near the Aleutians,
but
by 1966
IWC
regulations
prevented the capture
of
blue whales.
North At/antic
When modern whaling began in the
North Atlantic, blue whales were the
preferred species due to their great
size.
The
first catches occurred
off
northern Norway in the late 1860's,
but
by 1882 whalers were catching
more
fin
than
blue
whales,
presumably because
of
declines
in
blue whale stocks (Committee for
Whaling Statistics, 1931). This pat-
tern was repeated as the industry ex-
panded
to
Iceland, the Faroe Islands,
Newfoundland,
Svalbard
(Spits-
bergen), and islands
off
the British
coasts. Catches
of
blue whales in each
of
these areas were generally high the
first 5-10 years, after which catches
of
fin whales predominated for a
few
years, and then catches declined
altogether, and the industry would
move
to
another whaling ground.
In
the peak years, catches
of
blue
whales numbered well over 300 per
year in the North Atlantic,
but
by the
post-World
War
I years, catches
began
to
average only 40-50 per year.
By 1952, catches fell to
15
or
less per
year, and the capture
of
blue whales
in this area was banned entirely
in
1960.
Southern Hemisphere
Whaling
in
the Southern Hemi-
sphere began
in
1904,
and
early
catches were predominantly hump-
back whales.
By
1913, however,
humpback whale catches had begun
to
decline, and the blue
and
fin whale
catches began to increase. In 1925, the
first floating factory ship able
to
pro-
cess whales on
board
was introduced
N. Atlantic
N. Pacific
S. Hemisphere
Antarctic
blue
pygmy blue
Pre-exploita-
tion stock
1,100-1,500
4,900
180,000
(150,000-
210,000)
10,000
Current
stock
100
1,600
(1,400-
1,900)
5,000
5,000
18
Marine
Fisheries
Review
40000
Figure
2.
- Catch
of
blue, fin, and
sei
whales
in
the Antarctic,
1920-75
(from
the Bureau
of
International Whaling Statistics).
30000
blue-
S'
u
20000
a
U
'0000
biological parameters
of
blue whales
are probably no longer current and
therefore may have little or no validity
at present. In addition, there are no
useful indices
of
abundance covering
the period since blue whale hunting
ceased in
1967.
Although there are oc-
casional sightings
of
blue whales,
there have been no recent surveys to
assess the stocks. The
few
sightings in
the Southern Hemisphere indicate
that they are still
at
very low levels
relative to their estimated pre-
exploitation population size. Given
the relative scarcity
of
blue whales
based on opportunistic sightings, the
low population estimates relative to
their initial abundance, and the low
intrinsic rate
of
increase noted for this
and other baleen whale populations,
to
date, there
is
no evidence that the
46(4),1984
blue whale stocks in the Southern
Hemisphere and North Pacific are
recovering. A local stock
of
blue
whales appears to be doing
well
in the
Gulf
of
St. Lawrence and
is
the object
of
whale-watching trips.
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K.
R.
1980. Conservation and manage-
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Whaling Stat., Oslo, Nor.,
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p.
Gambell,
R.
1976. World whale stocks. Mam-
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19
... The frequency variations corrected from the general linear decrease, as measured by or for the antarctic blue whale, show a general increase between October and April and a decrease afterwards. These variations can be interpreted in the mark of the yearly reproduction-feeding cycle of the antarctic blue whales (Mizroch et al., 1984;Sears and Perrin, 2018). During austral summer, a feeding period, less songs are detected and the pressure of reproduction seems lower. ...
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... Quant aux baleines bleues pygmées, elles s'alimenteraient en zone subantarctique, et remonteraient vers les eaux tropicales pour hiverner (Ichihara, 1966;Ichihara et al., 1981;Kato et al., 1995). Cependant, la localisation des routes de migration et aires d'hivernage et de reproduction est encore mal connue Mizroch et al., 1984;Branch et al., 2007;. L'observation visuelle n'étant pas efficace pour combler ce manque d'information, les chercheurs mettront alorsà profit l'activité vocale intense des grandes baleines pour lesétudier. ...
Thesis
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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.
... Knowledge of the actual distribution of blue whales (Balaenoptera musculus; Linnaeus, 1758) is incomplete throughout most of its range (e.g., Mizroch et al., 1984;Mate et al., 1999;Branch et al., 2007). Population numbers have dropped worldwide as a consequence of an intensive harvesting period, and no complete record of the species' distribution previous to commercial whaling exists. ...
... La especie más pequeña de mamífero es el murciélago hocico de cerdo (Craseonycteridae thonglongyai) de Tailandia, que mide 33 mm de largo y pesa no más de 2 grs. (Hulva y Horacek 2002) y la más grande la ballena azul (Balaenoptera musculus) con 30,5 metros de largo y un peso de 150 toneladas (Mizroch, Rice, y Breiwick 1984). ...
... Differences in reaction characteristics were noted between species, including wound severity and duration as confirmed by significant modeling results. There are marked body size differences between the two subject species (12 m, 35 tons and minimum of 21 m, 100 tons for gray and blue whales, respectively; Mizroch et al. 1984;Rice et al. 1984). Gray whales have a greater prevalence of swellings and depressions compared to blue whales suggesting greater reactivity to skin and blubber layer insults. ...
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Tags have been used to examine migration routes and habitat use of large whales for >40 yr, however, evaluation of tag wound healing has largely been short-term, anecdotal or generalized. This study developed methods for systematic photographic assessment of long-term external consequences of tag placement , to determine potential differences in wound healing between species and tag types and thus advise future tagging efforts to possibly minimize undesirable side effects. Tag site appearance and healing characteristics were evaluated by two reviewers and a time series evaluated by five veterinarians from photographs during 995 postdeployment encounters with 34 gray and 63 blue whales tagged in the North Pacific. Blue whale resightings were less frequent, but spanned a longer time period due to earlier tag deployments than the more frequent gray whale follow-up observations. Swelling occurred in 74% of reencountered gray whales, with the highest frequency 6 mo postdeployment. Swellings were common in blue whales with early tag designs but rare with current models.
... In fact, it is assumed that blue whale distribution is largely governed by food requirements, almost year-round, which may explain their extensive roaming (Reeves & Clapham, 1998;). Most reproductive activity (i.e., mating and calving) takes place during the winter but there is no knowledge about the existence of specific breeding or calving grounds (Mizroch et al., 1984). This is in contrast with what is known form the closely related humpback whale, that performs seasonal migrations between the same feeding and breeding grounds every year. ...
Thesis
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Long-range acoustic communication represents one of the main modalities to transmit information and maintain social relationships among distant individuals. By examining variation in long-range signals, we can gain insights into their function as well as the processes underlying the variation. Since communication and social behaviour are tightly linked, variation in acoustic signals can reflect behavioural patterns that are important to better understand the sociobiology of a species. Moreover, changes in vocal behaviour can also be induced by factors interfering with acoustic communication, such as anthropogenic noise. In my thesis, I investigated patterns of variability in the long-range male vocal displays (‘songs’) of North Atlantic blue whales (Balaenoptera musculus) at the level of the population, the individual, as well as in relation to the social and behavioural context. I also examined whether seismic noise affected the production of blue whale ‘calls’, transient discrete vocalisations used by both sexes in short-range social contexts. Blue whales are invaluable for the study of variation in long-range signals because they live in a highly fluid social environment, and their songs - redundant, patterned sequences of infrasonic sounds - can be heard over hundreds of kilometres. I collected simultaneous behavioural observations and acoustic recordings in the field and analysed the temporal and acoustic structure of blue whale songs. I found that multiple features differed between the songs of blue whales from the eastern and western North Atlantic. It is thought that due to the extensive singing during their basin-wide roaming, blue whales throughout the North Atlantic may be physically and/or acoustically sympatric. The song divergence found here was likely dependent on ecological factors, but could also have been driven by mate choice. In fact, songs are thought to be male reproductive displays, suggesting that female preferences for specific traits could have accounted for the observed differences. Blue whale songs also showed inter-individual variation and may thus convey information relevant to distinguishing between singers. Considering that multiple senders can be active at the same time, individual song differences are likely used by conspecifics to assess individuals. Since blue whales roam highly dispersed, singing might play a role in mediating inter-individual interactions from a distance (e.g. mate attraction). This hypothesis was supported by the fact that songs were always produced by single steadily moving males and appeared to be directed to an unknown audience. In contrast, I found that in stationary situations (feeding, socialisation) and in the presence of females nearby, infrasonic sounds composing a song were emitted singly or in short irregular sequences (fragments). This suggests that in a stationary short-range situation, the repetition and redundancy found in songs is superfluous because potential receivers are in close physical and visual range. Fragments might suffice to indicate the presence of a signaller and efficiently transfer individual information. Finally, I found that blue whales consistently increased call production when exposed to seismic survey activity. The observed response presumably represents a compensatory behaviour to the rise in ambient noise from the seismic survey. Increasing call production could enhance the probability of receivers to detect the signal (‘information theory’). Since the response was observed at low noise levels, this finding has substantial management and conservation implications. This thesis increases our knowledge about the use of long-range vocalizations in blue whales, particularly with respect to mate attraction and also about compensatory vocal behaviours in response to interfering anthropogenic noise. It shows that variation can occur at multiple levels of the signal and that blue whale songs are multicomponant signals that might have evolved to cope with a variable socio-ecologial environment. ZUSAMMENFASSUNG: Langstrecken akustische Kommunikation ist das beste Mittel, um Information zwischen entfernten Individuen auszutauschen und somit soziale Verbindungen auch auf Distanz aufrecht zu erhalten. Beim Untersuchen von Variationen in Langstrecken-Signalen können wir Einsicht über die Funktion der Signale gewinnen und über die Faktoren, welche zu diesen Variationen geführt haben. Weil Kommunikation und Sozialverhalten stark miteinander verbunden sind, können Variationen in akustischen Signalen Verhaltensmuster wiederspiegeln, die wichtig sind, um die Soziobiologe einer Art besser zu verstehen. Zudem, können Veränderungen im akustischen Verhalten auch von externen Faktoren bewirkt werden, welche die akustischen Kommunikation beeinträchtigen, wie zum Beispiel anthropogener Lärm. In meiner Dissertation habe ich Variationsmuster in den Langstrecken- Signalen von nordatlantischen Blauwalmännchen (Balaenoptera musculus) untersucht, den sogenannten ‚Gesängen’, und zwar auf der Ebene der Population, des Individuums, sowie im Zusammenhang mit dem Verhalten und dem sozialen Umfeld. Ausserdem habe ich den Einfluss von seismischem Lärm auf die Produktion von ‚Rufen’ untersucht. Rufe sind flüchtige Signle, die unregelmässig erzeugt werden und im Repertoire der Männchen sowie der Weibchen vorkommen, meist bei sozialen Interaktionen. Blauwale sind interessant für Studien im Bereich von akustischen Variationen, weil sie in einem sehr veränderlichen sozialen Umfeld leben und ihre Gesänge - redundante, strukturierte Sequenzen von Infraschallsignalen – über hunderte von Kilometer gehört werden können. Ich habe gleichzeitig akustische Aufnahmen und Verhaltensdaten im Feld gesammelt sowie die zeitliche und akustische Struktur von Blauwalgesängen analysiert. Dabei habe ich festgestellt, dass die Gesänge von West- und Ost-Atlantik Blauwalen sich in mehreren Eigenschaften unterschieden. Wegen des kontinuierlichen Singens während der weitläufigen Wanderungen, sind Blauwale innerhalb des Nordatlantiks sehr wahrscheinlich akustisch oder physisch sympatrisch. Die Gesangsunterschiede waren zum Teil auf ökologische Faktoren zurück zu führen, könnten aber aufgrund von sexueller Selektion enstanden sein. Man nimmt nämlich an, dass es sich beim Blauwalgesang um ein Balzverhalten handelt. Im Falle der beobachteten Unterschiede könnten also auch weibliche Vorlieben für gewisse Gesangseigenschaften zugrunde liegen. Blauwalgesänge wiesen auch individuelle Unterschiede auf, welche Informationen beinhalten könnten, die beim Unterscheiden der Sänger relevant sein könnten. Wenn man bedenkt, dass mehrere Individuen gleichzeitg singen können, ist es plausibel, dass individuelle Unterschiede von Artsgenossen verewendet werden, um Individuen abzuschätzen. Weil Blauwale weit entfernt von einander herum ziehen, könnte das Singen bei interindividuellen Interaktionen auf Distanz eine wichtige Rolle spielen (z. Bsp. um Weibchen anzulocken). Dies wird auch dadurch bekräftigt, dass Gesänge immer von einzelnen, konstant schwimmenden Männchen erzeugt wurden und allem Anschein nach einer unbekannten Zuhörerschaft gerichtet sind. Im Gegensatz dazu wurden in stationären Situationen (Fressen, Sozialverhalten) und immer in Anwesenheit von Weibchen, Einzelnoten oder Gesangsbruchstücke produziert. Dies weist darauf hin, dass in einer stationären Situation, wo Individuen in Reichweite voneinander sind, ein repetitives Wiederholen wie bei den Gesängen nicht erforderlich ist, weil die möglichen Empfänger in der Nähe sind. Zum Schluss, habe ich gezeigt, dass Blauwale, die seismischem Lärm ausgesetzt waren, konsistent mehr Rufe produzierten. Diese Antwortreaktion stellt möglicherweise ein Kompensationsmechanismus dar, um den Lärmeinfluss zu überwinden. Eine Rufzunahme würde die Wahrschienlichkeit erhöhen, dass Empfänger das Signal erkennen können (‚Informationstheorie’). Weil die Tiere bereits bei rlativ niedrigen Lärmwerten reagierten, könnten diese Forschungsergebnisse auch wichtige Folgen für den Artenschutz haben. Diese Dissertation trägt zum besseren Verständnis von Langstrecken-Kommunikation bei Blauwalen bei, vor allem im Bezug auf Balzverhalten und Partnersuche, sowie von Anpassungsmechanismen, um den mit der Kommunikation interferierenden Lärm zu überwältigen. Sie zeigt auch, dass Variationen auf verschiedenen Ebenen der Signalstruktur auftreten, und dass Blauwalgesänge Multikomponenten-Signale darstellen, die sich höchstwahrscheinlich entwickelt haben, um in einem sozial sowie ökologisch variablen Lebensumfeld zurecht zu kommen.
... Estimates of the blue whale population in the North Pacific range from about 1400 to 3500 Mizroch et al., 1984; Yochem and Leatherwood, 1985; Barlow, 1994, and the number of animals found along the coast of central California appears to be increasing Calambokidis et al., 1990; Barlow , 1994. Little is known about the numbers or distribution of blue whales off the Pacific Northwest. ...
Article
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Blue whale calls were recorded off central California in the Fall of 1993. These calls were characterized as to duration, frequency downsweep, intercall interval, and sound‐pressure level. Average values were determined from 303 calls, including up to three harmonics (fundamental downsweep from 18.9 to 17.2 Hz over 16 s). These frequency‐domain characterizations were then used to develop numerical time series (kernels) that, when convolved with the original time series, produce correlation peaks indicating the presence of blue whale calls (matched filter). When harmonics were present in the data, a combined kernel, including the fundamental frequency and first harmonic, improved the signal to noise ratio over use of the fundamental kernel alone. These matched filters were able to detect blue whale calls even in very ‘‘noisy’’ time series. When applied to hydrophone recordings from three U.S. Navy SOSUS (SOund SUrveillance System) arrays, it is possible to produce locations for blue whale calls by timing the arrival of individual calls and applying least‐squares techniques. This information can be used to increase our knowledge of blue whale distribution in the northeast Pacific. The methods described here may also be extended to other species that employ low‐frequency vocalizations or to other ocean areas.
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This chapter discusses the factors that force the ecosystem to change. Physical changes include climate and geophysical forces. The Earth's climate system includes the atmosphere, ocean, cryosphere, and land, and changes in one affect the others through transfers of matter and energy. Interannual and interdecadal changes in the Gulf of Alaska ecosystem are primarily forced by the atmospheric or oceanic components of the climate system. The chapter also gives an overview of (1) the biological interactions among the species, (2) harvesting and predator control by man, (3) effects of disease on populations, and (4) the effects of man's wastes in the ocean. Exotic species can disrupt marine ecosystems. Competition is when populations compete for the same resources, which are in limited supply, with adverse effects to one or both competing populations. Commensalism is when the benefits accrue to only one species, and the host is unaffected. Marine ecosystems are composed of tangled food webs reflecting complex linkages of predators and prey. Food chains and food webs are convenient graphical depictions of the flow of energy, carbon and nutrients throughout an ecosystem. Reproductive competence is perhaps the highest ecological relevance of all the physiological responses.
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With coverage on all the marine mammals of the world, authors Jefferson, Webber, and Pitman have created a user-friendly guide to identify marine mammals alive in nature (at sea or on the beach), dead specimens in hand, and also to identify marine mammals based on features of the skull. This handy guide provides marine biologists and interested lay people with detailed descriptions of diagnostic features, illustrations of external appearance, beautiful photographs, dichotomous keys, and more. Full color illustrations and vivid photographs of every living marine mammal species are incorporated, as well as comprehendible maps showing a range of information. For readers who desire further consultation, authors have included a list of literature references at the end of each species account. For an enhanced understanding of habitation, this guide also includes recognizable geographic forms described separately with colorful paintings and photographs. All of these essential tools provided make Marine Mammals of the World the most detailed and authoritative guide available! * Contains superb photographs of every species of marine mammal for accurate identification * Authors collective experience adds up to 80 years, and have seen nearly all of the species and distinctive geographic forms described in the guide * Provides the most detailed and anatomically accurate illustrations currently available * Special emphasis is placed on the identification of species in problem groups, such as the beaked whales, long-beaked oceanic dolphin, and southern fur seals * Includes a detailed list of sources for more information at the back of the book.
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A. G. Tomilin Zveri: SSSR I Prilezhashchikh Stran (The Mammals of the USSR and Adjacent Countries). Vol IX. Kitoobraznye (Cetacea). Publ. Acad. Nauk USSR, Moscow. 756 pp., XII pI. (in color), 146 figs., 196 tables, Appendix (7 tables). 1957. [In Russian.] After the death of S. I. Ognev in 1951, V. G. Heptner was chosen as general editor of the remainder of this important series. The present volume, begun by Tomilin under the direction of Ognev, is the first to come out since Vol. VII appeared in 1950, and is fittingly dedicated to Ognev, the founder of the series and teacher of both Heptner and Tomilin. The first six pages of the text are devoted to “Sergei Ivanovich Ognev and his ‘Mammals of the USSR,’ ” a review and obituary by Heptner. In this section, incidentally, it is explained that Vol. VIII was to include the remaining subfamilies of rodents not covered in earlier volumes: Murinae and Cricetinae, to be prepared by Ognev; Gerbillinae, to be written by Heptner. Ognev was only part way through the genus Rattus when he died and the work was not completed. I could find no further mention of the fate of Vol. VIII. The reader is directed to an earlier review by Quay (Jour. Mamm., 32: 472–474, 1951) for the …