|
SCIENTIFIC NAME
Eubalaena australis (balaena for “whale”, australis for “south”)
SIZE
Right whales reach a maximum length of 17 m and a weight of 80 to 90 metric
tons.
ANATOMY
These are black, stocky animals and the only large whales that lack a dorsal
fin. With short, paddle-shaped flippers and prominent patches of callosities
(raised skin patches) on their broad heads, together with their slow moving
behaviour make them very easy to identify. Many individuals have large white
patches, mostly on the ventral surface and during breaching these markings
regularly lead to observers identifying it as a killer whale. About 4% of
calves are born almost completely white, but will change to an overall grey
colour within the first year. Both these white markings, as well as the
callosities, which are markedly different on all individuals, are very
useful in identification. Callosities are rough, raised skin patches,
essentially precisely where hair would grow on a humans face – above the
eyes, on the chin and above the upper lip. They are inhabited by parasites,
which cling to and feed off the discarded or dead skin. The function of
callosities remains a matter of speculation. Whereas all toothed whales have
a single blowhole (nostril), baleen whales have double blowholes, and
southern right whales are unique with their typical V-shaped blow
(condensation on exhaling).
FEEDING
Southern right whales are specialized filter feeders, using their finely
meshed, long baleen plates to trap their prey. They do not undertake the
spectacular feeding display of humpback whales but rather use a steady
open-mouthed movement, nor do they feed on such a large variety of
organisms. Right whales almost exclusively feed on copepods or krill, which
are only present in large accumulations in the cold sub arctic and sub
Antarctic waters, and a few cold-water upwellings on the edge of continental
shelves.
REPRODUCTION
Both calving and mating takes place in the sheltered bays along the
coastlines of the southern and northern continents in temperate seas (13 to
20°C). It is during the winter months that they leave their feeding grounds
and migrate to the warmer and more hospitable in-shore waters, where they
clearly do not engage in any substantial feeding for between 4 and 6 months.
It makes perfect sense to give birth to their calves in relatively warm
water, as the neonates lack the adequate insulation of adults and would
likely die of hypothermia in the cold, stormy polar waters. Shallow, sandy
beaches are also clearly preferred for calving, as this prevents the
new-born calf from sinking too deep to get to the surface for its first
breath. “Midwives” often assist with this and are thought to oftentimes
being related to the birthing cow. Calving is thought to occur only every 3
to 5 years, with single young born after a gestation period of 12 months.
After birth the calves have access to copious amounts of milk (600 litres
per day have been suggested), and within 3 months the calf is ready to make
the journey back to the feeding grounds. Calves are born at 5 to 6 m in
length and grow at a rate of around 3 cm per day. The lactation period is
estimated at between 4 and 8 months.
The mating of right whales usually involves several males
attempting to copulate with one female, often displaying quite forceful
behaviour towards the other males in the process. It seems apparent that
they will mate successively and that each subsequent male’s sperm will at
least partly displace that of the previous one. Thus it has been reasoned
that whichever male mates last, has the best chances of becoming the father
of the offspring. Mating takes place mostly in spring and toward mid-summer
only some cow-calf pairs remain along the coast. It is estimated that right
whales live to be 90 to 100 years.
DISTRIBUTION
Right whales have a circumpolar distribution and inhabit sub arctic and sub
Antarctic waters between 30° and 50° north and south. Due to over
exploitation the northern population of right whales is virtually extinct,
but in the Southern Hemisphere populations show a slow increase of around 7%
per annum since international protection in 1935. An estimated 3000 to 4000
southern right whales are distributed into 3 major populations; the largest
contingent frequenting the South African coast, another along the
Argentinean coast of Patagonia and a third in southern Australia. Still but
a fraction of initial stocks, much of the role right whales play in
eco-systems and even more in respect of their social behaviour remains a
mystery. How much genetic exchange takes place between these populations is
of great interest to scientists. Both the introduction of new genes to any
of these small populations, as well as the contamination by any afflictions
would be great significance to the continued sustainability of the southern
right whale.
WHALES & MAN
Whales have been hunted by man for many centuries, but it was with the
advent of technology that whale populations world-wide were taking serious
losses, until several species were driven almost to extinction by the
mid-1900s. One of the most seriously affected was the right whale, so named
because it was the “right” whale to pursue; frequenting the same inshore
areas year after year, being slow moving and floating when dead, and most
importantly being very rich in oil and baleen. Curiously, very little
antagonistic behaviour toward man has ever been observed in unwounded whales
and even after decades of intensive persecution, humans and boats were
clearly not identified as the “enemy”. Whether this is due to a positive
disposition or some kind of kinship towards man or the inability to adjust
to changing environmental factors, or even a lack of intelligence, remains a
matter of speculation. Yet, for such large-brained animals not to react with
some kind of adversity to their persecutors seems out of synch with the
behaviour of virtually all other species. However, particularly due to this
inability to defend itself these enigmatic giants are worthy of our
whole-hearted efforts to protect for all future generations. It is a
frightening thought, that even a slight rise in the temperature of the
world’s oceans may impair the production of adequate krill reserves
essential to sustain even this small remaining population of right whales.
back to top
|
