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CSS Dixieland
Probing the depths of knowledge
These essays by P. A. Stonemann, CSS Dixieland, cover a wide range of
historical, philosophical, scientifical and technical subjects. Each page
deals with a particular topic, divided into sections and explained by itself.
Every page shows at its top hyper links to every other page. The Start page
also has short descriptions of the other pages. CSS Dixieland expresses
gratitude to the readers that make this work meaningful.
This Web document has been tested with KDE Konqueror, graphic HTML interpreter
for Linux. It may not be rendered correctly by other graphic HTML interpreters.
It will probably be correct when rendered by text-only HTML interpreters (visual,
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Uniform Resource Locator:
Whales Biology page
The mysterious whales of Abrolhos Islands
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Description
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Description
A puzzle of enigmas
Among the mysteries of Nature, Humpback whales present a stubborn resistence
to let us know many aspects of their life. Researchers are baffled with more
questions than answers. Some of these enigmas are listed in this essay, a few
hypotheses are proposed. The most challenging of them is perhaps their mode
of communication: like it also happens with other cetaceans, there is strong
evidence suggesting that Humpbacks possess a complex linguistic code. May it
be that they indeed have a language ? And how rich that language may prove to
be for expressing abstract thought ?
Let us dive with those huge mammals in the following lines, in our quest for
probing the Depths of Knowledge.
The Humpback whale
The humpback whale is a baleen whale and a rorqual whale that sings amazing
songs. It performs complex and cooperative fishing techniques. The humpback
has a bulky head with bumpy protuberances (tubercles), each with a bristle.
Humpbacks are acrobats of the ocean, breaching and slapping the water. They
live in pods and have two blowholes. The name humpback describes the motion
that it makes as it arches its back out of the water in preparation for a
dive. The top of its body is dark blue or black, it may show some mottled
markings. The colour of its bottom surface varies widely from all black to
all white, through various degrees of marbling. Its dorsal fin is variable in
shape, from almost flat to tall and triangular. The flippers are the longest
of any animal, approximately one third of the body length. Humpback whales
are commonly found in coastal or shelf waters in high latitude areas in
summer, feeding in the cold, productive waters. In winter, they migrate to
mating and calving grounds in tropical or sub-tropical waters.
The Megaptera novaeangliae, or Humpback whale, is the most acrobatic species
among the giant cetaceans. Its fins are the biggest of any whale, reaching in
length one third of its body, and almost always richly covered with marine
barnacles. The gigantic animal likes to slap or slide a fin on the water
surface, to stay for some seconds with the head or the tail out of the water
in vertical position, or even to go out of the water in a spectacular jump
and to fall back noisely, rotating on itself. These demonstrations of
strength and agility captivate tourists, that every summer flock by the
thousands to see and photograph the attractive Mysticeti (whales with baleens
in their mouths, the other sur-order of the Cetaceans is that of the
Odontoceti, dolphins and porpoises with teeth in their mouths). In spite of
the circus-like acrobatic activity having been observed many times, nobody
knows what its purpose may be. Whales must know, but scientists stay divided
by the hypotheses of being an elimination of parasites, or else to call the
attention of other whales, or else just for fun. Other well hidden secrets of
Humpback whales are:
Along all the inferior side of the jaw they present some characteristic
protuberances, each of them with a sole projection of keratine. They are
supposed to be sensory organs for detecting movements in the water, or
perhaps for communication with other whales, but there is absolutely no
certainty. Humpback males sing tunes that last for some minutes, and after a
short interval they repeat identical tune in the whole. The serenade may last
for hours or even for days. It is surmissed that its intention be to attract
the attention of females, because females never sing, but nothing is known
for sure. It may be only a joyful game, or out of a certain musical
inclination. Even more surprising: Humpback whales have no vocal cords !!!
Considering that they only sing while being submerged, never on the surface,
and that they are lunged animals and therefore they need to go partly out of
the water for breathing, the singing feat is a mistery that leaves scientific
researchers perplexed. There is no way to know how they manage to produce the
sounds. It is possible, but not at all proved, that their ventral plates play
a part in that function.
Their songs have been recorded by means of immersed microphones, and then
carefully studied with the help of computers. The typical frequency range is
between 40 Hertz and 5 Kilo Hertz, though they are quite capable of emitting
sounds ranging from so low as 20 Hertz to so high as 9 Kilo Hertz. This in
itself is not so impressive to us, opera singers can do it at least in one of
the extremes of the scale, and go up and down at will. What perhaps would be
curious to some is the verified fact that their songs change slightly from a
year to the next, but in a given year they are identical for all humpback
males of each of the three large ocean areas in which they are distributed:
the North Atlantic, the North Pacific, and the Southron parts of the
Atlantic, Pacific and Indian Oceans. This means that the language or dialect
of each of these three groups is different from the other two. Here we have
another interesting mystery: will it be that they be capable of communicating
messages through their songs ?
It is not clear that the songs of a male Humpback modify dramatically the
behaviour of other Humpbacks, though such modifications have been observed in
the sounds emitted by dolphins. It would be anthropocentrical to excess to
deny the possibility of the Humpbacks possessing a language for each of the
three big oceanic groups in which they are distributed. The evidence is not
conclusive, but some patterns of their behaviour support strongly this idea.
For instance, among all whales the Humpbacks seem to be those who have
developed to its maximum a technique for fishing. When finding a school of
fish, a Humpback calls the others. Several of them form a compact group and
submerge to some metres of depth. They begin to rotate in a circumpherence,
each whale following the tale of its predecessor. They coordinate very well
their masterly swimming, in a manner that they always stay exactly under the
shoal. At a given instant, all the whales release huge air bubbles, that in
rising to the surface form a barrier that provokes confusion in the fish.
Simultaneously, and without any collision or obstacle among them, the
Humpbacks swim to the surface while taking mouthfuls of water and fish. They
expel most of the water and swallow the fish. They must have some signal that
allow that perfect sinchrony, but we do not know what that signal might be.
The fact that whales are the biggest animals that ever existed in this
planet, some of them even bigger than the huge saurians of the Triassic,
Jurassic and Cretacic periods, means that their study might potentially be a
dangerous activity for human researchers. They are not hostile on purpose
against humans, except if being hurt by them, but they do not care much if
accidentally they hit a diving scientist. The hit may kill the human, and
being a martyr of Science is not so attractive for most sages.
The Megaptera novaeangliae inhabits in all the world oceans except in the
frozen poles, though some specimen has been reported very near the pack ice.
It is a mammal who can resist cold waters if necessary, but who obviously
prefers warm waters, and probably for this reason, and also because of
availability of food, migrates annually from a certain wintering area to
another certain summering area, that year after year are the same areas for
each group of matrilineal ancestry. Only a sub-group that inhabits in the
Arabian Sea seems to be non-migratory: it spends in the same area the whole
year round. To know these things implies for us to be able to recognise
individuals, and considering that trying to attach on them any kind of plate
or wireless emitter is not a very feasible procedure, the best solution is to
photograph them. In effect, the colour patterns among whales are so
characteristically individual as lines in zebras or finger-prints in humans.
Their abdomen may be from completely white to completely black, with all
intermediate shades or also with motted marks.
In spite of grouping sometimes for fishing, they are not in reality animals
who establish long standing social bounds, for what it seems. Most of the
time they fish alone, and except in specific areas and times of the year,
they do not show a marked proclivity to form tight groups. Every two or three
years mothers give birth to a single calf, after eleven to twelve months of
gestation. Very seldom they have twins, less than once in a hundred births.
The calf is for the first time helped by its mother in going to the surface
for breathing, and before thirty minutes have passed from birth, the baby can
already swim at will. Because of being a mammal, it is evident that it will
feed on milk, but it does that in a rather curious manner: the mother
releases enormous amounts of milk very rich in lipids, in fats, and because
this milk is of lower density, lighter in mass per volume than sea water, it
stays forming a plate more or less stable on the sea surface. Immediately the
calf darts to the delicious meal and swallows it at a speed that would leave
a hundred bull-calves open mouthed in amazement. The lactation of a baby whale
is performed at least twice a day, and it lasts for about a year. Gradually,
the young whale will begin to eat the solid food that in immense quantities
will form its diet for the rest of its adult life: small fish, molluscs and
crustaceans, in particular the tiny crustacean known as krill, that seems to
be the favourite of the whale every time that it find a large mass of them.
Taxonomy
Systematic classification of Megaptera novaeangliae
The Megaptera novaeangliae or Humpback whale is a marine mammal, a baleen
whale of the Sub-order Mysticeti. It is one of 76 known cetacean species.
It belongs to the family of the rorquals, a family that also includes the
Blue whale, Fin whale, Bryde's whale, Sei whale, and Minke whale. Rorquals
have two characteristics in common: dorsal fins on their backs, and ventral
plates running from the tip of the lower jaw back to the belly area. The
shape and colour pattern on the Megaptera novaeangliae's dorsal fin and
flukes (tail) are as individual in each animal as are lines in zebras or
fingerprints in humans. The discovery of this interesting fact changed the
course of cetacean research forever, and the new form of research known as
"photo-identification," in which individuals are identified, catalogued and
monitored by photographic means, has led to valuable information about such
things as whale population sizes, migration, sexual maturity and behaviour.
The oldest known scientific descriptions of this species were made by
Borowski in 1781 and by Bonnaterre in 1789. The Etymology of the scientific
name Megaptera novaeangliae is this: the genus name "Megaptera" derives from
the Greek "mega" meaning "big, large" and "pteron" meaning "wing, flipper",
and refers to the Humpback whale's big flippers. The species name
"novaeangliae" is Latin, not Greek. It refers to New England, North America,
where the Humpback whale was first studied by these philosophers of Nature.
Other Names:
English: Bunch, Gubarte, Hump whale, Hunchbacked whale.
For systematic classification purposes, this is the accepted Taxonomy of
Megaptera novaeangliae:
Kingdom Zoa (also called "Animalia", heterotrophic digestive beings)
Taxonomic number of the Megaptera novaeangliae: 180 530
Main Anatomical Characteristics
Weight, Size and Colour
The Humpback whale is a stout, thick bodied baleen whale of medium size,
measuring as adult 11 to 18 metres and attaining a weight of 23 to 50
Megagrammes, with an average of 36 Megagrammes (1 Megagramme = 1 000000
grammes). Adult males measure 12 to 14.5 metres, with an average of 13.5
metres. Adult females measure 13.5 to 15 metres, with an average of 14.5
metres. One specimen was measured in 18 metres. The females are slightly
bigger than the males, as with all baleen whales. Newborns are about 4.3
metres. The four chambered heart of the average Humpback whale weighs about
200 Kilogrammes. The humpback is distinguished by its long flippers, of one
fourth to one third the length of its body. These flippers have a series of
bumps (called knobs or tubercles), two of which are found in consistent
positions on the leading edge. The length of the flippers and the bumps on
their front edges distinguish the humpback from other whales. The head is
covered by round bumps on the top front, edging the jaws, and on the lower
jaw. Each bump contains at least one stiff hair. The purpose of these hairs
is not known, though they may be sensory organs that allow the whale to
detect movement in nearby waters. The head of a Humpback whale is broad and
rounded when viewed from above, but slim in profile. Their large flukes are
concave with a serrated trailing edge, and show individual patterns, a
characteristic used to identify individuals for research purposes. Humpback
whales possess 14 to 50 ventral grooves at their throats. These grooves
extend from the chin to slightly beyond the navel. They allow the throat to
expand for the huge intake of water during filter feeding. These whales also
have 270 to 400 pairs of dark grey or black fringed overlapping baleen plates
hanging from each side of the upper jaw, where teeth might otherwise be
located. The typical number is about 330 pairs, one plate on each side of the
mouth, with coarse grey bristles hanging from the jaws. Each plate is about
0.6 to 0.75 metres long and 0.35 metres wide. These plates consist of a
fingernail-like material called keratin that frays out into fine hairs on the
ends inside the mouth near the tongue. They play an important part in the
lunging feeding that is characteristic of these Mysticeti. During feeding,
large volumes of water and food can be taken into the mouth because the
plated grooves in the throat expand. As the mouth closes, water is expelled
through the baleen plates, which trap the food on the inside near the tongue
to be swallowed. The body is not as streamlined as in other rorquals, but it
is quite round, narrowing to a slender peduncle (tail stock).
The body is black on the dorsal (upper) side, and mottled black and white on
the ventral (under) side. This colour pattern extends to the flukes. When the
Humpback whale "sound" (go into a long or deep dive) it usually throws its
flukes upward, exposing the black and white patterned underside. This pattern
is distinctive to each whale. The flippers range from all white to all black
dorsally, but are usually white ventrally. Humpbacks come in four different
colour schemes, ranging from white to black through grey and mottled. There
are distinctive patches of white on underside of the flukes (tail). These
markings are unique to each individual whale, like a fingerprint. The
humpback's skin is frequently scarred and may have patches covered with
diatoms. Humpbacks have huge, mottled white flippers with rough edges that
are up to one third of its body length, these are the largest flippers of any
whale. The flippers may have barnacles growing on them. The deeply-notched
flukes (tail) are up to 3.5 metres wide. Humpbacks have a small dorsal fin
toward the flukes. Although Humpback whales have a variety of individually
unique markings and colouration patterns, the underneath surface of the
flukes provides the best opportunity for identifying individuals. When a
humpback dive deeply, it will frequently lift the flukes straight out of the
water in a fluke-up dive, revealing the colouration and marking or scar
pattern on the ventral surface. Approximately 10000 Humpback whales have been
identified using photographs of these features (Kemf & Phillips 1994). About
two thirds of the way back on the body is an irregularly shaped dorsal (top)
fin. The flukes (tail), which can be 5.5 metres wide, is serrated and pointed
at the tips. At close range, the humpback is one of the easiest whales to
identify. At a distance, however, there can be some confusion with other
large whales, especially with Right, Grey, and Sperm whales. This is largely
due to the similarity in their bushy blows. When a closer look be obtained,
humpbacks are generally unmistakable, distinguished by their massive flippers
and robust body plan.
Physiology and Pathology
Nothing is known for certain about sleep in baleen whales such as the
Humpback whale, although it is often assumed that, like some dolphins, they
rest one half of the brain at a time. This is presumably essential to a
voluntary breather (Clapham & Mead 1999). Humpback whales breathe air at the
surface of the water through two blowholes located near the top of the head.
They spout (breathe) once or twice per minute at rest, and four to eight
times per minute after a deep dive. Their blow is a double stream of spray
that rises to 3 or 4 metres above the surface of the water. At least three
different species of barnacles are commonly found on both the flippers and
the body of the Humpback whale. It is also home for a species of whale lice,
Cyamus boopis. Humpback whales have a life expectancy of 45 to 50 years,
though some individuals are estimated to have lived as long as 77 years
(Nowak 1999). Both males and females mature sexually at around 4 to 6 years,
with an average of 5 years. At this age, the average length is 12 metres for
both males and females. Physical maturity is not reached until 8 to 12 years
after sexual maturity (Clapham & Mead 1999). The current male to female ratio
in several studied populations is thought to be close to 1:1 (Clapham & Mead
1999). Calf survival rates have been estimated at 0.875 (standard error of
0.047), adult survival rates at 0.96 (standard error of 0.008), for the
summer feeding population in the Gulf of Maine (Clapham & Mead 1999).
Swimming and Diving
Humpback whales can dive for short time to a depth of 150 or 200 metres. To
shallower depths, diving behaviour varies by time of year. In summer most
dives last less than 5 minutes, and dives exceeding 10 minutes are unusual.
In winter dives may last 10 to 15 minutes, and dives of more than 30 minutes
have been recorded. In this season, many long-diving whales appear to be
submerging to rest, an activity which commonly takes place at the surface on
the summer feeding grounds (Clapham & Mead 1999). Humpbacks are the most
acrobatic of all whales, engaging in often spectacular aerial behaviours.
Their feats include breaching, lobtailing and spyhopping. In breaching, they
throw themselves completely out of the water head first, twist in the air,
and fall on their back slapping the water with a tremendous splash, sometimes
while twirling around. They can swim on their backs with both flippers in the
air. They also engage in lobtailing, sticking their tail or raising their
huge flukes out of the water into the air, swinging them around, and then
slapping them on the surface, repeatedly slamming down the tail. In flipper
slapping, they using their flippers to slap the water, making a very loud
sound. Spyhopping is another humpback activity in which the whale pokes its
head out of the water for up to 30 seconds to take a look around. All these
displays are seen at all times of year and among all age classes. They may be
done purely for play, they may be used to loosen skin parasites, they may
serve for communication (perhaps as a warning to the rest of the pod), or
they may have another social meaning, their purpose is not known. Humpbacks
lobtail more during rough and stormy sea condition. Relative to other whales
in their family, humpbacks are not fast swimmers. Average speeds of animals
travelling or migrating range from 8 to 15 Kilometres per hour, about 4 to 8
Knots. The maximum speed reported was a burst of 27 Kilometres per hour,
about 15 Knots, by a wounded whale who was being chased by a whaling boat
(Clapham & Mead 1999).
Vocalisation and Singing
Humpback whales are the noisiest and most imaginative whales when it comes to
songs. They sing long, varied, complex, eerie and beautiful songs that often
include recognisable sequences of squeaks, grunts and other sounds. The songs
have the largest range of frequencies used by whales, from 20 Hertz to 9 Kilo
Hertz, but mostly emitted between 40 Hertz and 5 Kilo Hertz. Only males have
been recorded singing, thought to be young individuals but sexually mature.
They sing the complex songs only in warm waters, perhaps for mating purposes.
In cold waters they make rougher sounds, scrapes and groans, perhaps for
communication while locating large masses of krill (the tiny crustaceans that
they eat). It is not certain how the humpbacks produce their songs. Whales
have no vocal cords and, because they sing while submerged, they cannot
afford to release large amounts of air to the exterior (Bonner 1989). Singing
is virtually ubiquitous in the species' breeding range in winter, and it has
occasionally been recorded on the feeding grounds in summer and autumn, as
well as on migration. They sometimes sing continuously for hours or even for
days. There apparently are dialects, in that the song of the whales in one
area differs to some extent from that heard in other areas. Whales in the
North American Atlantic population sing the same song, and all the whales in
the North American Pacific population sing the same song. However, the songs
of each of these populations and of those in other areas of the world are
uniquely different. A typical song lasts from 10 to 20 minutes, but it may be
as short as 6 minutes or as long as 35 minutes (Bonner 1989). The song is
repeated continuously for hours at a time, and changes gradually from year to
year. There are six basic types of song, each of which can be sung in one of
several variations. In the terminology of bird songs, the humpback sings a
true song, consisting of an ordered sequence of themes comprising motifs and
phrases made up of syllables. The syllables are the simplest part of the
song, and they have been given more or less descriptive names: moans, cries,
chirps, yups, ooos, surface rachets and snores.
Fishing Techniques
Humpback whales (like all baleen whales) are seasonal feeders and carnivores
that filter feed tiny crustaceans like krill (mainly Euphausia superba),
copepods, cephalopods, plankton, and small fish, including herring, mackerel,
capelin, pink salmon, Arctic cod, walleye pollack, sardine, anchovy, haddock
and sandeel from the water. They are gulpers (not skimmers) that alternate
swimming and gulping mouthfuls of plankton or fish. Concentrated masses of
prey are preferable for this method of feeding. An average-sized Humpback
whale in the Northron Hemisphere will eat 2 to 2.5 Megagrammes of plankton,
planktonic crustaceans and small schooling fish each day during the feeding
season in cold waters (about 120 days). Those in the Southron Hemisphere do
likewise, but their diet is mostly composed of Antarctic krill. They eat
twice a day, about 1 or 1.4 Megagrammes of food daily. The Humpback whale
feeds in colder waters during spring, summer and autumn, then migrates to
winter ranges in tropical seas, where it calves and breeds. Migrations of the
Humpback whale are among the longest of any mammal, and are known to reach
almost 8 Megametres of distance. The social organisation of the Humpback
whale is extremely fluid at both ends of the migratory cycle. With the
exception of mother and calf pairs, groups are typically small and unstable,
and individuals frequently change companions. Humpbacks cooperate in hunting
and have developed a unique method of rounding up highly concentrated masses
of prey. This method is called bubble-net fishing. This involves one or more
whales diving at about 15 metres beneath a school of fish, krill or plankton,
forming a circle from 3 to 30 metres across, then swimming upward in a
spiral, while releasing streams of air from their blowholes and creating
bubbles. The bubbles rise in a cylindrical curtain around the fish and seem
to form a barrier through which the prey will not pass. The whales then swim
up through the giant and concentrated mass, feeding a large and hearty meal
as they go.
Acoustic coordination of behaviour by a lead whale has been suggested, but
not conclusively demonstrated (Clapham & Mead 1999). A bubble cloud, which
seems to be unique to the North Atlantic population, is a single burst of
bubbles up to 20 metres across, which presumably functions to trap prey
between the rising cloud and the surface (Wilson & Ruff 1999). Like other
rorquals, humpbacks fast during migration. Most feeding occurs during the
summer, in high latitudes. Being gulp-feeders, they feed in discrete events,
rather than continuously filtering their prey as do some other whales (the
skim-feeders, such as the North Atlantic Right whale). Typically, the
Humpback whale lunges into a prey school and engulfs a huge volume of water
and food. This process is aided by the whale's long, flexible throat grooves,
which expand during a feeding lunge and thus greatly increase the capacity of
the whale's mouth. The water is forced out through the whale's baleen plates.
The prey are trapped in the whale's mouth, by the fringe of hair that lines
the inner surface of the baleen plates, and then swallowed (Wilson & Ruff
1999). Humpbacks rarely feed in winter, foraging during summer in areas of
prey concentration such as upwelling regions. They exhibit a wide range of
fishing habits intended to concentrate prey, which may be employed by lone
individuals or by groups. Bubble-netting and lob-tail feeding are well
documented strategies. Bottom feeding has also been documented. Prey species
include:
Fish: Ammodytes dubius, Clupea harengus, Mallotus villosus, Scomber scombrus,
Oncorhynchus spp.., Boreogadus saida, Theragra chalcogramma, Pollachius
virens, Ammodytes americanus, Melanogrammus aeglefinus, Engraulis mordax,
Pleurogrammus monopterygius, Thaleichthys pacificus, Ammodytes hexapterus,
Gadus macrocephalus, Eleginus gracilis, Sebastes spp.
Invertebrates: Meganyctiphanes norvegica, Euphausia pacifica, Thysanoessa
spinifera, Thysanoessa raschii, Thysanoessa longipes, Mysis oculata,
Parathemisto libellula, Eualus gaimardii, Pandulus goniurus, Calanus spp.,
Euphausia spinifera, Euphausia hemigibba, Nyctiphanes australis, Municia
gregaria, Euphausia superba, Parathemisto gaudichaudi
Reproduction
The gestation period lasts about 11 to 12 months (Clapham & Mead 1999).
Calving occurs primarily in the winter season, lasting from October to March
in the Northron Hemisphere and from April to September in the Southron
Hemisphere). The peak birth months in the northron and southron hemisphere
populations are early February and early August respectively (Clapham & Mead
1999). Breeding is strongly seasonal. Most courtship and mating behaviour
occurs in winter. Females come into estrus in mid-winter, and testosterone
production and spermatogenesis peak at that time in males (Wilson & Ruff
1999). The average interbirth interval is of approximately 2.4 years (Clapham
& Mead 1999). Most female Humpback whales give birth every 2 to 3 years.
Intervals between calving of 1 to 5 years have also been observed. North
Pacific: Gerber & DeMaster cited observations of birth intervals that yielded
estimates of annual reproductive rates on breeding grounds of 0.58 calves per
female per year, and on feeding grounds of 0.38 calves per female per year.
Another estimate of average birth interval of 2.31 (standard error of 0.26)
yielded a corresponding annual birth rate of 0.43 (standard error of 0.075)
calves per female per year (Gerber & DeMaster 1999). Calves nurse for up to a
year, although they may begin to feed independently at approximately 6
months. The great majority of calves leave their mothers during, or shortly
before, their second winter. Average lengths at independence (one year of
age) were approximately 9.8 metres for both males and females (Clapham & Mead
1999). Humpback whale breeding occurs mostly in the winter to early spring,
while near the surface and in warm, tropical waters. The calf is born tail
first (this is normal for cetaceans) and near the surface in warm, shallow
waters. The newborn instinctively swims to the surface within 10 seconds for
its first breath, it is helped by its mother, using her flippers. Within 30
minutes of its birth the baby whale can swim. The newborn calf is from 3 to
4.5 metres long and weighs from 0.9 to 2.5 Megagrammes. There is almost
always one calf, twins being extremely rare, about one pair of them in a
hundred births. The baby is frequently nurtured with its mother's rich milk,
which has a 45% to 60% of fat content, drinking 40 to 50 Kilogrammes daily.
The youngster is weaned to solid food at about one year of age. Mother and
calf may stay together for a year or longer. Humpback whales reach puberty at
4 to 7 and sexual maturity at 4 to 15 years of age, typically 6 to 10 years,
or when males reach about 11.5 metres and females about 12 metres of length.
Organisation in groups
Humpbacks travel in large, loose groups. Most associations between humpbacks
are temporary, lasting at most a few days. The exception is the strong and
lasting bond between mother and calves. In the summer feeding season,
individuals may feed alone or together. Stable groups which remain together
over weeks or even for several feeding seasons have been recorded in the Gulf
of Maine and Alaska, but these represent a clear exception to the general
pattern of social behaviour during summer. Such groups do not appear to
consist of related animals, and indeed kinship seems to be of little
importance among Humpback whale associations (Clapham & Mead 1999). In the
winter breeding season, animals are usually found alone or in groups of 2 to
15 (most frequently 3 to 5). A female and young calf are commonly accompanied
by another adult, evidently a male. However, the pair bond is not stable.
This escort male is aggressive toward other males that approach. Other males
may join the group, and jostling for position near the female takes place.
One of the newcomers may displace the original escort. No stable groups have
been documented on the breeding grounds. Although they generally occur singly
or in small groups, larger aggregations develop in feeding and breeding
areas. On the breeding grounds, males compete for access to estrous females,
apparently using complex songs as part of their breeding display. Calves are
born on wintering grounds in tropical and subtropical regions.
Habitat and Range
Humpback whales live at the surface of the ocean, both in the open ocean and
in shallow coastline waters. When not migrating, they prefer shallow waters.
They migrate from warm tropical waters where they breed and calve to Arctic
or Antarctic waters where they eat. There are three separate populations of
humpbacks: those living in the North Pacific Ocean, those in the North
Atlantic Ocean, and those roving the oceans of the Southron Hemisphere from
the Arabian Sea to Antarctica. The Humpback whale occurs in all oceans and
adjoining seas of the world, ranging from the tropics almost to the edges of
the pack ice in the polar regions. There appear to be three geographically
isolated populations, one each in the North Atlantic, the North Pacific, and
the Southron Ocean. Although commercial whaling seriously depleted all
humpback stocks, and these whales are vulnerable to ship collisions,
entanglement in fishing gear, and disturbance (even serious injury) from
industrial noise, Humpback whales have demonstrated remarkable resilience and
many of the stocks are recovering. Humpback whales are commonly found in
coastal or shelf waters in high latitude areas in summer, feeding in the
cold, productive waters. In winter, they migrate to mating and calving
grounds in tropical or subtropical waters, where they are generally found
associated with islands or off-shore reef systems. These whales frequently
travel across deep water during migration (Clapham & Mead 1999, Wilson & Ruff
1999). The Humpback whale is a relatively eurythermic animal, occupying cold
temperate to tropical waters. The Humpback whale occurs in the Antarctic
Peninsula & Weddell Sea, Eastron Polynesian Islands Marine Ecosystems,
Galapagos Islands Marine Ecosystems, Grand Banks, Great Barrier Reef, Panama
Bight Marine Ecosystems, and Southron Caribbean Sea (Olson & Dinerstein 1999).
Migration
Humpback whales take long seasonal migrations. They mate and calve in
tropical waters during the winter, and then travel to cold polar waters
during the summer, to feed. Adults do not eat during the summer in the warm
waters, but live off their layer of blubber composed of fat. The young calves
feed on rich mother's milk. Humpbacks normally navigate at 2.5 to 8 knots
(4.5 to 15 Kilometres per hour, about 1.3 to 4 metres per second), but can
double those speeds in bursts, when in danger. Feeding speeds are slower,
about the half of the normal navigation speed (a fourth of the maximum
speed). They have incredible powers of endurance, travelling over 5
Megametres during each seasonal migration. They cover on average about 60
Kilometres daily. The Humpback whale feeds in colder waters during spring,
summer and autumn, then migrates to winter ranges in tropical seas, where it
calves and presumably breeds. Migrations of the Humpback whale are among the
longest of any mammal, and are known to reach almost 8 Megametres. Migrations
to and from the tropics are loosely staggered by sex and state of maturation.
Lactating females are among the first to leave the feeding grounds in late
autumn, followed by immature animals, mature males, "resting" females, and
lastly pregnant females. In late winter, this order is broadly reversed
during the migration back to high latitudes (Clapham & Mead 1999). Recent
studies have challenged the widespread belief that all Humpback whales
migrate every year, and a population in the Arabian Sea appears to be unique
in that it remains in tropical waters all year-round (Wilson & Ruff 1999).
Found in all the world's oceans, most populations of Humpback whales follow a
regular migration route, summering in temperate and polar waters for feeding,
and wintering in tropical waters for mating and calving. In the Arabian Sea,
a year-round non-migratory population of humpbacks appears not to follow this
general rule.
Conservation status. Threats and reasons for decline
Humpback whale populations were very reduced by whaling in all major oceans.
Because their feeding, mating, and calving grounds are close to shore and
because they are slow swimmers, Humpback whales were an easy target for early
whalers. They were taken by coastal and oceanic whaling operations until the
1960's, when it was generally realised that they were nearing extinction.
Commercial harvesting of Humpback whales was banned in the North Atlantic in
1956, in the Southron Ocean in 1963, and in the North Pacific in 1966
(Klinowska 1991). The International Whaling Commission gave them world-wide
protection status in 1966, but the Communist Soviets illegally captured tens
of thousands of these whales between 1966 and 1973, when they were forced by
international pressure to abandon their characteristical hateful behaviour.
Whaling on this species was minimal at the end of the XX century (Clapham &
Mead 1999), with only some subsistence hunting practiced from immemorial
times by some inferior human races, using artisanal methods, in the Caribbean
Sea and in the South Pacific Ocean. Humpback whales have demonstrated a
remarkable resilience, and while some stocks are still depleted, others are
showing evidence of strong recovery (Reeves 2003). Known threats to Humpback
whales include entanglement in debris or in fishing gear, ship strikes,
excessive industrial or traffic noise, and destruction of coastal habitats,
though it is questionable whether the mortality involved in these threats be
significant at the population level. Existing data suggest that baleen
whales, including Humpbacks, do not carry high contaminant burdens (Clapham &
Mead 1999). There may globally exist between 30000 and 40000 Humpback whales,
or about 30% to 35% of their original population. The North Pacific
population was estimated to have been reduced to only around 1000 animals by
decennia of commercial whaling, but fortunately, this number is higher now.
Population count
Humpback whales are found in all the major ocean basins, and like other
baleen whales they migrate long distances. In summer, humpbacks migrate
poleward to exploit the high productivity of the cold waters. Humpbacks
travel to warm tropical waters in winter, where they concentrate on mating
and calving. The Humpback whale is better studied than other balaenopterid
species, and migratory patterns are known for some stocks.
North Pacific. Four stocks are believed to exist:
First stock: winters off the coast of Mexico (Low-Baja California, Gulf of
California, Mexican mainland) and summers off the coasts of High-Alta
California, Oregon, and Washington State.
Second stock: winters in off-shore Mexican waters, near the Revillagigedo
Islands. Summer grounds unknown.
Third stock: winters in the central North Pacific and Hawaiian Islands,
summers in Alaska (Prince William Sound) and British Columbia.
Fourth stock: winters in the westron North Pacific, near Japan and Taiwan,
summers in the Bering Sea and the coast of the Aleutian Islands, west of the
Kodiak Archipelago.
North Atlantic: in the eastron North Atlantic, Humpback whales summer off
Iceland, Scotland, Norway, and Novaya Zemlya in the Barents Sea. The only
known wintering ground in the eastron North Atlantic is near the Cape Verde
Islands. In the westron North Atlantic, five separate feeding aggregations
are found:
1: Iceland-Denmark Strait
Photo-identification indicates that whales from all five of these groups
migrate to the Caribbean for the winter, concentrating on Silver Bank and
Navidad Bank near the Dominican Republic. Other known wintering grounds are
Samana Bay in the Dominican Republic, the northwest coast of Puerto Rico, the
Virgin Islands, and the eastron Antilles all the way to Venezuela. Some
whales have also been sighted in northron waters during the winter, showing
that not all Humpback whales migrate to wintering grounds every year.
Northron Indian Ocean: a poorly studied resident stock, which does not
migrate, is found in the Arabian Sea.
Southron Hemisphere: wintering grounds include Abrolhos Bank, Brazil, the
coasts of Gabon, Angola, Congo, Sofala Bank in Mozambique, Madagascar, and
near Cape Leveque in westron Australia. In summer, whales are found in well
defined feeding areas in Antarctic waters, in waters near South Shetland and
South Georgia, and along the west and east coasts of Africa, Australia, and
South America.
The number of Humpback whales is estimated between 10 000 and 15 000
world-wide. Humpback whales are still an endangered species, though since the
prohibition to hunt them became fully effective in the 1970's, they are
slowly recovering their past numbers.
Status and Population Trends according to estimations given by the I.U.C.N.
in 2004:
1960's: vulnerable, decreasing.
Oceans and Seas Where the Humpback whale Is Currently Found:
In 2004, this species occurs in the Antarctic, eastron central, northeast,
northwest, southeast, southwest and westron central Atlantic Ocean, the
Antarctic, eastron and westron Indian Ocean, the Antarctic, eastron central,
northeast, northwest, southeast, southwest, and westron central Pacific
Ocean, and the Arctic, Mediterranean and Black Seas (I.U.C.N. 2004).
Countries Where the Humpback whale Is Currently Found:
In 2004 it occurs in Angola, Argentina, Australia, Bangladesh (Bengala),
Brazil, Canada, Cape Verde, Chile, the two Congos, Dominican Republic,
Ecuador, Fidji, France, Iceland, India, Indonesia, Iraq, Japan, Kenya, the
two Koreas, Madagascar, Malaysia, Mexico, Mozambique, New Zealand, Norway,
Pakistan, Panama, Peru, Poland, Russia, Solomon Islands, South Africa, Sri
Lanka (Ceylon), Saint Vincent and the Grenadines, Tanzania, United Kingdom,
United States, Vanuatu and Venezuela (I.U.C.N. 2004).
Population estimates
In the World:
Pre-whaling, before the XVII - XIX century: about 150000 (Klinowska 1991).
In the Westron North Atlantic:
Pre-whaling, before the XVII - XVIII century: about 10000 (Nowak 1999).
In the Eastron North Atlantic:
Pre-whaling, before the XVII - XVIII century: unknown, estimated about 5000
(Klinowska 1991).
1991: Probably below 500 (Klinowska 1991).
In the North Pacific:
Pre-whaling, before the XVIII - XIX century: unknown, estimated between 10000
and 15000 (Klinowska 1991).
In the Northron Indian Ocean:
1985: over 500 (Klinowska 1991).
In the Southron Ocean (of the Atlantic, Pacific and Indian Oceans):
Pre-whaling, before XVIII - XIX centuries: 100000 (Nowak & Paradiso 1983).
History of distribution
The Humpback whale occurs in all oceans and adjoining seas of the world,
ranging from the tropics almost to the edges of the pack ice in the polar
regions. It feeds in higher-latitude colder waters during spring, summer and
autumn, then migrates to winter ranges in tropical seas, where it calves and
breeds. Because of the reversal of seasons, the populations of the Northron
Hemisphere are not in equatorial waters at the same time as those of the
Southron Hemisphere. The Northron and Southron Hemisphere populations are
regarded as separate, but they are not usually considered to be separate
species or sub-species. There appear to be three geographically isolated
populations, one each in the North Atlantic, North Pacific and the Southron
Ocean.
North Atlantic:
In the North Atlantic, Humpback whales feed off the Northeastron United
States (from the Gulf of Maine to the mid-Atlantic States), Newfoundland and
Labrador, Greenland, Iceland, and Norway. Each of these sub-populations is
relatively discrete, with regional fidelity determined matrilineally.
However, in the winter, whales from all North Atlantic feeding grounds
migrate to common breeding areas in the Caribbean Sea, where they mix both
spatially and genetically. The principal winter breeding range is around the
Greater and Lesser Antilles. Primary areas are at Silver and Navidad Banks,
and along the coast of the Dominican Republic. Other concentrations include
the westron edge of Puerto Rico and the area from the Lesser Antilles south
to Venezuela. The area of the West Indies that includes Silver Bank, Navidad
Bank and Samana Bay represents the largest known breeding ground in the world
for this species (Clapham & Mead 1999, Wilson & Ruff 1999).
North Pacific:
During the summer, Humpback whales in the North Pacific migrate and feed over
the continental shelf and along the coasts of the Pacific Rim, from Point
Conception, California north to the Gulf of Alaska, Prince William Sound and
along the Aleutian chain into the Westron North Pacific. They spend the
winter in three separate wintering grounds:
1: The West coast of Low-Baja California, Gulf of California, mainland
Mexican coast from southron Sonora to Jalisco, and around Revillagigedo
Islands.
Although it is generally thought that there is little mixing of Humpback
whales between the eastron and westron North Pacific, some exchange between
these regions clearly occurs, as documented by sightings of the same
identifiable individuals in both regions (Wilson & Ruff 1999).
Southron Ocean:
In the Southron Hemisphere there are summer concentrations off the southron
ends of continents and around such sub-Antarctic islands as South Georgia. In
the autumn the Southron Ocean population migrates north to the coasts of
South America, South Africa, Australasia and various South Pacific islands.
In tropical areas of the Southron Hemisphere, humpbacks generally are found
in their wintering areas, coastal or sheltered waters in the tropics where
they breed and give birth, from June to December, but this varies among
individuals and across populations (Rosenbaum 2003).
Specific Areas:
Arabian Sea: the sole known exception to the typical seasonal migratory
pattern is a population in the Arabian Sea, which is unique in that it
appears to both feed and breed in tropical waters (Clapham & Mead 1999).
Coast of Westron Africa: in 1998 groups of whales were first observed off the
coast of Gabon, including groups involved in behaviour only seen in mating
areas (Walsh 1999).
Madagascar: a new wintering ground for Humpback whales was identified in Baie
d\92Antongil in 1996. Mothers were observed with newborn calves, suggesting
that it be a calving and nursing area (Rosenbaum 1997).
Hawaii: detailed observations of individuals indicate that at least a
percentage of the population returns to Hawaii every year. It is thought that
they have used Hawaiian waters only during the last two hundred years.
Northron Indian Ocean: it appears that there may be a small, possibly
resident population in the Northron Indian Ocean, although this could be a
wintering area for a component of the population summering in the Antarctic
(Klinowska 1991).
Hyper links
The Megaptera novaeangliae
The documents listed below provide a rich information on the Humpback whale.
They should be studied with attention, for they contain some interesting
facts that have not been explained in the present document, or they extend
details that have only been mentioned here.
Animal Information
Enchanted Learning
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Scientific enigmas surrounding these cetaceans,
the biggest animals that have existed in Earth
Walkyrie who takes our dead heroes to Walhalla in Asgard.
Wagner Frost Illustration
Taxonomy
Characteristics
Hyper links
French: M\E9gapt\E8re, Baleine \E0 Bosse, Baleine du Cap, Baleine \E0 Taquet,
Rorqual \E0 Bosse, Rorqual du Cap, Rorqual \E0 Taquet.
Spanish: Ballena Jorobada, Ballena de Joroba, Rorcual Jorobado, Rorcual de
Joroba.
Portuguese: Baleia Jubarte.
Sub-kingdom Metazoa (Animalia composed of many euchariotic cells)
Phylum Chordata (animals with chordium -dorsal string-)
Sub-phylum Vertebrata (animals with vertebrate chordium)
Class Mammalia (mammals)
Sub-class Theria (viviparous mammals)
Infra-class Eutheria (placentary viviparous mammals)
Order Cetacea (whales, orcs, dolphins and porpoises)
Sub-order Mysticeti (with baleens in their mouths)
Family Balaenopteridae (rorquals, true whales *)
Genus Megaptera ("Big flippers")
Species novaeangliae ("from New England")
(* Orcs or "Killer whales" are not true whales, they are part of the
Sub-order Odontoceti -with teeth in their mouths-, as are also dolphins and
porpoises)
(Courtesy of the Integrated Taxonomic Information System)
2: Southwest Greenland
3: Southron Labrador and east of Newfoundland
4: Gulf of Saint Lawrence
5: Gulf of Maine - Nova Scotia
1970's to 1980's: endangered.
1994: vulnerable, increasing.
1996 to 2004: vulnerable, increasing (criteria: A1ad).
1988: 12000 (Primack 1993).
1992: over 28000 (N.M.F.S. 1994).
Late 1990's: 37000 (rounded sum of Chivers 1999 for the North Atlantic,
Gerber & DeMaster 1999 for the North Pacific, and N.M.F.S. 1994 for the
Southron Ocean).
1979-1986: 5500, based on photo-identification, or 6500, based on the rate of
discovery of new individuals (Klinowska 1991).
1992: 5500 (N.M.F.S. 1994).
Late 1990's: about 8600 (Chivers 1999, discounting 2000 in the East Atlantic).
1992: 1000 (N.M.F.S. 1994).
Late 1990's: about 2000 (Chivers 1999 estimated 10600 for the whole Atlantic).
1976: 1200 to 1600 (Klinowska 1991).
1983: 900 (Klinowska 1991), of which several hundred winter around Hawaii
(Nowak & Paradiso 1983).
1992: 2000 (N.M.F.S. 1994), of which about 700 winter around Hawaii (Nowak
1999).
1997: 6000 (Gerber & DeMaster 1999, but Clapham & Mead 1999 say that the
number was probably higher).
1994: Perhaps about 500 (Kemf & Phillips 1994).
1965: probably below 3000 (Curry-Lindahl 1972).
1990: 12000 (Klinowska 1991).
1992: 20000 (N.M.F.S. 1994).
2: The Hawaiian Islands from Kauai to Hawaii.
3: Around islands south of Japan, such as Mariana, Bonin, Ryukyu and Taiwan.
Information on the Megaptera novaeangliae
http://www.animalinfo.org/species/cetacean/meganova.htm
Information on the Megaptera novaeangliae
http://www.enchantedlearning.com/subjects/whales/species/Humpbackwhale.shtml
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