Order cetacean, which is
the largest order of marine mammals, has two suborders, one is mysteceti, which
is the order of baleen whales and another one is odontoceti, which is the
suborder containing toothed whales. This suborder also includes dolphins and
porpoises. There are several differences between baleen whales and toothed
whales. The most important among them, as the name itself indicates, toothed
whales have teeth whereas baleen whales have baleens, which help them to filter
feed krill’s and other small organisms. Toothed whales are usually smaller
compared to baleen whales, even though sperm whale and baird’s beaked whale are
exceptions. In toothed whales, males are always larger than females, whereas it
is opposite in case of baleen whales. Toothed whales have only one blowhole
whereas baleen whales have two blowholes.
Let us take a look at
the general taxonomy of toothed whales in brief. There are about 65 species of
toothed whales in total, including oceanic and river dolphins and porpoises. I am
not going to mention all of them here, but mention a few important ones among
them and their specialty. This suborder contains nine families. They are:
1)
Physeteridae: Sperm whale
2)
Kogiidae: Dwarf sperm whale and pygmy
sperm whale
3)
Lipotidae: Baiji or Chinese River Dolphin
4)
Pontoporiidae: La Plata Dolphin
5)
Iniidae: Amazon River Dolphin
6)
Platanistidae: Gangetic Dolphin
7)
Monodontidae: Narwhal and Beluga whale
8)
Phocoenidae: Porpoises
9)
Delphinidae: Oceanic Dolphins
10)
Ziphiidae: Beaked whales
Among these nine
families, Physeteridae, Iniidae (Even though its status as being monotypic
family is a subject of discussion today because of the status of Bolivian River
Dolphin, which will be discussed later), Lipotidae, Platanistidae and
Pontoporiidae are monotypic families (Families containing a single extant species).
Other five families contain different number of species. Delphinidae is the
largest family of odontoceti, consisting of 38 species. More than half of the
toothed whales come under this family. Common bottlenose Dolphin and killer
whales (Orcas) are the best examples for the members of this family.
·
Sperm
whale (Physeter catodon or Physeter
macrocephalus): Sperm whales are the largest species of toothed whales.
They are the only members of family Physeteridae.
Males are about 50-60 feet long and can weigh up to 55 tons. Females are
usually smaller, about 35-40 feet in length and weigh only half as much as
males. The largest known male specimen reached a length of 67 feet and weighed
more than 60 tons. Sperm whales are named after the white jelly like substance named
spermaceti which is present in their huge square shaped head, which is about
one third of their body length. This liquid was mistaken to be sperm in earlier
days and hence this animal got its name ‘sperm whale’.
·
Killer
whales (Orcinus orca): Also called orcas,
killer whales actually belong to oceanic dolphin family Delphinidae and subfamily Orcininae.
Even though genetically they are dolphins, they are called whales because of
their large size. An adult male can reach a length of 30 feet. They are highly
sociable and always move in groups containing a dozen or more whales. Their black
and white appearance makes them one of the most beautiful cetaceans. They are
predatory animals and they feed on seals, sea lions, dugongs, manatees and
other large cetaceans. A group of killer whales sufficient in number can attack
even very large whales like blue whales and fin whales also! More than half of blue
whales observed near Antarctic region had scars of killer whale attacks on
their bodies.
·
Narwhals
(Monodon monoceros): Narwhals are members
of family Monodontidae and subfamily
Monodontinae. They are famous for
their single tusk which protrudes from their mouth. This tusk is present only
in males and it helps them while fighting for females. Even though males have a
single tusk, there are some cases where they had two tusks. Two tusked males,
even though less in number compared to single tusked ones, are not too rare. These
whales grow to a length of 13-18 feet and weigh around 800-1600 kg (males) and
11-14 feet and 500-1000 kg in weight. Tusks of males, even though have a
formidable appearance with a length exceeding 9-10 feet, are hollow and weigh
only 8-10 kg.
·
Beluga
whale (Delphinapterus leucas): Beluga
whales are also called white whales, because of their beautiful milky white
appearance. They belong to family Monodontidae,
subfamily Delphinapterinae. They are
about the same size of narwhals. Difference is that they don’t have tusk and
are pure white in color, contrary to bluish black color of narwhals.
·
Baiji
or Chinese river Dolphin (Lipotes vexillifer) : Baiji,
which is the only member of family Lipotidae,
is an example of how human interruption with nature can destroy a large animal
and lead it to complete extinction. Since 2006, no individual was sighted in
any part of china and it has been declared as functionally extinct. Extinction of
this wonderful Dolphin is a result of excessive fishing, hydro electricity
generation and other human activities in rivers. In august 2007, a Chinese man
reported that he saw a very large white animal swimming in a river, but his video
was too blurred to identify that animal.
·
Gangetic
river dolphin (Platenista gangetica) : There are
two subspecies of Gangetic river Dolphins, namely Gangetic river Dolphins (Platenista
gangetica gangetica) and Indus River Dolphins (Platenista gangetica minor).
They belong to family Platanistidae.
These are the only dolphins which are found in Indian rivers. They are also called
blind river dolphins, because their eyes are almost vestigial and they are
covered by a membrane of skin. They are also called south Asian river dolphins.
·
Amazon
River Dolphin (Inia geoffrensis)
: This Dolphin is found in Amazon, world’s largest river. They belong to family
Iniidae. There are two recognized
subspecies, namely Amazon River Dolphin (Inia geoffrensis geoffrensis) and Bolivian River Dolphin (Inia
geoffrensis boliviensis), but today they are being treated as two separate species.
Even though it is so, some taxonomists still consider Bolivian River Dolphin as
a subspecies of Amazon River Dolphin.
·
Pilot
whales: There are two species of pilot whales, which belong
to family Delphinidae, subfamily Orcininae and genus Globicephala.
Long finned pilot whale (Globicephala melas) and short finned
pilot wahle (Globicephala macrorhyncus) are almost similar in their
appearance except their fins, which are long and short respectively, as the
name itself indicates. Adults can grow 3.5-6.5 meters long and can weigh about
1-4 tons.
·
Porpoises:
Porpoises
are members of family Phocoenidae. They
are very small in size and range from 5-8 feet in length and weigh between
30-200 kg. They are the smallest group of cetaceans. Even though they look
similar to dolphins, they are distinguished from Dolphins by their shorter and flattened
beaks and teeth which are spade shaped, which are different from conical teeth
of dolphins. Word ‘porpoise’ actually means ‘small dolphin’. There are six
species of porpoises in three genera.
Unfortunately, none of
these wonderful creatures are safe today. They are being killed by man for
several reasons. Whether knowingly or unknowingly, we are all being responsible
for the destruction of these animals by our various activities. Baiji is an
example only and it is not the first and surely will not be the last animal to
pay for the greed of human beings. Let us save at least the remaining species
with care and let our younger generation also see these animals and admire
wonders of nature!