How polar bears survive the Arctic

This video from Alaska is called Grizzly vs. Polar Bear.

From Wildlife Extra:

Gene study reveals how polar bears cope with killer lifestyle

A study of the genes of polar bears reveals how quickly they evolved to handle the extremes of life in the high Arctic, and why, and how they cope with being profoundly obese. A comparison between polar and brown bears has found that the former is a much younger species than previously believed, having diverged from brown bears less than 500,000 years ago to spend life on sea ice. There, the bears subsist on a blubber-rich diet of marine mammals that would result in cardiovascular diseases in other species. The relatively short time that has passed in its evolution and how it evolved was what interested the scientists.

The study, published in the journal Cell, was a collaboration between Danish and Chinese researchers and a team from the University of California Berkeley, including Eline Lorenzen and Rasmus Nielsen.

Unlike other bears, fat comprises up to half the weight of a polar bear. “For polar bears, profound obesity is a benign state,” said Lorenzen. “We wanted to understand how they are able to cope with that. The life of a polar bear revolves around fat. Nursing cubs rely on milk that can be up to 30 per cent fat, and adults eat primarily blubber of marine mammal prey. Polar bears have large fat deposits under their skin and, because they essentially live in a polar desert and don’t have access to fresh water for most of the year, rely on metabolic water, which is a by product of the breakdown of fat.”

The genome analysis comes at a time when the polar bear population worldwide, estimated at between 20,000 and 25,000, is declining and its Arctic sea ice habitat is rapidly disappearing. As the northern latitudes warm, the polar bear’s distant cousin, the brown or grizzly bear is moving farther north and occasionally interbreeding with the polar bear to produce hybrids that have been called ‘pizzlies’. This is the possibly the same process that led to the emergence of polar bears in the first place.

The bears’ ability to interbreed is a result of a very close relationship, Nielsen said, which is one-tenth the evolutionary distance between chimpanzees and humans. “It’s really surprising that the divergence time is so short. All the unique adaptations polar bears have to the Arctic environment must have evolved in a very short amount of time.”

These adaptations include not only a change from brown to white fur and development of a sleeker body, but big physiological and metabolic changes as well. The genome comparison revealed that over several hundred thousand years, natural selection drove major changes in genes related to fat transport in the blood and fatty acid metabolism. One of the most strongly selected genes is APOB, which in mammals encodes the main protein in LDL (low density lipoprotein), known widely as “bad” cholesterol. Changes or mutations in this gene reflect the critical nature of fat in the polar bear diet and the animals’ need to deal with high blood levels of glucose and triglycerides, in particular cholesterol, which would be dangerous in humans.

What drove the evolution of polar bears is unclear, though the split from brown bears coincided with a particularly warm 50,000-year interglacial period known as Marine Isotope Stage 11. Environmental shifts following climate changes could have encouraged brown bears to extend their range much farther north. When the warm interlude ended and a glacial cold period set in, a pocket of brown bears may have become isolated and forced to adapt rapidly to new conditions.

There is potential for the polar bear research also to have applications in the study of human’s lifestyles. “Polar bears have adapted genetically to a high fat diet that many people now impose on themselves,” said Nielsen. “If we learn a bit about the genes that allows them to deal with that, perhaps that will give us tools to modulate human physiology down the line.”

See also here.

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Polar bears’ Valentine’s Day

This video is called Mother Polar Bear and Cubs Emerging from Den – BBC Planet Earth.

From eNature blog:

Three Guys For Every Girl— Why Male Polar Bears Have A Tough Time Getting A Date

Posted on Wednesday, February 05, 2014 by eNature

Valentine’s Day is coming up and love is in the Arctic air.

So what’s the best place for a male Polar Bear to meet a potential mate?

The experts recommend going to a prime seal-hunting spot. But finding such a spot is only the beginning of the challenge.

Nature Doesn’t Make It Easy

One reason a male Polar Bear must work overtime for a date is that females of the species don’t breed every year or even every other year. A female Polar Bear usually breeds only once every three years, which means that males outnumber eligible females three-to-one at the start of breeding season in the spring.

So competition for female attention is fierce, and males must fight one another, sometimes viciously, for the privilege of mating.

The Girls Can Play Hard To Get

Further complicating matters is the fact that female Polar Bears enjoy a good chase and will lead pursuing males across the ice for miles and miles.

In some cases, a chase can cover more than sixty miles—not for the timid or the weak of heart.

And we all thought it was tough to get a date to the Prom!

Without the vibrant color of a cardinal or the sweet song of a sparrow, how does a seabird go about attracting its mate? Here.

St Valentine’s Day is traditionally the time when birds start to choose their mates, with egg-laying for most resident species commencing in March or April. For a handful of birds, including Tawny Owl, Mistle Thrush and Dipper, nesting may already be under way in February, but numbers of these three early breeders are falling rapidly, according to the British Trust for Ornithology’s (BTO) BirdTrends report, published on-line today: here.

The secret of how the polar bear copes with a high-fat diet without getting a heart attack can be found in the creature’s genetic makeup according to scientists who have analysed the genome of the world’s greatest living land predator: here.

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Swedish young Arctic foxes research

This video is called Arctic Fox Raids Polar Bear Kill.

From National Geographic:

In the winters of 2012 and 2013, National Geographic grantee Anders Angerbjörn and his Ph.D. student, Rasmus Erlandsson, studied an extremely threatened species, the Scandinavian arctic fox. The current population numbers fewer than 150 individuals in mainland Europe so many of the young foxes are having difficulty finding a non-related partner. Other threats to the species include competition from the red fox for the scarce small rodents they both depend upon for food. Angerbjörn and Erlandsson monitored the arctic fox population in Västerbotten and Norrbotten, Sweden, to identify the best territories for further conservation actions. This included tagging the baby foxes, which proved to be a challenge.

“When catching arctic foxes it is easy to believe that the smaller ones are the easiest to handle. In some aspects it is true. Their teeth are smaller and the jaws less powerful. Combined with a naïve lack of aggressive attitude it seems to make up for an easy piece of work to ear-tag a 700-gram cub. Well, sometimes it is, but just as human children have a hard time keeping still, the really small cubs do too.

“We handle the foxes in a bag while tagging, and the trick is to keep the animal still between your thighs while kneeling. And here comes the tricky part. How do you keep a small, wild fox still? You cannot apply too much force—it is barely a kilo of an endangered carnivore you are dealing with. You really do not want to hurt it. Just as with small children the best tool is patience, but at the same time you want the handling to be as short as possible.

“One particular cub had a technique I had never experienced before as it insistently tried to turn [onto] its back, for no obvious reason. I had to reach the ears, so I quickly turned the cub upright. The cub stayed still for a few seconds, and then began to roll onto its back again. The same maneuver, once again! And again! Finally, I got the tags in place, and after making measurements and taking some samples, I finally released the little fellow and it disappeared like lightning into the den.”

—Ph.D. student Rasmus Erlandsson, team member with Anders Angerbjörn, Global Exploration fund grantee

Arctic walrus and polar bear

This video is called Polar Bear Versus Walrus Colony – BBC Planet Earth.

From Thin Ice Blog:

The king of the haulout

Posted by Tom Arnbom on August 16, 2013

A WWF-led research team, a Canon photographer, and crew are traveling to Siberia’s Arctic coast on the Laptev Sea, to help solve a scientific mystery. …

We are heading out in the mist after an overnight stop at the larger Beigihevs island. More and more seabirds are passing the boat – a sign that we’re entering richer seas.

After a few hours we see a sandspit at distance. Yes! a few walrus, no more than maybe 30 individuals. YES! there are more than 400 of them, and in the middle, on a small piece of ice, is the king — a fat male polar bear. It is like sitting in a smorgasbord.

We are now 50 km south of Maria Pronchistcheva Bay. We will head up to the bay before deciding where we should camp. We have found the Laptev walrus, and the work can soon begin.

- Tom

What’s a haulout?

Walruses sometimes congregate in large numbers on land – this is called a “haulout”. In some areas where sea ice levels have decreased, we are seeing extremely large haulouts as the walruses abandon the ice and head to shore. On a previous trip through the Russian Arctic in 2009, WWF researchers encountered an enormous haulout of about 20,000 individuals. This is what it looked like:

This video says about itself:

While on the Northeast Passage expedition, the WWF Arctic Programme’s Geoff York and the rest of the crew of the ‘Explorer of Sweden’ witnesses the incredible – and worrying – sight of an estimated 20,000 walrus on shore at Ryrkaipiy on the Chukchi Sea in Russia. Here’s some amazing footage. For more information about the WWF Arctic Programme and the reasons behind the haulout, please visit

Polar bear’s collar camera view, video

This video from the USA says about itself:

Aug 2, 2013

A collar camera attached to a Polar bear at Oregon Zoo is providing a unique insight into the species. Whenever Tasul plays, swims, eats and sleeps a specially-designed collar tracks her movements, however slight.

It has an accelerometer attached to it which traces Tasul’s steps in three dimensions.

The research project is in collaboration with the US Geological Survey.

Research wildlife biologist, Anthony Pagano, said: “It records changes [in position] along three different axes: up and down, back and forth, and side to side.”

The technology works in a similar way in which the phone is tipped upside down.

Scientists hope the data that is collected can help them understand how polar bears in the wild are coping with changes in their environment, primarily because of climate change. Report by Ashley Fudge.

Svalbard gulls, plover and polar bear

Glaucous gulls, Svalbard, 7 June 2013

Spitsbergen, 7 June 2013. Just east of the pond where we saw the long-tailed ducks, there are, of course, the dog cages and the common eider nesting colony. There are glaucous gulls there as well.

Glaucous gull couple, Svalbard, 7 June 2013

A glaucous gull couple standing on the snow behind the eider duck colony.

Glaucous gull couple on pole, Svalbard, 7 June 2013

Sometimes, they sit on the poles around the dog cages.

Just past the dog cages, where the Adventdalen road begins, a polar bear traffic sign. It warns about polar bears in the whole archipelago.

Polar bear traffic sign, Svalbard, 7 June 2013

This polar bear on a warning traffic sign was the only polar bear which we saw in Spitsbergen (except for a stuffed one at the airport, and polar bears as depicted as symbols of Svalbard on buildings).

Ringed plover, Svalbard, 7 June 2013

In the river valley opposite the dog kennel, a ringed plover.

Polar bear-brown bear relationship, new research

This video is called Mother Polar Bear and Cubs Emerging from Den – BBC Planet Earth.

From Wildlife Extra:

DNA study clarifies how Polar bears and brown bears are related

“In retrospect, I think we were wrong about the directionality of the gene flow between polar bears and Irish brown bears,” she said.

March 2013. At the end of the last ice age, a population of polar bears was stranded by the receding ice on a few islands in south-eastern Alaska. Male brown bears swam across to the islands from the Alaskan mainland and mated with female polar bears, eventually transforming the polar bear population into brown bears.

Evidence for this surprising scenario emerged from a new genetic study of polar bears and brown bears led by researchers at the University of California, Santa Cruz. The findings, published March 14 in PLOS Genetics, upend prevailing ideas about the evolutionary history of the two species, which are closely related and known to produce fertile hybrids.

Limited hybridisation

Previous studies suggested that past hybridization had resulted in all polar bears having genes that came from brown bears. But the new study indicates that episodes of gene flow between the two species occurred only in isolated populations and did not affect the larger polar bear population, which remains free of brown bear genes.

At the centre of the confusion is a population of brown bears that live on Alaska’s Admiralty, Baranof and Chicagof Islands, known as the ABC Islands. These bears–clearly brown bears in appearance and behaviour–have striking genetic similarities to polar bears.

“This population of brown bears stood out as being really weird genetically, and there’s been a long controversy about their relationship to polar bears. We can now explain it, and instead of the convoluted history some have proposed, it’s a very simple story,” said co-author Beth Shapiro, associate professor of ecology and evolutionary biology at UC Santa Cruz.

Shapiro and her colleagues analysed genome-wide DNA sequence data from seven polar bears, an ABC Islands brown bear, a mainland Alaskan brown bear, and a black bear. The study also included genetic data from other bears that was recently published by other researchers. Shapiro’s team found that polar bears are a remarkably homogeneous species with no evidence of brown bear ancestry, whereas the ABC Islands brown bears show clear evidence of polar bear ancestry.

More in common with female Polar bears than males

A key finding is that the polar bear ancestry of ABC Islands brown bears is conspicuously enriched in the maternally inherited X chromosome. About 6.5 percent of the X chromosomes of the ABC Islands bears came recently from polar bears, compared to about 1 percent of the rest of their genome. This means that the ABC Islands brown bears share more DNA with polar bear females than they do with polar bear males, Shapiro said.

To understand how hybridization could lead to this unexpected result, the team ran simulations of various demographic scenarios. “Of all the models we tested, the best supported was the scenario in which male brown bears wandered onto the islands and gradually transformed the population from polar bears into brown bears,” said first author James Cahill, a graduate student in ecology and evolutionary biology at UC Santa Cruz.

Cross mating still occurs occasionally

This scenario is consistent with the known behaviour of brown bears and polar bears, according to co-author Ian Stirling, a biologist at the University of Alberta in Edmonton, Canada. Mixing of polar bears and brown bears is seen today in the Canadian Beaufort Sea, where adult male brown bears wander onto the remaining sea ice in late spring and sometimes mate with female polar bears, he said. In areas such as western Hudson Bay and the Russian coast, polar bears are spending more time on land in response to climate warming and loss of sea ice, a behaviour that could have left polar bears stranded on the ABC Islands at the end of the last ice age.

Young male brown bears tend to leave the area where they were born in search of new territory. They may well have dispersed across the water from the Alaskan mainland to the ABC Islands and hybridized with polar bears stranded there when the sea ice disappeared.

“The combination of genetics and the known behaviour of brown and polar bears hybridizing in the wild today tells us how the ABC Islands bears came to be: they are the descendants of many male brown bear immigrants and some female polar bears from long ago,” Stirling said.

The findings suggest that continued climate warming and loss of arctic sea ice may lead to the same thing happening more broadly, said co-author Richard E. (Ed) Green, an assistant professor of bio molecular engineering in UCSC’s Baskin School of Engineering. “As the ice melts in the Arctic, what is going to happen to the polar bears? In the ABC Islands, the polar bears are gone. They’re brown bears now, but with polar bear genes still present in their genomes,” he said.

The first genetic studies of ABC Islands brown bears looked at their mitochondrial DNA, which is separate from the chromosomes and is inherited only through the female lineage. The mitochondrial DNA of ABC Islands brown bears matches that of polar bears more closely than that of other brown bears, which led some scientists to think that the ABC Islands brown bears gave rise to modern polar bears.

Nuclear DNA

The new study looks at the “nuclear DNA” carried on the chromosomes in the cell nucleus. It is the latest in a series of genetic studies of polar bears published in recent years, each of which has prompted new ideas about the relationship between polar bears and brown bears. A 2010 study of fossils and mitochondrial DNA supported the idea that polar bears evolved from the ABC Islands brown bears. But a 2011 study of mitochondrial DNA from extinct Irish brown bears showed an even closer match to polar bears and suggested that polar bears got their mitochondrial DNA from hybridization with Irish bears. Shapiro, a co-author of that study, said she now thinks the Irish brown bears may be another example of what happened in the ABC Islands, but she can’t say for sure until she studies their nuclear DNA.

“In retrospect, I think we were wrong about the directionality of the gene flow between polar bears and Irish brown bears,” she said.

Different theories

Two studies published in 2012 sought to determine when the polar bear lineage diverged from the brown bear lineage using nuclear DNA data. The first, published in April in Science, put the split at 600,000 years ago and concluded that polar bears carry brown bear mitochondrial DNA due to past hybridizations. The second, published in July in Proceedings of the National Academy of Sciences, suggested that brown bears, black bears, and polar bears diverged around 4 to 5 million years ago, followed by repeated episodes of hybridization between polar bears and brown bears.

The new study does not address the question of how long ago polar bears diverged from brown bears, but it may help sort out the conflicting results of recent studies. “It’s a good step in the right direction of understanding what really happened,” Shapiro said.

The study does indicate that the divergence of polar bears from brown bears was only half as long ago as the split between the brown bear and black bear lineages, said Cahill. “We can tell how long brown bears and polar bears have been separate species as a proportion of how long ago they separated from more distantly related species, but putting a year on it is very difficult,” he said.

Green noted that efforts to understand the relationship between polar bears and brown bears has been complicated by the unusual case of the ABC Islands brown bears. “It’s as if you were studying the relationship between humans and chimpanzees and your analysis included DNA from some weird population of humans that had hybridized with chimps. You would get very strange results until you figured that out,” he said.

In addition to Cahill, Green, Shapiro, and Stirling, the co-authors of the new paper include postdoctoral researchers Tara Fulton and Mathias Stiller, undergraduate Rauf Salamzade, and graduate student John St. John at UC Santa Cruz; Flora Jay and Montgomery Slatkin at UC Berkeley; and Nikita Ovsyanikov at the Wrangel Island State Nature Reserve in Russia. Green and Shapiro direct the UCSC Paleogenomics Lab. This research was funded by the Searle Scholars Program.

The great white bears of the frozen north may face a difficult future. Each summer, the sea ice on which they rely to hunt seals is getting thinner and smaller in extent – threatening to upset their way of life: here.

Polar bears older than biologists used to think

This video is called other Polar Bear and Cubs Emerging from Den – BBC Planet Earth.

From Science:

Nuclear Genomic Sequences Reveal that Polar Bears Are an Old and Distinct Bear Lineage

Frank Hailer1,
Verena E. Kutschera1,
Björn M. Hallström,
Denise Klassert,
Steven R. Fain,
Jennifer A. Leonard,
Ulfur Arnason,
Axel Janke


Recent studies have shown that the polar bear matriline (mitochondrial DNA) evolved from a brown bear lineage since the late Pleistocene, potentially indicating rapid speciation and adaption to arctic conditions.

Here, we present a high-resolution data set from multiple independent loci across the nuclear genomes of a broad sample of polar, brown, and black bears.

Bayesian coalescent analyses place polar bears outside the brown bear clade and date the divergence much earlier, in the middle Pleistocene, about 600 (338 to 934) thousand years ago. This provides more time for polar bear evolution and confirms previous suggestions that polar bears carry introgressed brown bear mitochondrial DNA due to past hybridization. Our results highlight that multilocus genomic analyses are crucial for an accurate understanding of evolutionary history.

See also here. And here.

July 2012. An analysis of newly sequenced polar bear genomes is providing important clues about the species’ evolution, suggesting that climate change and genetic exchange with brown bears helped create the polar bear as we know it today. The international study found evidence that the size of the polar bear population fluctuated with key climatic events over the past million years, growing during periods of cooling and shrinking in warmer times: here.

Will more climate change mean more pizzlies (polar bear-grizzly bear hybrids)? Here.

As climate changes, polar bears switch to polluted food: here.

Thanks to global warming polar bears now risk starvation during their wait for ice to form: here.

Shrinking Arctic sea ice has left polar bears scrambling to find food, and they’ve taken to eggs in a big way, which is bad news for many seabirds. A polar bear in the Northern Hudson Bay region can eat hundreds of seabird eggs at a sitting: here.