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Published on July 6th, 2011 | by Yellow Magpie2
The Polar Bear: An Indicator Of A Failing World?
The polar bear is the largest land carnivore in the world. Although a supremely powerful animal, what is most striking about this creature is not its size but the fact it has thrived where it is. These animals are amazingly adapted for the harsh land that is the Arctic. Sadly, the polar bear may be on the decline and an early indicator of the deteriorating health of the world’s ecosystem.
The Evolution Of A Top Predator
Scientists still do not know how the polar bear evolved. Their icy environments means that polar bear fossils are almost impossible to find. DNA evidence suggests that roughly 200,000 years ago brown bears, who were found throughout much of the world, were trapped by the encroaching ice sheets in Siberia during one of the Earth’s many ice ages.
Surrounded by ice, the brown bears were forced to adapt and so became the polar bears that we recognise today. The colour of their fur changed to help them to avoid being seen by seals and their ears grew smaller to help with the much colder climate of the arctic.
The Start Of A Worrying Trend?
Scientists have begun to notice that some polar bears are displaying unusual characteristics – deformities. They set about trying to find the root cause as to why these abnormalities were appearing.
It is thought one of the main reasons for this is human-caused pollutants which accumulate as they move up the food chain. Although we may believe that these pollutants are not affecting us the truth is far different.
Phytoplankton, a mico-organism, produce nearly half of the world’s oxygen through photosynthesis – the other half comes from plants and trees. However, they are even more important to our climate as they absorb vast quantities of carbon dioxide which is responsible for our current global warming. Check out Yellow Magpie’s The Melting Ice: The Harsh Reality Of Global Warming for further insight. Without phytoplankton it is arguable that the Earth would not be able to support life as we know it. These organisms are being affected by human pollution.
What has this to do with the polar bear? Ultimately, because these bears are top predators anything that happens in the lower food chains has even more dramatic consequences for them as the effects are magnified the higher up in the chain you go. Polar bears are the apex predators in the Arctic region.
The White Coat That Isn’t White
Polar bears are so well insulated that the lose very little heat. This is the key to their survival in one of the coldest places on Earth. This ability to tolerate extremely cold condition of less than minus 60 degrees Celsius (minus 80 degrees Fahrenheit) is underlined by the realisation that these animals do not hibernate in winter. Perhaps the most remarkable attribute of their tolerance of cold is that they can regularly swim in water that is just above freezing point.
A larger body mass also helps to conserve as much heat as possible. Composed of two layers a soft-underlayer which keeps the bear well-insulated and a longer outer layer of guard hairs which keep water and snow from reaching the inner layer. Underneath the layers of fur is black skin which helps to absorb the sun.
The individual hairs are actually hollow but more startlingly they are clear not white. The appear from from the surrounding snow and sky. This colourlessness is also critical for warmth because white surfaces reflect heat. The clear fur thus passes on heat to the black skin which absorbs the heat of the sun’s light. The skin the radiates heat, warming up the trapped layers of air between the fur and this is what keeps the polar bear warm.
An Animal Of Adaptation
The skulls of polar bears are very different from other bears. Unlike other bears, the polar bears head is long and thin, allowing them to stick their heads into narrow holes in pursuit of seals.
Polar bears store a lot of fat which helps them to survive in lean times. Large polar bears can eat as much as 50 kilograms (120 lbs in one meal) of animal fat. An extensive network of blood vessels along the digestive tract absorb virtually all of the fat they obtain from seals. Because the fat is such a high source of food, polar bears will often leave their preys muscle untouched.
Eating such huge quantities of fat should pose significant problems for polar bears. To prevent heart disease and high cholesterol. Polar bears produce a potent amount of bile which allow them to digest fat safely.
An Early Warning System For A Planet In Distress
Pollution is having a devastating effect on polar bears and damaging virtually all of their biological systems. Male polar bears that have been examined show deformities in their testis and penile bones as well as lesions as shown by Channel 4’s Inside Nature’s Giants. Some polar bears are displaying all the hallmarks of being hermaphrodites or intersex. All of these changes are gravely threatening their chances of reproduction and survival.
Scientists maintain that PCBs (polychlorinated biphenyl), which are found in many plastics, are one of the biggest contributors to the plight of both the polar bears and the planet. PCBs act in much the same way as dioxins do. Dioxins mutate the cells and cause abnormalities in the reproductive system. PCBs also cause problems for the immune system and, like dioxins, accumulate in fatty tissue.
Since the 1930’s companies have known that about PCBs’ toxicity. Since 2000 virtually all types of production of PCB has been outlawed. Although its effects could still be causing damage.
PCBs are just one type of persistent organic pollutants (POP) – the role of these group of chemical agents has yet to be understood and the substances themselves are still awaiting classification. It is POPs that most have scientific researchers worried.
Polar bears are an indicator of the deteriorating state of the world’s ecosystem mainly due to the fact they eat such large amounts of fat. These animals, as top predators, may be the first of many to suffer from POPs unless we get our manufacturing processes as safe as possible.
- Polar bears can be as long as three metres (ten feet).
- They can weigh as much as 800 kilogrammes (1,700 lbs). Adult females are usually at least half the size as adult males.
- Polar bears can live to be as old as 25 years. The oldest recorded bear was 43-year-old female.
- They are found only in the Arctic region.