Ursus arctos
Ursus arctos
The brown bear (Ursus arctos Linnaeus, 1758) is a large mammal belonging to the Ursidae family.
Systematics –
From the systematic point of view it belongs to the Eukaryota Domain, Animalia Kingdom, Subarign Eumetazoa, Superphylum Deuterostomia, Phylum Chordata, Subphylum Vertebrata, Infraphylum Gnathostomata, Superclasse Tetrapoda, Class Mammalia, Subclass Theria, Infraclasse Eutasheria, Family Order Ursidae and then to the genus Ursus and to the U. arctos species.
Based on recent DNA analyzes, the following subspecies are recognized:
– Ursus arctos arctos; Eurasian brown bear;
– Ursus arctos beringianus; Kamchatka brown bear; Kamčatka Peninsula and Paramušir Island;
– Ursus arctos collaris; Siberian brown bear, present in Siberia (with the exception of the areas inhabited by the brown bears of Kamchatka and Amur) and also in northern Mongolia, in the northern extremity of Xinjiang and in the eastern one of Kazakhstan;
– Ursus arctos crowtheri; Atlas bear (extinct);
– Ursus arctos formicarius; carpathian bear;
– Ursus arctos gobiensis; Gobi bear; Mongolia;
– Ursus arctos horribilis; grizzly bear; Canada and the United States;
– Ursus arctos isabellinus; Himalayan brown bear, present in Nepal, Pakistan and northern India;
– Ursus arctos lasiotus – Amur brown bear (or “Ussuri brown bear”, “black grizzly” or “horse bear”), present in Russia: Southern Kuril Islands, Sakhalin, Coastal Territory and Ussuri River Region / Amur south of the Stanovoj range. China: Northeastern Heilongjiang. Japan: Hokkaidō, in Japan there is also another species: Ursus thibetanus;
– Ursus arctos marsicanus; Marsican brown bear, present in central Italy;
– Ursus arctos meridionalis; Northern Caucasus;
– Ursus arctos middendorffi; kodiak bear (or ‘Alaskan coastal brown bear’); islands of Kodiak, Afognak, Shuyak, Admiralty, Chicagof and Baranof (Alaska), plus other islands in southeastern Alaska and along the mainland coast of southeast Alaska;
– Ursus arctos nelsoni; Mexican grizzly bear (extinct);
– Ursus arctos eachevi; lives east of the Kolyma River;
– Ursus arctos piscator; Bergman’s bear (extinct);
– Ursus arctos pruinosus; Tibetan blue bear; Western China;
– Ursus arctos syriacus; Syrian brown bear; Middle East;
– Ursus arctos yesoensis – Hokkaidō brown bear; Japan.
Geographic Distribution and Habitat –
The brown bear is now widespread in an area that includes: Austria and the Pyrenees, the Italian Alps (Trentino), Abruzzo (Marsicano brown bear – Ursus arctos marsicanus), Yugoslavia, Albania, Greece, Hungary, Scandinavia, Poland, northern Russia, the Caucasus , Turkey, mountains of central Asia and northern India.
At one time brown bears populated Asia, in the Atlas Mountains, in the African Maghreb, in Europe and in North America; unfortunately in some areas today they are extinct and in other areas their populations have significantly decreased. There are an estimated 200,000 brown bears in the world today. The largest populations are found in Russia, with 120,000 specimens, in the United States with 32,500 and in Canada with 21,750. There are fragmented populations in the European Union.
In the North American area, brown bears live mainly in Alaska, but their range also extends eastward, through the Yukon and the Northwest Territories, and southward, through British Columbia and the western half of Alberta. Isolated populations are found in northwestern Washington, northern Idaho, western Montana, and northwestern Wyoming. 95% of the brown bear population of the United States lives in Alaska, although it is slowly but steadily repopulating the western states along the Rocky Mountains and plains as well.
As for the European area, there are 25,000 brown bears divided into ten fragmented populations, from Spain in the west, to Russia in the east, and from Scandinavia in the north to Romania and Bulgaria in the south. They are extinct in the British Isles, extremely threatened in France and Spain, and endangered in most of central Europe. The brown bear is the national animal of Finland. The Carpathian brown bear population, the largest in the European Union, is estimated to comprise between 4,500 and 5,000 bears.
The population of brown bears in the Pyrenees mountain range, between France and Spain, is so low, between fourteen and eighteen, almost all males, that in the spring of 2006 bears, mostly females, from Slovenia were released to relieve the imbalance between the sexes and preserve the presence of the species in the area, despite protests from French breeders.
As far as the natural habitat of the Brown Bear is concerned, this is represented by the wooded and rocky mountains, little frequented by man; it also prefers areas where there are abundant streams.
In general, brown bears prefer semi-open places and usually live in mountainous areas.
In the arctic regions, the potential habitat of the brown bear is increasing. The warming of those areas has allowed the species to go further north, in what were once the exclusive domain of the polar bear. In non-arctic areas, habitat destruction is seen as the main threat, followed by hunting.
North American brown bears seem to prefer open places, while in Eurasia they mostly live in dense forests. The Eurasian bears that colonized America are believed to have been tundra-adapted animals, such as the brown bears of the Chukchi Peninsula on the Asian coast of the Bering Strait, which are the only Asian brown bears that live year-round in the lowland tundras like their American cousins.
Description –
The Brown Bear is an animal of considerable size and weight.
It weighs between 100 and 700 kg and its largest members compete with the polar bear for the title of the largest terrestrial carnivore in the world.
It has a head-body length between 1.7 and 2.8 m and a height at the withers between 90 and 150 cm.
The tail is 10-12 cm long and the males are 38-50% larger than the females.
Brown bears also have a large hump of muscle on their shoulders which distinguishes them from other species.
The forelimbs end with legs equipped with claws up to 15 cm long which are mainly used for digging. The brown bear’s claws are not retractable and have relatively blunt tips. The head is broad and rounded with a concave facial profile, which is used to distinguish it from other bears.
Like all bears, brown bears are plantigrades and can stand upright on their hind legs for quite long periods of time.
The smallest subspecies is the Syrian brown bear, whose mature females weigh less than 150 kg. The largest subspecies of brown bear are the kodiak bear and coastal Russian bears and the Alaskan grizzly bear. The largest wild kodiak bear whose weight was recorded exceeded 1100 kilograms.
Bears raised in zoos are often heavier than wild ones, as they are given regular feeding and have limited movement. In zoos, bears can reach 900 kilograms.
The size seems to be related to the availability of food and the various subspecies are distinguished from each other more on the basis of nutrition than geographical distribution.
As for the fur, it has thick cloaks of blond, brown, black, or formed by a mixture of these colors. The outer guard hairs of brown bears often have a white or silver tip, giving these animals a “grizzled” appearance (from which grizzly derives).
Biology –
The reproduction cycle of Ursus arctos begins with the mating season which runs from the end of May to the beginning of July. Being periodically monogamous, brown bears stay with the same partner for a period ranging from a few days to a couple of weeks. Females become sexually mature between the ages of 5 and 7, while males usually mate only after a few more years, when they are large and robust enough to compete successfully with other males for their rights to coupling.
Due to the delayed implantation process, a female’s fertilized egg divides and wanders free in the uterus for six months. During winter hibernation, the fetus adheres to the uterine wall and the cubs will be born after a period of eight weeks, while the mother is sleeping. If the mother has not accumulated enough fat to survive through the winter, the embryo does not implant and is reabsorbed by the body.
The female gives birth to one to four cubs, usually two, although there have been cases of bears with five cubs, although it is not unusual for females to adopt others’ young. Litter size depends on a number of factors, such as the mother’s age, geographic distribution, and food availability. Older females tend to produce larger litters.
At birth, the little bears are blind, toothless and hairless, and weigh less than 0.4 kilograms.
They feed on their mother’s milk until spring or early summer, depending on the climatic conditions. The cubs, which weigh between 6, 8 and 9 kilograms during this period, are developed enough to follow their mother and start feeding on solid food. They stay with her for between two and four years, during which they learn various survival techniques, how to learn which foods have the highest nutritional values and where to find them, how to hunt, how to fish, how to defend themselves and where to hibernate.
The learning of the small courses is based on following and imitating the actions of the mother during the period with which they remain with her. Brown bears also practice infanticide. An adult male can kill another bear’s cubs to make the female sexually receptive. For this reason, the young climb up a tree as soon as they spot an adult male.
Ecological Role –
From the behavioral point of view and its habits, the Ursus arctos is a predominantly nocturnal and solitary mammal, although in the places where there is greater availability of food many specimens can gather, which form social hierarchies based on age and size.
Arrived in the winter period it falls into hibernation: for this reason, during the summer, it stores more than 180 kg of fat, which it needs to make up for the food that it cannot get, being in a state of torpor for several months. Although they do not fully hibernate and can wake up easily, both sexes prefer to take shelter in a sheltered place in the winter months, such as a cave, crevasse or large hollow log.
Furthermore, the brown bear is omnivorous from a food point of view and feeds on a wide range of plant products, such as berries, roots, sprouts and mushrooms, as well as animals, such as fish, insects and small mammals. Despite their reputation, most brown bears are not particularly carnivorous and up to 90% of their diet consists of plant matter. The structure of the jaws has evolved to adapt to these eating habits, but despite this these animals always have the strong and sharp canine teeth typical of real predators.
The diet, however, varies considerably from area to area.
They range from the Yellowstone bears that eat huge numbers of moths during the summer, more than 40,000 per day, representing 1/3 of their diet, to the bears in some areas of Russia and Alaska, which feed mainly on loaded salmon. of eggs and this nutrition and the abundance of this food allow the bears of these areas to reach enormous sizes.
Brown bears are also predators, also hunting deer (Odocoeilus spp .; Dama spp., Capreolus spp.), Red deer (Cervus elaphus or American wapiti), moose (Alces alces), caribou (Rangifer tarandus) and bison ( Bison bison spp., Bison bonasus).
When brown bears attack these animals, they tend to choose young ones, as they are easier to catch. When hunting, the brown bear uses its sharp canines to bite its prey in the neck.
From some observations made in the Eastern Alps it has been seen that, at least in that area, the brown bear kills herbivores to feed not so much on the meat, but rather on the semi-digested grass present in the stomach, which is often the only part to be eaten.
Bears also feed on carrion and use their size to intimidate other predators, such as coyotes, wolves, pumas and black bears, away from their prey. Brown bears are very strong, even when viewed in several respects; a large specimen can break an adult bison’s neck or spine with a single leg.
Adult brown bears are not afraid of colliding with other carnivorous predators: they can compete alone with packs of wolves and big cats, often chasing them away from the prey they have killed, because they have such strength and size that they cannot be preyed upon.
Finally, the coexistence relationship between bear and man.
In some situations it can come into conflict with man and his economic activities, especially in densely populated regions and where the environments chosen by this animal overlap with the areas used for breeding, agriculture and beekeeping. since, being a food opportunist, he finds it convenient to use these alternative food resources.
Normally the brown bear is not an aggressive and dangerous animal, since it usually has a shy behavior and tends to avoid encounters with humans as much as possible. In some circumstances, however, some bear specimens become familiar with man and his anthropic activities; however they are not to be considered dangerous as they generally do not develop aggressive behaviors. Established cases of aggression are always described as borderline situations, often caused by humans by approaching injured or trapped animals, females accompanied by chicks, or by disturbing bears at wintering or feeding sites, or circumstances in which the the bear sees in man a danger or a competitor to access a food source. Generally the behavior chosen in the event of an accidental encounter with the man is escape.
According to the IUCN, globally, some populations are in sharp decline and this can lead to the risk of survival of some subspecies or to the drastic decrease of some populations, so much so that in some cases, some repopulations have to be made.
Guido Bissanti
Sources
– Wikipedia, the free encyclopedia.
– Gordon Corbet, Denys Ovenden, 2012. Guide to the mammals of Europe. Franco Muzzio Publisher.
– John Woodward, Kim Dennis-Bryan, 2018. The great encyclopedia of animals. Gribaudo Editore.