Special Adaptations
Although dolphins live in the ocean, they are not fish. Instead, the 33
species are all members of the order Cetacea, a taxonomical group
that includes whales and porpoises. They are further classified into the
sub-order odontocetes, or ‘toothed whales.’ This means that dolphins
are mammals, giving birth to live babies and nursing their babies with
milk. As mammals, they have warm blood, and breath with lungs
instead of gills. Like whales and porpoises, they do not breathe through
their mouths or noses, but through a blowhole, which is a hole located
on the top of the dolphin’s head. Their mouths are lined with numerous
small, sharp teeth, which they use to catch fish and other food.
Dolphins are not picky eaters, and consume a wide variety of small fish,
squid, and other marine animals. They employ numerous different
tactics to hunt their food, including chasing fish onto beaches where
the fish cannot swim or breathe, and then leaping out of the water
themselves to collect their meal. Another favorite hunting technique is
using their flippers to ‘bat’ the fish into the air, stunning them and
making them easier to catch. Some dolphins also work in cooperative
groups, designing complex hunting plans so that all the members will
have enough to eat.
One of the most interesting features about dolphins is their unique way
of locating objects in dark or murky water. Dolphins are capable of
diving as deep as 200 meters (650 ft.) beneath the ocean’s surface,
and can find themselves in areas where sunlight does not penetrate.
Although they do not have very good eyesight, they can still find things
by means of echolocation, or ‘dolphin sonar’. To use echolocation, the
dolphin sends out a series of short clicks. The sound waves ricochet off
objects in the water, and return to the dolphin. The dolphin interprets
these echoes to determine the size, shape, distance, and even
material or relative speed of other objects.
Dolphins are social animals, traveling, playing, and eating in herds that
can range from two to one thousand animals. Living in herds helps
protect the dolphins from predators such as orcas, or killer whales. If a
herd of dolphins is attacked by killer whales, the healthy adults will form
a defensive ring, protecting the calves and sick or injured members of
the herd.
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