Polar Bear Morphology

[OldGreenGrolar]

So much for the myth that polar bears jaws are 'weak' 😄. Their jaws might be be 'weaker' than a brown bear in terms of crushing but they can still slice and can cause damage to animals (like belugas and walruses) heavier than themselves too. In my opinion, polar bear's jaws strength are underrated.

[King Kodiak]

Jun 14, 2019 18:53:55 GMT -5 OldGreenGrolar said:

So much for the myth that polar bears jaws are 'weak' 😄. Their jaws might be be 'weaker' than a brown bear in terms of crushing but they can still slice and can cause damage to animals (like belugas and walruses) heavier than themselves too. In my opinion, polar bear's jaws strength are underrated.

I agree with you yeah. Definatly underrated going by the above report. We have seen the pics of the damage their jaws can cause.

[King Kodiak]

POLAR BEARS (URSUS MARITIMUS), THE MOST EVOLUTIONARY ADVANCED HIBERNATORS, AVOID SIGNIFICANT BONE LOSS DURING HIBERNATION


Abstract

Some hibernating animals are known to reduce muscle and bone loss associated with mechanical unloading during prolonged immobilisation,compared to humans. However, here we show that wild pregnant polar bears (Ursus maritimus) are the first known animals to avoid significant bone loss altogether, despite six months of continuous hibernation. Using serum biochemical markers of bone turnover, we showed that concentrations for bone resorption are not significantly increased as a consequence of hibernation in wild polar bears. This is in sharp contrast to previous studies on other hibernating species, where for example, black bears (Ursus americanus), show a 3-4 fold increase in serum bone resorption concentrations posthibernation,and must compensate for this loss through rapid bone recovery on remobilisation, to avoid the risk of fracture. In further contrast to black bears, serum concentrations of bone formation markers were highly significantly increased in pregnant female polar bears compared to non-pregnant,thus non-hibernating females both prior to and after hibernation. However, bone formation concentrations in new mothers were significantly reduced compared to pre-hibernation concentrations. The de-coupling of bone turnover in favour of bone formation prior to hibernation, suggests that wild polar bears may posses a unique physiological mechanism for building bone in protective preparation against expected osteopenia associated with disuse,starvation, and hormonal drives to mobilise calcium for reproduction, during hibernation. Understanding this physiological mechanism could have profound implications for a natural solution for the prevention of osteoporosis in animals subjected to captivity with inadequate space for exercise,humans subjected to prolonged bed rest while recovering from illness, or astronauts exposed to antigravity during spaceflight.© 2008 Elsevier Inc. All rights reserved.

... The bear gets its energy from stored fats, and muscle mass is not lost, but renewed ( Lohuis et al., 2007). The products of catabolism, such as urea, are not excreted but recycled ( Nelson et al., 1975;Floyd et al., 1990; Barboza et al., 1997) and the bone tissue does not suffer losses but is actively remodelling (Donahue et al., 2006;Lennox and Goodship, 2008;McGee et al., 2008), although at a lower rate than during the active season. During hibernation the synthesis of proteins is made from the ni- trogen compounds produced thanks to the recycling of the reab- sorbed urea. ...

... In conclusion, we provide both in vivo and in vitro evidence supporting the expression of circadian rhythms in bears during winter dormancy. These findings, along with earlier work in grizzly bears [64] and polar bears add to the mounting evidence that these closely related species may exhibit an evolutionarily advanced form of torpid biology [65, 66]. ...

www.researchgate.net/publication/5603402_Polar_bears_Ursus_Maritimus_the_most_evolutionary_advanced_hibernators_avoid_significant_bone_loss_during_hibernation/amp

[OldGreenGrolar]

Size
.
The polar bear is the largest land carnivore.

Male polar bears (boars) grow two to three times the size of females (sows). Boars weigh about 350 to more than 650 kg (772-1,433 lb.) and are about 2.5 to 3 m (8.2-9.8 ft.) long.

Sows weigh about 150 to 250 kg (331-551 lb.) and are about 1.8 to 2.5 m (6.0-8.2 ft.) long. Pregnant females can weigh as much as 500 kg (1,102 lb.).

The largest polar bear ever recorded was a male weighing 1,002 kg (2,209 lb.) and measuring 3.7 m (12 ft.) long .



Coloration
.
The coat can vary from pure white to yellow to light brown depending upon season and angle of light.





Limbs
.
The hind limbs are longer than the forelimbs. This makes the large, muscular hind end stand higher than the shoulders.

Feet are five-toed paws.

Polar bears have large paws compared to body size, reaching 30 cm (12 in.) in diameter. The large paws of a polar bear act like snowshoes, spreading out the bear's weight as it moves over ice and snow.

The forepaws are round and partially webbed. The hind paws are elongated.

Each toe has a thick, curved, non-retractile claw. The claws are used for grasping prey and for traction when running or climbing on ice.

The sole of a polar bear's foot has thick, black pads covered with small, soft papillae (dermal bumps). The papillae create friction between the foot and ice to prevent slipping. Long hairs growing between pads and toes also help prevent slipping.



Head
.
A polar bear's head is oblong and relatively small compared to body size. The muzzle is elongated with a "Roman-nosed" (slightly arched) snout.

The nose is broad and black.

Teeth.

Polar bears have 42 teeth, which they use for catching food and for aggressive behavior.

Polar bears use their incisors to shear off pieces of blubber and flesh.

Canine teeth grasp prey and tear tough hides.

Jagged premolars and molars tear and chew.

Polar bears swallow most food in large chunks rather than chewing.

A polar bear's eyes are dark brown, set relatively close together, and face forward.

The ears are small compared to those of other bears - an adaptation that enables them to conserve body heat.





Tail
.
The tail is small, about 7 to 12 cm (2.8-4.7 in.) long.





Hair
.
Polar bears are completely furred except for the nose and footpads.

A polar bear's coat is about 2.5 to 5 cm (1-2 in.) thick. A dense, woolly, insulating layer of underhair is covered by a relatively thin layer of stiff, shiny, hollow guard hairs. Guard hairs may be as long as 15 cm (6 in.).

Though really translucent, the hairs appear white because of their highly reflective quality. Oxidation from the sun, or staining, can make the hairs look yellow or brown.

Polar bear fur is oily and water repellent. The hairs don't mat when wet, allowing the polar bears to easily shake free of water and any ice that may form after swimming. Ice forms when the wet fur is exposed to air temperatures at or below freezing.

Polar bears completely molt (shed and replace their fur) annually, in May or June. The molt can last several weeks.



Skin
.
A polar bear's skin, visible only on the nose and footpads, is black. The black color enables the bear to absorb sunlight energy to warm its body.


seaworld.org/animals/all-about/polar-bear/characteristics/

[OldGreenGrolar]

Polar bears could hold key to osteoporosis cure, study says.

RESEARCH CARRIED out by an Irish scientist into polar bears may have “profound implications” for the treatment of osteoporosis…

RESEARCH CARRIED out by an Irish scientist into polar bears may have “profound implications” for the treatment of osteoporosis, it has been claimed.


The research has found that female polar bears, do not lose any significant bone mass despite hibernating for six months.


From October to March pregnant female polar bears do not eat or drink, yet in the same period they go through pregnancy and birth, and feed their cubs, emerging from hibernation in a state of semi-starvation.


Despite having their calcium levels severely depleted by nursing, they emerge from their dens with normal levels of bone mass.


The findings, by Alanda Lennox, a TCD graduate and zoologist at University College London, and orthopaedic specialist Allen Goodship have been published in the science journal Comparative Biochemistry and Physiology.


Bone packing during long periods of inactivity is the opposite of what happens in other mammals. Even the brown bear are highly susceptible to fractures on emerging from hibernation, while humans, who have been bedridden for a long period , are at risk of fractures and permanent weakening of the bone structure.


A total of 21 pregnant female polar bears were monitored in the Hudson Bay area of northern Canada from early autumn to spring when they usually hibernate. Blood samples from two biochemical markers for bone formation showed that female polar bears build up their bones before entering hibernation.


Having established that polar bears have an extraordinary physiological mechanism for preserving bone structure, Ms Lennox said they intended to publish further research on why this is the case. Explaining why polar bears appear to defy nature while in hibernation could lead to breakthroughs in research for treating osteoporosis in humans either through drugs or dietary intake.


It could also help bone loss in animals subjected to captivity and even astronauts subject to anti-gravity during space light. Bone mass loss in low gravity is seen as one of the main impediments to long-distance space missions.


“It is quite an investment on their part for them [polar bears] to go physiologically through this whole six-month process of starvation and inactivity, predisposing themselves to the potential of fracture on emergence, yet we have just shown that they don’t do that,” said Lennox.


Women are four times more likely to get osteoporosis, mostly as a result of hormonal changes after the menopause. The scientists involved in research on polar bears believe hormonal changes associated with pregnancy are the reasons why the animals are so efficient at maintaining bone mass levels.


“This is at the concept stage. We are hoping to get to the stage where we can say it definitely has implications for use as a natural model to show that osteoporosis can be prevented,” she said.


The theory the scientists are working on is that hormonal changes when polar bears become pregnant causes them to produce an excess of bone mass before they enter the den. So, they can afford to lose bone mass and still show normal levels when they emerge from hibernation.


“If we can figure out the specifics of a physiological mechanism for doing this, then perhaps we could use a similar mechanism as a method of preventing the huge bone loss seen in immobilised humans as a consequence of a stroke or spinal injury,” Lennox said.

www.irishtimes.com/news/health/polar-bears-could-hold-key-to-osteoporosis-cure-study-says-1.1266118?mode=amp

[OldGreenGrolar]

Persistent pollutants push polar bear penises to breaking point.

Bear penile bone study found higher risk of brittleness linked to ingestion of toxic chemicals


Male polar bears don’t have it easy. The Arctic ice shelf is vanishing and food is growing scarce. But now scientists are worried that exposure to toxic chemicals is causing osteoporosis in polar bears – which could result in their fragile penis bones snapping, making mating impossible.

Danish scientists have found that those polar bears exposed to the highest levels of persistent organic pollutants – including the pesticide DDT, fungicides and solvents – are more likely to have a condition called osteopenia, a precondition for osteoporosis. Bone strength decreases with age, so the researchers studied the penis bones of 349 polar bears in their prime – between three and nine years old.

The researchers obtained the bones from bears that were legally killed in Inuit subsistence hunts between 1996 and 2015. Where available, they also looked at tissue samples from the dead bears to determine their exposure to pollutants.

By combining this data with measurements of persistent organic pollutants in different Arctic environments, the researchers found that bears living in East Greenland, the most polluted region of the Arctic, had an inflated risk of brittle bones. These bears had an average t-score, used as a measure of bone mineral density, of -1.44. Anything below -1 is defined as osteopenia.

‘This indicates that some bear populations are not just threatened by climate change but also are at risk because of pollution,’ says Christian Sonne, a veterinarian at the Arctic Research Centre at Aarhus University and co-author of the study. ‘It is affecting their sexual organs and maybe even their reproductive capacity.’

Polar bears only mate once a year, with the male often tracking the female for more than 100km and engaging in bloody battles with other males. The penis bone gives the male extra staying power for the ensuing week of frequent, frantic mating. But with osteopenia on the rise, Sonne fears these bones could break under the pressure, making male polar bears infertile.

Whether persistent organic pollutants are the primary cause for brittle bones is not yet understood, but the researchers found a clear correlation between exposure to pollutants and osteopenia in polar bears. Persistent organic pollutants are carried to the Arctic by precipitation, ocean currents and animals that eat polluted food in warmer climates.

Due to a lack of other food, the East Greenland bears have recently started to eat harp and hooded seals, two species that have high levels of these pollutants.

‘These persistent pollutants don’t break down and therefore accumulate at progressively higher levels at each [food chain] stage,’ says Jean-Pierre Desforges, an Arctic researcher also at Aarhus University, who was not involved in this study. ‘Since polar bears feed on other top predators, this makes them most susceptible to toxic accumulation.’


References

T Daugaard-Petersen et al, Environ. Int., 2018, 114, 212 (DOI: 10.1016/j.envint.2018.02.022)

www.chemistryworld.com/news/persistent-pollutants-push-polar-bear-penises-to-breaking-point/3008799.article

Looks like only pollution affects polar bear bone density.

[King Kodiak]

Reply # 40....damn thats not good news. That is why i hate industries that pollute everything and contribute to global warming. They are killing the polar bears in every way possible.

[OldGreenGrolar]

Jan 2, 2020 17:18:59 GMT -5 King Kodiak said:

Reply # 40....damn thats not good news. That is why i hate industries that pollute everything and contribute to global warming. They are killing the polar bears in every way possible.

True. Nothing reduces the polar bear bone density except pollution . Once again, it is man's fault.

[OldGreenGrolar]

Credited to Verdugo.
theworldofanimals.proboards.com/post/53612/

[OldGreenGrolar]

Weight of a female plolar bear:

Once again, the polar bears at Nanuk Polar Bear Lodge have us wondering what they are doing and thinking. We had a big female, probably pushing 1,000 pounds, around for a couple of weeks. She was a Churchill bear with two ear tags, and only the fourth tagged bear we have ever seen at Nanuk over the years.

www.churchillwild.com/big-female-polar-bear-den-hunting-at-nanuk-polar-bear-lodge/

[King Kodiak]

Jan 3, 2020 20:41:59 GMT -5 OldGreenGrolar said:

Weight of a female plolar bear:

Once again, the polar bears at Nanuk Polar Bear Lodge have us wondering what they are doing and thinking. We had a big female, probably pushing 1,000 pounds, around for a couple of weeks. She was a Churchill bear with two ear tags, and only the fourth tagged bear we have ever seen at Nanuk over the years.

www.churchillwild.com/big-female-polar-bear-den-hunting-at-nanuk-polar-bear-lodge/

Great find there. An 1000 lb female polar bear, that is the largest female polar bear i ever heard of.

[OldGreenGrolar]

A female polar bear which weighs 1000 pounds is usually pregnant but again there is nowhere that indicates the polar bear sow is pregnant.

[OldGreenGrolar]

BIG FEMALE POLAR BEAR DEN HUNTING AT NANUK POLAR BEAR LODGE?

Once again, the polar bears at Nanuk Polar Bear Lodge have us wondering what they are doing and thinking. We had a big female, probably pushing 1,000 pounds, around for a couple of weeks. She was a Churchill bear with two ear tags, and only the fourth tagged bear we have ever seen at Nanuk over the years.

She didn’t really do much but lay around, although she did have an excuse. She had joined in with a few other bears a few days earlier and eaten approximately 200 pounds of a seal that one of them had managed to drag up on to a sandbar. I think I wrote about her earlier, regarding the trouble she was having traveling in the heated days, with all the fat she was carrying.

Recently we had a couple of occasions where we found her walking up the Opoyastin River. It appeared that she was fishing, but we were not lucky enough to see her catch anything. She would walk slowly upstream with her entire face in the water weaving back and forth looking for something under the water. About a week ago she moved on and we have not seen her since. The odd thing is that we have not found her down the coastline either to the east or the west.

Last night during Andy’s (Polar Bear Guide Andy MacPherson) presentation a thought came to me. What if she was wandering up the river looking for an earthen den? We always talk about the animals following the path of least resistance, so why wouldn’t a polar bear walk right up the river instead of through the willows and moose trails. She could walk in the shallows effortlessly and swim through the deep holes where needed. This would also help keep her cool for the long trek of up to 100 km, until she found a suitable denning site in the deep insulated peat.

This is a little early if we go with the late September/October thoughts that the scientists have, but we have a very fat and healthy female who is in her prime and likely pregnant, so why would she stick around the coast with other bears.

It’s quite exciting to think we may have actually seen a female on her way to the denning area, but nearly impossible to prove. We’re hoping to see her again in the spring during our cub emergence program, when we watch for moms and cubs moving from their dens and out to the ice to hunt.

Only time, and a little bit of luck, will tell!



www.churchillwild.com/big-female-polar-bear-den-hunting-at-nanuk-polar-bear-lodge/

Here is the whole article.

[OldGreenGrolar]

Once again, the account below shows polar bears are not true white bears:

We all know that this creature found in the coldest place part of the earth. They seems like cute but they are meat eaters.They can harm people and they eat fish too. What we saw on pictures and television are all true except their colors. There original color is yellow. They just turn into white because of the cold temperature that make there body white.


www.google.com.au/amp/s/almiraamoy.wordpress.com/2011/11/22/the-true-color-is-yellow/amp/

[tom]

Jan 4, 2020 5:47:05 GMT -5 OldGreenGrolar said:

BIG FEMALE POLAR BEAR DEN HUNTING AT NANUK POLAR BEAR LODGE?

Once again, the polar bears at Nanuk Polar Bear Lodge have us wondering what they are doing and thinking. We had a big female, probably pushing 1,000 pounds, around for a couple of weeks. She was a Churchill bear with two ear tags, and only the fourth tagged bear we have ever seen at Nanuk over the years.

She didn’t really do much but lay around, although she did have an excuse. She had joined in with a few other bears a few days earlier and eaten approximately 200 pounds of a seal that one of them had managed to drag up on to a sandbar. I think I wrote about her earlier, regarding the trouble she was having traveling in the heated days, with all the fat she was carrying.

Recently we had a couple of occasions where we found her walking up the Opoyastin River. It appeared that she was fishing, but we were not lucky enough to see her catch anything. She would walk slowly upstream with her entire face in the water weaving back and forth looking for something under the water. About a week ago she moved on and we have not seen her since. The odd thing is that we have not found her down the coastline either to the east or the west.

Last night during Andy’s (Polar Bear Guide Andy MacPherson) presentation a thought came to me. What if she was wandering up the river looking for an earthen den? We always talk about the animals following the path of least resistance, so why wouldn’t a polar bear walk right up the river instead of through the willows and moose trails. She could walk in the shallows effortlessly and swim through the deep holes where needed. This would also help keep her cool for the long trek of up to 100 km, until she found a suitable denning site in the deep insulated peat.

This is a little early if we go with the late September/October thoughts that the scientists have, but we have a very fat and healthy female who is in her prime and likely pregnant, so why would she stick around the coast with other bears.

It’s quite exciting to think we may have actually seen a female on her way to the denning area, but nearly impossible to prove. We’re hoping to see her again in the spring during our cub emergence program, when we watch for moms and cubs moving from their dens and out to the ice to hunt.

Only time, and a little bit of luck, will tell!



www.churchillwild.com/big-female-polar-bear-den-hunting-at-nanuk-polar-bear-lodge/

Here is the whole article.

Picture is from the article. 1000 lb female Polar, she's HUGE !!

[OldGreenGrolar]

Male Polar Bears Have Longer Hairs on Their Front Legs for Mating.

One of the surprising polar bear facts is that polar bear fur is not completely white! There is a thick layer of hair close to the polar bear’s skin that is the best pair of thermal underwear nature could provide!

Polar bears have an outer layer of fur made up of guard hairs. These guard hairs are actually hollow and transparent. As polar bears get older, their coats often yellow. Enjoy that new white suit while it’s fresh!

Another one of the interesting polar bear facts about fur is that male polar bears have longer hairs on their front legs. It’s speculated that these hairs are an important part of the mating process and are used to attract female polar bears.

interesting-facts.com/polar-bear-facts/#male-polar-bears-have-longer-hairs-on-their-front-legs-for-mating

[OldGreenGrolar]

If the polar bear could adapt to warmer temperatures, it could be called the green bear 😉.

[King Kodiak]

Guard hairs on the polar bear prevent heat loss by absorbing heat in the form of infrared radiation.




asknature.org/strategy/fur-absorbs-infrared-radiation-to-prevent-heat-loss/

[OldGreenGrolar]

May 11, 2020 9:10:16 GMT -5 King Kodiak said:

Guard hairs on the polar bear prevent heat loss by absorbing heat in the form of infrared radiation.




asknature.org/strategy/fur-absorbs-infrared-radiation-to-prevent-heat-loss/

That is one reason why they overheat quickly especially outside their natural environment. 
It’s not that they lack stamina. I personally believe that if polar bears did not overheat, they would have just as much stamina as the brown bears.

[Polar]

Polar bears are known to swim for hundreds of miles at a time in their natural conditions, I would argue more muscular endurance than most other bears due to their constant walking and swimming. Probably more instantaneous power as well due to their "catch the seal before it swims again" lifestyle.