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Series 12
thetelegraph.com.au/classmate
Dolphins hold a special place in human affection. Possessing a
level of intelligence and a sophisticated social system like our
own, they often seem to get on well with us. There are stories of
dolphins rescuing people who have fallen overboard from ships and
dolphins still often follow ships into harbour when the ships
return from a voyage. These apparently
fun-loving creatures are actually voracious predators, living in
one of the harshest environments on Earth, from rivers worldwide to
tropical and subpolar oceans. They have been woven into our
mythology and art. But while we think of ourselves as friends, many
threats to dolphins come from humans.
Email [email protected] Phone 9288 2542For Free
teacherresources visit
thetelegraph.com.au/classmateEditor: Troy Lennon Additional
writing: Marea Donnelly Graphics: Paul Leigh and Will Pearce
SourcES & furthEr Study
BookSSources and further studyA Field Guide To The Mammals Of
Australia, by Peter Menkhorst and Frank Knight (Oxford)
WEBSITESAustralian Department of Sustainability, Environment,
Water, Population and Communities:
environment.gov.au/coasts/species/cetaceans/index.htmlMarine Parks
WA: marineparks.wa.gov.au/Howstuffworks Dolphins:
http://animals.howstuffworks.com/mammals/dolphin-
info.htmOrganisation For The Rescue And Research Of Cetaceans in
Australia: orrca.org.auWhales and Dolphins of Australia:
http://au.whales.wildiaries.com/Encyclopaedia Britannica:
britannica.com
Mythology and cultureSome of the earliest depictions of dolphins
were painted by people in caves on the island of Misool in West
Papua as early as 3000BC. Australian Aborigines considered the
animal
sacred, telling Dreamtime stories about them and depicting them
in their art. The
ancient Minoans and other ancient Greek cultures also depicted
dolphins in bright,
cheerful paintings in frescos on the walls of homes, palaces and
tombs. Painted around 2000BC, the exact significance of dolphins in
Minoan culture
is not known. The ancient Greeks of later eras, however,
associated dolphins
with the god of the ocean Poseidon. Various gods were said to
have used dolphins as minions
or as transport, for example, Apollo changed into a dolphin to
escape an island. The ancient Chinese
believed the dolphins in the Yangtze River contained the spirit
of a drowned princess. The
natives of the Amazon forest once believed that the
pink-coloured freshwater dolphins
in the river, known as boto, could transform into beautiful
humans who would come to parties at night and seduce people.
What is a dolphin?A dolphin is any one of about 40 species of
cetacean from the family Delphinidae (oceanic dolphins) or
Platanistidae (river dolphins). The order Cetacea includes whales,
porpoises and orcas (killer whales). Dolphins are generally smaller
than their whale cousins although some species in the dolphin
family are known by the name of whale, such as pilot whales. All of
the species known by the name of dolphin are shorter than 3m. The
smallest cetacean species is New Zealands Cephalorhynchus hectori
or Hectors dolphin, which grows to only about 1.4m. Like whales
they have a spout. All dolphins have teeth, are carnivorous, give
birth to live young and are social animals living together in
schools of between five and 1000.
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DiD YoU know? A male dolphin is known as a bull,
a female is a cow and a young dolphin is a calf.
The killer whale is also a member of the family delphinidae and
therefore a kind of dolphin.
Bottlenose dolphins can swim at speeds of up to 30km/h.
Dolphins have teeth, but they do not actually chew their food.
The cone-shaped teeth are used primarily to catch their prey, which
is swallowed whole.
The pink, or Amazon River dolphin, Inia geoffrensis, can swim
upside down. It has pink colouring and a hump rather than a
prominent dorsal fin.
The average gestation period (length of pregnancy) of a
bottlenose dolphin is about 11-12 months, while the orca has a
gestation period of 17 months.
Natural historyDolphins have been around much longer than humans
and our ancestors. The first dolphin fossils appear in the record
from the Miocene epoch between about 23.8 million and 16.4 million
years ago. All the species of dolphin that exist today were found
in the Miocene and there are several extinct species.
different on porpoiseDolphins differ from porpoises in that the
latter are generally more compact, have flattened snouts and have
shovel or spatula-shaped, rather than cone-shaped, teeth.
Dolphin spotters guiDeThe bottlenose dolphin, can be commonly
seen anywhere on the coast of Australia at any time of year.
Throughout the tropics, there are also Indo-Pacific humpback
dolphins and our own river dolphin, Australian snubfin dolphin,
which is found in no other country. If you know where to look and
what to look for, there are many opportunities to see dolphins from
organised trips or even from shore. This information is covered in
any number of guides, including the iPod / iPhone Field Guide To
The Whales And Dolphins Of Australia, New Zealand And The Antarctic
(published by Wildiaries).
See http://home.wildiaries.com or Email: [email protected]
Bottlenose dolphins, are natural acrobats and will sometimes
swim with surfers. Picture: Getty Images
24
Dolphins
Short snout
Smaller shape
Pointy dorsal fin shape
PoRPoiSE
DolPhin
straNded cetaceaNsIf you find a beached dolphin immediately call
the 24-hour ORRCA Marine Mammal Rescue Hotline 9415 3333 or the
National Parks and Wildlife Service (Outside Australia, call your
wildlife authority) and advise of the exact location.
Things you shoulDnT Do
do not do anything that will injure yourself or others.
do not push the animal back to sea.
do not use the fins or flippers as handles.
do not cover or obstruct the blowhole or eyes.
do not try to feed the animals.
Things you can Do keep the animal upright. keep the tail and
fins wet. Shade the animal. keep onlookers quiet and well back. for
your safety, please keep clear of the tail. keep talking and other
noises down to
a minimum. Wait for trained rescuers to arrive. Protect yourself
from the elements (make sure
you have water and protection from the sun or cold). Please note
as many physical characteristics
as possible. this information will assist experts in determining
the species.
courtesy of orrcA (organisation for the rescue and research of
cetaceans in Australia)
www.orrca.org.au
Dolphin species irrawaDDy
Dolphin (Orcaella brevirostris)
Found in northern Australia and South-East Asian estuaries,
mangroves and rivers. It is 1.8-2.75m long, has a bulging forehead,
short beak, and 12-19 teeth on each side of each jaw. It is a
slate-blue to slate-grey in colour, lives in groups of up to 10 and
eats fish and crustaceans.
inDo-pacific humpback or speckleD Dolphin (Sousa chinensis)It is
estimated only 100 Indo-Pacific humpbacks survive in inshore
tropical and subtropical waters from northern NSW to Shark Bay in
Western Australia.
They grow 2-3m long, are usually pale grey, have a long,
slender
beak and a large triangular dorsal fin. They are also found off
south-
ern China, Indonesia, and in the Indian Ocean to
southern Africa.
boTTlenose Dolphin (Tursiops truncatus)With their friendly
nature, bottlenose dolphins are a favourite with surfers. They are
named for their short, rounded snout, described as bottle-shaped.
Their large dorsal fin is slightly hooked and their body is
generally grey, fading to an off-white belly. Two forms of
bottlenose, inshore and offshore, are recognised. They grow from
2-4m long. Bottlenose swim in pods of two to more than 1000. An
abundant species, they are found in temperate waters around the
world.
rough-TooTheD Dolphin (Steno bredanensis)Named for the vertical
ridges in their teeth, this long-beaked dolphin is
black-to-dark-grey, and grows from 2.55-2.8m. It usually lives in
deep tropical and warm temperate waters around the world.
common Dolphin (Delphinus delphis)Common dolphins have
attractively marked flanks of yellow, buff and grey patches against
a dark grey upper body and white belly, and grow to 2m. A
long-beaked and a short-beaked form are recognised. Common dolphins
favour continental shelf and surface waters in the Atlantic and
Pacific Oceans in temperate and tropical zones.
souThern righT whale Dolphin (Lissodelphis peronii)Named for the
Greek words lisso (smooth) and delphis (dolphin). Its common name
comes from the right whale, which also lacks a dorsal, or top, fin.
It is at least 3m long, has a streamlined body and a short beak. It
has a black back with white below and lives in deep waters south of
NSW, to Africa and South America.
Dusky Dolphin (Lagenorhynchus obscurus)A smaller species, dusky
dolphins are about 2m long and dark blue-black on their tails and
dorsal (upper) sides. A dark band runs diagonally across their
flanks from their dorsal fins to their tail. Found only in southern
waters, from Tasmania to New Zealand, Africa and South America,
they live in groups of 100 or more. Known for their acrobatics,
they favour bow-riding and seem to enjoy contact with boats and
people.
Most recently discovered:
snubfin Dolphin (Orcaella heinsohnii)This odd looking (but cute)
dolphin was discovered in 2005. Until then it was thought to be the
Irrawaddy dolphin. DNA profiles and skull measurements by
scientists proved it is a distinct species. It averages 2m, has a
short. stubby dorsal fin, a round melon-like head with no beak and
is cream to dark brown. Its blowhole is a little to the left. It
lives off northern Australia, from WA to Queensland, in rivers,
estuaries and coastal waters, in groups of six to 15. Australian
snubfin dolphins are not acrobatic.
burranan (Tursiops australis)One of three new dolphin species
found since the 1800s, it was identified last year and named after
an Aboriginal phrase meaning large sea fish of the porpoise kind.
Before this, it was thought to be one of two bottlenose dolphin
species. About 100 were found in Port Phillip Bay and 50 in
saltwater coastal lakes around Gippsland. Researchers want it
listed as endangered. It only reaches 2.5m long and has three-toned
colouring.
cone-shaped teeth on a dolphin
Poseidon
