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Post by oldindigosilverback on Jul 10, 2021 6:57:11 GMT -5
polarbearfacts.net/polar-bear-skull/
Polar Bear Skull – Skull Information and Facts
Polar bears (Ursus maritimus) are the most powerful terrestrial carnivores in the Arctic Ocean. In this article we are going to tell you interesting facts about polar bear skull and how it is different from other bears. They will share many morphological features with other strongest carnivores. Carnivorous animals have certain physiological features in common such as jaw, teeth, claw, eyes, and skull. Archaeologists and scientists have long researched the skull of Ursids let alone polar bears. In northern Alaska archaeologists discovered the king polar bear skull following the 2014 storm. The skull tells us about 1,300 years old ecological behavior.
The polar bear’s skull is a typical of any other land carnivores. Bears unlike other carnivores have relatively deep and flattened mandibular fossa. The mandibular fossa is called jaw hinge. Polar bear’s jaw can hardly move sideways though it opens up and down quite freely. The jaw hinge resembles dog’s mandibular fossa.
Definition of Skull
The skull is often defined when describing the entire skeleton of the head. Sometimes only cranium comes under the definition of a skull. The cranium is a part that encloses brain, sensory organs, and head. The primary characteristics of an animal are often defined in respect to the primary characteristics of a skull.
Polar Bear versus Brown Bear’s Skull
As compared to the brown bear’s the polar bear’s skull appears to be longer and elongated. They also possess longer nose than brown bears. The principle characteristics of a skull are same in all bears with only few differences. Here we are going to discuss polar bear’s skull and compare it with brown bears’.
Polar bears have one of the largest skulls in the bear’s family—second only to brown bear’s skull. Viewing it laterally the brown bear’s skull seems like little wider whereas white bears have narrower skull across the palate. This is primarily because condylobasal length to zygomatic width ratio is greater in white bears.
The length-width ratio finally makes the skull narrower. The length-to-width ratio in brown bears is 1.59 whereas in polar bears the ratio is 1.63. It appears as if ratio calculations do not reflect as much the actual difference of the skull because in reality the difference should be more than it suggests. Calculations aren’t wrong but our perception may be! The reason behind the different visual impression is that brown bears have skull little taller as well as there is an overhanging occiput. Furthermore, there is no brow ridge in the brown bear’s skull the absence of which makes the skull rather curvy from canines to the cranium (brain, sensory organs, and upper jaw).
King Polar Bear Skull discovered in Alaska
Archaeologists recently discovered the king polar skull in the northern Alaska. Scientists believe that the skull is one of the largest ever recorded in polar bears which is why they call it a king polar bear skull. The 16-inch-long skull is thought to be 1,300 years old. Besides, archaeologists also say that the discovery of skull might give us hints about indigenous people who lived alongside the mammoth predator.
The king polar bear skull is likely to take us back in time predating 4,000 years old. Studies indicate that the skull is of an adult polar bear. The forward facing eyes resemble much to the modern bears but it is different from the modern bears. “We don’t know the exact size (of the entire animal), but we do know it was a huge bear,” Jensen, an Utqiaǵvik-based archaeologist, described.
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Post by oldindigosilverback on Jul 10, 2021 7:03:09 GMT -5
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Post by oldindigosilverback on Jul 10, 2021 7:03:32 GMT -5
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Post by oldindigosilverback on Jul 10, 2021 7:04:06 GMT -5
The size of polar bears in captivity: Unlike the brown bear, polar bears in captivity are rarely overweight or particularly large, possibly as a reaction to the warm conditions of most zoos. www.projectnoah.org/spottings/11801217Captive polar bears. In an ideal world there would be no polar bears in zoos, for if ever there is an animal that doesn’t belong in a zoo it’s the polar bear.These Arctic giants have huge ranges in the wild, traveling many of hundreds of miles in their search for food. They have evolved over millennia to exist and thrive in the harsh environment of the Arctic. It is our belief, based on considered scientific evidence, that polar bears are a species that should never be bred in captivity, nor should they be actively sourced for captivity from the wild. However, even if this ideal state were to be achieved, there would still be problems and issues around what to do with cubs found orphaned in the wild and “problem bears” captured in populated areas. Sadly, most captive polar bears are kept in facilities, and often in climates, which are totally unsuitable. Only a very few facilities provide sufficient space for the bears to live anything approaching a contended and fulfilling life. So it is not surprising that many captive polar bears manifest symptoms of extreme stress, such as continually shaking their heads, pacing up and down their enclosures or swimming in a stereotypical fashion. Captive polar bears, along with orcas and other cetaceans, suffer from more sickness and psychologically related illness than any other animals kept in captivity.We are compiling a comprehensive directory of all the polar bears currently kept in captivity and of the facilities where they are kept. If you would like to help with this work then please get in touch. We have three main goals: An end to all captive polar bear breeding programmes. Many of the cubs born in captivity die within a few years, or even months, of birth. Breeding polar bears in captivity can never “save the bears” from extinction, nor repopulate the wild. No captive-born polar bear has ever been successfully released into the wild; indeed to do so would be contrary to IUCN regulations.The upgrading and improvement of substandard facilities holding captive polar bears to provide modern, state of the art “off exhibit” and “on exhibit” areas that meet the highest possible standards for housing, enrichment, general welfare and veterinary services. Air conditioning, water features and a total area of at least 8,000 square metres (2 acres) per animal are, we believe, the minimum essential for high welfare standards to be maintained. Where the above cannot be achieved facilities must be closed, with the polar bears transferred to modern, high standard facilities in sanctuaries or zoos. www.bearconservation.org.uk/polar-bears-in-zoos/
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Post by Gorilla king on Jul 10, 2021 9:17:50 GMT -5
Polar Bear Fur Isn’t (Technically) White – It’s Translucent!
If you were asked, “what color is polar bear fur?” the obvious answer is “white.” It certainly looks white and yes, for all intents and purposes, polar bear fur is white. But perhaps you’ve noticed that sometimes a polar bear looks yellow, gray, or even green. Why is that? Do some polar bears have different color coats? Does the coat color of a polar bear change with the environment? Do polar bears just need better shampoo? Before we get to the bottom of why polar bears appear to have such a range of colors, it’s important to know a key fact about polar bear fur. Polar bear fur isn’t technically white…it’s translucent. That’s right, a polar bear’s outer coat consists of guard hairs that are actually devoid of pigment and are essentially “clear” hollow tubes. Curious polar bears approach a camera in the water near an iceberg in Alaska. " data-medium-file="https://i0.wp.com/commonnaturalist.com/wp-content/uploads/2014/02/bernardspitpolarbear_en-ca11853608857_1366x768.jpg?fit=300%2C169&ssl=1" data-large-file="https://i0.wp.com/commonnaturalist.com/wp-content/uploads/2014/02/bernardspitpolarbear_en-ca11853608857_1366x768.jpg?fit=780%2C439&ssl=1" loading="eager" src="https://i0.wp.com/commonnaturalist.com/wp-content/uploads/2014/02/bernardspitpolarbear_en-ca11853608857_1366x768.jpg?resize=780%2C438&ssl=1" alt="Curious polar bears at Bernard Spit in Alaska swimming and approaching a camera." class="wp-image-763 jetpack-lazy-image jetpack-lazy-image--handled" width="780" height="438" title="Curious polar bears at Bernard Spit, AK" data-recalc-dims="1" data-lazy-loaded="1" style="box-sizing: border-box; border-width: 0px; border-style: solid; border-color: currentcolor; --tw-shadow:0 0 #0000; --tw-ring-color:rgba(59, 130, 246, 0.5); --tw-ring-inset:var(--tw-empty, ); --tw-ring-offset-color:#fff; --tw-ring-offset-shadow:0 0 #0000; --tw-ring-offset-width:0px; --tw-ring-shadow:0 0 #0000; display: inline-block; vertical-align: middle; height: auto; max-width: 100%; border-radius: inherit;">Curious polar bears at Bernard Spit, AK. Image: Steven Kazlowski/ Barcroft Media Now I’m sure you want to know how it is that a polar appears white (and yellow, green, etc.) with all that translucent fur, so let’s talk about the structure of that fur. The Structure of Polar Bear Fur Mammalian hair is composed of keratin which is typically organized into three layers. The cuticle is the outermost layer and is comprised of a very thin, translucent layer of overlapping “scales.” Below the cuticle is the cortex which consisted of long, spindle-shaped cells and may contain pigment granules (in the case of colored hair) along with corticle fusi (which are essentially air spaces). Lastly, in certain hairs of some animals, an additional layer known as the medulla is present. The medulla is essentially a structured, air-filled core that is quite well-expressed in many arctic animals such as polar bears. In the case of polar bears, the guard hairs consist of a thin cuticle encasing a well-developed cortex and a wide medulla. The cortex in these hairs is devoid of pigment and the medulla is essentially a wide airspace. Light hitting this fur is subsequently scattered in all directions giving the appearance of a white bear. So, when you see a polar bear and perceive it as a big, cuddly mass of white fluff, you’re eyes are actually interpreting the scattering of all wavelengths of visible light rather than a color produced by pigments. commonnaturalist.com/2014/02/10/polar-bear-fur-isnt-technically-white-its-translucent/
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Post by tyrannosaurs on Jul 10, 2021 10:46:42 GMT -5
Radiative Properties of Polar Bear Hair: The polar bear’s ability to survive in the harsh arctic night fascinates scientific and lay audiences alike, giving rise to anecdotal and semi-factual stories on the radiative properties of the bear’s fur which permeate the popular literature, television programs, and textbooks [1–5]. One of the most interesting radiative properties of polar bear fur is that it is invisible in the infrared region. Some theories have attempted to explain this by claiming that the outer temperature of the fur is the same as that of the environment. However, this explanation is unsatisfactory because surface radiation depends on both the surface temperature and the surface radiative properties [6 www.researchgate.net/publication/228489376_Radiative_Properties_of_Polar_Bear_Hair
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Post by tyrannosaurs on Jul 10, 2021 10:53:29 GMT -5
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Post by tyrannosaurs on Jul 10, 2021 10:54:20 GMT -5
"Polar Bears have two types of fur. They have thick, woolly fur close to the skin that keeps them warm. They also have hollow guard hairs that stick up and protect the bears from getting wet. These guard hairs are like drinking straws and are clear-colored (not white). The white-looking coat camouflages them well in the snow and ice. Under the fur, Polar Bears have black skin. They also have a thick layer of fat (up to 4 inches thick) under the skin that helps keep them warm." www.enchantedlearning.com/subjects/mammals/bear/Polarbearcoloring.shtml
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Post by tyrannosaurs on Jul 10, 2021 10:56:43 GMT -5
Polarbears are also called white bears because of thewhite appearance of their fur, but polar bear's hair is not white, free of pigment with a transparent, hollow corethat scatters and reflects visible light. Some indi-viduals may appear yellow or even light browndue to oils in their fur from prey they consume.The skin of polar bears is black. Source: www.researchgate.net/publication/338410206_Bear_Morphology
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Post by tyrannosaurs on Jul 10, 2021 11:01:25 GMT -5
Internal anatomy of the polar bear: www.google.com/amp/s/polarbearfacts.net/polar-bear-anatomy-internal-anatomy/%3fampAnimal physiology. Summer declines in activity and body temperature offer polar bears limited energy savings: Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of "ice" bears in summer is unknown, "shore" bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation. Copyright © 2015, American Association for the Advancement of Science. www.researchgate.net/publication/280117539_Animal_physiology_Summer_declines_in_activity_and_body_temperature_offer_polar_bears_limited_energy_savingsBehavioural and autonomic thermoregulation in Malayan sun bears (Helarctos malayanus) and polar bears (Ursus maritimus): www.researchgate.net/publication/340429173_Behavioural_and_autonomic_thermoregulation_in_Malayan_sun_bears_Helarctos_malayanus_and_polar_bears_Ursus_maritimus
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Post by tyrannosaurs on Jul 10, 2021 11:01:51 GMT -5
That's it, these are all the sources I saved about this topic...
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Post by tyrannosaurs on Jul 10, 2021 11:09:37 GMT -5
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Post by tyrannosaurs on Jul 10, 2021 11:12:44 GMT -5
Polar bear teeth: www.google.com/amp/s/polarbearfacts.net/do-polar-bears-have-sharp-teeth/%3famp"Scientists weren’t able to explain history of polar bear’s teeth until in 2004 when they discovered 130,000 – 110,000-year-old polar bear jaw bone. This was the oldest jaw bone and its discovery answered many questions and solved numerous puzzles on the skull anatomy of a polar bear. The fossil was found on Prince Charles Foreland. Fossil studies suggest that the polar bear’s molar teeth transformed into a new form around 10,000 – 20,000 years ago and the shape was entirely different from those of brown bear’s teeth. Before that time polar bears and brown bears shared similar teeth characteristics. The arctic bears separated from their brown cousins during the Pleistocene period probably in the eastern Siberia. Polar Bears possess typical carnivorous heterodont dentition. Heterodont dentition explains much about the polar bear’s feeding behavior. It is an anatomical explanation of teeth which means that the animal possess more than one tooth morphology. They have teeth of different lengths and shapes. Perhaps you’d love all these interesting polar bear teeth facts. Polar Bear Teeth – Do Polar Bears have Sharp Teeth? The polar bear’s teeth are classified into three categories namely; incisors, canines, and cheek teeth (molars and premolars). While larger teeth such as incisors and canines are fixed rostrally the molars and premolars are set caudally inside the mouth. There is a long gap between the functional canine and molariform teeth. Inside the gap lie the first premolars which are vestigial. Thanks to this big gap that allows the bear to pierce into the thick bodies of seals and more importantly without facing any interference from the cheek teeth. Unlike in brown bears the cheek teeth in polar bears are significantly reduced in size and also the carnassials are more pronounced in white bears than in brown bears. These carnassials truly reflect the predatory lifestyle of an arctic bear. Their teeth are perfect to grab the prey and tear it apart. Brown bear’s teeth are well adapted to grinding grasses whereas polar bear’s teeth definitely serve no such purpose. While male polar bears possess larger and heavier canines than those of females the molar arcade is same in both sexes. The ratio of condylobasal length to zygomatic width (L/W) is 1.59 in brown bears but in polar bears the ratio is 1.63. If we look at the canines the difference appears to be greater than the actual measurements. The incisors are attached to the premaxillary bone. The premaxillary bone is attached to the upper jaw of an animal bearing teeth. However canines lie in the maxilla which is quite adjacent to premaxilla. While molar teeth are flat and are mainly used in chewing, the canines, premolars, and incisors are primary or deciduous teeth. The molars grow from maxillae whereas the premolars sprout from the maxillary bones. Polar bears’ teeth serve different functions and none of them resembles the other. This can truly be troublesome provided the bear loses tooth in fight. If one of the teeth is broken then it probably affects the dietary habits of a polar bear. Polar bear’s primary teeth appear to replace vertically and once in a lifetime. This means that if a polar bear loses her deciduous teeth the second time then it must learn to live without deciduous teeth." "Functions of Polar Bear Teeth Incisors are primarily used either for slicing or for chipping food. The bear can also use (pointed) incisors for cutting thick skin of a seal. The cheek teeth are equally effective in that they help they facilitate in crushing and grinding the food before the molars chew it. Several characteristic features of a skull make up the carnivoran adaptation of a polar bear. The powerful temporal muscles and fossae are used to rip the flesh and also for killing the prey. These muscles also play a part when the bear holds the prey temporarily. Polar bear however cannot divide the flesh inside her mouth with these muscles. The temporal muscles are only used to tear prey. The polar bear’s jaw movement has a limited horizontal motion in fact they are not able to move the upper and lower jaws on sideways. They can have a smooth vertical movement though. Polar bears have shallow mandibular fossae which resembles like that of a dog. They are thought to possess much pronounced dentary as compared to other marine mammals." How do polar bears eat food? "Polar bears are more likely to swallow food than they chew. The jaw muscles act in coordination with each other to pass the food via oral cavity through the larynx. The bones of the head likely facilitate in swallowing process. The hyoid apparatus which holds the larynx in place supports the tongue is extremely significant while swallowing and feeding. Muscles that will move the hyoid apparatus up and down occur in between basihyal and tongue. How Many Teeth Does a Polar Bear have? Polar bears are arguably the most carnivorans in the bear family. The only characteristic adaptation that makes icy bears the most carnivorous is their sharp teeth. The polar bear has 42 teeth in total with the cheek teeth appear to be more pointed than in the brown bears. Besides the bear’s canines are not only sharper but also greater in size than in brown bears. These large canines describe the exclusive meat-eating ability of a bear more than any other teeth. Polar bears have dental formula of 3.1.4.23.1.4.3 which they share with all other Ursids." The video:
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Post by tyrannosaurs on Jul 10, 2021 12:59:05 GMT -5
A body composition model to estimate mammalian energy stores and metabolic rates from body mass and body length, with application to polar bears: Many species experience large fluctuations in food availability and depend on energy from fat and protein stores for survival, reproduction and growth. Body condition and, more specifically, energy stores thus constitute key variables in the life history of many species. Several indices exist to quantify body condition but none can provide the amount of stored energy. To estimate energy stores in mammals, we propose a body composition model that differentiates between structure and storage of an animal. We develop and parameterize the model specifically for polar bears (Ursus maritimus Phipps) but all concepts are general and the model could be easily adapted to other mammals. The model provides predictive equations to estimate structural mass, storage mass and storage energy from an appropriately chosen measure of body length and total body mass. The model also provides a means to estimate basal metabolic rates from body length and consecutive measurements of total body mass. Model estimates of body composition, structural mass, storage mass and energy density of 970 polar bears from Hudson Bay were consistent with the life history and physiology of polar bears. Metabolic rate estimates of fasting adult males derived from the body composition model corresponded closely to theoretically expected and experimentally measured metabolic rates. Our method is simple, non-invasive and provides considerably more information on the energetic status of individuals than currently available methods. "We estimated that 31% of the mass of storage is composed of muscles while 44% of the mass of structure is composed of muscle. Given the added pressure climate change has imposed on polar bear energy acquisition and use, our estimates highlight the role of muscles in long-term energy stores." Source: www.researchgate.net/publication/26681193_A_body_composition_model_to_estimate_mammalian_energy_stores_and_metabolic_rates_from_body_mass_and_body_length_with_application_to_polar_bears"Percentage of published polar bear toxicology research papers (n = 180) in relation to type of tissue(s) analyzed. As more than one tissue type may have been analyzed in a single paper, the combined percentages of all tissue types exceed 100%." Source: www.researchgate.net/publication/318200832_On_the_integration_of_ecological_and_physiological_variables_in_polar_bear_toxicology_research_A_systematic_reviewAge structure: www.researchgate.net/figure/Age-structure-of-independent-3-yr-polar-bears-captured-in-the-1970s-and-2000s-in-Davis_fig2_242650902Source: www.researchgate.net/publication/242650902_Population_ecology_of_polar_bears_in_Davis_Strait_Canada_and_Greenland
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Post by tyrannosaurs on Jul 10, 2021 13:03:36 GMT -5
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Post by tyrannosaurs on Jul 10, 2021 13:23:04 GMT -5
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Post by tyrannosaurs on Jul 10, 2021 13:46:47 GMT -5
Quantitative Support for a Subjective Fatness Index for Immobilized Polar Bears: www.researchgate.net/publication/227782664_Quantitative_Support_for_a_Subjective_Fatness_Index_for_Immobilized_Polar_BearsAdequate stores of body fat are essential for survival and reproduction of polar bears (Ursus maritimus). However, polar bear body fat levels can be difficult to quantify in the field. For >30 years, biologists have subjectively estimated relative fatness of immobilized polar bears by assigning individuals a rating from 1 to 5, with 1 being leanest and 5 most obese. Although previous studies suggested this fatness index (FI) rating accurately reflects large-scale differences in body condition, its relationship to more quantitative measures of condition has not been explored. We compared the FI rating of individual polar bears in western Hudson Bay and the Beaufort Sea to 2 quantitative measures of body condition: the Quetelet Index (ratio of mass to length2) and the relative lipid content of adipose tissue. We found a significant relationship between FI rating and both Quetelet Index values and adipose lipid content. Our data demonstrate that the FI rating accurately reflects overall body condition, regardless of polar bear age, sex, or nutritional phase. We suggest that continued field use of the FI rating could provide valuable information on ecological effects of large-scale environmental change on polar bear populations. landscapesandcycles.net/blind-polar-bear-researchers.html
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Post by Gorilla king on Jul 14, 2021 13:47:00 GMT -5
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Post by Gorilla king on Jul 14, 2021 14:05:44 GMT -5
This chart is from reply #16, very good study there tyrannosaurs :
This is the Fatness index (FI) rating of polar bears from Western Hudson Bay handled from 1980-2006. The ratings are from 1 to 5, with 1 being leanest and 5 most obese.
Most have ratings 2, 3, and 4, very few bears had a rating of 5. Take a look at the adult males in Autumn, out of 1125 specimens, only 9 had a rating of 5, and 733 (most of that sample) had a rating of 3 which is the best rating.
As we can see by the total, most bears had a rating of 3, which means:
3-Bear has healthy appearance, vertebral processes or hip bones not visible but upper third to half of the spinal column can be felt under the skin, detectable layer of fat between skin and muscle over rear half of body, thickening slightly but detectably over lower rump.
RESULTS
Among all 5,496 polar bears handled in WH between 1980 and 2006, we assigned 6.4% an FI rating of 1, 24.3% a rating of 2, 57.5% a rating of 3, 10.2% a rating of 4, and 1.5% a rating of 5 (Table 1)
Representative photographs of polar bears with fatness ratings of (a) 1 (Beaufort Sea, Apr 2006), (b) 2, (c) 4 (Western Hudson Bay, 1993), and (d) 5 (Western Hudson Bay, 1984).
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Post by oldindigosilverback on Jul 15, 2021 2:48:43 GMT -5
The polar bears with rating 5 are probably pregnant females.
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