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Humpback
whale - Megaptera novaeangliae
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Humpback Whale Statistics
Maximum length: 18m (59ft), average
12.9 m (42ft) males, 13.7 m (45ft) females.
Adult weight: around 25 - 35 tonnes, maximum of around 48
tonnes.
Life span: 50 years
Sexual maturity: 4 - 7 years
Gestation: 11-12 months
Birth length: 4 - 5m (15-16ft)
Birth weight: 2000kg (4400lbs)
Dive duration: up to 30 mins, usually only 6 - 7 mins
Distribution: all oceans, Humpbacks don't appear to cross the
equator so populations separated.
Current world population: 30 000 - 40 000 / pre-whaling 100 000
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Humpback whales are so called because of the habit
of raising and bending the back in preparation for a dive, accentuating the
hump in front of the dorsal fin. They have relatively the longest flippers of any
baleen whale which may be up to a third of the total body length, these have a range
of uses from feeding to social signalling.
These are probably the best known of the large whales as they
often collect in groups along coasts where they feed and breed, drawing attention
to themselves by their behaviour. Breaching, lob tailing and flipper-slap are common
and often occur several times in a row.
Humpbacks are slow swimmers and so allow tourist boats
- and in the past, whalers - to get close. They can swim at
The skin is covered with a whole range of warts and bumps and
there is a particularly rich fauna of barnacles that encrust the whale (there are
whole groups of "whale barnacles" types that are found nowhere else but on whales).
Like other baleen whales, the food
of humpbacks is small plentifully abundant schooling fishes and large zooplankton.
The precise diet is almost certainly different for different populations though
has not been studied in any detail for the majority. In Antarctica, the diet is
dominated by krill (like almost every other mammal in Antarctica). In other seas,
the diet may include anchovies, mackerel, sand eels, herring, capelin, pollock and
cod.
Humpbacks have a wide range of feeding
methods such as:
 | Co-coordinated feeding and herding of
prey species including "bubble netting". This is a particularly
impressive technique where one or two whales dive down below
a shoal or swarm of prey and then swim back slowly toward the
surface in a spiral. As they swim they slowly blow bubbles which
arise in a circle and drive the prey in a panic towards the
centre of the circle. The whale/s then thunder straight up through
the middle with their mouths open and get a more concentrated
mouthful of food. |
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| Disabling fish by striking shoals of them
with their flippers or flukes. |
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| Synchronized lunges at shoals of fish
or invertebrates by a number of whales side by side. This
disorients the prey and while they dash out of the way of one
whale, they may swim directly into the path of another. |
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As well as cooperative behaviour,
competition has been seen between animals feeding together in large fish or plankton
concentrations. The whales have been observed rushing to the surface together while
pushing and shoving each other with mouths full and throats distended. Humpbacks
feed mainly during the summer season in high latitudes in the Arctic or Antarctic
and do not feed during the winter while on the breeding grounds.
Social behaviour - Humpback
whales are usually seen alone or with one other whale, they may form small groups
of 4 or 5 individuals, very rarely larger. These groups are loose and unstable and
are made and break up easily. They used to be thought to be made up of family groups
or mating pairs, though this is now thought to be unlikely. The only long-term grouping
of any sort is between mother and calf, though sometimes a male may accompany them
and become aggressive to any other male approaching, probably a result of having
mated with the female and not wanting any other male to mate with the female (the
whales don't "know" this of course, it's all instinctive).
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The
bushy "blow" of a humpback whale from the double blowhole is quite characteristic,
even at a distance.
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