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**Hook** · Posted: Fri Dec 21, 2007 10:31 am Post subject: [ARTICLE] - Ice World : Part 1

By SharkSense (aka Silvershark) - Listed at The Forum Directory

Ice World

The polar regions are the coldest places on earth. For half of the year, the sun never rises above the horizon, the only light coming from the dancing auroras in the sky. The rest of that time, the sun never sets always lingering low in the sky but never sharing the heat received at lower latitudes. The angle of the earth mean the suns rays that do reach the polar regions are spread out over a wide area, travelling through more atmosphere dispelling them even further. Cooling the poles even further, the ice itself simply reflects the much of the precious sunlight. Yet some creatures are able to cling to survival here in these bitterly cold ice worlds, one of the harshest of environments on earth.

Arctic

To the far north lies the Arctic, a vast area encompassing parts of Canada, Russia, Iceland and the whole of Greenland. A huge sheet of ice covers much of the Arctic Ocean while the tundra dominates the more southerly parts of the region. Winter can see temperatures here drop to less than -60°C, yet life manages to survive.

Roaming this icy world is the largest terrestrial predator alive today - the polar bear. In the spring, mothers emerge from their dens dug into ice and snow where their cubs were born bald, blind and helpless. During these first months of her cubs life, the mother never feeds instead sustaining both herself and her offspring on the fat reserves she built up over the spring. The return of the sun heralds their emergence into their icy world. Having grown fur and opened their eyes within the confines of the den, the cubs take their first steps out into the sunlight. For the mother, there is now an urgency to find food. Six months have passed since she last fed and her reserves are running low. Once her cubs are able to walk confidently on the ice, she sets off in search of a meal. She and her cubs though may not travel unescorted.

Arctic foxes live alongside the bears and often follow them in the hopes of scavenging from their kills. These opportunistic predators thrive in the cold Arctic regions and are the only foxes that have seasonal colour changes. In the winter when snow covers most of the ground, the foxes develop a dense white coat that provides both warmth and camouflage. In spring their white coat is lost, replaced by a grey-brown or blue coat that provides better camouflage when the snow has melted and the tundra bursts into bloom.

With the return of the sun, plants that lay dormant over the dark winter months sprout and grow rapidly. There are no trees out on the tundra for the ground is frozen preventing them from developing the deep roots they need to support themselves, but low-growing plants can survive and 1,700 different species have been recorded growing in the tundra habitat. Among them is the Arctic Willow. These spread out along the ground rather than growing upwards. Summer sees colour burst out across the tundra as plants start to flower such as fireweed and Alpine Azalea. With the blooming of the flowers, insects emerge. The Arctic bumblebee travels from flower to flower sipping nectar and transferring pollen as it does so. With their bodies covered in a dense layer of hairs, these bees can maintain a higher temperature than other insects and that enables them to be active earlier. Dragonflies too emerge along with a few butterflies and moths. As the weather warms, plagues of mosquitoes emerge. For the caribou that migrate vast distances to reach the fresh new growth, these biting insects are a major nuisance. The caribou remain constantly on the move making mini-migrations to get away from the insects. In years with high numbers of mosquitoes, their effects on the caribou can be devastating as the constant movement to escape the insects means they aren't feeding to build up fat reserves for the harsh winter months.

There is more than just the mosquitoes around to bother the caribou though. Arctic wolves also roam the tundra, and they have been searching for the caribou. These pack-hunting predators have been waiting for their arrival, the caribou determining how successful the years breeding season will be for many of these efficient carnivores. remaining in her underground den, the alpha female nurses her cubs while waiting for the pack to return with food. Should they fail to find enough prey, the cubs will starve. But even where prey is readily available, there is still the problem of catching it.

Working as a team, the wolves make the herds of caribou run following closely on their heels, but they don't attack straight away. Working carefully to split some of the caribou from the main herd they look for a sign of weakness among the herd to signal an easy target. The slightest limp can make all the difference as to whether a caribou becomes a target or not. Once selected, the pack work together to single out the target separating it from the other. But even now, the hunt isn't over. In a test of stamina, the predators and their prey engage in a chase that can last for hours before the prey either becomes exhausted and collapses allowing the wolves to move in for the kill, or the wolves give uo the hunt.

Flight isn't always the response that the prey chooses though. Bison are a much larger and more dangerous prey than the caribou, and while these large members of the cattle family will sometimes flee from the wolves they also have an alternative strategy. Circling the vulnerable young, the adults stand their ground charging at any wolf that comes too close. With their powerful bodies, they could easily kill a wolf not fast enough to get out of the way. When the prey fights back, the wolves usually take the safer method and head elsewhere to find an easier target.

Other migrants are also attracted to the tundra in the spring, among them greater snow geese that arrive in Canada to breed. There are fewer predators in the tundra, though Arctic foxes will snatch eggs and chicks if they get the chance, and the geese find safety in numbers. While the geese pair for life and couples reunite year after year, the buff-breasted sand piper has a different method of breeding. These small waders that feed on small insects and other invertebrates create leks - a patch of ground that the male defends to display in with the best males being found towards the centre and subordinates creating leks around him in the hopes of getting lucky. Here they display to the females, flashing the silvery white undersides of their wings in order to draw their attention. The females move from lek to lek, comparing the different males before eventually choosing a mate. The female is then left to brood and care for her chicks alone - the males take no parental responsibility. In fact, by the time their eggs hatch they are already on their way back to their wintering grounds.

The tundra animals need to be wary of the predators that attack not only from the ground, but from the skies. The Gyrfalcon is the largest falcon in the world with a wingspan of over 4 feet. In the Arctic, the falcons start nesting before the temperature has risen below 0°C, their young hatching in time to see the arrival of the feast of migrants. While the falcons nest on cliffs overlooking their realm, snowy owls lay their eggs on the ground in a shallow scrape. They, along with many other tundra predators, are highly dependant upon an abundance of lemmings - small rodents related to voles - for the survival of their young, for these are the main part of their diet. In poor lemming years, many owls don't attempt to breed at all whereas in years where lemmings reach very high densities, the female can lay as many as 14 eggs. Each chick needs around two lemmings a day to ensure it's survival with as many as 1,500 lemmings been taken by a family before the young leave to fend for themselves.

Away from the land is the realm of the Arctic Ocean. This too is a environment rich in life, for the seas bloom with plankton, the base of the marine food web. Here, many of the most charismatic animals swimming the seas gather, among them the smiling beluga whales. When born these small whales that reach a length of around 5 metres are grey, but upon reaching maturity at around seven years old for females, nine for males they have turned a uniform white. Related to the belugas is the strange narwhal, the males easily identified by their long spiralling tusks that were once sold as unicorn horns. The purpose of this tusk, formed from an incisor projecting from the upper jaw, remains a mystery. The current theory is that it is used in establishing dominance and attracting females, however new research has found that their tusks are also covered in a sensory network of nerves that may detect the water conditions through which the whale is swimming. These too thrive in the cold Artic waters feeding on fish, squid and shrimp and alongside them are their much larger relatives, the great whales. The bowhead whale lives in the Arctic all year round, protected from the icy cold waters by a layer of blubber that can be two feet thick. Reaching a length of over 60 feet, these whales depend upon some of the smallest Arctic creatures for their survival - plankton. Once these giant mammals, like most of the other whales, were hunted nearly to the point of extinction. Now though their numbers are recovering though some populations still only number in the hundreds.

Deeper into the Arctic sea lies an opportunistic predator. Appearing slow and sluggish, the Greenland shark can reach length of over 20 feet, but its behaviour is deceptive. For when it locates prey, it can attack with lightning speed capable of disabling seals and even small cetaceans. They do this despite being virtually blind. A tiny copepod called Ommattokoita elongata lives attached to the cornea of most Greenland sharks eyes. But even the sharks need to be wary of the top predators in these oceans - the orca, or killer whales. However, the efficiency of these predators is hampered by their dorsal fins which make moving through the ice covered oceans difficult and so these are mainly summer visitors to the Arctic, heading South with the return of the winter leaving the Arctic to those species that are able to withstand the freezing of the pole and the long days of total darkness.

Author: Silvershark

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