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Polar Bears - Data, Pictures and Videos
Polar Bears - Data, Pictures and Videos
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Polar Bears - Data, Pictures and Videos
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Photo and information credits: Marco Gaiotti Photography
"A polar bear photographed in late September in Kvitoya island. The bear was eating seaweeds to fill its stomach, in order to satisfy its hunger."  *This image is copyright of its original author
Question from Kika: Is it true that polar bears have black skin underneath all the fur? And if so, why?
Answer from Dr. Thea Bechshoft: Yes, that is absolutely true! Actually, it is mostly true: polar bears are born with pink skin. See this video Image of polar bear cub with pink skin  *This image is copyright of its original author But it turns black around the age of 4 months. The color of the skin is easily seen on the bear’s nose, lips, and under its feet. You can see the black skin in this picture of a polar bear in Buffalo Zoo:  *This image is copyright of its original author This bear had to go through surgery because of an ankle injury. In connection with this procedure, the veterinarian had to shave a bit of her fur off, and as you can see, the black skin is visible through the hair that was growing back while she was in recovery. So why do polar bears have black skin? Interestingly, no albino polar bears have ever been reported in the wild or in zoos, which indicates to me that having black skin (and dark eyes) is apparently very important in this species. Our two best explanations as to why having black skin is essential to polar bears are both related to the sun: Firstly, darker colors are better at absorbing heat from the sun, which is an advantage to a polar bear trying to stay warm in the cold Arctic. Secondly, the dark color is likely protecting the bear against harmful UV radiation from the sun. Generally speaking, darker skin (or rather, higher concentration of the dark pigment called melanin in the skin) has been found to provide better protection against the sun’s UV rays. This goes for a wide range of organisms, from humans to blue whales. In the case of the polar bear, the sunlight it is exposed to is intensified when it is reflected off of the snow, sea ice, and water that make up the bear’s environment most of the year.
Photo and information credits: Alex Kirichko
The Game. Alaska, October 2016.  *This image is copyright of its original author
Sometimes reality is FAR more frightening than fiction.
 *This image is copyright of its original author
 
Post #78; I would have to view more evidence before believing this. I have seen some very convincing fake-documents and stories posted before.
Photo and information credits: Brice PETIT Photography
Ours Polaire, Ursus Maritimus Banquise par 82°50'N (Nord du Spitzberg) Septembre 2013, 22h01  *This image is copyright of its original author
Photo and information credits: Jayanth Sharma
The higher Arctic is a fascinating place. At any given point, every day the landscape changes due to various factors like wind, current etc. So for a Polar Bear, it is usually not the usual place to be when she has two little teddy bears to care for. So most of the mothers and cubs I have seen in the past has been on land or near land. But this year was exception, this mother bear and her cubs were the highlight of the trip. Less than a year old, the cubs are completely at ease in the open sea ice and they cooperate with mum going about their daily lives. This was shot in August this year and as some of you know I have two expeditions lined up for 2017, one in July and another in August and we have half the spots taken on both departures.  *This image is copyright of its original author
Polar bears with shoulder humps:
 *This image is copyright of its original author Ignore the grizzly on the right, and focus on the left with the polar bear.  *This image is copyright of its original author  *This image is copyright of its original author Notice how polar bears can have a good shoulder hump (like their brown counterparts), although a bit less in size, but still noticeable. 
The Polar bear alongside the boat is a massive individual. Perhaps 1500 pounds?
A scientific analysis on the mating mechanics of polar bears:
"In conclusion, we modelled the mating system of polar bears to identify circumstances leading to a component Allee effect of reduced female mating success. The model is intentionally simple, predicting mating success from male and female densities using only four parameters, with predictions insensitive to two of them. It incorporates, however, key biological mechanisms of the mating system and performs equally as well as more complex models in explaining the observed pairing data. To evaluate the generality of the model, it would be desirable to assess whether the model performs equally in other polar bear populations. Our model could next be coupled with a population dynamics model to explore whether and how a component Allee effect translates into a demographic Allee effect, and aid the development of optimal sex-specific harvesting strategies. Female mating success, as discussed here, is just one component of female reproductive success, which is further influenced by the rate of successful pregnancies as well as cub mortality. Furthermore, demographic stochasticity could lead to random fluctuations in the population sex ratio, and thus affect the number of males and females available for mating, particularly at low population sizes (Legendre et al. 1999; Stephens et al. 1999; Møller & Legendre 2001; Engen et al. 2003; Sæther et al. 2004). Such fluctuations would then, in turn, affect female mating success. This interaction merits further exploration." Modelling the mating system of polar bears: a mechanistic approach to the Allee effect
Well, here we have another very in depth explanation of interaction between Polar bear and Brown Bear by Dr. Thea Bechshoft, Please take some time to read it carefully.
Question: Val, Jannicke, and Lauge have all been asking me about the relationship between polar bears and brown bears - are the two bear species closely related and do they mate? Answer by Dr. Thea Bechshoft: Yes, polar bears and brown bears are closely related. Exactly how close is a harder question to answer though! There is only one species of brown bear, even if it is sometimes known under other names such as grizzly bear, Kodiak bear or spirit bear. Likewise, there is only one species of polar bear. Both of these bear species have a common ancestor that they evolved from. However, although some studies suggest that the evolutionary split that lead to the brown bear and the polar bear being two separate species may have happened as far back as 4-5 million years ago, there is still disagreement as to when exactly the split happened. Historically, both bear species inhabited an enormous geographical range. Because the split happened at different times in the different areas, the DNA results vary depending on which area and what time period is investigated - 10 million years ago in Siberia, 1 million years ago in Scandinavia, 1 thousand years ago in Greenland, or 10 years ago in Canada: each study is likely to give you a somewhat different answer. Despite being two different species, polar bears and brown bears can still breed with each other, and even produce fertile offspring. A few zoos interbred the two bear species (a long time ago, before animal ethics was really something most people cared about), but now we mainly see crossbreeding between the two species because of climate change: Polar bears are nothing without sea ice and seals, and so their range, historically and now, have been continuously diminishing as the ice has retreated northwards. However, the exact opposite is true for the brown bears: their food (plants, insects, small animals) has moved north as the climate has gotten milder, and so the brown bears have started moving further north too, into what is otherwise considered polar bear territory. In other words, one of the current consequences of climate change is that polar bears and brown bears may actually meet more often than they used to. However, although polar bears and brown bears are each other’s closest relatives, their biology is sufficiently different that they only meet under relatively specific circumstances. Polar bears are specialized to living on the sea ice and hunting seals. When/if they are forced to stay on land they are basically starving while waiting for the sea ice to re-form. Grizzlies, on the other hand, are specialized to living on land, eating a largely vegetarian diet (and hibernating during the winter months). During spring or summer, however, the two bear species may meet where land meets ocean, e.g. scavenging for anything edible that may have washed up along the shore. Every now and then these encounters will be romantic in nature, resulting in what is known as “grolar” or “pizzly” polar bear/grizzly hybrid cubs. Based on what has been observed in the field so far such cubs generally seem to have a polar bear mother and a grizzly father. This means that the cubs will be raised as polar bears, and thus be highly likely to mate with a polar bear once they themselves reach reproductive age. In other words - under the current climate - the grizzly DNA will (over generations) disappear from the bloodline. A few stories have been in the news lately on how the interactions between the bears (in Canada) are changing: http://www.cbc.ca/news/canada/manitoba/g...-1.3118936 and http://www.polarbearsinternational.org/n...-territory If you go online to look at pictures of polar bear/grizzly bear hybrids, remember that grizzly bears can be any color between dark brown and light beige, a fact which seems to have confused quite a few of those who’ve posted pictures on various websites. A lot of pictures I've seen labeled as hybrids are not. For examples of how a grolar may actually look, see here:  *This image is copyright of its original author  *This image is copyright of its original author
Post #87 is telling a totally different theory of polar bear evolution; saying that perhaps 4 or 5 million years ago both the polar bear and the grizzly evolved from a common ancestor - as did the grizzly and the cave bear. Then Dr. Thea Bechshoft goes on to say that the split from the common ancestor happened at various intervals... ?
IMO... the other theory makes better sense. A group of brown bears migrated far to the north, were stranded, and the survivors evolved into polar bears. Exactly when is an ongoing debate. (01-05-2017, 09:55 PM)brotherbear Wrote: Post #87 is telling a totally different theory of polar bear evolution; saying that perhaps 4 or 5 million years ago both the polar bear and the grizzly evolved from a common ancestor - as did the grizzly and the cave bear. Then Dr. Thea Bechshoft goes on to say that the split from the common ancestor happened at various intervals... ? There is some alternative theory suggests that the hybridization between the Cave bear and the Brown bear had eventually created a new species known as the Polar bear. |
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