Back in 1980s scientists studied the polar bear locomotion and established that polar bears were not energetically efficient walkers. The study was carried out not in the natural environment. In fact scientists observed bears walking on treadmills. According to them, polar bears consume more oxygen and heat storage in comparison to other land mammals.
They thought that the polar bear’s morphology was not well developed for it to walk rather efficiently. The long forelimbs of an ice bear is meant to capture more than anything else. Polar bear’s excellent hunting strategy and thermoregulation is what makes them a serious predator. However, they are the most mobile animals of all quadrupeds. Scientists have yet to discover the locomotion in polar bears in their natural habitat.
How Do Polar Bears Move Around?
Polar bear travels vast distances using cues to navigate through the arctic habitat. Scientists believe that they need to understand these cues in the light of bear’s own locomotion without comparing it to the movement of other species.
Polar bear’s walking is its most familiar gait and it looks like pigeon-toed because bear’s forepaws are directed inwards. They are able to gait as well as gallop but they cannot trot.
Polar bear’s walking is its most familiar gait and it looks like pigeon-toed because bear’s forepaws are directed inwards. They are able to gait as well as gallop but they cannot trot. If you happen to look at a walking bear from behind you can probably notice the prominent sway in her hips. Mature males often appear (during walk) as if their rear legs are turning around while viewing it from behind.
Image Courtesy: Educational Technology Clearinghouse – University of South Florida
Polar Bears Walking Speed
Goes without saying that polar bears are not proficient walkers as much but their typical gait speed is about 5.5 km/h. Furthermore, bears can maintain this much for extended period of time. They do however relax a little during the journey. The minimum gait speed is around 1 km/h. Scientists noted the average speed of 4 km/h which they were able to sustain for as long as 20 hours. Few specimens did show up maximum stamina as they were able to sustain 4 km/h for up to 40 hours.
Polar bears are not proficient walkers as much but their typical gait speed is about 5.5 km/h. Scientists noted the average speed of 4 km/h which they were able to sustain for as long as 20 hours.
During warmer months in the Hudson Bay polar bears appear to remain inactive; the walking habits become limited throughout the season. They do nevertheless charge for their alternative prey such as waterfowls and caribou. Typically ice bears are slow animals for they never sprint like tigers do. The heat which is produced during the activity is likely to be dispersed in a very little time consequently leaving nothing to store. The maximum limit for polar bear walking is about 7.9 kilometers per hour.
Polar Bear Cubs Walking
Studies suggest that polar bear cubs get too tired in too little time. This is due to the number of strides they have to take in order to keep up with their mother’s speed. Since number of steps is going to define the energy cost per gram of a body weight. The greater is the frequency of steps the greater is the energy consumed.
Adults on the other hand do not seem to require too much energy (in walking) for while they are heavier the longer strides help them to cover the same distance in less time.
Lately scientists have observed the migration of polar bears in the northwestern Canada, Beaufort Sea and Chukchi Sea of Alaska. They conclude that polar bears rely on sea ice so much so that they cannot live without the it. They will move with the ice. However the bear’s movement is not so random as scientists previously thought nor do they passively follow the ice movements. Perhaps it’s time to discuss how do polar bears migrate in the tundra. You’d like these interesting polar bear migration facts.
Do Polar Bears Migrate? – Polar Bear Migration Routes
Depends on the region polar bears move in a linear fashion and their movement is far greater than many other terrestrial predators. Polar bears’ close association with the sea ice suggests that the bear has varied productivity patterns and it mainly depends on the habitat characteristics.
Biologists calculated the annual distance covered by a polar bear in a straight line and estimated at 6,200 kilometers but averaging 3,415 kilometers. Polar bears typically move at a speed of 4 km/h which they are able to sustain for longer periods.
They are thought to cover as much as 50 km/h in a single day. Polar bears walk 50 kilometers without resting.
The activity areas of female polar bears are recorded at 149,000 square kilometers. The largest area is estimated at 597,000 km2 whereas the smallest is about 13,000 km2.
In the Beaufort Sea polar bears relatively travel more probably due to the dynamic behavior of the sea ice. The average activity area is estimated at 244,463 km2. They will cover 5542 km of mean distance each year.
When the ice moves at 15.5 kilometers per day the bear moves at 14.1 kilometers each day. A polar bear always moves against the ice probably due to the fact that it provides grip over the ice.
Scientists haven’t been able to fully understand how polar bears migrate in the tundra. Polar bear migration. Photo by World Journeys
Polar Bear Movement in the Canadian Arctic Archipelago
In the Canadian Arctic Archipelago the ice movement is greatest and so as the polar bear’s. In the Davis Strait and Baffin Bay ice bears travel great distances. The unpredictable behavior of the sea ice in Chukchi Sea, Beaufort Sea, and Baffin Bay makes the polar bear movement predictable. The greater is the volatility of sea ice the greater is the movement of the polar bear.
The largest monthly activity in the Beaufort Sea is likely to be observed in June and July as well as in November and December. Polar bear travels the most during these periods. From May to August polar bears largely move towards north whereas in October their direction is towards south. (See in detail: How Do Polar Bears Move?)
Polar bear movements decrease in October because the ice begins to freeze in the southern Beaufort Sea. October is probably the first month when the shallow waters will cover with thin ice sheet.
Unlike in Beaufort Sea the greatest movement of polar bears inhabiting Viscount Melville Sound is in May to July. They will further increase their movements in January.
The summer movements are also high; the reason behind that is the quick retreating of sea ice.
Polar Bear Migration Map. Do polar bears migrate? Photo by Polar Bears International
Polar Bear Movement in the Viscount Melville Sound
In the southern and northern Beaufort Sea the peak movements occur in November and December. Polar bear movements become lowest in May.
During winter in Viscount Melville Sound polar bears do not appear to move much. This is because of the occurrence of thick ice sheet. However ringed seals are present in fewer numbers in Viscount Melville Sound as compared to those in Alaska or West Greenland.
In the Viscount Melville Sound ringed seals live in tidal cracks and pressure ridges and they find it difficult to come to the surface for breathing because the water is covered with multilayered ice sheet. On the contrary the ice in the southern Beaufort Sea seems to be volatile allowing seals to breathe with ease.
As it turns out polar bears in the Beaufort Sea spend much of their time foraging for seals whereas those living in the Viscount Melville Sound are known to rest and conserve energy.
Nonetheless, polar bears inhabiting the Viscount Melville Sound have one advantage over the Beaufort Sea bears that is, the predictable behavior of sea ice in the Viscount Melville Sound.
The ice in the Viscount Melville Sound doesn’t appear to move much which means that bears can predict the precise areas for hunting seals in early winter. Same is not the case with bears living in the Beaufort Sea because they cannot identify the hunting areas due to changing character of the sea ice.
The constant change in the ice of Beaufort Sea and Baffin Bay requires polar bears to be more creative. Polar bears must learn to devise new foraging strategies each passing month or even day.
Do Polar Bears Migrate? – Polar Bear Migration – Video
Polar bear (Ursus maritimus) is the largest carnivorous land mammal living today. The only other bear nearly the size of polar bear is her close relative Kodiak brown bear. Scientists aren’t sure which one is bigger. Biologists also refer polar bear as a marine mammal because the bear spends so much of its time in water. Polar bears love to swim and they are outstanding swimmers. Unlike any other bear species, arctic bears can swim for days without stopping. In this article we are going to compare the polar bear’s size with some of the largest land mammals such as Siberian tiger and Kodiak brown bear.
Polar Bear is the Largest Carnivorous Mammal
Siberian tigers are some of the biggest carnivores with the maximum weight of about 465 kilograms. Yet another terrestrial species is Kodiak brown bear that weighs up to 751 kilograms. Siberian tigers and Kodiak bears are one of the largest mammals in the animal kingdom but polar bear exceeds all of them in weight. The largest male polar bear weighs as much as 1,002 kg (2,209 lb) kilograms which qualify it as the largest terrestrial land mammal.
Tallest Mammal
The large Kodiak Brown reaches the height of about 9 ft 8 in. whereas polar bears can have the height of about 11 ft 1 in. A male Siberian tiger is 11 feet tall. The maximum shoulder height of adult polar bears is 5 ft 3 in while Siberian tigers are only 50 inches in shoulder height. The Kodiak bears are extremely close to the polar bear’s height at about 4.9 feet at the shoulder.
An adult male polar bear is twice the size of an adult female polar bear. Polar bear is the largest carnivorous land mammal. Photo by Natural Habitat Adventures
Polar Bears are Extraordinarily Powerful
Unlike any other terrestrial carnivorans polar bears are super powerful. The polar bear’s skull and neck are strong enough to pull 600 pounds prey out of water. This implies that icy bears are so much muscular that they are able drag the prey nearly the size of their own. No other mammal—not even the Siberian tiger or Kodiak brown bears are comparable in strength to the polar bear’s powerful neck. Although the brown bear’s skull is greater than that of polar bear’s yet the latter possess narrower skull because it allows her to reach the prey hidden into the sea ice.
Polar Bears possess Strongest Claws
Kodiak brown bears are quite closer to polar bears in strength but they are overshadowed by the arctic bears in terms of claws’ strength. Polar bears have arguably the strongest claws which are stronger than the Kodiak bears and heavier than the black bears.
Polar bears (Ursus maritimus) are unquestionably resilient to the arctic environment. Their adaptation to stay warm in an unbelievably cold temperature is something that makes them matchless in the mammalian world. Thanks to its insulating ability, white color, and dense fur that not only makes the bear warm but also camouflages her in the arctic ice. The thick and fuzzy jacket prevents the polar bear from catching cold in the icy water.
How Do Polar Bears Stay Warm?
The insulating phenomenon of polar bears is not as simple but scientists are putting their best to reason out how polar bears can stay warm in such a freezing temperature of the Arctic Circle. Latest findings suggest that polar bear’s hairs are likely to perform the functions of a heat pipeline. According to scientists as the sunlight touches the tiny hair it travels to the end and enters the polar bear’s skin. They believe that the bear’s hair seems like fiber-optic cable in function.
Thanks to its insulating ability, white color, and dense fur that not only makes the bear warm–it also camouflages her in the arctic ice
There is a scientific belief that the polar bear’s coat serves as a protector in that it attempts to bring warm particles of the air into tiny pores. However the modern studies suggest that the pelt also performs another insulating function. This function is performed within the polar bear’s coat. Polar bear’s skin emits the body heat as infrared light which in turn bounces around within the coat just like a table tennis ball. The infrared rays are thought to move back and forth between the hairs. According to the research the bear’s hair neither absorbs light nor does it scatter light absolutely. In fact they partially perform both.
Biologists maintain that the density of hairs is what actually defines the reflection of light. If the hair density is greater the light reflects many times with some of it returns back to the skin.
Polar bears appear to make themselves warm via three kinds of heat transfer: convection, conduction, and thermal radiation. Conduction is the process in which the heat waves travel through the medium but the materials do not move whereas in convection the movement is primarily caused within a fluid. However the most useful (of these) is thought to be the thermal radiation.
Scientists have long believed that the hot air traps inside the polar bear’s body in the same way as it does in some housing insulations. The coat performs the given function.
Thermal Radiation
Scientists seem to count on thermal radiation as compared to convection or conduction. According to them polar bears use thermal radiation to keep warm in the cold. In thermal radiation the energy is discharged in the form of electromagnetic waves. Human’s skin gets heated in the similar fashion. Similarly if someone wears a shiny jacket the heat waves radiate from the human body is likely to smack the jacket and scatter while keeping the heat inside.
All living organisms release heat which can be seen through night-vision goggles. The goggles are able to detect the infrared radiation but polar bears are so perfectly insulated that no such radiation or heat is observed even through goggles. The heat is trapped 100% inside the bear’s body. The polar bear’s pelt appears to possess the same temperature as its surroundings.
Scientists finally conclude that the polar bear fur partially absorbs heat radiation and partially scatters it. The heat waves are thought to travel in different directions after being scattered and re-emitted. The sunlight doesn’t believe to keep bears warm in fact it is the scattering of light off the fur that warms the animal. “The more animal reflects the [infrared] light, the more efficient the insulation”, American Institute of Physics.
The latissimus dorsi are the muscle sheets which lies at the mid-central back of the body. These sheets play a significant role in the heat regulation. During swimming the heat is discharged through conduction whereas on land the heat is primarily lost by convection. Above the surface polar bears often lie on the back and wave their legs in the air to cool her body. In order to stable body temperature bears will drink water in excess.
Polar bears may also change to sternal posture in which they move their feet backwards or sometimes curling paws around their body. By so doing bears can reduce their temperature from 36o C to 27o C.
On the icy surface, polar bears spread their legs so that their body releases heat. On land when polar bears are overheated they just dig small depressions and relax into it.
The heat loss during swimming is extremely important because the bear generates heat in the submerged water which in turn is probably neutralized by the heat loss.
While polar bear’s fur shows outstanding insulating property the pelt seems to have poor insulative ability. They will maintain stable body temperature by bringing change in subdermal vascularization and other adaptive mechanisms in order to compete with the cool environmental conditions. The subcutaneous fat also serves as insulating material. Bears lose additional heat via foot pads and shoulders.
The polar bear’s fur is 55 mm in thickness which is pretty fair insulation. However some of the hairs are rough and they do not insulate heat as effectively. During swimming polar bears lose heat 20 – 25 times faster than in the open air. But in disturbed water the bear is likely to lose heat nearly 50 times that in the air.
The heat loss during swimming is extremely important because the bear generates heat in the submerged water which in turn is probably neutralized by the heat loss. Soon after swimming the bear shakes her body to shed the water from her fur in order to make sure that the pelt insulates properly. Polar bear’s posture and respiration also affects the heat loss phenomena.
Polar bears are highly efficient in finding out numerous biological mechanisms to cope with the heat loss. One such adaptation is that they can cool their external tissues which create an insulating shell and their body goes warm. This is known as regional heterothermy. According to the researchers, white bears (by doing so) prevent the extreme heat loss during swimming in the icy water. The bear must adopt this mechanism on almost regular basis for the melting of arctic ice indeed makes swimming harder and longer.
The peripheral muscles and subcutaneous fat serve as important insulators especially during swimming. Polar bear’s fur doesn’t appear to insulate well in water in fact the bear finds shelter in a windy weather. They will also discharge heat through the thin muscle sheets which are present on the torso. Alongside torso bears also lose heat via snout and footpads. The significant player in the peripheral insulation is the peripheral tissue without which the insulation might never be possible.
During swimming the skin temperature is relatively higher. The heat dissipation often puts check on the polar bear’s ability to engage in physical activities for long periods. For instance bears can hardly perform exercise for more than 15 minutes.
At birth the polar bear cubs have only 5-mm-long coat and there are only 600 – 700 hairs per square centimeter. They don’t seem to cover with subcutaneous fat nor do the fats surround kidneys. They are not yet prepared to challenge the freezing environment of the Arctic.
Once they attain weight of about 8.5 – 9.5 kilograms they can stable their body temperature 30o C to 0o C with a slight increase in the metabolic rate in temperatures below 10 degree centigrade. However weak polar bear cubs may be as against adults the physiological insulation is good enough to sustain constant temperature while swimming.
During swimming the water temperature ranges from 0 – 2o C but the core body temperature of a cub is stabilized at 38.5o C. If cubs keep walking for as long as 29 minutes their temperature alleviates to 400 C.
Polar bear hibernation does not occur like black bear or grizzly bear hibernation. Black and grizzly bears, unlike polar bears, are true hibernators. Polar bears probably do not hibernate in a way other mammals do. They just enter into a specialized winter dormancy. This is little different from natural hibernation. During winter dormancy polar bears can also reduce their heart rate and possibly metabolism and temperature. Let’s see how do polar bears hibernate.
Do Polar Bears Hibernate? – Polar Bear Hibernation
Female bears dig dens in snow and they remain asleep for 4 to 8 months. They become absolutely inactive during this period. Polar bears neither eat nor do they drink in fact they do not even urinate whilst they are hibernating. In spite of all this inactivity females appear to have stable mineral levels with a constant body mass.
Many researchers estimate the level of blood metabolites which is almost fully maintained. This is quite remarkable in that the animal loses half of its weight inside the den while maintaining the metabolite level stable.
During hibernation or dormancy polar bears make up the deficiency of water from fat catabolism. By so doing they are able to maintain stable fluid level within the body.
Hibernation is an adaptation that allows some species of mammals to store fat when the feeding is good, and then burn it off slowly at a lower metabolic rate while in a deep resting state when food is unavailable, usually, but not always, during winter. True hibernators such as some rodents, bats, or insectivores experience a significant decline in heart rate, their body temperature may approach 0°C (32°F), and it may take some time to arouse them because they have to expend stored energy to restore the body to its normal temperature before it can function properly again. The largest mammals that are true hibernators are marmots. Bears are too large to lower their body temperature to very low levels because they would simply not have enough energy to be able to reheat such a large mass back to its normal operating temperature.
Bears also need to maintain a much higher body temperature than true hibernators because they also still need to be able to maintain the physiological demands of pregnancy, birth, and nursing the young. Although bears sleep soundly, they are easily aroused and can, if necessary, defend themselves.Although most species of bears go into dens during the winter, they have some important differences from the so-called true or deep hibernators. From research done on captive bears, we know that the heart rates of hibernating black and grizzly bears are capable of slowing to 10 to 12 beats per minute, or even lower sometimes, but their body temperature only declines to about 31-35°C (88-93°F). The heart rate of a polar bear held in an artificial den decreased to 27 beats per minute after about a month. The deep body temperature of two female polar bears hibernating in natural dens during the winter ranged between 35 and 37°C (95-98.6°F).
Hibernation in Black and Grizzly Bears
Hibernation and seasonal food scarcity for polar bears differ considerably from those of black and brown bears. Firstly, only gestating female polar bears enter dens during the winter, while the rest of the population remains active. Secondly, for many polar bear populations, the period of greatest food deprivation is the open water phase of late summer and early autumn, just when black and grizzly bears are consuming most extensively in order to accumulate fat reserves with which to endure the upcoming winter.
One of the most interesting chapters in our understanding of the “hibernation-like” state in polar bears, and hence how they have adapted their physiological needs to the vagaries of the arctic environment, originated with the late Ralph ag in Nelson. He wondered how black bears could hibernate through the winter at near-normal body temperatures without eating, drinking, or producing any urine or faeces. When hibernating, the black bear produces all the water it needs by chemical pathways from its stored fat; then it reduces the by-products without producing waste materials. Nelson thought if he could figure out how this was done, there might be enormous benefits to humans with kidney problems.
Nelson found that he could define a bear’s physiological state by the ratio of the concentrations of two chemicals in the blood, urea and creatine. Creatine is produced by normal muscle activity and its level in the blood remains pretty H much the same all the time. However, the amount of urea in the blood goes up when an animal is eating and becomes very low when it stops eating and lives only on its fat.
Walking Hibernation in Polar Bears
After some experimentation, Nelson defined the urea-to-creatine (U/C) ratio (that is, the number of units of urea in a sample of blood divided by the number of units of creatine) of a hibernating black bear as any anything less than 10. He then examined blood samples taken from non-feeding polar bears on the western coast of Hudson Bay during the ice-free period in the late summer and fall. He found that the U/C ratio was at a a similarly very low level in them as well. Thus, even though the bears were not in dens and were still active, they were (in the physiological sense) hibernating. This gave rise to the rather intriguing term “walking hibernation”.
A curious aside to this finding is the observation of an old Inuk hunter on the Labrador coast, passed on to a visiting anthropologist, sometime prior to 1916. He said that old male polar bears hibernate in caves along the coast in the summer when there was no ice. As in Hudson Bay, open water prevails along the coast of Labrador for many months in the summer, so we now know that similar hibernation-like responses must occur in the bears there. It has always intrigued me that an observant Inuk hunter noted the parallel between the summer behaviour of polar bears in caves and the winter behaviour of bears in dens.
Nelson and some of his colleagues then came to Churchill to work with our group so he could learn more about how polar bears evolved to live in the arctic environment. We selected polar bears of various sizes for non-harmful experiments, sometimes while other bears wandered by and gazed curiously at the goings on. By looking at the U/C ratios over the next couple of years, we found that female polar bears coming out of the denning area in the spring were in a similar physiological state to that of hibernating black bears. More interesting though, were the results from polar bears spending the late summer and fall along the Hudson Bay coast. At the same time that non-feeding bears were in “walking hibernation”, polar bears feeding in the dump had the be- same U/C values as non-hibernating (feeding)| black bears. The astonishing conclusion was that members of the same polar bear population could be in completely opposite physiological conditions at the same time and place, depending on whether they were feeding or not feeding. That is something a black bear cannot do.
Andy Derocher, Nelson, and Ian Stirling then conducted some preliminary feeding experiments on several polar bears being held in captivity. They had not been fed for some time and had the low U/C ratios characteristic of the hibernation-like physiological state. When they were fed for a few days. the ratios went up, as we expected. However, once food was no longer available, the U/C ratios dropped again after about a week. Remarkably, these results indicated that polar bears could move the physiological state of a fasting bear, to one of a feeding bear, and back to that of a fasting bear, all within a period of a couple of weeks. The contrast with terrestrial bears is dramatic. If you stop feeding a black bear or a grizzly in summer, it will starve to death. Thus, it appears that one of the most remarkable physiological adaptations of the polar bear to life in the arctic environment, where the availability of food is both variable and unpredictable for much of the year, is its ability to change its metabolic state as needed. This allows the bear to maximise the efficiency of its use of stored energy, and not be limited to changes controlled by photoperiod or other seasonal signals.
No subsequent research on this topic has yet been done, though it could be very informative to repeat and extend those experiments one day. Recently, however, another study on wild polar bears gave some results similar to those obtained from the captive bears. From direct observation, we know that when searching for a breeding female, or when courting one, male polar bears may not actively hunt for extended periods of time, although if one of them catches a seal, or they encounter a carcass, both the male and female may feed on it.
In an analysis of the U/C ratios of polar bears from the Beaufort Sea in spring, Seth Cherry found, again, that bears in the same area at the same time could be in either a hibernation-like or non-hibernation physiological state. In particular, a larger proportion of adult males were not feeding, apparently maximising their time for searching for breeding females and then courting them. They could afford to do this because the major feeding period of the year overlaps, but largely follows, the most active part of the breeding season. Thus, a temporary shortfall in energy intake can be compensated for fairly soon afterward. Most important though, since active hunting may absorb up to a third of a bear’s time under normal conditions, it allows the male to slow its metabolic rate slightly and make maximum use of its stored energy to increase its searching and courting time which in turn will improve it chances of finding a mate and passing on its genes.
Do Polar Bears Hibernate? – Polar Bear Hibernation – Video
Polar bear eyes are set in such a way that the animal can look forward with a binocular vision. However the bear’s eyes also enable her to have a pretty good vision of the sideways. Polar bear’s eyes are one of the least understood physical features. Scientists are carrying out research on the anatomy of eyes but so far with little success. Much of the information is speculated as to how far a polar bear can see on the sea ice.
Scientists from Russia report that polar bears have poor eyesight. Certain biologists however believe that white bears have been underestimated in sight. They are able to see things, animals or even humans from long way off. It is just that we (scientists) couldn’t come up with the appropriate scientific explanations.
How Far Can a Polar Bear See? – Polar Bear Vision
The spherical-shaped polar bear’s eye allows it to visualize things on land but not underwater. In marine mammals the eye lens is usually spherical because it provides a shortest focal length for a given diameter. However in polar bears the lens doesn’t seem to provide any such acute vision underwater. The white bear’s eye possesses a circular pupil.
Polar bears have got the ability to see animals under low-light conditions which helps the bear to hunt at dusk. The iris in the eye is brown and it doesn’t appear to change its color.
Can Polar Bears See Color?
Polar bears are dichromats meaning they are able to match any color they see with a mixture of only two colors. This particular trait is extremely rare in humans. Humans typically possess trichromatic color vision. Polar bears are known to see colors though not in a way humans do. Perhaps thanks to nature that white bear’s eyes are small which makes it less vulnerable to snow blindness. The greater is the eyes the greater is the risk of snow blindness.
Andrew E. Derocher writes in his book, Polar Bears: A Complete Guide to their Biology and Behavior“I was wearing a bright fluorescent orange jacket…..One rainy day when I approached 8-month-old cubs (their mother was drugged), I noted that they were greatly agitated and bolted when I approached. Sensing that something was wrong, I removed my new jacket. I could now approach the cubs.”
Polar bears can see long and short cones. The short-wave cones are thought to be rather susceptible to blue light whereas long cones to yellow light. There is a middle cone that is prone to the green light. Humans possess the middle cone which is what makes them trichromatic. It means that polar bears can’t see green light. However it’s logical to assume that polar bears don’t need to see green light on the icy habitat. Their eyes are equipped with rods which allow them to see things at night. This is a highly useful trait in the long nights of the Arctic.
Although polar bear do not typically rely on their vision they can see reasonably well perhaps not as bad as one might anticipated. How far can a polar bear see? Photo by Eyes On You Safaris.
Why Can’t Polar Bears Go Snow Blind?
The visible portion of the eye is small which is good because there can be 24-hour sunlight with continuous snow blowing in the Arctic Ocean. If humans were to spend that much time on the sea ice they would probably go blind in just few hours.
Snow blindness occurs when the ultraviolet light reflects from the snow to the eye surface causes the latter to burn. No wonder it is highly painful but polar bears are oblivious of it. Scientists have yet to figure out the scientific answer.
Other animals such as Ground Squirrels can also avoid snow blindness but they have yellow pigment in their cornea which prevents the squirrels from ultraviolet reflection. The yellow pigment serves as sunglasses. There is no such pigment in the polar bear’s cornea. Biologists maintain that white bear’s eye must have something that acts as a protector but they don’t know what it is. However there’s one thing they know (for sure) that polar bears do not suffer from snow blindness.
The polar bear claws are not only relatively curved–they are also shorter in length in comparison to the brown bear’s. Brown bears seem to possess the longest and heaviest claws. But polar bear claws supersede black bears in claws’ length and weight. The bear’s claws are not only meant to grip prey properly but can also clamber over snow or rocks. They are black in color and lack pigment just like polar bear hair. Let us learn many more interesting facts about polar bear claws.
Polar Bear Claws – How Long are Polar Bear Claws?
Polar bears’ claws are sharper and longer than that of black bear’s. They have a typical length of about 3.5 inches (9 cm). They are black-brown in color but the tips of the claws display light brown shade. The claws becomes white as the bear grows older. The subadult bears seem to have brown-bronze colored claws. Polar bear claws aren’t only short and curved, they are pretty sharp too. Andrew E. Derocher, one of the leading polar bear scientists, suggests that:
One should bear in mind that the polar bear claws are sharp. More than once I have cut my hand while repositioning the claw.
The claws are so much curvy that their undersides are deeply scooped which is probably an adaptation to dig well on the dense icy surface. Scientists have found that the polar bear right claws are more likely to receive injuries as compared to the left claws. This indicates that ice bears use their right claws and forelimbs more often which in turn makes them right handed animals.
Polar bears have non-retractable claws that is to say that they can neither pull it back nor can they show it when needed. Tigers on the other hand have retractable claws and they only show them during hunting. Thus polar bear claws are more susceptible to injury whereas tiger’s claws are relatively thought to be safer.
They seem to possess smaller claws and larger forepaws. The reason is that polar bears spend a great deal of time in water as they are remarkable swimmers. Polar bear’s forepaws assist them in paddling. It also facilitates the bear in climbing on snow and ice or hauling-out lairs of seals.
Polar bear have long been hunted in Canada, Greenland, and Russia for their claws which are exported to the other parts of the world. However Canadian authorities put on ban on the commercial trading in polar bear’s parts.
Polar bears (Ursus maritmus) are the largest of the land carnivores. They are solitary predators. Unlike most other carnivores (such as wolves) white bears will never hunt in groups. The nomadic polar bear doesn’t seem to rely on one hunting technique. The bear uses unique strategies that take months to learn and which is why adults typically prefer to kill prey as compared to young bears. Young bears will spend their initial two years of training with mother. The mother teaches her kids several techniques as well as how to survive in the natural habitat.
Polar Bear Behavior – Polar Bear Behavior Facts
Feeding Behavior
Polar bears regularly feed on ringed and bearded seal but they also prey on larger prey such as beluga whale and walrus. The last two preys are rare because they are not as nutritious as seals. Seals provide blubber which is quite helpful during dormancy. However if white bears couldn’t find seals they would rely on coastal and terrestrial plants but the change in diet is temporary. Biologists believe that polar bears kill around 44% of seal pups each year. This has been observed in the Prince of Wales Island and Cornwallis Island.
Polar bears have got massive body and they need 2 kg (4.4 lbs) of fat every day. They do so by killing large number of seals in mid-June to mid-August when seals are abundant. Nonetheless, polar bears are able to spend months in starvation—an adaptation quite useful in warmer months when the sea ice melts.
Polar bears reach maturity after 5 – 6 years of age. The female gives birth to 1 – 2 cubs. The small litter size and predation at an early age are reasons for polar bear’s mortality. The female plays a major part in raising cubs. During starvation when the food is scarce the mother will not be able to raise two cubs at a time. It means that she may feed only one cub. It happens when twins are born. The birth usually occurs in November and December. Adult males rarely take part in nursing. The job must be done by a mother alone which is quite tough because alongside feeding she must protect them from adult males.
Photo by Arctic.ru
Non-territorial Carnivorous
White bears are mercurial creatures. They keep moving and they don’t seem to mark territories. This is probably an adaptation to adjust with different environmental stressors. The change in weather leads to a change in bear’s territory.
Bears rely heavily on seals. During summer when the sea ice melts bears could not hunt their primary prey i.e. seals. As it turns out, they must keep moving and make homes where seals are abundant. The movement in polar bears is associated with their survival. The only way to survive is to follow the prey. That is why polar bears do not defend their territories.
Nevertheless polar bears can be highly aggressive. Past incidents show that polar bears do attack humans but that occurs only when they are provoked. Hungry bears are highly dangerous and they may attack humans if they must. Normally white bears will walk away and avoid confrontations.
Vast Home Range
Polar bears possess extremely vast territory. The range is so wide that scientists are unable to measure the extent of its territory. This is one reason why biologists couldn’t come up with reasonable estimates of polar bear population.
The polar bear (Ursus maritimus) doesn’t seem to have any special anatomical adaptations despite the fact that it is the only bear species that spends almost the entire life in water. The large body size of a bear prevents the heat loss—thereby making it warm even in frigid arctic weather.
Polar Bear Anatomy
Musculo-Skeletal System
Reproductive System
Gastro-intestinal System
Circulatory System
Urinary System
Respiratory System
Polar Bear Musculo-Skeletal System
According to The American Society of Mammalogists the polar bear’s neck muscles are extremely strong and powerfully developed. This can be evident from the fact that ice bears can easily pull a 600-pound seal with their neck. Apart from neck muscles the hind limbs are also thought to develop perfectly not only to support the weight (when the bear stands on its hind feet only) but also for gripping on the sea ice.
The study of the American Society of Mammalogists showed that the wild specimen appear to have testes of varied sizes. Polar bear’s testes are of different sizes in different seasons. For instance in May the testes grow up to 39.4 +/- 3.5 cm² whereas in late October the size measured at 27.3 +/- 2.0 cm². The small glandular ampullae lie at the distal ends of vasa deferentia. Polar bears have small prostate gland.
A mother polar bear is nursing her cubs. Polar bear anatomy. Photo by Fine Art America.
How Many Nipples Do Polar Bears have?
The female polar bear possesses four teats or nipples all of which are functional. Four teats make up two pairs; the front pair (anterior) is only moderately posterior to the axillae and measures around 4 cm from the midline on both sides. The other two teats measure up to 15 cm further posterior. The front pair of nipples lies very close to the front legs (only just behind) whereas the second pair lies further to the back.
Functional Mammae
There are typically four functional mammae in other bear species but in female polar bear there can be four or five functional mammae. The one extra gland is situated at the posterior of the usual glands. The gland measures 4 cm from the middle on the back abdomen.
One of the females found by the Society seems to possess two extra teats measuring 15 cm anterior to the vaginal orifice. These two extra nipples are found in inguinal region. Scientists found that none of the two nipples had milk; both were non-functional. The female also possesses os clitoris.
The gastrointestinal system of polar bears behaves quite differently in summer and winter. The system is directly associated with the feeding habits which is why it responds almost immediately to the polar bear’s type of food. When polar bears eat a lot of sea blubber (mostly they do) they appear to discharge dark jellylike faeces in a liquid form. This is mainly because the seal blubber is low in fibre.
Studies further suggest that there is a significant change in the gut transit time. When an ice bear consumes seal muscle the timing is 13.8 +/- 5.4 hours and when she eats sea blubber the gut timing is 38.0 +/- 8.0 hours. Similarly if a bear feeds on fish the timing is 12.3 +/- 1.9 hours.
The polar bear faeces are more large rounded in shape and appear like a small cylinder. The color of the faeces is dark black or brown. The captive bear drops faeces after every 17 – 22 hours especially when it is fed with ringed seal carcass. However when a bear only eats blubber then the transit time increases and it reaches up to 36 hours. The fish-eating polar bear in captivity is likely to discharge faeces in 14 hours.
Polar Bear Circulatory System (Heart Beat Rate)
The average heart beat rate in adult polar bears is 60 to 90 bpm however in cubs the rate reaches high up to 130 beats per minute. The high bpm in cubs is mainly because of their activity level. When the bear relaxes the pulse rate is 45 – 60 bpm. Similarly when the polar bear is asleep the heart rate gets down to 30 – 40 bpm. The pulse rate of a polar bear during running reaches up to 150 beats per minute. However the typical pulse rate in an active bear is around 130 bpm. During winter if the bear starves the rate falls down to 27 bpm.
Polar Bear Urinary System
The polar bear’s kidneys appear to be lobulated in shape. Unlike kidneys of any other carnivore the ice bear kidneys seem to have as many as 65 lobules. This is the greatest number of lobules in any carnivorous mammal.
Polar Bear Respiratory System
Polar bears have a typical respiratory rate of 15 – 30 breaths per minute. However the breath rates go higher in warmer months. When the bear is asleep rates are only 5 breaths per minute. Polar bears are also seen panting and when they do the breath rates are as high as 105 – 133 every minute. Similarly when the bear charges for the prey in short bursts breaths are greater than usual.
Blubber Fat or Obesity in Polar Bears
The subcutaneous fat is the primary cause of obesity in polar bears. Adult bears have a dense layer of subcutaneous fat measuring 5 to 10 cm in thickness. Adult females in particular become obese weeks before they go into their materiality den. Females are thought to possess as much fat as containing 45% of the bear’s weight.
Polar bears have 4-cm-thick blubber layer which is covered with 2-mm-thick muscle sheets. The thickness of polar bear’s torso is about 0.5 to 3.0 mm. The muscle sheets are likely to be based on the broadest muscle of the back latissimus dorsi.
The supply of blood is sufficed to entertain the entire sheets of muscles. Numerous veins and arteries run from the body musculature via intramuscular blubber layer along the way to the latissimus sheets. The polar bear’s veins are 2 – 4 mm in diameter. The gap between the veins measures around 3 – 5 cm. The veins erupt from the dorsal edge of the bear’s muscle and enter the body core.
The polar bear’s limbs seem to have rich supply of blood with blood vessels go side by side—ranging from knees all the way to the ankle. The body or flesh at the top of the rear legs is known as rump. In polar bears there is a thick blubber pad that dominates the rump. The blubber pad measures about 11 mm in thickness.
Polar Bear’s Adipose Tissue
Studies further reveal that the adult polar bears’ (male and female) consist of 18.7 – 17.5% adipose fatty tissue. The content of fats is only slightly higher in captive bears as compared to the wild population. In fact the examination of few specimens reveals that the deposits of fats are almost the same in wild and captive bears. However the quantity of adipose tissue in captive polar bears is significantly greater than that of wild bears. Scientists also found that the number of adipocytes is greater than they expected.
The greater number of fatty deposits clearly reflects on the polar bear’s diet in captivity. Since the wild bears must spend days or even months in fasting the deposit of fats is relatively low. While polar bears are fairly rich in Vitamin A the level of Vitamin D3 in the bear’s blubber is estimated as 406.17 +/- 139 (mean +/- SD). The level of Vitamin D3 is quite high in fact higher than most invertebrate-eating mammals. Nonetheless, it is lower than mammals which feed on vertebrates.
It is quite amazing that polar bears have adapted to the harsh arctic environment where most land mammals could hardly survive one day. Thanks to the physiological, structural, and behavioral adaptations of a polar bear that allow her not only to survive but also to live like many Arctic mammals. These adaptations are likely to arise when animals are forced to live in different habitats. This occurs gradually during which the bear learns to adapt herself with the environment. This is called adaptation.
In order to know these adaptations in detail one must understand how polar bears have evolved to live on the sea ice. While the powerful paddle-like feet provides absolute support to the body weight dense fur, specialized teeth, and sharp nose facilitates the bear in swimming, eating, and smelling respectively. Let us discuss then how do polar bears adapt to the tundra.
How Do Polar Bears Adapt to their Environment?
Scientists believe that polar bears might have evolved from grizzly bears some 70,000 to 100,000 years ago. The white bears have probably adapted their ecological behavior from grizzly bears and both the species appear to have separated in the glacial periods. This explains why Ursus maritmusseem to share quite similar characteristics with Ursus arctos.
The formidable polar bear’s feet are strong enough to support and balance the entire weight of the body on the sea ice. Besides support feet also facilitates the bear in swimming. Adult bears have their feet measuring 30 cm across. The polar bear’s paws are very handy in walking on the snow ice. The dermal pumps on the paws assist the bear to grip.
Unlike brown bears’ polar bears have claws which provide the animal firm grip not only on the ice but also on the prey. The short but powerful claw allows the white bear to hold the prey and the latter finds it impossible to escape. The brown bear’s paw is not that stocky.
Polar bears are one of few animals that can detect smell from kilometers away. It is often said about white bears that they smell you before you see them. They are thought to discover seals from a mile away even when the prey is moving underneath the snow.
While know only little about polar bear’s hearing sense they can probably hear up to 25 kHz. They are known to possess hearing sense as powerful as that of a human. White bears have less sharp hearing as compared to dogs even though the former is able to communicate in low frequencies.
While polar bears have acute sense of smell they do possess pretty good sight. They are able to visualize things and can probably recognize colors.
Sense of touch
Polar bears are often seen touching things with their nose, tongue, and claw. However the statement lacks any scientific explanation whatsoever.
Polar bears are insulated by their dense furry coat. How do polar bears adapt to the Arctic. Photo by childrensmuseumofphoenix.org
Polar Bear Structural Adaptations
Structural adaptations of a polar help her to adapt with different environmental stressors such as the bear white fur which camouflages her in the snow. Structural adaptations also include adaptations as to how a white bear will protect her from the predators.
Fur and Coat
Polar bears possess white coat which goes pale yellow as the bear grows older. In captivity the yellowish coat is rather common and prominent because of the humid conditions. Sometimes the captive bear gives a shade of green color which is probably due to the algae that grows inside polar bear hair. Adult males seem to have longer hairs on their legs. These hairs continue to grow till the age of 14 years. Scientists say that adult males show long hairs to attract females.
The dense layer of the coat not only serves as an insulator but it virtually makes the bear to disappear in the white background. The primary prey seal finds it hard to detect the polar bear and when it does so it’s almost too late.
Polar Bear Behavioral Adaptations
Dormancy
Brown bears hibernate but polar bears do not! White bears become inactive in season as they go into dormancy state. Adult females which are expecting babies usually become dormant. Adult males, though not active, do move around in search of prey. The dormancy state is not a true hibernation. During dormancy the bear lowers her metabolism and rely exclusively on the available fats.
Feeding Behavior
Polar bears predominantly prey on ringed and bearded seals which qualifies them as the most carnivorous bear of all Ursids. They hunt seals mostly underwater and rarely on land.
How Do Polar Bears Adapt to their Environment? – Video
