To fight against low temperatures and stand up to the extremely harsh weather conditions of the Far North, animals have to provide themselves with very specific protective measures. Which explains why only a few species spend the entire year in the coldest regions of the planet.
Out of the 3,200 species of mammal catalogued in the world, there are about forty or so in the Arctic, seventeen of which manage to live in the area covered permanently with ice: thirteen land mammals, three pinnipeds and one cetacean.
There are even fewer birds that live permanently at these latitudes. Fewer than ten species manage to do so all year round, four of which live in the harshest part of all. All other Arctic animals are migratory.

Land mammals
In winter, the Arctic is covered in snow at all times. So it is hardly surprising to discover that in these conditions, only twenty or so land mammals are able to stay loyal to the Far North all year round. These are the polar bears, grizzlies (or brown bears), musk oxen, caribou (or reindeer), moose, wolves, Arctic fox, Arctic hare, ermine, Arctic ground squirrels and lemmings.

In comparison with their close relatives in warmer climes, they are larger on account of the fact that they have to generate more heat. Another feature is that their fur is made up of two thicknesses, which ensure excellent insulation, very dense down on the inside and a coat of long, rigid hair ("overhair") on the outside, creating a highly effective protective layer.

To survive, they not only have to keep warm, they also have to feed themselves. And each animal has its own strategy for doing just that. Some, like hares, voles or lemmings dig through the snow to reach the buried vegetation. Others, like bears or ground squirrels, make the most of the summer to build up stores of fat that will enable them to hibernate on a full stomach. Ground squirrels, like wolves, foxes or ermine, keep food hidden for the times when the cold is at its most ferocious.

On top of these main strategies come highly specific tactics. In the tundra, hares chew the frozen shrubs for a long time to soften them; ptarmigan find their food on the branches of the few dwarf willows, while the musk oxen root for moss, lichen and dried grass.
Out on the ice, the polar bear waits patiently next to air holes made by the seals until they return to the surface. The carcases of unfortunate pinnipeds are picked clean by foxes, which also feed on the remains of large mammals abandoned by wolves, and which also use their highly developed senses of hearing and smell to locate small animals underneath the blanket of white for their day-to-day diet. There is certainly plenty going on under the layer of snow, which acts as a heat insulator, keeping the temperature in the burrows and galleries 7 or 8ºC higher than outside. So it is with the threat of ermine and weasels hanging over them that the few small mammals that live in the tundra all year round have to exist: voles, lemmings and shrews. The latter - which eat insects - are able to find a wide choice of larvae, earthworms and insects.

Sea mammals
The hub of the food chain in Arctic waters, plankton, need oxygen and nutrient salts to develop. The polar seas are rich in the first element, but are lacking in the second. By contrast, it is something that abounds in the Atlantic and Pacific. Needless to say that where these waters meet the Arctic Ocean, plankton have a field day. This is when there is a real explosion of life at every level. Endless shoals of herring, fish of every kind and surface crustaceans descend with relish on the favourite "snack". In turn, these shoals attract the greed of many predators. These include average-sized fish (sich as cod and mackerel) of birds of all types, of course, as well as two sorts of marine mammal: pinnipeds and cetaceans.

Pinnipeds
Pinnipeds include sea lion, seals and walruses. Sea lion (which are easy to identify from seals by their small external ears that look like backward-facing cones) often prefer temperate and warm regions. The two other families live in the colder regions, one mainly and the other totally.

Taking their name from the fact they are animals "with feet in the form of flippers" (which is what 'pinniped' means), pinnipeds spend a good proportion of their lives in the water. This is the reason why these mammals are considered to be marine. In fact, they are ancient land mammals that have adapted to living in water. This evolution can be seen from a series of modifications, most of which come into play when they dive: their nostrils and ears close automatically, their breathing is "shut off", with lungs almost totally emptied of oxygen, which is stored in their blood... Other related mechanisms even make it possible to stand up to the water pressure when diving deep. Yet they have not lost all contact with the land. They give birth and raise their young on land: beaches, rocky outcrops or floating ice floes.

To protect themselves from the cold, pinnipeds can count on three gifts from Mother Nature : a layer of air trapped in fur with one or two thicknesses, glands whose function is to produce oil that make the fur waterproof a thick layer of fat under the skin which in addition to its role as a store of food for times when they go without food or are feeding their young, also forms a highly effective thermal barrier. When the winter is at its peak, all of these protective devices do not stop the pinnipeds from resorting to their ultimate stratagem, which consists of staying in the relative comfort of the seas, where the temperature never falls below -2°C.

Cetaceans
As warm-blooded animals that breathe using lungs, cetaceans mate, give birth and feed their young like any other mammal. However, over a period of several million years, these ancient land creatures have undergone some radical changes which have made them lose all contact with the land. In most cases, nostrils called 'blowholes' have appeared on the top of their head to enable them to breathe without having to leave the water completely and without having to stop swimming. This simple example of a much more fundamental form of evolution today enables some whales and sperm whales to remain under the water for up to 120 and 90 minutes respectively.
Cetaceans, which have a layer of fat under their skin that serves both as thermal insulation and a reserve store of food, are divided into two sub-orders.

Birds
There are very few birds that remain in the Arctic all year round - only nine of them, in fact. These include gyrfalcons, large crows, snowy owls, ptarmigan and Arctic redpoll.
But in particular we should stress the four winged residents that live in the harshest conditions: grey-headed eiders that stay in close proximity to the icy waters at all times, black guillemots, which never leave the coast of the extreme continental north or the open Arctic seas, as well as the white and pink gulls, which never stray from the part of the icecap closest to the open water, where they catch fish.

These nine exceptions apart, every other species is migratory. In fact, some birds accomplish impressively long journeys, with the out-and-out record held by some Arctic terns, which travel from the Far North to the southern regions of the Antarctic - a round-trip of over 35,000 kilometres...
And there are good reasons for them coming in such great numbers and sometimes from vast distances: plenty of food, fewer predators than in the south, unending daylight. The Arctic summer has plenty to attract birds which, when the weather turns fine, literally flock in their millions to the Far North to find a mate, buils a nest, sit on their eggs and raise their chicks.
Sea birds find everything they need in polar seas that are incredibly rich, teeming in fish, molluscs, crustaceans and zooplankton. Insect-eating birds have a field day with the enormous variety of insects that swarm in the tundra.
Plant-eaters find their fill eating the mass of berries and plant seeds. As for birds of prey, there are plenty of carcases, small mammals, eggs, chicks and birds to feast on.
In terms of the time available, the polar surroundings leave very little room for manoeuvre. Even when all goes well, the birds have very little time to reproduce. And if - by misfortune - the summer is less good than usual, the snow may melt too late or, worse still, will not melt completely at all. In those years, the great cycle of life misses a turn: no mating. And no chicks.
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Arctic Flora

Many people imagine the Arctic to be a region of snow and ice where no plants grow. In point of fact, there is absolutely no truth in this, either in time or space. Some regions of the Arctic abound in plants that have succeeded in adapting to the short growing season, as well as to the severity of the average temperatures of the Far North.
The tundra in fact has two faces. For the majority of the year, the climate is as harsh as the land is barren, and the North winds are unrelenting. But during the (brief) summer season, the snow melts, multicoloured flowers bloom and migratory species swarm in from everywhere.

Permafrost Land above the water level in the Far North is charcaterised by a layer of earth and rock that is frozen at all times: this is called the permafrost (or pergelisol). However, the Arctic only encompasses part of that geographic area of the world where the ground is iron-hard and virtually impermeable, which in some regions extends up to 56º latitude north. In fact, permafrost covers nearly a fifth of the world's land surface, from Alaska to Greenland via the northern halves of Canada and Russia. It varies greatly in thickness from one region to another. In Siberia, it extends down to depths as great as 1,400 metres, while in more southerly areas, it is a metre thick at most. Another difference is that with the effect of the summer warmth, the thaw of the surface layer is just a few centimetres in the north, while is extends down several metres in sub-Arctic regions. Final feature: going from north to south, the configuration of the permafrost changes from continuous to intermittent, then to sporadic.

It is easy to forget that just a metre down, the ground is permanently frozen (see box below). And we virtually lose sight of the fact that the amount of rain and snow that falls on the tundra every year is a little over 200 mm. As this quantity is the equivalent to amounts recorded in deserts, the tundra is often called a "cold desert". But a name is only a name. Because the low temperatures restrict evaporation sufficiently to allow the tundra to retain its reserves of water more easily. Also, the solid barrier of the frozen subsoil prevents the precious liquid from penetrating too deeply.

There are five main groups of vegetation in the tundra :

Marco Nazzari (The Far North, Gründ, 1998, p. 86) suggests cataloguing the different species of plants based on the type of ground in which they grow.