Information

Mammals: White or polar bear

Mammals: White or polar bear

Systematic classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
Kind: Ursus
Species: U. maritimus - Phipps 1774

White or polar bear (Ursus maritimus) that until the 80s of the twentieth century, was inserted by taxonomist biologists in the genus Thalarctos, with the species Thalarctos maritimus, is a quadruped, eutherian, placental mammal, specifically the largest terrestrial carnivore on Planet Earth (together with other back species), afferent to the superclass of Gantostomes (Gnathostoma), class Mammals (Mammalia), subclass Placentates (Placentalia), order Carnivores (Carnivora), suborder Fissipedi (Fissipedia), family Ursidi (Ursidae), subfamily Ursini (Ursinae), genus Orso (Ursus).
Bears, large plantigrade carnivores (so called, because they rest during walking on the whole sole of the foot, contrary to digitigrade animals, such as felines, which rest on the fingertips), are widespread mainly in the cold and temperate regions of the Northern Hemisphere or North; they constitute one of the most homogeneous and best characterized families of the order to which they belong.
Biologists currently describe seven genera to which a number of species on which there is no unanimous agreement are traced, also in the context of the International Commission for Zoological Nomenclature (ICZN).
The general anatomical characteristics of the Ursids, which form general tendencies, agree that all species are easily recognizable by their always very remarkable size, which are accompanied by squat and somewhat massive forms.
The back is always humped at the shoulders, the neck is short and wide, and the head which is very massive, ends with a muzzle with a straight profile and a progressively truncated cone shape.
The eyes are rather small and equally the rounded ears are.
The legs are robust and powerful and end with a very wide sole of the feet, used for walking, hence the definition of "plantigrade"; the feet are armed with strong non-retractable claws.
The tail is always reduced to a short stump, the fur is always very thick and abundant, even if some species have more satin hair.
In comparison with other carnivores, bears have a teeth more adapted to shredding plant foods, although this matter as we will see is not so present in the polar bear diet, so the posterior molar is very developed in almost all species, while in the other families of the order as in the Felidae (Felidae) and in the Canidae (Canidae) it is reduced, or completely absent.
Most of the species of bears have twelve incisors (six upper and six lower), these are ascribed in the Ursida family (Ursidae) and in the Ursini subfamily (Ursinae), while for the Sloth bear (Melursus ursinus), which has only four incisors in the upper jaw, biologists have created the subfamily of Melursini (Melursinae).
Historically and ethnozoologically, the relationship between the various species of bear, especially the largest and most ferocious and Man (Homo sapiens), has always had a conflicting nature.
Since prehistoric times, for example with the Bear of the caves (Ursus spelaeus, lived in Eurasia in the Pleistocene), now extinct, especially with gigantic proportions, the primitive man was in struggle.
Obviously given the size and ferocity, the human being was his prey, at least until he was able to build offensive tools, which allowed him through forms of organized hunting in a group, not to always be on the side of those who succumbed.
Over the centuries, in the most urbanized areas, lorso often devastated the herds and flocks of breeders, so humans hunted it for this purpose, as well as to taste its meat and use its fat and fur; in fact the meat of all the back species is edible, therefore human being feeds on it.
Not only tribal populations such as the Eskimos who hunt polar bears, but also the so-called "civilian", to sell their meat in the form of gigantic steaks in restaurants, as is still the case today in many cities in different Canadian and Siberian provinces, to the point that there are also bear farms, where some less aggressive species are bred for this purpose.
In addition, due to the destruction over time by the human being, the ecosystems and biotopes in which the various back species live, as due to increasing pollution, these animals are increasingly threatened in various geographical areas.
In the case of the Polar Bear (Ursus maritimus), the melting of Arctic polar ice adds to the other phenomena of environmental degradation mentioned above, the International Union for Control of Nature (IUCN), has established today a status of "vulnerable".
The hunt to which they were subjected, especially for sporting purposes by shooting them from a helicopter in flight, allowed until the mid-80s of the last century, made a substantial contribution to their decrease.
Today this stupid hunting activity is fortunately prohibited by world decree and polar bear, it is now a strictly protected species, especially by the Russians; only a few items of clothing are allowed per year, only to the Eskimo tribes, who feed on meat and use its fat and fur for their survival.
Numerous are their dens for the winter, near the human settlement on the island of Wrangel, an island of the Arctic Ocean, between the Chukci Sea and the East Siberian Sea.
Environmental pollution, mainly in the past (until all the 80s of the last century), of fuels from the combustion of which in cars were produced exhausts containing lead, or even today for the use in agriculture of some insecticides such as DDT which is chemically stable and which become irreversibly fixed, entering the food chain, into living organisms, have shown and show all their harmful effects even in the isolated lands of the Arctic Circle and the North Pole; in fact traces of their atmospheric presence have been measured, in the ice and in the fat of polar bears, where urban traffic and agriculture are obviously absent.

White or polar bear - Ursus maritimus (photo www.hicker-stock-photography.com)

White bear cubs

Zoogeography

Polar bear (Ursus maritimus), populates the Arctic coasts of the Northern Hemisphere, going only slightly and only in some regions, south of the Arctic Circle.
It is widespread along all the coasts of Greenland, New Zemlia (or Novaja Zemlja, a Russian archipelago consisting of two major islands separated by the Strait of Matockin), Spitzbergen (a Norwegian island, the largest of the Svalbard archipelago) and the large Canadian Arctic islands (Baffin, Victoria, Ellesmere, Banks etc.); on the mainland, they are then present on the northern coasts of Siberia, Canada and Alaska.
In Europe, it meets in northern Norway, in the Canin Peninsula in Russia and in part of Iceland; occasionally then, it can go hungry even further south.
Outside the Arctic Sea, these large bears can be found in the Kuril Islands (an archipelago of 60 islands located between the northeastern part of the Japanese island of Hokkaido and the Russian peninsula of Kamciatka), in Sachalin (a Russian island in the northern Pacific offshore of the east coast of Russia), in Kamciatka (or Kamchatka, a peninsula off the extreme eastern reaches of Russian territory, just above the archipelago of the islands of Japan), in Newfoundland and in Nova Scotia (respectively an island and a federal province Canadian).

Ecology-Habitat

In reality, polar bear, rather than a inhabitant of the coasts of the islands, can be considered an animal that spends part of its time in the sea and part on the edges of the Pack (a layer of sea ice, produced by the crumbling of the pack ice).
He is an excellent swimmer, fast and agile in diving; it is also able to run with considerable speed on ice and snow.
It is an exclusively carnivorous species, although when its prey is scarce it also feeds on berries, lichens and other rare plant forms of those areas such as the Polar Poppy and the Silene acaule and of the plants of the Arctic Tundra (today unfortunately, especially in winter, finding less and less food often goes south, for example in Alaska and you see it looking for something to eat among the garbage of small urban centers), while most bears are omnivorous (feeding on both vertebrate meat such as fish, mammals, both insects, berries,
mushrooms and honey); specifically lUrsus maritimus it feeds on seals and offspring of walruses, cetaceans (such as those of beluga and narwhal) and fish.
Polar bear, is the last link in a food chain that begins with plankton and reaches the bear, through fish and seals.
The concentration of vitamin A increases along the food chain and vertebrates accumulate excess in the liver.
The concentration in the polar bear's liver is so high that it is toxic to both humans and many other animals.
Polar biologist K. Rodahl found 26,700 International Units (IU) of vitamin A per gram of liver from a polar bear killed in Greenland; some rats died having eaten 0.5-0.7 g of this liver per day for about a week.
Of a proud character, he does not hesitate to attack the human being and to kill him, even if he is not disturbed by his face.
But thanks to its particular distribution area, this urside has never been the cause of human massacres or pets, living in almost uninhabited areas.
Basically, outside the human being, it has no predators, so it can be defined as an Apex-predator.

Morphophysiology

This species differs most from all the others, for its way of life and for its morphological characteristics.
Indeed lUrsus maritimus together with the Kodiak or Alaskan Bear (Ursus middlendorffi), is the species that reaches the largest size of the family.
The males have a total length of almost three meters, for a weight not far below the ton, the females do not exceed 2.10 m in length for about 300-400 kg in weight, obviously before giving birth and breastfeeding.
Polar bear, compared to the Brown Bear (Ursus arctos), has a more slender shape, with proportionally smaller head and more elongated muzzle.
The legs are exceptionally robust, with a very wide sole and toes joined together, up to half of their length, by means of a skin membrane suitable for promoting swimming in the sea.
The fur is very thick and long, to adapt to the environment, uniformly white in color that tends to yellowish over time and in very old specimens it becomes decidedly yellow.
It has a very developed adipose panniculus, lives on average 25-30 years in nature and
even reaches 40 in captivity.

Ethology-reproductive biology

Males are sexually mature from the fourth year onwards, females already in the third year of life can procreate.
The period of mating for polar bear is towards the end of winter and the beginning of spring. The period in which females are available for mating are infrequent since a female does not mate until she has the young to look after, this means every three years. Lestro lasts a few days and during this period the male and female form a couple.
The pregnancy period varies between 195-265 days, in this period the future mother builds a den in the snow and eats to double her weight.
The den is never too far from the coast to facilitate the search for food.
The female white back generally gives birth to two babies by pregnancy; these are born
in the winter following mating and inside the den where near the
Relief the mother closes herself, no longer eating.
As soon as they are born, they are blind and naked weighing about 1-2 kg, the particular structure of this igloo and the heavy size of the mother, are sufficient to provide him with all the warmth they need.
The milk that the mother supplies him for several weeks is very rich in fats and proteins, so much so that with the arrival of the following spring, when they come out of the den, they reached a weight of about 20-25 kg; the babies will then come into contact with the outside world at about 3-4 months of postnatal life, the mother will bring them with her, while she has lost a lot of weight for breastfeeding and is no longer nourished, she goes looking for food on the pack to regain the physiological weight .
The detachment from the mother occurs only in the third year of life, rather late in the world of mammals, throughout this period the mother teaches the young hunting techniques,
the dangers of the Pack, knowing how to juggle and swim in the open sea, knowing how to find a suitable den.


Video: Male Polar Bear Fight Club - Ep. 2. Wildlife: The Big Freeze (January 2022).