Evolution and Systematics
Though bears family do not form large number of species or genera they have nevertheless long been the subject of debate when it comes to classification. One such example is that in the years gone by systematists have placed Giant Panda in the subfamily of Ursidae. Other bears including sloth bear, polar bear, and Malayan sun bear are classified in the Ursus genus, but at times they do fall in the genera Helarctos, Thalarctos, and Melursus. Brown bears (U. arctos) are often grouped as a separate species; grizzly bear (U. horriblis), and Alaskan brown bear (U. middendorffi). Furthermore, Red panda (Ailurus fulgens) was previously believed to be a member of Ursids but later it was classified in the family of Ailuridae.
The Ursidae is thought to have emerged in Asia, and is most closely associated with the canids (dogs and the like), ailurids (lesser panda), procyonids (raccoons and relatives). Of all bear species giant panda is deemed to be the most primitive. Scientists have made many attempts to figure out the precise relationships of other bears. According to fossil studies spectacled bear (Tremarctinae) might have diverged from the remaining bears that belongs to the subfamily of Ursinae. The fossil records also suggest that Asiatic black and American black bears are closely related while brown and polar bears stands close to one another.
Bear Facts for Kids
- Giant panda is considered to be the most primitive of all bear species.
- Polar bear and brown; Asiatic bear and American black bear stand close to one another.
- The polar bear is the only species that has entirely white fur though the skin is black.
- The sun bears have very long tongue with the help of which they reach out honey—the favorite item in their diet.
- Malayan sun bear is the smallest bear species.
- Polar bear is the largest bear.
- The spectacled bear is the only species inhabiting Southern Hemisphere.
- Polar bear is most widely distributed in the Northern Hemisphere.
- Bears are primarily solitary animals.
- They are strong territorial animals.
- They have a strong sense of smell as they smell anything from as far as 1 km (0.6 mi).
- Polar bears are the best swimmers as they can cover 100 km through swimming.
- Sun bears are the best tree-climbers and they like to eat honey.
- Bears mainly hunt at daytime.
- Giant Panda (Ailuropoda melanoleuca)
- Malayan Sun Bear (Helarctos malayanus)
- Sloth Bear (Melursus ursinus)
- Spectacled Bear (Tremarctos ornatus)
- American Black Bear (Ursus americanus)
- Brown Bear (U. arctos)
- Polar Bear (U. maritimus)
- Asiatic Black Bear (U. thibetanus)
While bears are believed to be dangerous for humans, bear attacks are few and fatalities are rare.
- Bears are large to medium-sized mammals with a very short tail, stocky limbs, and plantigrade feet.
- The coat varies from species to species but generally the color is dark brown to black and fur is often variable sometimes within the same species. For example in American black bear the color ranges from reddish, black, brown to whitish.
- Certain species have unique white lines on the face down the way to the throat. Spectacled bear is one such example as it displays whitish rings around its eyes.
- Brown bears have fairly long hair on the shoulders that indeed shapes a lion’s mane. Others such as sloth bear have long fur all over its body.
- Bears have quite large head with eyes facing forward and they have round modest ears.
- The teeth are both molars and premolars including canines that are employed for crushing making up the omnivorous diet. The spectacled bear and giant panda have flattened molars that are best to chew herbivorous diet. The sloth bear fancy eating termites and they lack incisors in upper jaw; this also explains as to why they have long tongue. The bear sucks up the insects because of the gap combined with naked lips. The sun bears are characterized by their long tongue as the tongue helps them in licking all the honey.
- The claws of bears vary in species but all are non-retractile. These claws are 2 – 4 in (5 – 10 cm) long in brown bears and they are light brown in color. The Asiatic black bear have relatively short claws with the length measuring at 2 in (4 – 5 cm).
- Males are typically larger than females.
- The Malayan sun bear is the smallest with the body length measuring only 4 – 5 ft (1.2 – 1.5 cm), with the average weight of male is 60 – 150 lb (27 – 70 kg). Brown bears and polar bears live at the opposite end of poles; male polar bears averaging 8 – 9 ft (2.4 – 2.7 m) in body length with the weight 900 – 1,300 lb (400 – 590 kg), male brown bears 5 – 8 ft (1.5 – 2.4 m), average weight 350 – 850 lb (160 – 385 kg).
- Bears have extremely wide range of distribution in the Northern Hemisphere. The polar bear is the most common species in this region as it roams around the circumpolar ice pack.
- Brown bear is the North American species and it is also found in the north to north-central Eurasia.
- The American black bear inhabit the northern Mexico all the way towards Canada. The sun bear and the sloth bear live in the Southeast Asia.
- Asiatic black bear have slightly larger distribution in that it extends from Afghanistan to southeastern Russia.
- The giant panda is found only in segments as it has the smallest distribution ranging from Tibetan plateau to southwestern China.
- The spectacled bear is the only species being found in the Southern Hemisphere, inhabits around the Andes (South America), sites include Colombia, Bolivia, Peru, Ecuador, and Venezuela.
There is a wide variety of habitats among bears and not a single species have one that are in common with other species. For example polar bears build their habitats in intense cold of Arctic which is a complete contrast to the tropical rainforests of southeast Asia where Malayan sun bear inhabits. The habitats of American black bears can be found in the marshes of southeastern states to the northern Tundra in Canada. They also make habitats in the mountain woods of western U.S. However, as against this, the shaggy-looking sloth bears fancy living in grasslands ranging from dry forests to the wetlands in India and indeed touching the foothills of Himalayas.
The grizzly brown bears or Kodiak bears have their habitats spread around the dense forests of North America including grasslands and tundra in the Northern Hemisphere; the spectacled bear are fond of lush green mountain forests in South America.
The Asiatic black bear predominantly exists in the woodlands of southern Asia while giant panda is only found in the bamboo forests of China.
All these bears have unique home ranges as Pandas have 2 – 3 mi2, but brown bears spread out up to 800 – 1,000 mi2 provided the food is short and habitat is poor.
Since all bears have remote geographical distribution, the behavior of half of the species is not precisely known. These species include Asiatic black, spectacled bear, sloth bear, and sun bear. General speaking, bears are solitary animals as they like to move around alone except when it comes to mating season or when the mother is with her cubs. Seldom does it happen that in brown bears, the young will stay with their mother for more than one or two years. Some researched reports say that sloth bears may form social groups and that sun bears stay with their mother after she gives birth.
Bears do occupy home ranges and they are strongly territorial animals. Male’s range typically overlaps with that of female’s.
They usually mark their territory by long stretches clawed into trees or simply by scent markings. In case of black bears, the male’s range may overlap but because of the fact that ranges are very large, it is highly unlikely that one bear would confront with the other.
Bears do respect each other even at feeding site. When the brown and black bears gather around to feed on salmon stream they try to maintain as much personal space as possible. However, when bears come across one another, they show dominance and large males tend to growl and at times, they charge to ensure their small feeding territory. Males compete with each other for females in the breeding season, but the pair is made only for one or two weeks.
Bears are named as lumbering animals precisely due to their large plantigrade feet and stout limbs that help them in moving rather slowly. If required, bears are able to move very quickly. Black bears run as fast as 30 mph (50 kph) whereas polar bears are quick so much so that they catch caribou on the Arctic tundra with ease. Sloth bear which seems more awkward can run faster than human though in short bursts.
Nearly all bears are expert at climbing trees especially sun bear that has adapted itself to climb trees in order to find honey; besides, it also sits high up the trees. Brown bears and polar bears are unable to climb but they are the best swimmers. Asiatic black bear can also swim very well. Polar bears are supreme swimmers so much so that they are termed as marine animals because they spend most of the time underwater. They swim across open-water expanses of up to 100 km (65 miles).
Bears are almost entirely nocturnal as they go active either at dawn or at dusk. Some species however do come out in daytime. Polar bear is one of them. Bears mostly hunt during daytime.
While most bears do not hibernate there are some (especially cooler climate bears) that enters into winter dormancy. During hibernation, the heart rate drops down whereas the body temperature slightly goes down. The body temperature of black bears drops from 100 F (38 C) to 88 – 93 F (31- 34 C). The female bears mostly give birth during winter dormancy. In the extreme cold climates, both male and female enter into hibernation except in case of polar bear where only female hibernates.
In the days of winter, bears rarely show themselves as they fancy staying in den, tunnels, hollow logs, and burrows in the snow and ice. The warm-climate bears never go into hibernation and they remain active all year round. These bears include sun, sloth, and spectacled bear.
Bears are opportunistic omnivores as they consume anything that comes in their way. Polar bear is a carnivorous species given that it hunts large marine mammals such as ringed seals (Phoca hispida) but it also feeds on berries and vegetation in summer. Polar bears are ambush hunters as they wait for the seal to show itself in order to overpower it with one whack of its mighty paw. Sometimes polar bear also stalks an elk in the open. The color of the coat allows polar bear to get as close as possible to the kill because the prey never sees it in the snow.
Unlike polar bears, other species like to feed on green vegetation, fruits, mostly tender stems, roots, and they also consume insects, small mammals, fish, or even carrion. Because brown bears are large they take moose, elk, and other ungulates. The giant panda which is found in the China primarily survives on herbivorous diet such as bamboo leaves, shoots, and stems. Sloth bears show strong preference for termites. Just as sloths like termites, sun bear likes to have honey in their diet. However, when it comes to using their claws they rip apart either bees nest or termites home to get the reward.
The spectacled bear is monogamous whereas others such as polar bear are polygamous. Bears for the most part mate in summer or in spring. The sloth bear mates all throughout the year but the females usually give birth in the winter season.
The cubs are naked and blind at birth with the weight averaging 11 oz (325 g) in sun bears to 21 oz (600 g) in polar bears and brown bears. Mostly females give birth to one to five cubs but the usual number is two. However, often the female raises only one cub at a time while others die. In the cool climates, the cubs are born during winter dormancy. In the hot conditions such as the sun bear, the female finds a suitable nesting site for her cubs; typically mother selects branches or thick vegetation. The weaning period for cubs ranges from two to five months but they continue to stay with their mother for two to four years. During these initial years, the mother teaches her cubs how to hunt and find food. They reach the maturity age from four to seven years old.
IUCN has included panda bear as endangered species precisely due to the widespread habitat destruction. In case of panda bear, not only does the increasing human population contribute towards habitat damage but also the increase in the household as family units led to the extinction of panda bear in particular. The rough estimate says that there are no more than 1,000 pandas remaining in the wild.
Alongside panda bear, certain other species have also suffered as a result of habitat destruction. One such example is brown bear which is believed to have disappeared in most of its former range. Now it inhabits only 2% within the continental United States. Sometimes it so happens that individual bear population suffers while the overall species number remains stable. Same is the case with American black bear. A few others are also deemed threatened including Ursus americanus floridanus. Many conservation programs have been implemented including hunting bans, educational programs to create awareness among masses, and habitat conservation programs are underway worldwide.
IUCN has listed spectacled, sloth, and Asiatic black bear as Vulnerable; while polar bear is Lower Risk/Conservation Dependent; and IUCN has listed sun bear as Data Deficient.
Several bears are usually hunted for their fur, meat, and trophy mounts. Additionally, the body parts of many bears are commercially significant in that gall bladder of sun bear and American black bear is employed for medicinal purposes particularly in China. Bears do attract a lot of people at zoos.