Transcript OL OOP Section 07 - CCMI - Central Caribbean Marine Institute

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OUR OCEAN PLANET
OUR OCEAN PLANET
SECTION 7 – POLAR SEAS
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REVISION HISTORY
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7. POLAR SEAS
7. POLAR SEAS
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7. POLAR SEAS
Although the polar regions and seas are cold, a great variety of
conditions exist in both the Arctic and Antarctic.
Towards the North and South Poles the cold is intense but at their
margins the climate can be almost temperate and a great deal of life
exists at these margins.
The ice can take many colours and hues including white, grey, blue
and turquoise. It can form huge mounds as icebergs or lie flat as a
vast sheet covering the surface of the water.
High winds in the polar regions can also cause huge waves and
blistering storms but there are also periods of calm and tranquillity.
In the summer, the polar regions have 24 hours of sunlight but in the
winter, there are months of darkness.
ARCTIC & ANTARCTIC REGIONS
The Antarctic (Southern) Ocean surrounds the Antarctic continent.
The Antarctic region is defined by a line where cold Antarctic waters
meet and sink below warm northern waters – this is called the
“Antarctic Convergence”.
The Arctic, however, is more complicated because it includes land
masses that stretch into temperate latitudes. Arctic life does not
exist above a mean upper temperature limit of 10°C (50°F). Thus,
the boundary is a meandering line that circles the top of the northern
hemisphere.
Important!
The Antarctic ice-cap contains
30 million cubic km (nearly 70%)
of the world’s freshwater. It
covers 98% of the continent and
is nearly 5 km (3 miles) thick in
places. In comparison, the
Greenland ice-cap contains just
2.5 million cubic km of water.
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ARCTIC AND ANTARCTIC DIFFERENCES
In spite of both the Arctic and Antarctic having cold, dark winters and
a large amount of ice, they are different places with very different
characteristics:
The Arctic:
A frozen ocean surrounded by the land masses of North America,
Greenland and Eurasia
The Arctic Ocean is colder than the Antarctic Ocean
The Arctic is significantly warmer than Antarctica
Land animals can cross the ice sheets during the winter
Antarctica:
A continent of rock with a thick ice-cap surrounded by the Antarctic
Ocean
Antarctic Ocean is warmer than the Arctic Ocean
Antarctica is significantly colder than the Arctic
Land animals cannot reach Antarctica because it is remote
REFERENCES & FURTHER READING
Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue
Planet: Seas of Life, Chapter 5, DK Publishing Inc., (2001), ISBN 07894-8265-7
Important!
The key seasonal factor that
governs animal behavior in polar
regions is the growth and
melting of sea ice. This either
allows or prevents access to
feeding and breeding grounds.
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7.1.1 The Arctic
The Arctic Ocean is small and is almost entirely
covered by a layer of ice several meters thick
(there is no rock). It is surrounded by the
northern fringes of the great land masses of
North America, Greenland and Eurasia. These
land masses are extremely important because
they affect the climate dramatically.
Land
absorbs much more of the sun’s radiation than
ice, warming the rock, fresh water and the air
itself. Moderate temperatures of 10°C (50°F)
can be reached in the summer and only certain
places like Siberia attain the intensely cold
temperatures of -50°C (-60°F) in the winter.
The Arctic has a variety of climates and habitats
including a frozen sea, the ice-cap of Greenland,
the forests of Scandinavia, and the Siberian
tundra.
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Greenland is somewhat analogous to the Antarctic plateau. It is high and cold and has glaciers
streaming down to the sea. However, it is much smaller than the Antarctic plateau (10% of the area) and
thus its impact is less. The coldest places in the Arctic are on the Greenland ice-cap and in Siberia, both
of which are far from the warming effects of the ocean.
In spite of the cold conditions, life exists in the Arctic. The Arctic Ocean is bordered by shallow
continental shelves, fed by rivers and mixed by currents. In spring, phytoplankton (e.g. diatoms) blooms.
Diatoms sustain the invertebrates that live within the sea ice. Copepods, which are a type of shrimp-like
crustaceans, are a critical component of the marine ecosystem since they form the base animal of the
Arctic food chain. They are the equivalent of the Antarctic krill and feed on phytoplankton. Numerous
animals, in turn, feed on them. Other invertebrates found in the Arctic include:
• Periwinkles
• Bivalves
• Crabs
• Amphipods
• Sea Stars
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Arctic animals are closely related to those of the northern Atlantic and Pacific oceans but may have
certain adaptations to the cold. For example, periwinkles avoid ice crystals forming in their tissues by
becoming dehydrated for the winter. They can then survive in temperatures as low as -15°C (5°F).
A variety of sea mammals are found in the Arctic including pinnipeds (e.g. true seals such as harp seals
and walruses) and cetaceans (bowhead whales, beluga whales, and narwhals). The largest predators in
the Arctic are the polar bear, Arctic fox and humans. Polar bears hunt ringed seals, harp seals and
beluga whales while Inuit people hunt a variety of animals including seals and whales for skin, blubber
and meat. Inuit people also hunt the narwhal for their long tusks and their skin, an important source of
vitamin C in the traditional Arctic diet.
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7.1.2 Melting Sea Ice
A recent concern about the North Polar region is
the rapid melting of the Arctic sea ice. The figure
to the right illustrates the extent of the sea ice at
the same time of year between 1979 and 2003.
Indeed, some reports suggest that the ice is
melting so quickly that Arctic summers could
actually be ice-free by the middle of the 21st
Century
Many scientists attribute this disturbing loss of ice
cover to global warming.
Global warming
suggests that the planet is getting slightly warmer
as a result of human activities, such as the
burning of fossil fuels (e.g. oil, coal, wood).
Burning fossil fuels releases gases, such as
carbon dioxide, into the atmosphere. Carbon
dioxide increases the atmosphere’s ability to hold
heat which contributes to the planet warming.
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Global warming is a contentious subject and two questions are often asked by sceptics:
 Is it really happening or are higher temperatures just normal fluctuation?
 If it is happening, is human activity the cause of it?
An enormous amount of research has been carried out to answer these questions and much evidence
has been gathered. The result is that most reputable scientists today are almost certain that global
warming is indeed occurring, and that humans are the cause of it.
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POTENTIAL EFFECTS
Irrespective of whether humans are causing global warming, the effects of the melting ice can still be felt.
Some of these effects include:
(a) Rising sea level and flooding
As ice enters the sea, the sea level may rise which can cause flooding in low-lying areas.
(b) End of polar bears?
The polar bear is a vulnerable species at high risk of extinction. Zoologists and climatologists believe
that the projected decreases in the polar sea ice due to global warming will reduce their population by
two thirds by mid-century. As the ice melts, the bears’ habitat decreases. Local studies show that 7 out
of 19 subpopulations are declining or are already severely reduced. In the U.S., the Centre for Biological
Diversity petitioned to list the polar bear as an endangered species under the U.S. Endangered Species
Act in 2005. The U.S. Fish and Wildlife Service also formally proposed to list the polar bear as a
threatened species on January 9, 2007.
REFERENCES & FURTHER READING
http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html - Arctic warming
http://www.nasa.gov/vision/earth/environment/Arctic_Warming_ESU.html - Arctic warming
http://news.bbc.co.uk/2/hi/science/nature/6610125.stm - Arctic ice melting
http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_3974000/3974997.stm - Arctic ice melting
http://www.msnbc.msn.com/id/6433717/ - Arctic warming
http://www.bbc.co.uk/sn/climateexperiment/ - Global warming
http://www.ncdc.noaa.gov/oa/climate/globalwarming.html - Global warming
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7.1.3 Arctic Life
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POLAR BEAR
The polar bear (Ursus maritimus) is native to the Arctic and is the
world's largest land carnivore. Males are generally much larger than
females. Adult males weigh 350–650 kg (772–1433 lb) and
measure 2.5–3.0 m (8.2–9.8 ft) in length while adult females weigh
150–250 kg (331–551 lb) and measure 2–2.5 m (6.6–8.2 ft). Its skin
is black and its fur appears white or cream. Thick blubber and fur
insulate it against the cold. The bear has a short tail and small ears
that help reduce heat loss, and a relatively small head and long,
tapered body to streamline it for swimming. The polar bear is semiaquatic and has adapted for life on a combination of land, sea, and
ice. It is the apex predator within its range and feeds on seals,
walruses and whales although it will eat anything it can kill.
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ARCTIC FOX
The Arctic fox (Alopex lagopus) is a hardy animal that can survive
frigid Arctic temperatures as low as -58°F (-50°C) in the treeless
lands of its home. The Arctic fox’s head and body is 46-68 cm (1826.75 in) long while its tail is 35 cm (13.75 in) long. Its weight is 3-8
kg (6.5-17 lbs). It has furry soles, short ears and a short muzzle
which are important adaptations to the cold. Arctic foxes live in
burrows and may tunnel into the snow to create shelter. Arctic foxes
have white (sometimes blue-gray) coats that act as very effective
winter camouflage. When the seasons change, the fox's coat turns
brown or grey providing cover among the rocks and plants of the
summer tundra. These colours help foxes effectively hunt rodents,
birds and even fish. In winter, arctic foxes will follow polar bears and
eat leftover scraps. Foxes will also eat vegetables when they are
available. The fox's thick tail (brush) aids its balance and is also
useful as warm cover in cold weather.
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WALRUS
Walruses (Odobenus rosmarus) are large marine mammals that are
found in the north Atlantic & Pacific Oceans. Walruses are
immediately recognizable by their prominent tusks, whiskers and
great bulk. Adult Pacific males can weigh 2,000 kg (4,400 lbs) and
are exceeded in size only by elephant seals among pinnipeds
(marine mammals with flippers such as true seals, eared seals and
walruses). Walruses reside near shallow oceanic shelves and
spend a significant proportion of their lives on sea ice in pursuit of
their preferred diet of benthic bivalve molluscs. They are relatively
long-lived, social animals and are considered a keystone species in
Arctic marine ecosystems.
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HARP SEAL
Harp seals (Phoca groenlandica) spend relatively little time on land
and prefer to swim in the chilly waters of the North Atlantic and
Arctic Oceans. These sleek swimmers feed on fish and crustaceans
and can remain submerged for up to 15 minutes. Harp seals are 1.9
m (6.2 ft) in length and weigh 180 kg (397 lbs). Harp seals return
each year to breeding grounds in Newfoundland, the Greenland
Sea, and White Sea. Here, males fight for mates with sharp teeth
and powerful flippers. After mating, females gather in groups to give
birth. Born on the ice, young harp seals are famous for their white
coats which are highly valued and have drawn hunters to the
Newfoundland breeding grounds for centuries. In the last few
decades, these grounds have become a scene of conflict between
sealers and animal rights activists. Modern hunts are better
regulated than in the past but the harp seal arguably remains the
most commercially important seal with hundreds of thousands killed
each year.
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BELUGA WHALE
Belugas (Delphinapterus leucas) are white whales and their unusual
colour makes them one of the most familiar and easily
distinguishable of all whales. Calves are born gray or brown and
fade to white as they become sexually mature around five years of
age. Belugas are comparatively small whales and are about 6.1 m
(20 ft) in length and 1,361 kg (3,000 lbs) in weight. They have
rounded foreheads and no dorsal fin, and distinctively flexible necks.
Belugas are social animals that generally live together in small
groups known as pods. They are very vocal with a diversified
language of clicks and whistles. Belugas feed on fish, crustaceans
and worms. They are common in Arctic Ocean coastal waters
though they are also found in sub-arctic waters. Arctic belugas
migrate southward in large pods when the sea freezes. Animals
trapped by the Arctic ice are often prey to polar bears and killer
whales.
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NARWHAL
The narwhal (Monodon monoceros) is a pale-coloured porpoise
found in Arctic coastal waters and rivers. Narwhals are 6.1m (20 ft)
in length and weigh 1,600 kg (3,500 lbs). In males, one of the
narwhal’s teeth grows through the narwhal’s upper lip into a spearlike, spiral tusk up to 2.7 m (8.75 ft) long. Scientists are not certain
of the tusk's purpose but it may be used in mating rituals to impress
females or battle rival suitors. Females sometimes grow a small
tusk of their own but it does not become as prominent as the male's.
Narwhals are related to bottlenose dolphins, belugas, harbour
porpoises and orcas. Narwhals travel in groups and feed on fish,
shrimp, squid, and other aquatic fare. They often swim in groups of
15-20 but gatherings of hundreds or several thousand narwhals
have been reported. These groups sometimes become trapped by
shifting pack ice and fall victim to polar bears or Inuit hunters. Orcas
also prey on narwhals in open waters.
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SEA ANEMONE
Sea anemones are simple animals (cnidarians) that are often
attached to the sea bottom. Sea anemones have cylindrical bodies
that are surrounded by upward-facing tentacles. The tentacles have
stinging cells on them which kill prey and move the food into a sea
anemone’s mouth. The mouth leads into the body cavity which
digests the food. A continuous current of water through the mouth
circulates through the body cavity and removes waste.
Sea
anemones are found in cold and warm waters. Many are colourful,
and large species can be 1 m (3 ft) in diameter.
PERIWINKLE
The common periwinkle is a species of small edible sea snail and is
a type of marine mollusc.
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DIATOMS
Diatoms are microscopic algae that can photosynthesize food using
sunlight. They have cells walls that are made of silicon and often
take beautiful shapes and forms. Along with other phytoplankton,
they are the base of the food chain upon which zooplankton and
other animals all ultimately depend.
REFERENCES & FURTHER READING
http://www.polarbearsinternational.org/ - Polar bears
http://animals.nationalgeographic.com/animals/mammals/arctic-fox.html - Arctic Fox
http://animals.nationalgeographic.com/animals/mammals/harp-seal.html - Harp seal
http://animals.nationalgeographic.com/animals/mammals/beluga-whale.html - Beluga Whale
http://animals.nationalgeographic.com/animals/mammals/narwhal.html - Narwhal
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7.2.1 The Antarctic
Antarctica is a continent which is covered with an
ice-cap. At one time, it was the center of the
super-continent Gondwanaland with South
America, Africa, Australasia and India grouped
around its perimeter.
The surrounding Antarctic (Southern) Ocean is
much larger than the Arctic Ocean. It is also
much warmer because it is contiguous with the
Pacific, Atlantic and Indian oceans (ice covers
just 2.6% of it).
Antarctica is completely isolated by the ocean
which no land animals (even good swimmers)
can cross.
Antarctica is also much colder than the Arctic.
This is because it is not significantly warmed by
the great landmasses of South America,
Australia or Africa which are too distant to have
an effect. It is also surrounded by a recurring
barrier of sea ice which grows out from the
continent every autumn.
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Antarctica is also much colder because it has a
comparatively high altitude. The average height
of the continent is 2,500m (8,200 ft) (North
America averages 720m (2,360 ft).
As a result of the isolation and altitude,
Antarctica is significantly colder than the Arctic
and temperatures in the Antarctic can reach 70°C (-95°F) or less.
However, Antarctica’s climate and temperature is not uniform. Antarctica’s plateau, with a higher latitude
and elevation above sea level is unrelentingly cold with mean temperatures of -40°C (-40°F) in summer
and -70°C (-95°F) in winter. The plateau icecap receives almost no rain or snow and, because of the
extreme cold, there is no moisture in the air. Thus, it is an icy desert where virtually no life survives. It is
the driest place on Earth with all water “locked up” in ice. However, at the perimeters of the continent, on
the coasts, it is much warmer. The mean temperature is 0°C (32°F) in the summer and -30°C (-20°F) in
the winter. There is rain here and the winds are stronger.
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In spite of the cold conditions, life exists in the Antarctic Ocean. Many invertebrates are found in the
Antarctic Ocean including:
 Krill
 Limpets
 Sea Stars
 Ribbon Worms
 Crustaceans
 Soft Corals
 Hydroids
 Sea Anemones
 Sponges
In spring, phytoplankton (e.g. diatoms) blooms. Diatoms sustain the invertebrates that live within the sea
ice. Krill (Euphausiacea spp.), which are shrimp-like crustaceans, are a critical component of the marine
ecosystem since they are the base animal of the Antarctic food chain.
Numerous animals feed on krill, including, fish, birds, crabeater seals and a variety of baleen whales
(including the humpback, right, blue, sei, fin and minke whales). These whales take in huge mouthfuls of
water and use hanging plates of baleen – a horny material made of keratin – in their mouths to sieve krill
from the water.
Antarctic krill (Euphausia superba) is opaque and pink in colour. It is about 6 cm (2.4 in) in length and
feeds on phytoplankton (microscopic single-celled algae and plants). It is among the largest of the 85
known krill species. The total estimated weight of krill in the waters around Antarctica ranges from 100500 million tonnes. During certain times of the year, they congregate in swarms so dense and
widespread that the swarms can be seen from space.
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Antarctic krill can live up to 10 years, an amazing longevity for such a heavily hunted creature. They
spend their days avoiding predators in the cold depths of the Antarctic (Southern) Ocean, some 100 m
(330 ft) below the surface. During the night, they drift up the water column toward the surface in search
of phytoplankton.
Alarmingly, there are recent studies that show Antarctic krill stocks may have dropped by 80 percent
since the 1970s. Scientists attribute these declines in part to ice cover loss caused by global warming.
This ice loss removes a primary source of food for krill, namely, ice-algae.
In spite of the diversity of sea life, Antarctica has very few plants and no freshwater fishes, amphibians or
reptiles. However, there are sea birds and sea mammals.
Penguins are perhaps the most famous inhabitants of the Antarctic with several species found here
including the emperor, gentoo, chinstrap and Adelie penguins.
Crabeater seals are found in abundance – numbering in the millions. In spite of their name, they mainly
eat krill.
The two largest predators in Antarctica are the leopard seal and killer whale, both of which will hunt
penguins and crabeater seals.
REFERENCES & FURTHER READING
http://en.wikipedia.org/wiki/Antarctica - Antarctica
Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 5, DK
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7.2.2 Ozone Layer Depletion
WHAT IS OZONE?
Ozone is a gas that occurs naturally in small amounts in the upper atmosphere (the stratosphere) and is
made up of three oxygen atoms (O3).
“GOOD” STRATOSPHERIC OZONE
Ninety percent of the ozone in the atmosphere sits in the stratosphere, the layer of atmosphere between
about 10-50 km (6.2-31.1 miles) altitude. The natural level of ozone in the stratosphere is a result of a
balance between sunlight that creates ozone and the chemical reactions that destroy it.
Ozone is created when the oxygen we breathe (O2) is split apart by sunlight into single oxygen atoms.
Single oxygen atoms can re-join to make O2 or they can join with O2 molecules to make ozone (O3).
Ozone is destroyed when it reacts with molecules containing nitrogen, hydrogen, chlorine, or bromine.
Some of the molecules that destroy ozone occur naturally but people have created others.
Ozone in the stratosphere absorbs most of the ultraviolet radiation from the Sun. Without ozone, the
Sun’s intense UV radiation would sterilize the Earth’s surface. Ozone screens all of the most energetic,
UV-c, radiation, and most of the UV-b radiation. Ozone only screens about half of the UV-a radiation.
Excessive UV-b and UV-a radiation can cause sunburn and can lead to skin cancer and eye damage.
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Increased levels of human-produced gases such as CFCs (chlorofluorocarbons) have led to increased
rates of ozone destruction, upsetting the natural balance of ozone and leading to reduced stratospheric
ozone levels. These reduced ozone levels have increased the amount of harmful ultraviolet radiation
reaching the Earth’s surface. When scientists talk about the ozone hole, they are talking about the
destruction of stratospheric, “good,” ozone.
Since “good” ozone protects life on Earth from the Sun’s ultraviolet (UV) radiation, its destruction is a
serious matter.
“BAD” TROPOSPHERIC OZONE
Although ozone high up in the stratosphere provides a shield to protect life on Earth, direct contact with
ozone is harmful to both plants and animals (including humans). Ground-level, “bad,” ozone forms when
nitrogen oxide gases from vehicle and industrial emissions react with volatile organic compounds (such
as paint thinners).
In the troposphere near the Earth’s surface, the natural concentration of ozone is about 10 parts per
billion (0.00001 percent). According to the U.S. Environmental Protection Agency, exposure to ozone
levels of greater than 80 parts per billion for 8 hours or longer is unhealthy. Such concentrations occur in
or near cities during periods where the atmosphere is warm and stable. The harmful effects can include
throat and lung irritation or aggravation of asthma or emphysema.
Thus, in the lower atmosphere (the troposphere) near the Earth’s surface, ozone is created by chemical
reactions between air pollutants from vehicle exhaust, gasoline vapours, and other emissions. At ground
level, high concentrations of ozone are toxic to people and plants.
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WHAT IS THE OZONE HOLE?
The ozone hole is a region of exceptionally
depleted ozone in the stratosphere over the
Antarctic that occurs at the beginning of the
southern hemisphere spring (August–October).
Satellites provide daily images of ozone over the
Antarctic region. The image (on the right) shows
the very low values centered over Antarctica
around October, 2004. Historically, the total
column ozone values of less than 220 Dobson
Units were not observed prior to 1979. From an
aircraft field mission over Antarctica, a total
column ozone level of less than 220 Dobson
Units is a result of catalyzed ozone loss from
chlorine and bromine compounds. For these
reasons, scientists use 220 Dobson Units (or
less) as the boundary of the region representing
ozone loss – the so-called “ozone hole”.
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CHLOROFLUOROCARBONS AND OZONE
The ozone hole is caused by chemicals called chlorofluorocarbons (CFCs). CFCs escape into the
atmosphere from refrigeration and propellant devices and processes. Once widely used in domestic
appliances and aerosol sprays their usage has been restricted in many countries. However, in the lower
atmosphere, they are so stable that they persist for years or even decades. This long lifetime allows
some of the CFCs to eventually reach the stratosphere.
In the stratosphere, ultraviolet light breaks the bond holding chlorine atoms (Cl) to the CFC molecule. A
free chlorine atom goes on to participate in a series of chemical reactions that both destroy ozone and
return the unchanged free chlorine atom to the atmosphere where it can destroy more ozone molecules.
REFERENCES & FURTHER READING
http://ozonewatch.gsfc.nasa.gov/facts/hole.html - What is the ozone hole?
http://ozonewatch.gsfc.nasa.gov/ - Ozone Hole Watch
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7.2.3 Antarctic Life
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LEOPARD SEAL
The leopard seal (Hydrurga leptonyx) is named for its black-spotted
coat. They are the most formidable hunters of all the seals and the
only ones that feed on warm-blooded prey such as other seals.
Leopard seals use their powerful jaws and long teeth to kill smaller
seals, fish, and squid. These effective predators live in frigid
Antarctic and sub-Antarctic waters, where they also eat penguins.
They often wait underwater near an ice shelf and snare the birds just
as they enter the water after jumping off the ice. They may also
come up beneath seabirds resting on the water surface and snatch
them in their jaws. Shellfish are far less dramatic prey but still an
important part of the leopard seal's diet. Leopard seals are true
seals. They have long bodies 3.5m (11.5 ft) in length and elongated
heads, and weigh up to 380 kg (840 lbs). Like most other seals,
leopard seals are insulated from frigid waters by a thick layer of
blubber. Though the leopard seal is known for its coat, it has not
been commercially hunted for its skin.
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EMPEROR PENGUIN
Emperor penguins (Aptenodytes forsteri) are the largest of all
penguins. An average bird stands some 115 cm (45 in) tall and
weighs 40 kg (88 lbs). These flightless animals live on the Antarctic
ice and in the frigid surrounding waters.
Penguins employ
physiological adaptations and cooperative behaviors in order to deal
with the incredibly harsh environment. For example, they huddle
together to escape wind and conserve warmth. Individuals take turns
moving from the cold perimeter to the relatively warm interior of the
group.
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ICE FISH
The Antarctic icefish are the largely endemic, dominant fish found in
the cold continental shelf waters surrounding Antarctica. They reach
about 33 cm (12 in) in length. Most icefish live at seawater
temperatures between –2°C and 4°C (28-39°F), but some sub-polar
species inhabit waters that may be as warm as 10°C (50°F) around
New Zealand and South America. Icefish lack a swim bladder and
the majority of species are therefore benthic (pertaining to the
bottom of a sea) or demersal (found at or near the bottom of the
sea). Icefish have evolved a variety of adaptations that permit
survival in the Antarctic Ocean. Many are able to survive in the
freezing waters because of the presence of an antifreeze
glycoprotein in their blood and body fluids. Another adaptation is
that while the majority of animal species have hemoglobin in their
blood, some icefish do not. These icefish are able to survive without
hemoglobin in part because of the high oxygen content of the cold
waters of the Antarctic Ocean and in part because oxygen is
absorbed and distributed directly by the plasma.
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KILLER WHALE (ORCA)
Orcas (Orcinus orca) or killer whales are the largest of the dolphins
and one of the world's most powerful predators. Killer whales are
9.7 m (32 ft) in length and weigh up to 5,443 kg (12,000 lbs). Orcas
are easily recognizable by their distinctive black-and-white colouring.
They eat fish, squid, and seabirds. They also hunt marine mammals
such as seals, sea lions and whales, employing teeth that can be 10
cm (4 in) long. Though they frequent cold, coastal waters, orcas can
be found from polar regions to the Equator. Females give birth
every 3-10 years after a 17-month pregnancy.
Killer whales form resident or transient pod populations (family
groups of up to 40 individuals). These different groups hunt different
prey and use different techniques to catch them. Resident pods
tend to prefer fish while transient pods target marine mammals.
Orcas herd schools of fish into tight circles to kill them. Orcas make
a wide variety of sounds and they use echolocation to communicate
and hunt.
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KRILL
Krill (Euphausiacea spp.) is a small shrimp-like crustacean that is
about 6 cm (2.4 in) in length.
Krill feed on phytoplankton
(microscopic, single-celled algae and plants) and they, in turn, are
the main diet of literally hundreds of different animals including fish,
birds and baleen whales. Simply put, without krill, most of the life
forms in the Antarctic would disappear. Antarctic krill can live up to
10 years, an amazing longevity for such a heavily hunted creature.
They spend their days avoiding predators in the cold depths of the
Southern Ocean, some 100 m (330 ft) below the surface. At night,
they drift up the water column toward the surface in search of
phytoplankton.
35
7.2 SOUTH
LIMPET
Limpets are marine molluscs with flattened, cone-shaped shells.
They live throughout the intertidal zone on the rocky coasts of most
oceans. A hard shell protects limpets from drying out and against
predators. At high tide, limpets search for seaweed on rocks. After
feeding, limpets always return to the same spot.
REFERENCES & FURTHER READING
http://animals.nationalgeographic.com/animals/mammals/killer-whale.html - Killer Whale
http://animals.nationalgeographic.com/animals/birds/emperor-penguin.html - Emperor Penguin
http://animals.nationalgeographic.com/animals/mammals/leopard-seal.html - Leopard Seal
http://animals.nationalgeographic.com/animals/invertebrates/krill.html - Krill
http://en.wikipedia.org/wiki/Icefish - Icefish
http://www.odu.edu/sci/cqfe/species%20studied/ocellated-icefish/ocellated-icefish.htm - Icefish
36
7.3 OCEAN LIFE
7.3 OCEAN LIFE
37
7.3 OCEAN LIFE
7.3 OCEAN LIFE
7.3.1 Pinnipeds
There are 5 groups of marine mammals today:
• Pinnipeds (True Seals, Eared Seals, Walruses)
• Cetaceans (Whales and Dolphins)
• Sirenians (Manatees and Dugongs)
• Sea Otters
• Polar Bears
The pinnipeds consist of the:
• True seals
• Eared seals
• Walruses
There are 33 pinniped species as follows:
• 18 True seals – e.g. Harbour seal, grey seal
• 14 Eared seals – e.g. Northern fur seal, California sea lion
• 1 Walrus – e.g. Pacific walrus (Atlantic walrus subspecies)
38
7.3 OCEAN LIFE
DISTRIBUTION
Found in all seas except in India and Southwest Asia
Still tied to land for breeding
Some are pelagic (relating to open ocean waters away from the
coasts and continental shelf areas). Others are found on loose pack
ice, fast ice, rocks, sand, and even upland.
POLLUTION EFFECTS
Entanglements – fishing line, fishing nets, etc. can cause
entanglement and possible injury and death, especially if the animal
is unable to break free and is snared by it.
Oil spills – toxic chemicals initially accumulate in the blubber.
Subsequently, when the animal fasts during breeding, fat reserves
are mobilized, releasing poisons into the blood and depressing the
immune system.
39
7.3 OCEAN LIFE
40
ADAPTATIONS
1. Temperature regulation – water absorbs heat 25 times faster than air
 Fat/blubber/hair – to maintain internal mammalian temperature of 36.5-37.5ºC (97.7-99.5ºF)
 Countercurrent heat exchange – a temperature regulation system consisting of a network of veins and
arteries in the extremities that allows an animal to retain or dissipate heat.
 “Jugging” – a posture sometimes assumed by sea lions and fur seals while resting in the water: one
fore flipper and both hind flippers are held above the surface and resemble a jug handle; used to
conserve heat.
 “Bottling” – a posture sometimes assumed by a seal resting in the water; the face and nose are
extended above the surface while the rest of the body remains vertically submerged.
2. Blood shunting – during dives, blood and oxygen is mainly sent to essential organs (e.g. brain)
3. Senses for navigation, foraging and communicating
 Echolocation (occurs in toothed whales; possibly occurs in baleen whales and pinnipeds)
 Vocalization for mating, auditory cueing (cow/pup)
 Hearing essential for predator/prey location (skull modified for directional hearing)
4. Tactile senses
 Walrus have 600-700 whiskers called vibrissae (singular vibrissa) – these are stiff hairs that project
from the face and serve as sensory receptors
 Ringed Seal vibrissae are 10 times more sensitive than land mammals
5. Sight
 In low light, pupils dilate to allow more light
 Walruses have small eyes because they are benthic (bottom) feeders where visibility is limited. They
use their vibrissae to feel for food such as molluscs on the bottom
7.3 OCEAN LIFE
MOST ABUNDANT PINNIPEDS
Crabeater Seal (Lobodon carcinophagus) – Southern true seal – 11-30 million animals
Ringed Seal (Phoca hispida) – Northern true seal – 6-7 million animals
RARE/ENDANGERED PINNIPEDS
Hawaiian monk seal (Monachus schauinslandi) – ~1000 animals
Mediterranean monk seal (Monachus monachus) – <300 animals
West Indian monk seal (Monachus tropicalis) – Extinct? Last reported in 1952
TYPICAL PINNIPEDS
(a) Phocid (True) Seals
Harbour seal (Phoca vitulina)
600,000+; widespread in N. Hemisphere; eats fish & invertebrates
Grey seal (Halichoerus grypus)
225,000+; N. Hemisphere (Britain & Ireland); eats fish, invertebrates & seabirds
(b) Otariid (Eared) Seals
California sea lion (Zalophus californianus)
160,000; California, Mexico & Galapagos; eats fish & cephalopods
Northern fur seal (Callorhinus ursinus)
1,300,000; N. Pacific Ocean (Japan to California); eats fish & squid
(c) Walruses
Walrus (Odobenus rosmarus) – Pacific & Atlantic Ocean; tusks in both sexes; eats bivalves
41
42
7.3 OCEAN LIFE
CLASSIFICATION OF PINNIPEDS
43
7.3 OCEAN LIFE
CLASSIFICATION OF PINNIPEDS
7.3 OCEAN LIFE
PINNIPED FEATURES
44
7.3 OCEAN LIFE
PINNIPED FEATURES
45
46
7.3 OCEAN LIFE
DIFFERENCES BETWEEN PHOCID, OTARIID & ODOBENID SEALS
Family
Phocidae (True Seals)
Otariidae (Eared Seals)
Odobenidae (Walrus)
Ear Pinna
No external
Yes, external
No external
Fore flipper
Furred, grooming use
Northern: short, broad long
claws
Southern: elongated, shorter
claws
Hairless palm
Elongated claws short, not
useable for grooming
Hairless
Short and square claws
short
Hind flipper
Cannot be turned forward
under body
Can be turned forward under
body and used for movement
on land
Used for grooming
Can be turned forward
under body and used for
movement on land
Used for grooming
Swimming
Hind flippers alternate side to
side, with lateral swinging of
lower body
Fore flippers not used
Fore flippers like oars
Hind flippers not used
Hind flippers alternate side
to side with fore flippers as
stabilizers
47
7.3 OCEAN LIFE
DIFFERENCES BETWEEN PHOCID, OTARIID & ODOBENID SEALS
Family
Phocidae (True Seals)
Otariidae (Eared Seals)
Odobenidae (Walrus)
Marine, Fresh
or Estuarine
Mostly marine but also fresh
and estuarine
Baikal seal, two ringed seals
are freshwater
Some harbour estuarine
Marine but occasionally
ascend freshwater rivers
Marine only
Breeding
System
Variable
Polygyny1
Polygyny1
Size variation
by sex
Variable
Sexual dimorphism2
Sexual dimorphism2
Lactation
periods
4 days – 10 weeks after birth
of pup
Several months to over 2
years after birth of pup
Two or more years after
birth of pup
Gestation
9.5-11.5 months
11-11.75 months
15 months
Delayed
implantation
0-6 months
0-4.3 months
4-5 months
Give Birth
Annually
Usually annually; sometimes
biennially
Biennially and longer in
older females
48
7.3 OCEAN LIFE
DIFFERENCES BETWEEN PHOCID, OTARIID & ODOBENID SEALS
Family
Phocidae (True Seals)
Otariidae (Eared Seals)
Odobenidae (Walrus)
Fasting
Females & males often fast
or feed little during lactation
and breeding
Females feed during
lactation, territorial males
fast during breeding
Females and males feed
during lactation &
breeding but reduced
during migration
Mammae
2 teats, except monk and
bearded seals with 4
4 teats
4 teats
Milk
Rich in fat
Less fatty
Less fatty
Pup growth
rate
Rapid
Slow
Slow
Polygyny (Polygynous)1: A breeding system in which one male mates with more than one female.
Sexual dimorphism2: Males are significantly larger than females. Males may also have distinctive
secondary sexual characteristics such as the male hooded seal’s inflatable nasal sac.
49
7.3 OCEAN LIFE
DIFFERENCES BETWEEN SEA LIONS & FUR SEALS
Family
Otariidae (Eared Seals)
Subfamily
Otariinae (Sea Lions)
Arctocephalinae (Fur Seals)
Overall Size
Larger than fur seals
Smaller than sea lions
Pelage (fur or hair
covering a mammal)
Short, coarse
Thick, luxuriant guard hairs keep
undercoat dry
Muzzle Shape
Rounded (California, Galapagos,
Japanese have sagittal crest in mature
males
Pointed
REFERENCES & FURTHER READING
http://www.imma.org – International Marine Mammal Association Inc.
http://www.marinemammal.net – Marine Mammal Net
http://www.seaworld.org – Sea World Animal Information Database
http://tmmc.org - The Marine Mammal Center
Waller, Geoffrey, Burchett, Michael and Dando, Marc, Sea Life, A Complete Guide to the Marine
Environment, Smithsonian Institution Press, Washington 1996. ISBN: 1-56098-633-6
7.3 OCEAN LIFE
7.3.2 Penguins
DESCRIPTION
Penguins are thickset birds with an upright stance on land. Unlike
most birds, penguins cannot fly but they are fast and agile swimmers
and are perfectly at home in the ocean, with some species spending
as much as 75% of their lives at sea, only coming ashore to molt
and breed. On land, penguins are slower and waddle or hop
awkwardly, although some Antarctic penguins can toboggan more
quickly over the ice on their bellies using their flippers and feet to
propel them along.
An adult penguin’s body has a dark dorsal surface and a light ventral
surface. This counter-shading helps conceal swimming penguins
from predators – a predator looking down in the water column
cannot easily distinguish a penguin’s dark dorsal surface from the
dark ocean depths while a predator looking up also cannot easily
distinguish a penguin’s light ventral surface from the light ocean
surface.
Penguins began to lose the ability to fly about 65 million years ago.
Over the course of 20 million years, their wings became smaller and
more flipper-like, their feathers became sleeker and waterproof, and
their bones and bodies became denser and heavier. By about 45
million years ago, penguins had become well-adapted to life
swimming and diving in the world’s southern oceans.
50
7.3 OCEAN LIFE
SPECIES
17 species – all penguins are found in the southern hemisphere
SIZE
Largest: Emperor penguin– 45 kg (99 lb) wt., 130 cm (51 in) ht.
Smallest: Little penguin– 1 kg (2 lbs) wt., 46 cm (18 in) ht.
FEATHERS & BLUBBER
Penguins rely on feathers and blubber to insulate them from the
cold. Penguin feathers are small and densely packed (~70 per sq.
inch). The downy base of each feather traps an insulating layer of
air against the bird’s skin while the tips of the feathers overlap to
form a waterproof outer coat. Oil from a gland at the base of a
penguin’s tail also helps waterproof the feathers – a penguin
regularly “preens” or spreads this oil over its feathers with its bill. A
layer of blubber (stored fat) also insulates penguins from the cold
and allows them to go without food for long periods of time while
they are molting or incubating their eggs. Typically, the colder the
climate, the thicker the blubber and “fatter” the penguin.
A penguin’s insulation is so effective that a penguin can actually
overheat. To allow excess heat to escape, penguins pant and cool
warm circulating blood through less insulated parts of their bodies,
such as their wings, faces and feet.
51
7.3 OCEAN LIFE
52
BILL
Penguins use their bills to capture prey, such as fish. Like all birds,
penguins don’t have teeth but they have soft, flexible bristles on their
tongues and in their throats, which helps them keep hold of prey and
prevent it from escaping.
LIFESPAN
In the wild, the lifespan of a penguin ranges from 6 years for the little
penguin to 10-11 years for the black-footed penguin to 50 years for
the emperor penguin, with an average lifespan of 15-20 years.
Protected in captivity, penguins can live much longer.
SWIMMING
Penguins are excellent swimmers. A penguin’s body is wedgeshaped and moves easily through water. A penguin’s flaps its
strong, flipper-like wings to propel itself forward while steering with
its wings, feet, and tail. Black-footed penguins can swim up to 24
kph (15 mph) – four times faster than the fastest human swimmer).
DIVING
Most dives to find prey are less than 50 m (164 ft) but some can be
much deeper. Emperor Penguins have been recorded diving to
depths of 400 m (1300 ft) and they can stay under water for as long
as 30 minutes.
Interesting!
Unlike other birds, penguin
bones are solid and heavier than
flying birds. This adaptation
allows them to swim and
submerge to hunt for prey but it
also means that they cannot fly.
7.3 OCEAN LIFE
53
DIET
A variety of fishes, squids, and krill (various small crustaceans)
NESTING BEHAVIOR
Penguins gather in colonies (“rookeries”) of hundreds or thousands
to nest and molt.
A nest is usually just a pile of rocks on bare
ground or a mound of grass and twigs, although some penguins,
such as the black-footed penguin, nest in real burrows or rock
crevices.
Males and mated pairs defend nesting territories that typically
extend from the center of the nest to the far reach of the owner’s bill.
Nest owners deter intruders through a variety of squawks, pecks,
and wing slaps.
Males call and display to advertise their territory and attract mates.
Mated pairs also call and display to one another as they court and
build their nest, and when they trade places on the nest.
Penguins form strong bonds with their mates and often breed with
the same partner for life. Both parents are essential for the chick’s
survival – if either parent is missing, the chick is unlikely to survive.
Interesting!
Penguins do not swim while they
molt because their feathers lose
their waterproof quality and they
would freeze in the cold water.
While they molt, they depend on
their blubber for warmth and
nourishment.
7.3 OCEAN LIFE
BREEDING & REPRODUCTION
Black-footed penguins lay 1-2 eggs at a time. The incubation period
begins mid-November to early December and continues for
approximately 5 weeks. These penguins use a special fold of skin
extending from the stomach to cover the eggs and keep them warm.
Emperor penguins incubate eggs by balancing them on top of their
feet (so that the egg never actually touches the ice) and covering
them with their stomach. Emperor penguins will huddle together for
warmth and incubate their eggs for many weeks weathering
Antarctic temperatures, winds, and storms.
Chicks are born covered in fluffy down. This down is replaced by a
woolly juvenile plumage as the chick gets older. It may be a year or
more before the juvenile plumage falls out to be replaced by black
and white adult feathers.
PARENTAL CARE
Male and female penguins share parental duties. While one parent
tends to the nest and offspring, the other will go off to hunt and feed.
When the feeding parent returns, it takes its turn on the nest and
regurgitates food for its chicks. As the chicks mature, both parents
may need to hunt to meet their growing offspring’s needs. If both
parents are away, chicks may gather in groups (“crèches”) for
54
55
7.3 OCEAN LIFE
PREDATORS
In the ocean, predators include leopard seals, fur seals, sea lions,
sharks and killer whales. On land, predators include foxes, snakes
and introduced predators such as feral dogs, cats, and stoats.
Antarctic and sub-Antarctic penguin eggs and chicks are also
susceptible to predatory birds, such as Antarctic skuas, sheathbills,
and giant petrels. Gulls and ibises also eat approximately 40% of
the black-footed penguin eggs.
Interesting!
All penguins are found in the
southern hemisphere but only
a few of the 17 species of
penguin actually live in
Antarctica (emperor, gentoo,
chinstrap and Adelie). Others
live in the sub-Antarctic, New
Zealand, Southern Africa and
South America. The
Galapagos penguin lives near
the Equator.
56
7.3 OCEAN LIFE
CLASSIFICATION
7.3 OCEAN LIFE
FEATURES
Size and colour of the head, eye, bill and body patterns are important in species identification.
Their range and whether or not they have a crest is also important in species identification.
Stiff-tailed1: Long tail compared to shorter-tailed penguins
Crested2: Flashy yellow or orange crests on the sides of their heads
57
58
7.3 OCEAN LIFE
ANTARCTIC & SUB-ANTARCTIC PENGUINS
Name
Weight
Height
Range
Description
Emperor
45
kg
99
lb
130
cm
51
in
Circumpolar Antarctica
Largest penguin. Pale yellow neck
King
15
kg
33
lb
94
cm
37
in
Sub-Antarctic, not
Antarctica
Second largest penguin. Orange
neck patches
Gentoo
6.4
kg
14
lb
89
cm
35
in
Circumpolar Antarctica,
sub-Antarctic &
Antarctic peninsula
Stiff-tailed1. Distinctive white band
over eyes & crown. Bill, legs and feet
orange-red
Chinstrap
6.4
kg
14
lb
76
cm
30
in
Almost circumpolar
Antarctica & subAntarctic
Stiff-tailed1. Narrow black chinstrap
on white face. Eye red; bill black
Adelie
4.1
kg
9
lb
71
cm
28
in
Circumpolar Antarctica
& sub-Antarctic
Stiff-tailed1. Black head and throat
with conspicuous pale eye. Bill dark
red
Macaroni
5.9
kg
13
lb
74
cm
29
in
Sub-Antarctic islands &
Antarctic peninsula
Crested2. Orange and yellow crest
joined across forehead. Eye red, bill
red. Waddles
Rockhopper
3.6
kg
8
lb
23
in
Sub-Antarctic, not
Antarctica
Crested2. Smallest crested penguin.
Similar to Macaroni but hops rather
than waddles. Yellow crest does not
meet on forehead.
58
cm
59
7.3 OCEAN LIFE
NEW ZEALAND PENGUINS
Name
Weight
Height
Range
Description
Fiordland
2.3
kg
5 lb
56 cm
22”
NZ, Tasmania
Crested2. Broad yellow crest reaches
base of bill. Diagnostic white stripes
across cheeks. Breeds in temperate
rainforests.
Royal
6.8
kg
15 lb
76 cm
30”
Macquarie Island,
NZ
Crested2. Largest crested penguin.
Similar to Macaroni but has a whitish
throat and face.
Snares
1.8
kg
4 lb
61 cm
24”
Snares Island,
south of NZ
Crested2. Like Fiordland but has
prominent pink gape. Black cheeks
and partly raised crest.
12 lb
69 cm
27”
South of NZ
Crested2. Like Snares but with
upswept brush-like crest.
7.7
kg
17 lb
79 cm
31”
South Island, NZ
Pale eye and distinctive yellow band
through eye and across nape.
Breeds in temperate forests.
1 kg
2 lb
46 cm
18”
South Australia
and NZ
Smallest penguin. Distinctive grey
and white plumage. Also known as
the Little blue Penguin or Fairy
Penguin.
Erectcrested
Yelloweyed
Little
5.4
kg
60
7.3 OCEAN LIFE
SPHENISCUS PENGUINS
Name
Humboldt
Magellanic
Black-footed
Galapagos
Weight
Height
Range
Description
5 kg
11 lb
66 cm
26”
Peru & Chile
Single breast band. Large bill
with pink base
4.1 kg
9 lb
71 cm
28”
Falklands,
Argentina & Chile
Two breast bands. Smaller
bill than Humboldt
5 kg
11 lb
71 cm
28”
Southern Africa
Black breast-band
(sometimes two). Eye black,
bill black. Also known as the
African penguin or Jackass
penguin.
2.3 kg
5 lb
53 cm
21”
Galapagos Islands
Two indistinct breast bands
and narrow white line from
eye to throat.
7.3 OCEAN LIFE
RANGE & DISTRIBUTION
61
7.3 OCEAN LIFE
RANGE & DISTRIBUTION
62
7.3 OCEAN LIFE
63
THREATS
• Oil spills
• Pollution
• Rubbish – penguins can ingest plastic and become tangled which causes injury and death
• Over-fishing has contributed to penguin population declines
• Introduced predators (e.g. dogs, pigs, ferrets) which prey on eggs, chicks, and even adults
• Although egg collecting was banned in 1969, illegal egg harvesting continues today
CONSERVATION
Currently, all penguin species are legally protected from hunting and egg collecting. The threat to each
penguin species varies – some species are not in any immediate danger while others are at great risk.
The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) lists the
Humboldt penguin as “endangered” or in danger of extinction, while the black-footed penguin is listed as
“threatened”, or likely to become endangered.
The World Conservation Union (IUCN) lists the erect-crested, yellow-eyed and Galapagos penguins as
“endangered”, the gentoo and Magellanic penguins as “threatened”, and the rockhopper, royal, Snares,
Macaroni, Fiordland, black-footed, and Humboldt penguins as “vulnerable”,.
Under the U.S. Endangered Species Act of 1973 (ESA), the Galapagos penguin is listed as
“endangered" (i.e. the species faces a very high risk of extinction).
7.3 OCEAN LIFE
64
REFERENCES & FURTHER READING
http://www.antarcticconnection.com/antarctic/wildlife/penguins/index.shtml - Antarctic Connection
http://www.seaworld.org/animal-info/info-books/penguin/index.htm - Penguins
Peterson, Roger Tory, Penguins, Houghton Mifflin Company, Boston, MA 1979. ISBN 0-395-27092-8
Waller, Geoffrey, Burchett, Michael and Dando, Marc, Sea Life, A Complete Guide to the Marine
Environment, Smithsonian Institution Press, Washington 1996. ISBN: 1-56098-633-6
7.4 ACTIVITIES
7.4 ACTIVITIES
65
7.4 ACTIVITIES
66
7.4 ACTIVITIES
7.4.1 Adaptations to the Cold
CORE ACTIVITY
(a) Match the animals to their adaptations to the cold by drawing a line between the animal and the
adaptation. (Note that some animals may have more than one adaptation).
7.4 ACTIVITIES
67
ANSWERS
(a) Match the animals to their adaptations to the cold by drawing a line between the animal and the
adaptation. (Note that some animals may have more than one adaptation).
7.4 ACTIVITIES
7.4.2 Pinnipeds
CORE ACTIVITY
(a) Add the following labels to the picture:
TRUE (PHOCID) SEAL
• Eye
• No external ear pinna
• Fore flipper
• Hind flippers for main propulsion. Cannot be turned forward under body on land.
EARED (OTARIID) SEAL
• Eye
• External ear pinna
• Fore flipper
• Hind flippers can be turned forward under body and can also be used for swimming and/or walking
(b) What are some endangered seals? What seals are abundant?
68
7.4 ACTIVITIES
69
7.4 ACTIVITIES
ANSWERS
(a) Add the following labels to the picture:
TRUE (PHOCID) SEAL
• Eye
• No external ear pinna
• Fore flipper
• Hind flippers for main propulsion. Cannot be turned forward under body on land.
EARED (OTARIID) SEAL
• Eye
• External ear pinna
• Fore flipper
• Hind flippers can be turned forward under body and can also be used for swimming and/or walking
(b) What are some endangered seals? What seals are abundant?
Hawaiian monk seal and Mediterranean monk seal are endangered
Crabeater and Ringed seals are quite abundant
70
7.4 ACTIVITIES
71
7.4 ACTIVITIES
7.4.3 Penguins
CORE ACTIVITY
(a) Add the following labels to the
picture of the penguin:
• Eye
• Pointed Bill
• Light Ventral Surface
• Dark Dorsal Surface
• Foot
• Tail
• Flipper-like wing
• Pale yellow neck patch
(b) Can polar bears prey on penguins? If not, why not?
(c) What preys on penguins?
72
7.4 ACTIVITIES
ANSWERS
(a) Add the following labels to the
picture of the penguin:
• Eye
• Pointed Bill
• Light Ventral Surface
• Dark Dorsal Surface
• Foot
• Tail
• Flipper-like wing
• Pale yellow neck patch
73
7.4 ACTIVITIES
74
(b) Can polar bears prey on penguins? If not, why not?
No. Polar bears live in the Arctic while all penguins live south of the Equator. Thus, polar bears and
penguins never meet in the wild.
(c) What preys on penguins?
In the ocean, predators include leopard seals, fur seals, sea lions, sharks and killer whales. On land,
predators include foxes, snakes and introduced predators such as feral dogs, cats, and stoats. Antarctic
and sub-Antarctic penguin eggs and chicks are also susceptible to predatory birds, such as Antarctic
skuas, sheathbills, and giant petrels. Gulls and ibises also eat approximately 40% of the black-footed
penguin eggs.