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CETACEANS-WHALES, DOLPHINS, AND PORPOISES
Marine mammals in the cetacean family include whales, dolphins,
and porpoises. Although whales spend all their time in the
oceans, they are mammals just like us. This means that they
are warm blooded, give birth to live young, nurse their young,
have traces of hair or fur, and must come to the surface to
breathe air through their lungs.
Millions of years ago, the ancestors of whales lived on land.
Scientists believe these land ancestors looked like small
dogs, were more closely related to hippos, and went into the
ocean about 60 million years ago. Over time, these ancestors
changed or adapted, to survive in their new ocean environment.
Their front legs turned into paddle-shaped flippers, they
lost their back legs, their tails grew larger and widened
to form flukes, and they developed a thick layer of fat, called
blubber, to keep warm in the ocean. Also, their skulls elongated
and the nostrils shifted to the back of their heads to aid
in breathing at the ocean's surface. They developed a series
of adaptations related to diving, which include the ability
to store more oxygen in their blood and muscles, and more
blood volume relative to their body size than land mammals.
Cetaceans are separated into two groups: toothed and baleen
whales. As their name suggests, toothed whales or odontocetes
have teeth. They also have one opening at their blowhole.
There are over 73 species of toothed whales, including sperm
and beaked whales, belugas and narwhals, porpoises and dolphins,
and even fresh water dolphins that live in rivers. They range
in size from the 60-foot (21.1 m) sperm whale to the 5-foot
(1.5 m) vaquita. Some toothed whales are quite unusual. For
instance, the beaked whales spend most of their time in the
deep water so they are rarely encountered, and new species
are still being discovered! Some beaked whales are odd looking,
and often only the males will have teeth (and only two at
that). The straptoothed whales have only two teeth, which
wrap around the top of their jaws so they cannot fully open
their mouths!
Toothed whales tend to be social and live in groups. Like
bats, they use echolocation or sonar to detect objects in
their environment. They produce sounds in the air passages
in their heads, which are then projected out in front of them.
The sounds bounce off solid objects and return to them (like
an echo), so the animals are able to get a "picture"
of what is around them. A lot of research is being done on
whale sounds. Many species, such as the sperm whale, seem
to have individually identifiable calls. Orcas (killer whales)
live in groups or pods and each pod has a dialect or accent,
just like we have accents depending upon which part of the
world we are from.
The baleen whales or mysticetes are the other group of cetaceans.
This group includes 11 species ranging from the smallest baleen
whale, the pygmy right whale at 21 feet (6.4 m) to the largest
baleen whale, the blue whale at 100 feet (30.5 m). Baleen
whales have two blowholes and instead of teeth in their mouths,
have hundreds of rows of baleen plates, which are made of
keratin, a substance in our hair and fingernails. They act
as filters for catching food. Most baleen whales feed by taking
a large mouthful of food and water, and then push the water
out through their baleen plates with their tongues. The food
gets trapped behind the baleen. Most baleen whales eat krill
(shrimp-like animals) or small fish. Right and bowhead whales
are baleen whales that feed in a slightly different way called
skimming. Water and food flows through a gap in the front
of their baleen plates, the food gets trapped inside the baleen,
and the water flows out through gaps on the sides of their
mouths.
Even though baleen whales eat very small animals, which are
low on the food chain, they are very large. For instance,
the blue whale is the largest animal on earth, weighing 150
tons. Baby blue whales gain 10 pounds (4.5 kg) an hour.
Many whales are endangered, largely due to past hunting.
Years ago, people used the oil from the blubber of whales
for all sorts of items, including oil burned in lamps and
ingredients for manufacturing lipstick. They also used whale
meat to eat or make pet food, sinews for tennis racquet strings,
and even used baleen as stays or supports in ladies underwear.
A waxy substance called ambergris, which is from a sperm whale's
digestive system, was used in making perfume. Ambergris was
very valuable, and a large lump found by a beachgoer was worth
a fortune.
Since 1986, there has been a temporary ban or moratorium
on hunting the large whales for commercial uses. However,
some countries still kill whales for "scientific"
purposes and others have illegally resumed commercial whaling.
This is controversial, because the products from these whales
are still used commercially. Many scientists question whether
the whales really need to be killed to learn the sorts of
things being studied.
Many people are concerned about the fate of the small whales
(the dolphins and porpoises). Thousands die every year from
getting caught in fishing nets and plastic trash. Toxins and
pollution in the ocean could be affecting the health of these
animals and their ability to fight off diseases. Around the
world, there has been an increase in reported strandings of
marine mammals. Other species are suffering due to loss of
their habitat. Sometimes, even whale watching can interfere
with and harass whales, if the boats venture too close to
the whales or separate mothers from calves. Small whales are
sometimes captured for display in aquaria and even hotels,
and many people question the quality of life and health for
these animals. Still others are being hunted and eaten in
some parts of the world.
In the recent past, popular movements helped to save the
whales from hunting. Unfortunately, the whales are not completely
safe. We need to understand and solve some of the problems
currently threatening whales. Let others know about the issues
and write to lawmakers. Also, if you ever have the chance,
try to see live whales in their wild ocean homes. You will
never forget it.
May be reprinted for scientific and educational purposes
Revised 2/02
Learn more about the following:
Odontocetes-toothed
whales
Dolphins
and porpoises
Mysticetes-baleen
whales
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Whales,
Dolphins & Porpoises - Cetaceans