whales or Orcas are probably the best known of the whales,
as large carnivores they have a keen intelligence that enables
them to be trained in captivity to do various tricks for rewards
and so have been kept in marine aquariums and "Sea-World"
type exhibits for many years. They are easily identified with
their distinctive black and white patterning.
are stocky in appearance compared to most whales which are
quite long and slim relative to their length. Males are significantly
larger than females (a trait known as "sexual dimorphism")
and have a large and prominent dorsal fin (the one in the middle
of their back) that can reach 6ft (1.8m) in height, the females
dorsal fin is usually less than half this height.
They are Odontocetes
or toothed whales and while they are quite small compared
to the great baleen whales (Mysticetes) they are at the very
top of the Antarctic food chain due partly to their formidable
array of teeth, but most of all due to the fact that they often
hunt in packs or "pods". Their tastes are wide ranging
from krill, squid, fish and sharks to penguins, seals and even
the much larger baleen whales.
Orcas in Antarctica
- photo Jean Cato / National Science Foundation
Orcas are the
largest of all carnivores on earth that feeds on a variety
of foods, they are found in almost all oceans, from the tropics
to the Arctic and Antarctic where they will go deep into the
pack-ice to hunt seals and penguins. They are commonest in coastal
waters and in cool temperate and sub polar seas.
They have very
sharp stout conical shaped
teeth, from 40-48 with equal numbers in each side of the upper
and lower jaws. The teeth can be up to 5cm (2") long. When
a pod of killer whales is feeding, they will co-ordinate their
movements by a continual stream of clicks and calls. Ever ready
to spot an opportunity, killer whales will even follow ice-breakers
at the start of the season as they cut paths through the ice
to reach deeper into the ice and perhaps get to seals and penguins
that were beyond their reach.
So adventurous and opportunistic
are killer whales in this respect, that groups of killer whales
are thought to have spent an entire winter living in and around
a polynia, an area of open water kept clear by currents
and winds while surrounded by miles of closed ice. These killers
were unable to return to the open ocean as they would have had
to have held their breath under the continuous pack ice for
longer than they were able.
In the days of commercial whaling,
while Orcas weren't very much hunted themselves (they were
much too small a catch to waste a harpoon on), they would often
follow the whaling boats and rush at the dead baleen whales
that were being flensed or towed alongside the boat ready for
flensing and feed on the carcass. As such, they were much disliked
by the whalers as they competed for the prey that they had just
captured. Not for nothing are these whales called the "wolves
of the sea".
An interesting aspect of the
ecology of Orcas discovered from studies of populations off
Washington state in the USA and up to Alaska is there are three
distinct types that are very similar but differ somewhat in
coloration in morphology (the way they look / proportions etc.)
but most of all in their behaviour. These three types are known
as "Residents", "Transients" and "Offshore",
they are discrete populations and little or no mixing between
them appears to take place.
Residents - These stay
in one location all through their lives and form very stable
communities. They tend to be mainly fish eaters which they are
thought to catch with the help of echolocation. Their dorsal
fins are more rounded at the top compared to the transients
that have more pointed dorsal fins.
Transients - Move around
more, they tend to feed on marine mammals, mainly seals. They
form pods with less members than residents and are not so loyal
to a particular pod.
Offshore - The least of
all is known about these (as they live mainly offshore) but
they form large pods and move following the edge of the continental
Though these groups have only
been studied to any depth in the North Western United States,
indications are that the behavioural types exist elsewhere too.
Orcas feed on a huge range
of prey. More or less, if they find it and catch it, they'll
at least have a go at eating it. Different pods of Orcas seem
to have different specialties of diet and will specialize
in a particular type of prey developing and becoming skilled
in the ways to capture that prey. For instance they have been
herding fish such as herring together into tight groups
and then slapping them with their tails to stun them.
Otherwise a herring would be a lot of effort and a small
mouth-full for such a large animal.
and unwary sea lions off the coast of Patagonia by chasing
after them right into the shallows and then lunging
with a great snap of their powerful jaws. Returning to sea
after a near stranding in these cases takes quite an effort
for the whale.
Attacking the great baleen whales
such as blue whale by tearing at and eating the great tongue.
A pod of 40 or so Orcas have been seen engaging in this
behaviour attacking a solitary huge adult blue off the coast
Breaking through sea ice from
below to surprise seals and penguins, or seeing them
on ice-floes and then pushing upwards on the floe to tip
the prey into the water. Alternatively two whales may rush
at an ice floe which is then washed over by a large wave
which dislodge the seal or penguin.
are often approachable by boats and are generally inquisitive.
They are frequently active at the surface showing such behaviours
as lobtailing, flipper-slapping, spyhopping, wave riding and
a hard surface such as rocks or even other whales is often seen.
It is thought to serve as a comfort movement and helps to remove
dead skin. Certain rock rubbing areas may be socially important.
Like all whales,
sound is very important to
killer whales. Researchers have even identified unique sounds
and discrete calls that are distinctive to certain pods and
family groups, to the extent that killer whale dialects can