Dolphins and
Porpoises
Dana Jacobs
Mr. Goldfarb’s class
March 23, 2012
Introduction
Imagine a dolphin-any kind-swimming in the ocean. Now imagine the same with
a porpoise. Got it? If you didn’t get the porpoise, it’s ok if you didn’t, this should help a
little.
Dolphins have a bigger melon (a pad of fat to help focus their sonar beams or
echolocation) and porpoises generally don’t have beaks/snouts and are smaller than
dolphins, seldom 6’6”. Porpoises have more triangular dorsal fins and are shyer than
dolphins.
Dolphins and porpoises are classified together in the group of cetaceans (si-TAYshuns) which is a group of toothed whales, porpoises, and dolphins. Although they are
both in cetaceans, they are in separate groups also. Dolphins in Delphinidae (del-FIN-ihday) which is the Latin word for dolphin, and porpoises in Phocenidae (foe-SIN-ih-day)
which is Latin for porpoise.
Dolphins and porpoises live all around the world in seas, oceans, lakes, rivers, and
some live in aquariums.
Dolphins and porpoises live close, but in some ways, live their life far apart.
Dolphin Description
There are 42 types of dolphins including the 4 river dolphins. The dolphin family,
or family Delphinidae, included the killer whale, Risso’s dolphin, the Amazon River
dolphin, and the long-snouted spinner dolphin. Dolphins can be all different sizes and
colors depending on what size, gender, and age that dolphin is. For example, the IndoPacific humpbacked dolphin adult is pink all over while the calves are black.
All dolphins are mammals, which mean that they are warm blooded, are born with
hair, and feed their young milk.
All cetaceans have a tail which consists of two tail flukes, two pectorial fins, two
eyes, a beak/snout, a blowhole, and a melon.
Dolphins can live in oceans, seas,
lakes, and rivers. Dolphins can see in and
out of water equally fine. They breathe
through an opening at the top of their
head called a blowhole which closes
when they go back underwater so they
don’t inhale water. Out of all the
amazing abilities dolphins have, they
can’t smell or swim backwards!
Dolphins have sharp, pointed
teeth to help them hold onto slippery
prey. That prey would be jellyfish, small
crustaceans, shrimp, or fish like salmon or codfish. Dolphins catch their prey by
producing a high pitched sound (too high for humans to hear) that bounces of anything in
front of them and comes back to the. From that sound, dolphins can tell the shape of the
object it bounced off of, and how far away it is. That sound is called echolocation.
The high speed of a dolphin is about 30mph. When dolphins leap into the air, it
makes them faster once they go back in the water. Also, when dolphins get in the water
from leaping, their pectiorial fins help stabilize them so they don’t spin around.
Dolphins pod sizes can vary from 3 or 4 to several thousand.
These things though, can differ from porpoises.
Porpoise description
There are many fewer species of porpoises than dolphins. 6. Harbor porpoise,
Dall’s porpoise, Burmiester’s porpoise, vaquita, finless porpoise (so named because it has
no dorsal fin), and spectacled porpoise, Those 6 species share the same characteristics
and behavior like the fact that porpoises do not form large pod, and the strongest social
bone is between a mother and its calf. Most
porpoises prefer shallow waters to deeper
waters. The vaquita only lives in the upper
quarter of the Gulf of California.
Most porpoises are shy and don’t
approach people or boats. Am exception to
that is the Dall’s porpoise. Because of this, if
makes it extremely hard to study most
porpoises.
Porpoises love to play.
The term ‘porpoise’ comes from the
Latin words porcus (pig) and picus (fish).
Dolphin Threats
Dolphins have many threats. The three main natural causes of death to dolphins
are parasites, diseases, and predators such as sharks and orcas.
Some man-made threats are boats, oil and gas rigs, and fishing nets. A boat can
harm a dolphin’s hearing- so they can’t echolocate as well- and behavior. Oil and gas rigs
can leak and get into fish which dolphins eat. When the dolphin eats the fish, the toxins
are then in them. The toxins go into female’s milk which the calf drinks and the toxins
spread generation through generation. Fishing nets are meant to catch fish, but dolphins
may get caught in a net or chase a fish into a net and follow the fish in the net. When
fishing nets are pulled on the boat, the fishers use an ax to open the nets and kill the fish.
This ax goes into a dolphin as well as the fish and kills them.
One of the biggest threats to a dolphin calf is an attack from a male adult of the
same species called infanticide where the male killed the calf. Infanticide is thought to
happen because the male wants to mate and thinks that if he kills a calf, the mother will
want a new calf and mate with him. This is practiced on porpoises.
Dolphins are also threats to smaller sea animals just as orcas and sharks are to
them.
Dolphin hunting
Dolphins use echolocation to find salmon codfish, squid, small crustaceans,
jellyfish, grouper, and sardine. Echolocation helps dolphins because if they can’t see
food, echolocation helps them find it. Echolocation
can even tell dolphins if a female is pregnant.
Dolphins and us may not eat and get their
food the same way as us, but dolphins and human
kids have 1 thing in common with the way they eat.
They both play with it!
Baby dolphin, or calves, can’t catch prey.
Dolphin Birth and Development
Dolphins are born tail first and need to
surface immediately to breathe. At birth, a baby
dolphin can be one third of its mother’s length and
weight and wants to eat as much as possible. Some
calves are born with whiskers but lose them after about a week.
Calves are easily spotted by predators because of the fetal folds which are dark
marks that are from being squished in its mothers belly for so long. Having twins is
highly unlikely and both twins are not likely to survive because they will be fighting over
who gets their mother’s milk and won’t get the amount of milk and neither calf will get
the amount of milk they need to have to survive.
But, how exactly are the mother and father chosen?
Dolphins work together hunting a school of
fish.
Dolphin mating
Dolphins don’t get married like humans do, so male dolphins compete for the
females by fighting and doing acrobatics. Once the couple forms, the dolphins separate
from the group and mate.
Once the dolphins mate, they separate and find another mate by doing this over
and over again.
Although dolphins mate many times, a female dolphin only has 1 calf each year
with an exception of unlikely twins.
Porpoise Threats
Like dolphins, porpoises can also get trapped in fishing nets. Another threat that
to porpoises share is oil and gas rigs because, like dolphins, porpoises also eat the oil
filled fish.
Even though infanticide mainly affects dolphin calves, this attack is sometimes
practiced on porpoises because male dolphins may think that porpoises are calves
because of their size.
Porpoises are also killed by predators such as sharks and orcas, parasites, or
diseases.
Porpoises are also threats to animals smaller than them just as orcas are to them.
For example, porpoises eat shrimp, squid, small crustaceans, and most fish like grouper
and sardine.
Porpoise birth and development
A finless porpoise mother cares
for her calf.
Porpoise calves are born very small and born tail
first because they must get a breath immediately when they
are born. They want to eat as much as and have fetal folds.
Fetal folds are dark lines on a porpoise’s body from being
squished in its mother’s womb.
Right when a porpoise is born, it must learn to keep
up with its mother and pod.
Porpoise Mating
Female Dall’s and harbor porpoises get pregnant year where as the other type of
porpoises get pregnant every two years.
Male porpoises compete for the females by doing their best acrobatics and by
fighting.
In the Bay of Fundi, female harbor porpoises give birth in May, then 6 weeks
later, they mate, become pregnant, and give birth again.
Bottlenose Dolphins
Bottlenose dolphins have a wide head and body, a short stubby beak, long
flippers, a moderately tall dorsal fin, and a marked crease between the melon and beak.
They can make up to 1,000 clicking sounds a second and are often seen in aquariums.
Bottlenose dolphin’s scientific name is tursiops truncantus and can be in schools
from 10-30 members. Bottlenose dolphins live close to shore but
can go out deeper in al oceans. They live in all oceans except for
those in the polar regions.
Bottlenose dolphins are confused with rough toothed,
Risso’s, Pan Tropical spotted, and Atlantic spotted dolphins.
At birth, a calf weighs 31-44 pounds and is 33-55” long.
Males can grow up to be 1,000 pounds and 8’-12’6” long. Females can grow up to 7’10”12’ long and weigh up to 570 pounds. Females normally live at least 50 years which is
more than males who normally live 40-45 years. Both males and females live shorter in
captivity.
It takes 12 months for calves to form. Once a baby is born, another female (not
the mother) bites the umbilical cord and brings the baby bottlenose up to the surface. In 1
year, the calf has doubled in size and is 7 timed heavier.
Dolphins often have things in common with other species like the bottlenose and
striped.
Striped Dolphins
Striped dolphins are medium sized dolphins with a streamlined body. No pattern
repeats on any dolphin but they always have a black stripe from behind their eye to their
tail.
At birth, striped dolphins weigh 15-22 pounds and are 32”-37” from head to tail.
Adult males weigh about 350 pounds and are 8’8” in length.
Females can get up to 7’10” head to tail and weigh 330 pounds.
Striped dolphins can live up to 58 years.
Striped dolphins work together when they hunt and are
also hunted for their meat.
They like to have the surface of the water about 75 degrees Fahrenheit but mostly
stick to deeper waters. They live in the Atlantic, Pacific, and Indian Oceans.
Striped dolphins begin reproducing at 7-15 years old and are pregnant for about
twelve and a half months. They give birth to 1 calf every 3-4 years.
Striped dolphins are different from porpoises like the harbor porpoise for
example.
Harbor porpoises
Harbor porpoises live in coastal waters off of the North Atlantic Ocean, North
Pacific Ocean, and the Black Sea.
At birth, harbor porpoises weigh 1113 pounds and are 28”-30”. Males can get
up to134 pounds and grow up to 5’2”.
Female adults weigh 168 and grow to 5’6”.
Harbor porpoises can live up to 24 years.
Harbor porpoises either don’t live in
very big pods or live alone. Near the end of
summer, the pods get bigger then decrease
in a few weeks.
Harbor porpoises are not always called ‘harbor porpoises’. Sometimes they are
called puffing pigs, common porpoises, puffers, or tumblers.
Harbor porpoises are common as well as Dall’s porpoises.
Dall’s porpoises
Dall’s porpoises’ dorsal fins are fringed with white or gray at the top. They are
stocky with a head that looks too small for its body.
Dall’s porpoises weigh 24 pounds and are 3’4” at birth. Males can get up to 370440 pounds and 7’3”-7’10”. Females can get up to 400 pounds and head to tail, are 6’11”.
Dall’s porpoises normally live 10-22 years.
They are named for William Dall who described them for the first time in1873.
Dall’s porpoises occur across the Pacific Ocean from California to Japan often in open
ocean.
Conclusion
Dolphins and porpoises are beautiful creatures with not-so-beautiful lives.
I realized that dolphins and porpoises have more in common than they do
different. Also, if people stop the things they are doing to harm them, porpoises might be
easier to spot and so will dolphins.
Imagine them. Jumping, playing, having fun. That’s not their whole life.
Works Cited
Read, Andrew. Porpoises, Vancouver: Voyageur Press
Stahl, Dean. Dolphins, Columbus, Ohio: The Childs World.
Davies, Nic. Dolphins, Italy: Raintree Steck-vaughn publishers
Petrie, Kristin. Striped Dolphins, Ednid, Minnesota: ABDO publishing
Reeves, Randal R., Stewart, Brent S., Clapham, Phillip J., Powell, James A. Guide to
Marine Mammals of the World, US: Chanticleer Press
Jhonson, Jinny. Ocean life Encyclopedia, London: Mondo
Julienne Jerome, le Bloase, Renee. The Dolphin: prince of the waves, Readers Digest
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