Brown bear (Ursus arctos)

The brown bear (Ursus arctos) is a bear that is found across much of northern Eurasia and North America. It is one of the largest living terrestrial members of the order Carnivora, rivaled in size only by its closest relative, the polar bear (Ursus maritimus), which is much less variable in size and slightly larger on average.

The brown bear's principal range includes parts of Russia, Central Asia, China, Canada, the United States(mostly Alaska), Scandinavia, and the Carpathian region (especially Romania), Anatolia, and Caucasus.The brown bear is recognized as a national and state animal in several European countries.

While the brown bear's range has shrunk and it has faced local extinctions, it remains listed as a least concern species by the International Union for Conservation of Nature (IUCN) with a total population of approximately 200,000. As of 2012, this and the American black bear are the only bear species not classified as threatened by the IUCN. However, the Californian, North African and Mexicansubspecies were hunted to extinction in the nineteenth and early twentieth centuries and many of the southern Asian subspecies are highly endangered. One of the smaller-bodied subspecies, the Himalayan brown bear, is critically endangered, occupying only 2% of its former range and threatened by uncontrolled poaching for its parts.The Marsican brown bear, one of several currently isolated populations of the main Eurasian brown bear population, in central Italy is believed to have a population of just 30 to 40 bears.

Behavior and life history
The brown bear is often described as nocturnal. However, it frequently seems to peak in activity in the morning and early evening hours. Studies have shown that activity throughout the range can occur at nearly any time of night or day, with bears who dwell in areas with more extensive human contact being more likely to be fully nocturnal. Furthermore, yearling and newly independent bears are more likely to be active diurnally and many adult bears in low-disturbance areas are largely crepuscular. In summer through autumn, a brown bear can double its weight from the spring, gaining up to 180 kg (400 lb) of fat, on which it relies to make it through winter, when it becomes very lethargic. Although they are not full hibernators and can be woken easily, both sexes like to den in a protected spot during the winter months. Hibernation dens may consist of any spot that provides cover from the elements and that can accommodate their bodies, such as a cave, crevice, cavernous tree roots, or hollow logs.

Brown bears have one of the largest brains of any extant carnivoran relative to their body size and have been shown to engage in tool-use (e.g. using a barnacle-covered rock to scratch its neck), which requires advanced cognitive abilities. This species is mostly solitary, although bears may gather in large numbers at major food sources (e.g., moth colonies, open garbage dumps or rivers holding spawning salmon) and form social hierarchies based on age and size. Adult male bears are particularly aggressive and are avoided by adolescent and subadult males both at concentrated feeding opportunities and chance encounters. Female bears with cubs rival adult males in aggression, and are much more intolerant of other bears than single females. Young adolescent males tend to be least aggressive, and have been observed in nonantagonistic interactions with each other.^[217] Dominance between bears is asserted by making a frontal orientation, showing off canines, muzzle twisting and neck stretching to which a subordinate will respond with a lateral orientation, by turning away and dropping the head and by sitting or lying down. During combat, bears use their paws to strike their opponents in the chest or shoulders and bite the head or neck. In his Great Bear Almanac, Gary Brown lists 11 different sounds bears produce in 9 different contexts. Sounds expressing anger or aggravation include growls, roars, woofs, champs and smacks, while sounds expressing nervousness or pain include woofs, grunts, and bawls. Sows will bleat or hum when communicating with their cubs.

Reproduction
The mating season is from mid-May to early July, shifting later the further north the bears are found. Being serially monogamous, brown bears remain with the same mate from a couple of days to a couple of weeks. Outside of this narrow time frame, adult male and female brown bears show no sexual interest in each other. Females mature sexually between the age of 4 and 8 years of age, with an average age at sexual maturity of 5.2–5.5 years old, while males first mate about a year later on average, when they are large and strong enough to successfully compete with other males for mating rights. Males will try to mate with as many females as they can, usually a successful one mates with two females in a span of one to three weeks. The adult female brown bear is similarly promiscuous, mating with up to four, rarely even eight, males while in heat and potentially breeding with two males in a single day. Females come into oestrus on average every three to four years, with a full range of 2.4 to 5.7 years. The urine markings of a female in oestrus can attract several males via scent. Paternity DNA tests have shown that up to 29% of cubs in a litter will be from two to three different males. Dominant males may try to sequester a female for her entire oestrus period of approximately two weeks but usually are unable to retain her for the entire time.Copulation is vigorous and prolonged and can last up to an hour, although the mean time is about 23–24 minutes.

Males take no part in raising their cubs – parenting is left entirely to the females. Through the process of delayed implantation, a female's fertilized egg divides and floats freely in the uterus for six months. During winter dormancy, the fetus attaches to the uterine wall. The cubs are born eight weeks later, while the mother sleeps. If the mother does not gain enough weight to survive through the winter, the embryo does not implant and is reabsorbed into the body. There have been cases of bears with as many as six cubs, although the average litter size is 1-3, with more than four being considered uncommon. There are records of females sometimes adopting stray cubs or even trading or kidnapping cubs when they emerge from hibernation (a larger female may claim cubs away from a smaller one). Older and larger females within a population tend to give birth to larger litters. The size of a litter also depends on factors such as geographic location and food supply. At birth, the cubs are blind, toothless, hairless, and may weigh from 350 to 510 g (0.77 to 1.12 lb), again reportedly based on the age and condition of the mother. They feed on their mother's milk until spring or even early summer, depending on climate conditions. At this time, the cubs weigh 7 to 9 kg (15 to 20 lb) and have developed enough to follow her over long distances and begin to forage for solid food.

The cubs are fully dependent on the mother and a close bond is formed. During the dependency stage, the cubs learn (rather than inherit as instincts from birth) survival techniques, such as which foods have the highest nutritional value and where to obtain them; how to hunt, fish, and defend themselves; and where to den. Increased brain size in large carnivores has been positively linked to whether a given species is solitary, as is the brown bear, or raises their offspring communally, thus female brown bears have relatively large, well-developed brains presumably key in teaching behavior. The cubs learn by following and imitating their mother's actions during the period they are with her. Cubs remain with their mother for an average of 2.5 years in North America, uncommonly being independent as early as 1.5 years of age or as late as 4.5 years of age. The stage at which independence is attained may generally be earlier in some parts of Eurasia, as the latest date which mother cubs were together was 2.3 years and most families separated in under two years in a study from Hokkaido and in Sweden most cubs on their own were still yearlings. Brown bears practice infanticide, as an adult male bear may kill the cubs of another bear. When adult male brown bears kill a cub it is usually because he is bringing the female into oestrus, as she will enter that state within 2–4 days after the death of her cubs. Cubs flee up a tree, if available, when they see a strange male bear, and the mother often successfully defends them, even though the male may be twice as heavy as she, although females have been known to lose their lives in these confrontations.
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Brown bear in Ligatne Nature Trails