Antarctic Animal Adaptations
Antarctica is a very harsh and extreme environment though is very rich in wildlife due to the very high productivity of the Antarctic Ocean during the summer months. Long days provide abundant light and copious nutrients brought to the surface layers by ocean upwellings along the Antarctic Convergence fertilize the growth of phytoplankton. Animals need to have a whole range of specializations to be able to take advantage of these conditions.
- Anatomical - Structures of the body.
- Behavioural - The manner in which animals move and act.
- Physiological - The internal functions of the
animal from biochemical, to cellular, tissue,
organ and whole organism levels.
Aptenodytes forsteriaa - more
How are Emperor penguins adapted to survive in Antarctica?
Largest of all penguins by a considerable margin. Animals of the very deep south and the only large animal that remains in Antarctica in the depths of the long dark winter night.
Anatomical AdaptationsLarge size retains heat - Emperors are twice the size of the next biggest penguin, the king, so are able to survive the winter fast and the extreme cold temperatures endured at this time
Short stiff tail helps balance on land, forms a tripod with heels on ice to give the least contact area to prevent heat loss
Chicks have soft down for insulation, this is a more effective insulator on land than the parents feathers, but of little use in the sea, they must moult before they can swim
Highly specialized bird skeleton a highly upright gait, short neck, short legs and long body
Powerful claws on the feet help to gain a grip on snow, ice or rock when emerging from the ocean or when tobogganing
Behavioural AdaptationsHuddle together in the winter to conserve heat, without this they wouldn't be able to survive the Antarctic winter
Unlike other penguin species, they are not aggressively territorial, hence the huddling (above)
Breed during the depths of the Antarctic winter, so the chicks are large enough to become independent during the summer abundance of food
No nest is made, eggs then chicks sit on the parents feet and covered by a fold of skin to keep them warm
When the female lays her egg, it is passed over to the male, the female then goes to sea and will not return for an average of 115 days
Physiological AdaptationsA complex heat exchange system allows 80% of heat in the breath to be recaptured in the nasal passages
They can dive to a depth of 1,800 feet (550 meters) and hold their breath for up to 22 minutes, so are able to reach and exploit food resources that other birds can't reach
The normal resting heart-beat is about 60-70 beats per minute (bpm), this goes up to 180-200 bpm before a dive as they load up with oxygen, as they hit the water, the rate drops to 100 bpm immediately slowing to 20 bpm for most of the dive
Males can make "milk" in the oesophagus which can be used to feed chicks in the winter before the female arrives back from fishing
Males can fast for up to 100 days
Pygoscelis adeliae - more
How are Adelie penguins adapted to survive in Antarctica?
One of the "classic" penguin species, the second most southerly after the Emperor. Breed in the far south, but leave it to head north with the onset of winter.
Anatomical AdaptationsCompact shape, low surface area to volume ratio to reduce heat loss
Very dense specialized feathers for insulation on land, fat layer under the skin for insulation in the sea
Short wings reduced to flippers for swimming underwater
Backward pointing barbs on tongue to stop slippery prey escaping
Black above and white underneath makes it harder to see in the sea, and helps warming / cooling on land, back or front to the sun according to whether they are hot or cold
Behavioural AdaptationsMigrate north at the end of the brief summer
Arrive in the south early in the summer season, to take best advantage of the seasonal abundance of food
Tobogganing sliding on their front while pushing with legs, saves a lot of energy in long journeys
Build a crude nest of stones to lift the eggs above ground level to prevent chilling from melting snow in summer
Gather at the ice edge in large groups before jumping in the sea in case of predators, increases individual survival chances
Physiological AdaptationsMuscle has large amounts of myoglobin to hold extra oxygen that is used up during a dive
A counter-current system in the legs means that the feet are kept just above freezing and operated by muscles in the legs via tendons, this reduces heat loss
During a deep dive, the heart rate slows from 80-100 down to 20 beats per minute
Able to cope with a high saline diet due to salt glands and kidneys that produce concentrated urine (like many seabirds, penguins can drink sea water and gain water)
Leptonychotes wedelli - more
How are Weddell seals adapted to survive in Antarctica?
The most southerly dwelling of all mammals. Live at the edge of pack ice wherever there is a breathing hole or tide crack.
Anatomical AdaptationsFore and hind limbs developed into flippers for swimming
Smooth, streamlined shape to pass easily through the water
A substantial blubber layer lies under the skin acting as insulation, so allowing the seals to swim indefinitely in frigid Antarctic waters down to -2C
Large eyes to help hunting prey under water and frequently under ice where light levels are very low
Whiskers (vibrissae) that help the seals feel their way in the dark when catching prey
Behavioural AdaptationsSeals keep open breathing holes in the ice by rasping back and forth with their teeth, so allowing them to live further south than any other mammal
They can swim large distances between breathing holes and cracks, finding the next hole using a form of sonar with high pitched sounds
They avoid the "bends" when diving by exhaling first and allowing the lungs and air passages to collapse
Males compete for underwater territories based around a breathing hole which gives access to females using the same breathing hole
They flush fish out that are hiding in broken up ice by blowing bubbles into it
Physiological AdaptationsWeddell seals can dive for over an hour, though 20 minute dives are more common. They can dive to 600m
The "cost" of diving in terms of extra oxygen consumption is about 1.5 x the sleeping rate - this is much lower than other diving seals and birds
The blood has high haemoglobin concentrations and can carry 1.6 times more oxygen than human blood
Weddell seal milk is one of the richest produced by any mammal, containing about 60% fat
The females mate shortly after giving birth, the embryo goes into a kind of hibernation for a few months so it is not born before the full year is up and it is the correct season
Euphausia superba - more
How are Antarctic krill adapted to survive in Antarctica?
A Crustacean member of the zooplankton, krill is a super-abundant organism about 4-5cm long that feeds on phytoplankton. Being unusually large for zooplankton they are eaten by just about anything and everything that comes across them
Anatomical AdaptationsVery fine filtering net or "basket" formed by 6-8 pairs of limbs that can capture phytoplankton down to 1µm (1 micrometer, a millionth of a meter), the smallest that there are, no other zooplankton of this size can do this
Small bioluminescent organs are found on several places on a krill's body, they have a reflector at the back, a lens at the front and can be directed using muscles, the function is not fully known, it may be connected with schooling or mating. For this reason krill are sometimes called "light shrimp"
Complex and highly developed compound eyes, one of the best visual structures in nature, though why this should be so in krill is a mystery
Behavioural AdaptationsSwarming behaviour similar to schools of small fish as a defence against predators, such swarms can have up to 10,000 to 30,000 individuals per cubic meter of sea water
In the winter and spring they are found beneath sea ice where they feed on algae growing on the under side of the ice which they rake off in a methodical manner like a lawn mower
Rapid backwards escape reaction in common with many other crustaceans with a pronounced flattened tail or telson, they can flip it backwards several times in succession to escape from danger - this is called "lobstering", you can probably guess why.
Usually krill stay in deep water during daylight hours and come to the surface at night, this helps them to avoid predators
Physiological AdaptationsCan withstand long periods of starvation (up to 200 days) by using their muscle as a reserve, the krill shrink in the process, this happens over the winter months when the krill are under seasonal sea ice and there is little or no photosynthesis
Despite very cold water temperatures, krill are highly active, backwards lobstering takes only 55 milliseconds (0.055s) from stimulus (optical) to triggering of the escape response
Female Antarctic krill can lay up to 10,000 eggs at a time, they can do this several times in a season
Balaenoptera musculus - more
Sulphur Bottom Whale
How are Blue whales adapted to survive in Antarctica?
The largest animal ever to have lived, larger than any dinosaur its huge bulk being supported by the sea. Not exclusively an Antarctic animal, the Antarctic subspecies B. m. intermedia is the largest of three subspecies. They can eat up to 4 tonnes of food a day in the Antarctic summer, they feed for about 8 months and then fast for 4 months living off their fat reserves.
Anatomical AdaptationsBaleen plates in the mouth instead of teeth. These are made of keratin, the same tough protein that makes hair and nails. They hang down from the upper jaw forming the two uprights of a triangle with the lower jaw being the flat third side. The bristly edges are filters to collect the krill in the water they gulp in before swallowing them when the excess water has been ejected.
55 - 68 ventral grooves that extend from the lower jaw to the navel. These allow a huge mouthful of water and food to be taken, expanding to about 6 times larger than normal size, the water is pushed out by the enormous tongue and food filtered out by the baleen plates.
A ridge in front of the blowholes (the two nostrils) which are located on top of the head. Pointing backwards means that they are not filled with water when swimming and being placed on top of the head makes it easy to breathe while lifting and exposing the smallest amount of the body possible.
Huge tail fin the size of two dinner tables that provide the propulsion for swimming. The smaller forward fins are for changing direction and the small dorsal (mid-back) fin helps with stabilizing straight swimming.
Behavioural AdaptationsBlue whales migrate to polar regions during the summer months of that region. There are distinct southern and northern populations which go to their respective pole, none go to both poles. They feed continuously during the super-productive summer months and then live entirely on their blubber reserves for about 4 months during the breeding season in warmer waters. Not all individuals migrate however.
Blue whales use sound to communicate with each other and also possibly as a means of finding krill swarms. They have been described as making the loudest noise made by any animal at 180 dB or more. These sounds can travel underwater for as far as 500 miles (800 km). They are very low frequency sounds down to 14hz, below the hearing limit of humans.
Usually found alone or in small groups of 2-4 individuals though occasionally and rarely in larger groups of up to 60 have been reported.
Physiological AdaptationsAdult blue whales have a daily energy requirement in the region of 6.3 million Kilojoules (1.5 million kilocalories). This is supplied by up to 3.6 tonnes or 40 million individual krill eaten per day which all have to be processed by the digestive system.
Like many other air breathing diving animals such as other whales, seals, and penguins, blue whales have muscles rich in myoglobin. This is an iron containing protein similar to haemoglobin that carries oxygen in the blood, but provides an extra in-situ store for longer dives exactly where it is needed.
Metabolism is able to cope with extended periods of plenty where extensive feeding allows the build up of many tonnes of blubber (stored fat) which is then used up during extended periods of starvation.