Whale Adaptations - Baleen whales - Mysticeti
How are blue, right, fin, sei, humpback, fin whales, the
large species found in Antarctica, adapted to survive in the
cold oceans?
The largest animals ever to have lived, larger than any
dinosaur, their huge bulk being supported by the sea. Not exclusively
Antarctic animals but often found in the frigid waters in both
north and south polar regions.
Large whales are able to live indefinitely in the
coldest seas on earth. If you were to fall into the
Antarctic Ocean, you would have about 15 minutes before hypothermia
set in, at this point you may pass out and drown, in any case
you would be dependent on someone else to get you out of the
sea, even if you were kept afloat with a life vest you would
be dead in 60-90 minutes. Whales however can live at the same
temperatures indefinitely if healthy and reasonably fed, they
just don't get hypothermia - ever. The reason for this is that
a large size with a low surface area to volume ratio, and a
blanket of blubber around the whole animal below the skin mean
that metabolic heat is retained to the degree that the coldest
seas are readily survivable.
They have a number of adaptations that enable them to live and thrive in the Polar regions, these can be broken down into:
- Anatomical - Structures of the body.
- Behavioural - The manner in which animals
move and act.
- Physiological - The internal functions
of the animal from biochemical, to cellular, tissue, organ
and whole organism levels.
Anatomical
Adaptations
Baleen plates in the mouth instead of teeth to filter food
in bulk from seawater. These
are made of keratin, the same tough protein that makes hair,
skin, nails, hooves and horns. There are two rows of plates that hang
down from the upper jaw forming two upright sides of a triangle
with the lower jaw being the third side. The inner edges of
these plates are bristly filters to collect food, usually smallish
very numerous animals such as krill in the water they gulp in.
A huge mouthful of water + food is taken in and the mouth
closed, then the water
is ejected by the tongue while the food is filtered out and
trapped inside the mouth to be swallowed when the water has
gone.
55 - 68 ventral grooves that extend from the lower jaw to the
navel (yes, whales have a belly button!) These allow
a huge amount of water and food to be taken into the mouth
allowing it to expand to
about 6 times larger than normal size (sometimes a bigger volume
than the whale itself). The largest
whales (blue whales) can eat up to 4 tonnes of food a day in
the Antarctic summer, they can feed for about 8 months and then
fast for 4 months living off their fat reserves.
Large whales have stretchy nerves in the muscle of the
floor of the mouth to allow for that expansion with water and
food to take place. This might not seem very significant,
but nerves are generally delicate structures and any stretching
will usually cause serious damage. The nerves in this part of
the baleen whale are elastic with a cord limiter to prevent
damage by over-stretching so preserving the still fragile structure
of the neurones that carry impulses to the muscles that expel
the water from feeding.
Lunge feeding may be a key development
in allowing whales to reach their enormous size, so stretchy
nerves could be a vital component in the evolution of large
whales.
A ridge in front of the blowholes (the two nostrils) which are
located on top of the head. Pointing backwards
means that they are not filled with water when swimming,
being placed on top of the head makes it easy to breathe
while surfacing and lifting the smallest amount of the body
possible, like a short snorkel.
A huge tail fin the size of two dinner tables that provide the
main propulsion for swimming. The smaller forward fins are
for changing direction and the small dorsal (mid-back) fin helps
with stabilizing straight swimming, it is the tail that provides
the power.
Behavioural Adaptations
Bubble netting. A feeding technique practised by humpback
whales, one or two whales dive down below a shoal or swarm of
prey, fish or invertebrates, they then slowly swim vertically
upwards towards the surface in a spiral. They blow bubbles as
they swim which float up in a circle and panic in towards the
centre. The whale/s then dash straight up through the middle
with their mouths open and get a more concentrated mouthful
of food.
Other whales may come in at this point too, as the
prey flee one predator, they are more likely to blunder into
the path of another, so co-operative feeding helps them all.

Lunge feeding. This is a technique whereby the whale
approaches a concentration of prey in the water and then lunges
at them with its mouth wide open and the floor of the mouth
distended enormously to engulf they prey and a large volume
of water at the same time. The water is then pushed out over
the baleen plates with the food being filtered out, so it is
a sort of batch filtering process. It may be combined with bubble
netting and/or co-operative feeding with other whales to help
concentrate the prey for the most satisfying mouthfuls.
Migration - Many whales migrate to the polar regions during the summer months
of that region. There are often distinct southern and
northern populations of species which go to their respective
pole, none go to both poles.
They feed continuously
during the super-productive summer months and then live entirely
on their blubber reserves for about 4 months during the breeding
season in warmer waters. Not all individuals migrate however
and in recent years, some humpback whales have been found around
Antarctica during the winter rather than 7,000km (4,350miles)
away off the coast of Africa where they were thought to be.
Whales use sound to communicate with each other and also possibly
as a means of finding krill swarms. Blue whales make
the loudest noise of any animal at 180 dB or more. These sounds
can travel underwater for as far as 500 miles (800 km). They
are very low frequency sounds down to 14hz, below the hearing
limit of humans, though they can be felt by divers in the water
at the time.
Physiological Adaptations
Large whales have enormous appetites, adult blues have a daily
energy requirement in the region of 6.3 million Kilojoules
(1.5 million kilocalories). This is supplied by up
to 3.6 tonnes or about 40 million individual krill eaten per day which
all have to be processed by the digestive system. This drives
the "inner furnace" of metabolic heat which keep the animals
comfortable and active in temperatures that would result in
hypothermia and death in most mammals in just an hour or two.
Like other air breathing diving animals such as seals, and penguins,
whales have muscles rich in myoglobin. This is an iron
containing protein similar to the haemoglobin that carries oxygen
in the blood, but provides an extra in-situ store for longer
dives exactly where it is needed deep in the most active muscles.
Their metabolism is able to cope with extended periods of plenty
where extensive feeding allows the build up of many tonnes of
blubber (stored fat) which is then used up during extended
periods of starvation, 8 months feeding, 4 months with no food,
but living off the reserves that were built up.
More about whales