Orcas
The “killer whale” is the largest species of dolphin in the
world. Like the panda, its black and white markings make it distinctive to
human eyes, making it one of the most recognizable animals on Earth. They are
an apex predator in the sea, as in they have no predators to fear – except
humans (of course). They are highly social and emotional animals, living in
social and family groups. They can swim fast (up to 34mph). Combined, they can
hunt and eat even a blue whale. Despite this killer reputation, no human has
ever been recorded to have died directly as a result of the actions of a wild
orca. In captivity, however, they have. Been confined in a tank those size is
equivalent to a human living in a small garden shed would drive any social
animal mad if kept in long enough. Even if their sharing a space with two or
three. You’ll hate it, won’t you?
Orcinus orca
Known as …
Orca/Killer Whale/Blackfish
Average Size
New-born 2.4m long
Adult Male 7.3m long
Adult Female 6.2m long
Average Mass
New-born 180kg
Adult Male 4,500kg
Adult Female 2,050kg
Abilities
Echo location
Verbal speech
Fast Swimmer
Hunting in packs
Teaching their young
Teachable by humans
Whale or Dolphin?
To the average person the difference between a whale and a
dolphin is the same as boats and ships – their size. To biologists, the two are
the same kind of creature - cetaceans (from the Latin cetus - “large sea
animal” - and the Greek ketos - “sea monster”). Cetaceans are streamlined, fish-shaped
creatures with flippers, no visible hind limbs, a horizontally-angled tail, and
thick blubber under their skin. They come in two varieties – ones with teeth,
odontocetes, (such as sperm whales, dolphins, narwhals and porpoises) and ones
that have a filter-like structure in their mouth (called a baleen), mysticetes,
(such as the blue and humpback).
The orca has teeth, making it an odontocete, the same group as dolphins. It shares a common ancestor with all dolphins, making it part of the Delphinoidea “super family,” the biggest group in the odontocete gang. Within this family it’s a Delphinidae (ocean dolphin), a very diverse group that is hard to generalize, which include the orca as well as the Māui dolphin (the smallest member). Within the ocean dolphins, the orca is in the Orcinus sub family, containing four known species. In short, the orca is technically a dolphin – the largest dolphin in the world. The orca is the only Orcinus species that is not extinct – let.
Male or Female?
Males are usually larger and bulkier than females. But the
biggest difference is their dorsal fins. The female has a shorter and curvier
fin than the male.
The largest recorded male orca was 9.8m long and weighed
10,000kg. The largest recorded female was 8.5m long and weighed 7,500kg.
Life of an Orca
Female orcas become breedable at between 10 to 13 years
old. They reproduce very slowly, with one calf about every eight years. Pregnancy
can last from 15 to 18 months, giving birth to a single calf at any time of the
year. They are nursed for at least a year.
Males usually live for about 30 years, but can live pass
60. Females usually live about 50 years, but can live up to 90. One is alleged
to have lived over 100 years. Like humans, orcas experience the menopause.
Calves are born with a yellowish or orange tint, which
later fades to white.
The calf’s saddle patch is less distant or non-existent.
Colouring
The orca’s distinctive skin colouring forms counter-shading
camouflage. From above, the black bends in with the dark coloured ocean water.
From below, the white blends with the sunlit water.
Behind the dorsal fin is a dark grey “saddle patch.”
Skin
An orca’s skin is different to most dolphins, having a
well-developed dermal layer with a dense network of muscle collagen fibres. It’s
coated in a film of oil to reduce friction with the water. Beneath it is a
layer of insulating blubber about 7.6-10cm thick.
Tail
The orca’s tail contains no bone or cartilage. It’s a dense
collection of connective tissue, connected up to muscles that make up the tail
end third of the orca’s body. Thanks to this, the orca is the fastest swimmer
of all whales, swimming at speeds up to 55kph (34mph). Like the flippers, the
tail contains a collection of blood vessels to help regulate body temperature.
Dorsal Fin
An infant orca’s dorsal fin is short and curvy. In
adulthood it remains so on females, growing up to 90cm tall. But on males it
becomes longer and straighter, growing up to 1.8m tall, especially on older
males.
Pectoral Fins
The orcas’ forelimbs are in the form of large, rounded
paddles. Used for steering they also contain a
collection of blood vessels to help regulate body temperature.
Brain
The orca has the second-heaviest brain among marine mammals
(sperm whale is first). MRI scans reveal
a brain well-wired for sensing their environment and capable of advanced
thinking. Their cerebral cortex (the outer layer of grey matter) is relatively
smaller than that in a human brain, but their white matter is made up of large
diameter myelinated axons. Sam Ridgeway, a neurobiologist from San Diego's National
Marine Mammal Foundation, describes this set up as "analogous to a
computer that has maybe less memory but bigger wires."
Senses
Orcas have good eye sight, both above and below the water,
and a good sense of touch. As in all cetaceans, orcas mostly use sound to sense
their surroundings, muchly through echo location. Their echo location skills
are said to be good enough to identify which species of fish is present roughly
50m away.
Mouth
Orcas have strong interlocking teeth with a powerful grip
to trap prey. The front teeth are inclined slightly forward and outward to
protect them from powerful jerking movements. They rip and tear their food and
don’t chew. They eat their prey whole or in chunks.
Orcas have 20-26 teeth per jaw - each cone-shaped and about
7.6cm (3in) long.
The jaw bone picks up sound and transmit it to the ear canal.
Penis
To reduce drag, the orca keeps its genitals tucked away in
a genital slit. He has to because the male orca has the largest penis of any
animal on Earth – measuring up to 2.4m (8ft) long!
Blowhole
Orcas are conscious breathers. They have to consciously regularly
swim to the surface to breath. The blowhole has a muscular flip that forms an
airtight seal while underwater.
In case you’re wondering, when born, a calf’s mother will
help push her child to the surface for them to take their first breath.
Heart
An orca’s heart beats about 60 beats per minute when on the
surface. To reduce oxygen consumption, it drops to 30 beats per minute when underwater.
The orca’s skeleton is a more robust version of that of a
typical dolphin.
How Whales Sleep
Because they have to consciously breath, all whales and
dolphins (including orcas) have developed a sort of double conscious. When they
need sleep half their brain switches off while the other half stays on and
alert to keep a look out and move to the surface to breath. You can observe
this by looking at their eyes. When they only close one eye. The open one is
controlled by the conscious half of the brain.
Comments
Post a Comment