Dolphins

Fact Sheets from the
Conservation Education Department
Dolphins
The Atlantic bottlenose dolphins,
Tursiops truncates, living at the
National Aquarium in Baltimore are
just one of approximately 70
species of dolphin. Dolphins are
actually small, toothed whales and
belong to the class Cetacea.
Fast Facts
Marine Mammals
Although the word "dolphin" is
Dolphins have hair, lungs to
sometimes associated with a dol-
breathe air, give live birth, and
phin fish, also known as a mahi
provide milk for their young.
mahi, a type of bony fish served in
PLAY! the new dolphin show gives visitors a look into
Echolocation allows dol-
restaurants, dolphins are marine
the world of dolphins and their amazing behaviors.
phins to find food and other
mammals. Like all mammals, they
objects in dark, murky water,
have hair, have lungs to breathe air,
skin that insulates their body against
where sight is nearly useless.
give live birth, and provide milk for
the cold water. Dolphins can dive
The Chinese river dol-
their young with mammary glands.
up to 300 meters (984 feet) below
phin is the most endan-
A dolphin's hair is in the form of
the ocean's surface, but they will
gered dolphin in the
whiskers on its chin when it is born,
rarely stay underwater for long peri-
world.
although the hair falls out shortly
ods of time. Dolphins use oxygen
after birth. Dolphins nurse their
much more efficiently than humans
Key Terms
young until they are old enough to
because they store O2 in their
eat solid foods. Since these animals
blood and muscles, rather than in
Echolocation - Use
have lungs, they must rise to the
their lungs. During deep dives, their
of sound underwater
surface to breathe. Dolphins
lungs and ribs partially collapse.
to sense the environ-
breathe through the blowholes on
ment.
top of their heads. Each time a dol-
Echolocation
phin surfaces, the flap over its
Although dolphins lack vocal
Mammals -
blowhole opens. The dolphin then
cords, they produce sound by push-
Animals that they
rapidly exhales and inhales, and the
ing air back and forth between air
have hair, have
flap closes. In one breath, dolphins
sacs below their blowholes. In this
lungs to breathe air,
may exchange up to 90% of the air
way dolphins can produce a series
give live birth, and
in their lungs, compared with a
of clicks and whistles, which they
provide milk for
human's air exchange, which is
use to communicate with one
their young.
approximately 15%.
another. Dolphins also produce
clicks to orient themselves underwa-
Melon - The fatty
Dolphin Adaptations
ter. Echolocation, a biological sonar,
bulge that looks
Animals living in the ocean have
consists of a series of clicks that
like the dolphin's
special adaptations that help them
are sent from the air sacs through a
forehead; it helps
survive. Mammals are warm-blood-
structure called the melon. The
direct sound travel-
ed, meaning they maintain a con-
melon is the fatty bulge that looks
ing through the
stant body temperature. Dolphins
like the dolphin's forehead; it helps
water.
have a layer of blubber under their
direct sound traveling through the

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water. When the sound hits an
also have a longer, more-pro-
Dolphins at the National
object, it will bounce back as
nounced rostrum, or "beak", and a
Aquarium in Baltimore
"echoes". The returning echoes
taller, more curved dorsal fin.
The National Aquarium in
travel through fat in the dolphin's
Baltimore has permits allowing
lower jaw and vibrate against its
Social Structure and
us to have dolphins. These per-
inner ear. By analyzing these, a dol-
Reproduction
mits are issued by the federal
phin can learn the size, density,
Dolphins separate themselves into
government and require that
speed, and direction of movement
social groups based on gender.
certain standards regarding ani-
of objects around them.
Females and calves associate in
mal care and public education
Echolocation allows dolphins to
groups, or pods, while males may
are met.
find food and other objects in dark,
roam individually or in "bachelor
Dolphins, and all marine
murky water, where sight is nearly
groups". Female calves stay with
mammals, are protected by the
useless.
their mothers' pod for life, but male
Marine Mammal Protection
calves leave the pod between two
Act. This law makes it illegal to
River Dolphins
and four years of age.
feed, touch, harass, or kill
Not all dolphins live near the
Dolphins reach sexual maturity in
marine mammals. It also makes
shore. Oceanic dolphins are often
six to ten years and reproduce in
it illegal to buy, sell, import, or
found miles from land. Other dol-
the spring. Gestation lasts approxi-
export products made from
phins, such as the Amazon River
mately eleven months and females
marine mammals.
dolphin, Inia geoffrensis, live in fresh-
give birth to one calf every two
Humans pose the biggest
water. The river dolphins are among
years. Mothers nurse the calves for
threat to dolphins. Our trash,
the most endangered dolphins. The
about a year. During this time,
especially plastics, ends up in
Chinese river dolphin, Leipo vexillifer,
"babysitters" from the pod may
the ocean where marine mam-
is the most endangered dolphin in
watch the calf while the mothers
mals often ingest it or become
the world; only an estimated 5 indi-
are feeding. If a mother becomes
entangled in it. Approximately
viduals are still alive. Fifty years ago
annoyed with the calf, or wants to
90% of all marine mammal
more than 6,000 of these animals
gain its attention, she slaps the
strandings are due to humans.
existed, but due to habitat destruc-
water surface with her tail.
By following simple sugges-
tion and human encroachment,
tions, people could make the
their population has plummeted.
History and Conservation
oceans much safer for dolphins.
Since the days of ancient Greece
Help by throwing trash
Dolphin Versus Porpoise
and Rome, dolphins have delighted
away properly, and recycling
Dolphins and porpoises are fre-
and intrigued people with their
whenever possible.
quently confused, however, there
inquisitive nature. They have even
Participating in local beach
are some slight differences between
been rumored to make friends with
clean-ups.
these two groups. Dolphins are usu-
boaters and bathers. Their curious
Support sustainable
ally more curious than porpoises,
behavior has convinced many peo-
seafood practices like “dolphin
and are more frequently seen.
ple that dolphins are very intelligent
safe” tuna.
Porpoises often swim away when
animals. When in aquariums and
human activity gets close. Dolphins
zoos they quickly learn behaviors;
are also larger than porpoises. For
they appear to be healthier when
instance, bottlenose dolphins often
they are presented with games and
reach more than 3 meters (10 feet)
tasks to perform. Although trainers
in length, and can weigh 650 kg
rate their intelligence as equal to
(1000 pounds) while harbor por-
that of smart dogs, scientists dis-
poises, Phocoena phocoena, rarely reach
agree as to exactly how "smart" dol-
more than 2 meters (6.5 feet) long
phins are. Until scientists devise a
or weigh more than 65 kg (145
way to measure intelligence, this
pounds). Porpoises have spade-
shall remain a mystery.
shaped teeth, while dolphins have
cone-shaped teeth. Most dolphins

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