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Taxonomical
status
| Appearance
| Distribution and migrations | Reproduction and development
Taxonomical status Killer whales (Orcinus orca) are members of the order Cetacea,
suborder Odontoceti.
Killer whales belong to Delphinidae family. Species name - Orcinus orca Linnaeus, 1758.
Appearance
Killer whales are the largest dolphins in the world. Male length
can reach 10 meters, females are smaller - up to just 8 meters in length.
You can discern the sex of the mature males by the size and shape of dorsal
fin: the male has an elongated dorsal fin, up to 2 meters high. Females
and subadult animals of both sexes have smaller sickle-shaped dorsal
fins.
One key species feature of killer whales is their coloration. Back and
sides of their large body are black; lower jaw, throat
and belly are white. On the rear
part of the body white colour goes up
| the sides, sometimes
culminating to the back. Two white patches are located before
the eyes and above them. Behind the dorsal fin there is an
asymmetrical saddle patch, which is used for photo-identification
of individual whales. In Arctic and Antarctic waters white
color can be masked by algae covering orca's skin and patches
have fawn or brown color. |
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In contrast to terrestrial predators killer whale is not very toothy.
There are just 10-14 teeth on the upper jaw and 8-14 on the lower.
During mouth closing upper jaw's teeth get into the space between
teeth of lower jaw, it helps while catching prey or biting the part
of it.
Distribution and migrations
Killer whales occur all over the World Ocean, near the coast and in
the open sea. In the Atlantic Ocean, orcas dwell everywhere from Greenland
to Antarctic seas. They are common visitors to the Mediterranean Sea. They
inhabit Indian Sea and Australia waters, and during summer season
they occurall around Antarctic seas. In Arctic their distribution
is discontinuous: orcas don't dwell in Eastern-Siberian Sea and Laptevih
Sea, but they live in Barentsev Sea, western and north-western part
of Karskoye Sea, near Murman coast and in the White Sea. On the Russian
Far East killer whales are often observed in Japanese and Ohotskoye
Seas, near Kamchatka peninsula, Komandor and Kuril islands, in Bering
Sea. At 1951 A.G. Tomilin noted that at Kamchatka coastal waters killer
whales had been often observed near Shipunskiy Cape, where rookery
of Steller sea lions was located, and at Olutorskiy and Avacha Gulfs.
Geographical distribution of killer whale
Reproduction and development
Pairing of killer whales was not observed in the nature, but studying
of stranded animals allows to suppose that impregnation take place
at summer season and early fall. Pregnancy duration is unknown, but
it is considered to be around 16 - 17 months. At Canada waters females
begin to give a birth since October till March. It is possible that
reproductive cycle of killer whales is varying in different areas,
for example, Russian researchers Y.I. Ivanova and V.À. Zemskiy reported
that birth of calves takes place during summer months, and Norwegian
researchers show that calves are usually born at fall season. Body
length of newborn is 250-270 centimeters, and yearling reaches 350
sm. Females grow during 10 years, and born first viable offspring
between 12 and 18 years old. Males arrive to adult female's size to
eighth year and continue growing till 15th year. Maturity of males
comes at 18 - 20 years old. Age establishment of growing males is
possible because of using HWR coefficient (height of the dorsal fin
to its width), each value corresponds to the fixed age of killer whale
male. Life span of killer whales isn't established exactly, but at
1987 year Olesiuk and his collegues observed two females, which age
was near 77 years old. Accounts of age for some females, based on
number and known age of their offspring have shown that these ladies
can come of 90 years old. Maximum life span of males can't be established
because they don't change since attaining their majority. But basing
on the proportions of the sex classes of animals of 35 years old it
is supposed that male life span is much lesser than female's and
don't exceed 50 - 60 years.
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