To see photographs of the Humpback Whale (Megaptera novaeangliae) click here.
Humpback Whale (Megaptera novaeangliae)
All images and text on this page are copyright
protected: © 2002 Kelvin Aitken.
All rights reserved. Students may use this information for personal research
only. Not for commercial use.
Humpback whales belong to the Rorqual family of cetaceans.
Female humpback whales grow to 19 meters and males to 17.5 meters.
There are two basic populations of humpback whales; the southern and northern.
Southern humpback whales have, on average, much more white colouration
on the belly extending onto the flanks while northern humpback whales
have only a small area of white on the belly, sometimes being completely
black or dark grey. That said some individuals may depart from this norm
with some southern members mostly or totally black on the belly. Their
seasonal migration separates the northern and southern stocks though there
may be some temporary intermingling of individuals whose late departure
may cross over with the early arrival of individuals from the corresponding
hemisphere.
Humpback Whales are distinctive in that they have the largest appendages
of any living animal, namely their knobbly pectoral fins which are close
to 1/3 of their total length. These pectoral fins may be completely white
or only white, or partly white, on the underside. The leading edge of
these fins are crenelated with a series of bumps and knobs, often with
encrusting barnacles. The pectoral fins are used for a variety of purposes
including banking, breaking, propulsion (though only slightly as the bulk
of their movement is controlled by the tail flukes), defence and as flails
during mating behaviour.
The upper surface of the head forward of the blowhole is covered in a
collection of protruding knobs which are also present under the tip of
the lower jaw. This latter small patch of chin knobs are often covered
in barnacles and are used on occasion to inflict scratches on the sensitive
skin of other whales during courting or social interaction. There are
two visible blowholes that are slightly raised above the contour of the
head which deliver a tall bushy blow. Some individuals have been seen
to control the muscles of the blowhole to deliver horizontal spouts perpendicular
to the bodies axis. The body is either dark grey to black with some having
a light grey mottling. The back of a Humpback Whale (Megaptera novaeangliae)
often has bumps and always shows pits and scars, similar to the appearance
of old acne marks, or fresh marks from cookie cutter sharks.
The tail is broad and often raised above the surface at the end of the
diving sequence. This behaviour is called fluking and allows each animal
to be individually recognised by the unique “fingerprint” of
crenelated indentations on the rear edge, and colour pattern on the underside,
of the flukes. These tattered patterns are present on each animal when
born and are added to depending on the individuals encounters with ice,
other humpbacks or orcas which bite at the tail flukes.
Females migrate to the tropics to take advantage of the warmer waters
to give birth to their calves which do not have the blubber reserves of
an adult to survive the polar winters. Calves are born, after a 12 month
gestation period, at 4.5-5 meters long and feed on very rich milk which
the female ejects from her mammary glands situated behind and below her
pectoral fins. The calf will continue to feed from its mother for 8-9
months after which it is weaned. Mature females give birth every two or
more years though some may give birth for some successive years. Male
humpbacks follow the female migration to the tropics to mate and engage
in boisterous social behaviour with fellow males and young sub-adults
of both sexes.
Humpbacks feed on a variety of krill (small shrimp-like animals), plankton
and small schooling fish. Their method of feeding employs their pleated
throat which expands greatly, like that of a croaking frog, as they gulp
in vast mixtures of water and prey. The whale then closes its mouth and,
using its huge tongue, pushes the mixture through the curtains of baleen,
surrounding the internal edges of its mouth, and out through its lips.
When this sieving process is completed the whale swallows the remaining
mass of food. This rich diet allows the feeding whale to store energy
in the form of blubber which is a thick, fibrous insulating layer of fat
and oil. Blubber is used as insulation in the cold polar feeding grounds
and also serves as an efficient energy reserve for their extensive summer
migration during which they fast.
One notable method of feeding is when a pod of humpbacks form a circular
net of bubbles to herd and condense schools of small fish. The net is
constructed when one or more whales swims in a circular pattern slowly
exhaling bubbles. When the upper bubbles reach the surface the whole pod
launches vertically up through the compacted school with their mouths
wide open, bursting through the surface in a spectacular group display.
While feeding occurs in the rich polar waters during the summer months
they have also been seen to feed on rare occasions in their tropical breeding
areas or during their migration.
Humpback Whales are a favourite with whale watch tours due to their wide
distribution and spectacular surface activity. This includes tail slapping,
pectoral fin slapping and breaching, the most spectacular form of behaviour
where the whale launches itself either partially or fully above the surface
in a display of awesome power and grace.