Whales

Whale weighs as much as 20 elephants but lives beneath the sea. The blue
whale is Earth\'s largest animal. Larger than the largest of ancient
dinosaurs, blue whales can grow to be more than 100 feet (30 meters) long
and weigh nearly 150 tons. Not all whales are so large. The much smaller
pilot whale grows to about 28 feet (8.5 meters) in length. And dolphins,
which belong to the whale family, range only from 3 to 13 feet (1 to 4
meters). Although whales spend their lives in the sea, they are, like
humans, warm-blooded mammals. After a baby whale is born, it nurses on its
mother\'s milk, just like the young of land mammals.
Whales are members of the order Cetacea, along with dolphins, porpoises, and
the narwhal. There are two basic types of living cetaceans: baleen, or
whalebone, whales of the scientific suborder Mysticeti; and toothed whales
of the suborder Odontoceti.
General Characteristics
Whales live in all of the open seas of the world, though some occasionally
enter coastal waters. Some species, such as the white whale, or beluga, may
travel upstream in large rivers. Some species migrate with the seasons;
others remain year-round in the same habitats, where they find their
preferred food.
The present-day distribution and abundance of some species has been greatly
influenced by the commercial whaling industry. Whalers eliminated or greatly
reduced the numbers of some species of baleen whales in certain oceanic
regions where whales once frolicked in abundance. This is particularly true
in parts of the Arctic Ocean and the eastern North Atlantic Ocean, where the
blue whale was almost completely exterminated in the early 1900s. Some
species of whales, however, are numerous today in the Arctic and Antarctic
regions.
The skin of whales is usually black, gray, black and white, or all white.
Some, such as the blue whale, have skin that is bluish-gray. The surface of
the skin is smooth, but like other mammals, whales have hair. Hair first
appears while the fetal whale is still developing inside its mother\'s womb.
In adult whales, hair is confined primarily to a few bristles in the head
region and is largely absent over most of the body. Whales that live in
polar regions are insulated from the extreme cold by a layer of blubber, or
fat, enveloping their bodies.
Baleen Whales

The baleen whales include the family of right whales, Balaenidae, so named
because whalers considered them "just right" easy to kill and full of oil
and whalebone. Among these are the black right whale (Eubalaena glacialis)
of both northern and southern seas. Scientists believe that those in the
western North Atlantic may be gradually increasing in numbers. However,
populations in the eastern North Atlantic and in both the eastern and
western North Pacific show no signs of recovery, and only a few remain in
each area. An estimated 1,500 to 3,000 occur in the southern oceans, with
little evidence of a significant increase in population sizes in most areas.
Some scientists place the southern right whale in a separate species: E.
australis. Black right whales reach lengths of 70 feet (21 meters) and are
black on the upper body. The underside is sometimes paler in color. The
baleen plates in the mouth may be more than 8 feet (2.4 meters) long.

Toothed Whales

The toothed whales include more than 65 species in six different families.
Among these are the true dolphins (family Delphinidae), which includes the
pilot whales (genus Globicephala) and the killer whale (Orcinus orca),
largest of the oceanic dolphins. Killer whales prefer coastal waters to the
open ocean. They hunt in schools and, though relatively small at 30 feet (9
meters), will attack other whales two or three times their size.
Two other families include the true porpoises (Phocoenidae), which are
marine species, and the river dolphins (Platanistidae), consisting of six
species of primarily freshwater or estuarine forms. The remaining three
families are the sperm whales (Physeteridae), the beaked whales and
bottlenosed whales (Ziphiidae), and the white whales and narwhal
(Monodontidae).
Evolution

Recent studies based on genetic sequences have confirmed that all cetaceans
were derived from a single ancestral stock and are closely related to the
hoofed mammals in the order Artiodactyla, made up of the even-toed mammals,
such as cattle, deer, and camels. Nevertheless, the evolutionary origin of
whales remains controversial among