Tag Archives: polar bear

Climate change is breeding ‘pizzly’ bears — hybrids between polar bears and grizzlies

Polar/brown bear hybrid at Osnabrück Zoo. Credit: Wikimedia Commons.

In response to sudden shifts in their habitats’ climate, many species cannot adapt so they are forced to change the location of their migration or foraging habitats. In some situations, this can result in some unexpected consequences.

Pushed by warming temperatures, grizzly bears are increasingly migrating north where temperatures are colder, while polar bears are moving south pushed by melting ice in the Arctic Circle. Inevitably, the two species crossed paths and interbred, producing hybrids known as “pizzly bears” or “grolar bears”, depending on how you look at it. Some of these hybrids may be fertile, which raises interesting questions about what bears in the Arctic may look like in the future.

The first pizzly was identified in 2006. Although there were reports of strange-looking bears prior to this date, it was only after Roger Kuptana, an Inuvialuit guide from Sachs Harbour, North West Territories, drew attention to a bear shot by an American sports hunter that polar bear and grizzly bear hybrids were taken seriously. DNA tests confirmed that the shot bear was indeed a hybrid — the first documented one in the wild. Previously, in 2004, two pizzly bear cubs were born in captivity after polar bears and grizzly bears were allowed to mate at Osnabrück Zoo in Germany.

Since then, at least eight more pizzly bear hybrids have been identified in the wild. In a 2017 study, researchers showed through a combination of field observations and genetic analysis that all eight hybrids sprung from a single female polar bear who mated with two grizzly bears.

“Grizzly bears have recently become more common on the Arctic Islands in the Inuvialuit Settlement Region, concurrently with a period of environmental change. Over the last decade, grizzly bear – polar bear hybrids have been confirmed within this region, triggering extensive discussion and speculation regarding the impact of hybridization on the parent species,” the researchers at the University of Alberta and the University of Calgary in Canada wrote.

Historically, grizzly bears ranged from Alaska to Mexico and from the Pacific Ocean to the Mississippi River. However, hunters and trappers have reported increasingly frequent sightings of grizzlies in Canada’s High Arctic, and scientists say climate change and human encroachment on their habitat is to blame for this northward migration.

The Inuvialuit Settlement Region, for instance, has seen its seasonal freeze pushed back from August to the end of September or even early October in the last 30 years. This means there are now more grasslands and other vegetation that are attractive to grizzly bears.

Meanwhile, polar bears are migrating from north to south due to loss of sea ice. Polar bears now stay longer on land and have to use more body fat to sustain their energy than decades ago. As a result, polar bears have experienced a drop in population, reduced survival rates, and a decrease in food.

In the middle, grizzly and polar bears met, and nature took its course. The two species only diverged about 500,000-600,000 years ago, so they are able to mate. However, the pizzly bear hybridization could be a threat to biodiversity, leading in time to the loss or replacement of existing species.

Polar bears are hyper-specialized animals that hunt seals and are less adapted than grizzlies to eating hard foods such as plant tubers or at scavenging carcasses. There are many unknowns at this stage, such as whether or not the hybrids are fertile, but it wouldn’t be preposterous to see polar bears replaced by grizzlies or even pizzly hybrids as the 21st century unfolds.

“We need to study the effects of hybridization on these bears. Most of the time hybrids are not more vigorous than either of the two species, as grizzlies and brown bears have unique adaptations for their particular environments. However, there are a few examples where hybrids can be more vigorous and better able to adapt to a particular environment, particularly if the environment is deviating from what it once was. This requires further study and careful monitoring. Time will tell if these hybrids are better able to withstand a warming Arctic,” Larissa DeSantis, a paleontologist and associate professor at Vanderbilt University in Tennessee, told The Independent.

Shrinking sea ice is threatening polar bears and narwhals, study shows

The amount of energy required by polar bears and narwhals to survive in the warming Arctic has increased by 3-400% in recent decades, according to a new study — and it’s pushing them to extinction.

Image credit: Flickr / Christopher Michel

The Arctic has been melting at three times the global rate over the past 30 years, limiting the hunting grounds of apex predators. Unsurprisingly, Arctic animals are desperately struggling to cope with the changes.

Researchers Anthony Pagano and Terrie Williams explained that creatures such polar bears and narwals are particularly vulnerable to sea ice deterioration in the Arctic because of their hunting behaviors and their diet, as well as their physiological adaptations. These features make them excellently adapted to normal Arctic conditions, but are limiting their ability to adapt to the changing climate.

The Arctic is currently warming more than twice as fast as the rest of the planet on average. This is driven by declines in sea ice cover, leading to a sea ice-albedo feedback mechanism. These phenomena have resulted in declines in September Arctic sea ice at a rate of 13.3% per decade since 1979. The current record low happened in 2012, which was 49% lower than average.

Previous studies have shown that sea ice retreat is happening 3–9 days earlier per decade and sea ice advance 3–9 days later per decade. Additionally, winter sea ice extent has declined at a rate of 3.4% per decade since 2000. Forecasts anticipate the Arctic could be largely ice-free in summer by mid-century — which would be devastating for wild animals.

More energy

Pagano and Williams measured the energetic cost of movement specifically for polar bears and narwhals and found that major ice loss translated into a significant increase in energy consumption. Simply put, because of the changing conditions, the animals need to waste much more energy to hunt. The higher energy demand and the limitation of access to seals, one of their main sources of food, leave the animals more vulnerable to starvation.

In the case of polar bears (the largest land carnivores), their ability to catch ice seals has historically enabled them to meet their high metabolic demands. They are ambush hunters, waiting at seal breathing holes and catching them. But as the sea ice breaks are now breaking earlier and retreating, their chance of catching seals is significantly diminishing, the researchers wrote.

The polar bears are now relying much more on terrestrial food resources, which have considerably lower energetic densities and lower overall digestible energy. For example, they calculated that a polar bear would have to eat 1.5 caribou, 37 Arctic char, 74 snow geese, and 216 snow goose eggs to equal the digestible energy of an adult seal.

“The Arctic world is so much more unpredictable for these animals now,” Williams, a co-author of the report, told The Guardian. “With a finite amount of oxygen in their muscles and blood, we find that the narwhals budget their speed, depth, and duration of dives to match the capacity of their internal scuba tanks. One miscalculation could result in drowning.”

Meanwhile, the changes in ice cover with Arctic warming present a different energetic challenge for narwals. They obtain much of their annual energy intake during winter by diving for Greenland halibut (a type of flatfish). They rely on breathing holes in the ice to replenish their oxygen stores when finishing each dive. But changes to the sea ice have made the presence and stability of the holes less predictable.

The loss of sea ice has also resulted in a larger presence of killer whales – new apex predators in the Arctic marine ecosystem. They are one of the few aquatic animals know to attack and kill narwhals, affecting their behavior and distribution. Responding to the presence of the whales, the narwhals exhibit evasive movements towards areas of dense pack-ice or move to shallow waters.

For the researchers, the declines in polar bears and narwhals will lead to declines in other ice-dependent marine mammals and some of their principal prey, such as Arctic cod that rely on sea ice-associated zooplankton. The decline “is likely to alter trophic dynamics and thus lead to rapid changes in the entire Arctic marine ecosystem,” they conclude.

The study was published in the Journal of Experimental Biology.

Polar bears after 2100? Not in “business as usual” emissions, researchers say

If humans don’t greatly reduce their greenhouse gas emissions in the following years, most of the populations of polar bears will struggle to survive beyond 2100, according to a new study.

Some populations are already close to their survival limits as the Arctic sea continues to shrink.

Credit Wikipedia Commons

Images of polar bears desperately looking for food have become the poster child for the effects of climate change — and for good reasons. Polar bears are the largest terrestrial carnivores on Earth, and they’re in major climatic trouble. The fate of polar bears is tightly linked to what happens on the Arctic’s sea ice — particularly to Arctic ice. Bears rely on it as a platform to catch seals, their prey of choice.

The new study, carried out by an international group of researchers, marks the first-time scientists have been able to predict when, where, and how polar bears are likely to disappear. Previous models didn’t account for the different Arctic living conditions and levels of sea ice subpopulations encounter.

The researchers looked at 13 of the world’s 19 polar bear subpopulations, which account for 80% of the total population of the species. The bears that live an area known as the Archipelago ecoregion in the Canadian Arctic were not included as the geography of the area made it too difficult to predict its future ice extent.

Image credits: Nature.

To predict what’s in store for polar bears, the study used two different greenhouse gas emissions scenarios. Under a moderate emissions scenario, polar bears in Russia and Alaska would face “possible” reproductive collapse by 2080. With a very high emissions scenario, polar bears in Canada’s Queen Elizabeth Island would be the only ones that would be able to survive. No matter how you look at it, if we don’t decrease our emissions substantially, polar bears are in big trouble.

The researchers also found that the length of time a bear can survive without food depends on the region and the condition of the bear, with cubs being the first to be impacted by extended fasting periods. The second-most vulnerable are adult females, followed by adult males and solitary females — which can fast for up to 255 days.

“What we’ve shown is that, first, we’ll lose the survival of cubs, so cubs will be born but the females won’t have enough body fat to produce milk to bring them along through the ice-free season,” said Dr. Steven Amstrup, chief scientist of Polar Bears International, who was also involved in the study.

Polar bears rely on energy reserves they accumulated during the winder hunting season to make it through the summer months. Despite they used to fast for months, their body condition, reproductive capacity and survival will eventually diminish if they are forced to go too long without food.

Unlike other species threatened by hunting or deforestation, polar bears can only be saved if their habitat is protected. Other creatures might have a chance of relocating in colder places, but polar bears have nowhere to go.

At any rate, saving polar bears won’t be easy. Previous research has shown that even if emissions are steeply reduced now, it will still take another 25 to 30 years for sea ice extent to stabilize.

The study was published in the journal Nature.

Arctic warms, polar bears switch diet: dolphins now on the menu

Known to feed mainly on seals, the images Jon Aars at the Norwegian Polar Institute captured of a polar bear dining on dolphins is a “culinary” first for the species. The photographs were taken in the Norwegian High Arctic, mid-April 2014. The bear was seen feeding on the carcass of one white-beaked dolphin, and covering another with snow.

“It’s full of proteins” – Bear.
Image via: huffingtonpost.com

“We think that he tried to cover the dolphin in snow in the hope that other bears, foxes or birds would have less of a chance of finding it. Maybe to be able to eat it a day or two later, once he had digested the first one,” said Aars.

Jon Aars published his findings in the June 1 issue of Polar Research, remarking that in the following ice-free summer and fall seasons they discovered another seven carcasses, believed to have been scavenged on by six bears.

“It is likely that new species are appearing in the diet of polar bears due to climate change because new species are finding their way north,” he told AFP.

Although they are a regular sight in the Norwegian Arctic during the summer when the ice has melted, they have never before been observed so far north during the other seasons, when the waters are still covered in ice.

Image via: straitstimes.com

But Norwegian scientists have reported two almost ice-free winters in recent years, which they believe could have attracted the mammals further north, and became trapped by dense ice blown into a fjord by strong north winds. Coupled with the strong retreat of ice all around the Arctic region, and with it, that of the seals that make up bears’ primary source of food, the dolphins were invited to dinner.

“They will eat any marine mammal given a chance,” Ian Stirling of the University of Alberta in Canada told New Scientist. “The bigger surprise was that the dolphins were entrapped before they could migrate south for the winter.”

Aars states that the bear likely used the same hunting techniques it used to catch seals, waiting for the animal to surface through a hole in the ice to breathe. “Even if they saw the bear, the dolphins did not necessarily have any other choice,” he said.

“I don’t think that this signifies a great upheaval” in the diet of the carnivores, said Aars. “It’s just that the polar bear is coming into contact with species they have not been used to meeting until now.”

Ringed seals are the polar bear's primary food source--but a beached whale means a feast! © Daniel J. Cox/Natural Exposures

As Arctic ice goes, so do the polar bears. Study finds land food is inadequate to keep them fed

After carefully calculating the net nutritional gain polar bears have from land-based food like caribou, berries or bird eggs, researchers found this is far from enough to compensate their typical fat-rich diet based on marine mammals. In consequence, as ice retreats and spring hunting season shortens polar bear populations are expected to fall dramatically. According to the study, two-third of the world’s polar bears will disappear by mid-century and by the end of the century the could follow, if the issue is not addressed.

Ringed seals are the polar bear's primary food source--but a beached whale means a feast! © Daniel J. Cox/Natural Exposures

Ringed seals are the polar bear’s primary food source–but a beached whale means a feast! © Daniel J. Cox/Natural Exposures

Arctic sea ice has seen a sharp decline over the past four decades, as the sea ice cover is shrinking and thinning, making scientists think an ice-free Arctic Ocean during the summer might be reached this century. Ice grows dramatically each winter, usually reaching its maximum in March. It melts just as dramatically each summer, generally reaching its minimum in September. But since 1979 when satellite observations came into operation, this sea ice has been regularly thinning year in, year out. Since 2002, ice extent at the summer minimum has not returned to anything approaching the long-term average (1979-2000).

Despite sea ice has fluctuated, natural cycles alone like the Arctic Oscillation aren’t enough to explain the steep decline. Instead, most scientists argue that natural variability and greenhouse gas emissions (and the resulting rise in global temperatures) likely worked together to melt greater amounts of Arctic sea ice. The table below put together by NASA summarizes Arctic ice loss since 1979.

September/March (minimum/maximum) September Average Extent (millions of square kilometers) March Average Extent (millions of square kilometers)
1979–2000 mean 7.0 15.7
1999/2000 6.2 15.3
2000/2001 6.3 15.6
2001/2002 6.8 15.4
2002/2003 6.0 15.5
2003/2004 6.2 15.1
2004/2005 6.1 14.7
2005/2006 5.6 14.4
2006/2007 5.9 14.7
2007/2008 4.3 15.2
2008/2009 4.7 15.1
2009/2010 5.4 15.1
2010/2011 4.9 14.6
2011/2012 4.6 15.2
2012/2013 3.6 15.1
2013/2014 5.4 14.8

During summer, polar bears spend of their time on land. It’s in Winter than they get to munch on their favorite food (seals), but because the ice has been thinning the winter their land stints have been getting ever frequent. Because a handful of sightings have been reported of polar bears snacking on land-based food, some biologists argued that the polar bears would compensate this way for the seal meat. A team at  the US Geological Survey (USGS) found that this would be insufficient, however. The bears put in too much energy searching for berries or chasing down caribou, so the net nutritional gain is far from enough to keep them fed.

“Current evidence suggests it is unlikely terrestrial foods can make up for the calories polar bears lose out on in places where they are staying onshore longer than they have in the past,” said study author Karyn Rode, a wildlife biologist at the USGS. “In western Hudson Bay, during years when polar bears spend more time onshore and the ice-free period is longest, survival rates are lowest despite observed terrestrial feeding.”

“A really large bear has high energetic costs when they get up to forage, and these [terrestrial] resources are typically lower in calories or widely dispersed,” said Rode.

It’s not just that it’s not worth it for the bears to forage land food, there’s simply not enough to spare. On land, polar bears compete for food with Arctic Grizzlies, who also struggle to find food. The study, published in Frontiers in Ecology and the Environment, also notes that all the goose eggs in Canada’s Hudson Bay could maintain the 900 local polar bears for just a day and a half. This would mean a dramatic loss to the local ecosystem.

polar bear

Pollution lowers polar bear penile bone density, threatening their mating abilities

Global warming is all fun and games until somebody breaks a penis! For a long time, scientists have been aware that chemical pollution makes polar bears’ testes and penis bone smaller. Concerns over polar bears’ mating potential have now grown after Danish researchers found pollution also reduces penile bone density, increasing the risk of fracture during mating.

Polar bears are not happy about this

polar bear

Image: Fan Pop

Yes, there are a lot of mammals that have bones in their penises, including chimps! However, biologists are still debating its function. Some believe it’s just a by-product of evolution, while others claim that it helps support the penis or stimulates females during coitus. Previously, Christian Sonne at Aarhus University, Denmark, and colleagues discovered that polar bears contaminated with high levels of pollutants called organohalogens reduces the size of the penile ball or baculum. This time, the team wanted to see what kind of effects a particularly nasty class of organohalogens, called  polychlorinated biphenyls (PCBs), has on the baculums.

Since the 1920s, PCBs had been widely used for industrial applications, including the production of  and rubber. A 2001 UN decision banned their use following conclusive reports that these harm health and cause cancer. But even if not one single molecule of PCBs was released since the ban was instated, it’s effects are still widely felt since it builds up in the atmosphere and is slow to break. The Arctic region is particularly vulnerable since this is where alarming concentrations of PCBs form, brought down by deposits of cooler air.

Polar bear baculum. Image: Marine Bio

Polar bear baculum. Image: Marine Bio

In collaboration with Canadian researchers, the team examined baculum specimens from 279 polar bears from north-east Greenland and Canada, all born between 1990 and 2000. Apparently, polar bear penile bones are easy to come buy since they’re often kept as trophies by hunters. It’s an actual sign that you have hunted and shot a bear, according to Sonne.

Using X-rays, the researchers calculated the calcium density and each bone. Comparing their figures against data on locally recorded levels of a range of harmful pollutants, they found a link between high PCB levels and low baculum density, as reported by New Scientist. As mentioned earlier, the role of the baculum is unknown by Sonne and colleagues believe a weaker peline bone significantly increases the risk of rupture. If this happens, a male will be unable to copulate. The paper was published in the journal Environmental Research.

Besides pollution, climate change is also contributing to the polar bears’ sexual demise in what seems to be a vicious cycle, according to Andrew Derocher at the University of Alberta in Edmonton, Canada.

“Skinny bears have higher levels of circulating pollutants, so the concern is that a bear that is nutritionally stressed may become more vulnerable to the effects of pollution at the same time,” says Derocher.

Next, the Danish researchers plan on tracking whether food shortages and pollution has triggered any evolutionary change in the polar bear population. It’s likely that many bears died over the past decades from pollution and those who’ve survived and those who follow may have responded in some way.

Brown-polar-bear hybrids at Germany’s Osnabrück Zoo. (c) Corradox/Wikimedia Commons

Animal hybridization accelerated by climate change

Brown-polar-bear hybrids at Germany’s Osnabrück Zoo. (c)  Corradox/Wikimedia Commons

Brown-polar-bear hybrids at Germany’s Osnabrück Zoo. (c) Corradox/Wikimedia Commons

What do you get when you cross a grizzly bear with a polar bear? Simple, a prizzly bear or golar bear, depending on the side you’re looking from. What about a narwhal with a beluga whale? A narluga! No, these aren’t childish word plays, nor elaborated photoshop attempts – these animals truly exist and come as a result of animal hybridization due to climate change, which has forced certain species to come into contact with related ones.

A recent study PLOS Genetics found, however, that hybridization – at least between polar, brown and black bears – is far from being  a new fad. The team of international researchers obtained genome-wide sequence data for seven polar bears, one ABC Islands brown bear, one mainland Alaskan brown bear, and a black bear (U. americanus). Subsequent analysis revealed ancient gene flow from the polar bear to the seemingly isolated ABC brown bear, however the reverse (brown bear to polar bear) wasn’t found.  As expected, polar bears and brown bears show similar pairwise genomic divergence from the black bear. Likewise, the polar bears, brown bears, and black bears all show similar genomic divergence from the giant panda (Ailuropoda melanoleuca).

Melting sea ice is accelerating hybridization, however, as polar bears are forced ashore to an Arctic habitat that’s increasingly hospitable.  In Canada there have been a number of reported sightings of peculiar looking bears, that are neither brown, black, nor polar, presenting coloring anomalies such as muddy-looking snouts and dark stripes down their back all on the body of a brown bear.

Stranded hybrid narwhal-beluga porpoise found on San Juan Island, May 21 2011. The hybrid lacks the narwhal signature tusk. (c)The Whale Museum

Stranded hybrid narwhal-beluga porpoise found on San Juan Island, May 21 2011. The hybrid lacks the narwhal signature tusk. (c)The Whale Museum

Hybridization isn’t reserved for bears, however. For instance, a 2010 published study lists  34 possible and actual climate-change-induced hybridizations, including those between narwhals and beluga whales or between northern and southern squirrels, among other.

While hybridization is good in most cases, since its a sign that species adapt, it might force some rare species into extinction. Hybrid species are met with a higher degree of infertility, even so since they’re more adapted, they might expel their parental lineage.

“As more isolated populations and species come into contact, they will mate, hybrids will form and rare species are likely to go extinct,” the authors wrote. “As the genomes of species become mixed, adaptive gene combinations will be lost.”

A good example is the now extinct Neanderthal population that was folded into the human gene pool thanks to early humans in Europe more than 47,000 years ago. For now hybridization is rather difficult to assess whether it’s good or bad, but studies such as these help deepen our understanding. More work in this direction is mandated, however, as sea ice melts even further in order to assess the dangers posed to species at risk.

story via Smithsonian

Oil barons and hunters threaten polar bear protection

As the global oil supply is starting to grow thin, the Arctic area seems to be more and more interesting to oil barons, but of course, there’s the problem of those pesky protected animals – so what do we do? Get rid of that, of course. A group of plaintiffs including the state of Alaska (who has already said they believe polar bears are just slowing the natural resources exploitation), hunters, and of all things, the California Cattlemen’s Association challenged the protected status of polar bears, deeming it as “arbitrary and capricious”.

It’s like one of those old movies or Captain Planet cartoons – basically, the big shots want to get the polar bears out of the picture so they can move on with their affairs, despite the obvious, irreparable damage which will be done to the environment. Polar bears have been declared endangered because their icy habitats are continuously retreating (as a consequence of global warming), and not only are they affected directly, but their prey is also affected. Still, Murray Feldman, a lawyer representing Alaska, and other appellants told the U.S. Court of Appeals for the District of Columbia that the decision to list polar bears as ‘threatened’ species was based on flaw models, and that polar bear populations will continue to remain stable even after the oil rigs are put in place.

How can I even get started with this? It’s common sense, polar ice has reached a historic minimum, and if the general trend continues, it will go lower and lower each year. Polar bears require … polar environment; without it, they will perish as a species. Also, oil rigs will create a number of associated environment hazards, all of which will contribute to the demise of the species (pollution, destruction of habitat, scaring off other animals, etc). Katherine Hazard, a lawyer for the Interior Department’s Fish and Wildlife Service explained that polar bears have been declared endangered following decade-long studies and reports.

“The agency needs to make a determination based on the best available science, which the agency did here.”

The interests are, of course, significant, so they aren’t challenging the status just on a whim. This is a serious situation, which could create an extremely dangerous precedent. If they will be allowed to go on with these shenanigans, if they will be allowed to continue with oil extraction plans, we will lose something much more important than resources: we will lose our humanity.

As shown in this image, the nuclear genomes of bears (black outline), suggest that polar bears and brown bears diverged from one another 4 to 5 million years ago, and that occasional exchange of genes between the two species (shaded gray areas) followed. Results from maternally inherited mitochondrial DNA (dotted line) indicates extinction (marked with an "X") and replacement of polar bear mitochondrial DNA around 160,000 years ago due to interbreeding between the two species. (c) Penn State University

Polar bears interbred with brown bears during warmer climate

A new research has found after analyzing the genomes of polar bears and brown bears that the two species interbred, after the two species split some 5 million years ago, during periods of warmer climate. Recent evidence suggests this is happening today as well, as an effect of global warming.

The team of scientists from Pennsylvania State University and the University at Buffalo, sequenced the genomes of polar and brown bears and found that polar bears evolved into a distinct species some four or five million years ago. Previously polar bears were thought to be a lot younger as a species, but this new research also takes into accounts its rather complicated interbreeding history with brown and black bears as well.

“Maybe we’re seeing a hint that in really warm times, polar bears changed their life style and came into contact, and indeed interbred, with brown bears,” says Stephan Schuster of Penn State.

Schuster and colleagues sequenced the genomes of three brown bears and a black bear and compared them with the genomes of polar bears, one modern and the other obtained from remains from a 120,000-year-old polar bear. “Very few vertebrate species have such comprehensive genomic resources available,” says Schuster.

As shown in this image, the nuclear genomes of bears (black outline), suggest that polar bears and brown bears diverged from one another 4 to 5 million years ago, and that occasional exchange of genes between the two species (shaded gray areas) followed. Results from maternally inherited mitochondrial DNA (dotted line) indicates extinction (marked with an "X") and replacement of polar bear mitochondrial DNA around 160,000 years ago due to interbreeding between the two species. (c) Penn State University

As shown in this image, the nuclear genomes of bears (black outline), suggest that polar bears and brown bears diverged from one another 4 to 5 million years ago, and that occasional exchange of genes between the two species (shaded gray areas) followed. Results from maternally inherited mitochondrial DNA (dotted line) indicates extinction (marked with an “X”) and replacement of polar bear mitochondrial DNA around 160,000 years ago due to interbreeding between the two species. (c) Penn State University

Previous research, which only looked at small segments of DNA, had polar bears as being only 600,000 years old as a distinct species. Data from Schuster’s team suggests after split between polar and brown bears, the two species remained isolated for some time, allowing genetic changes to accumulate, before interbreeding more recently, their analysis indicates.

“We showed, based on a consideration of the entire DNA sequence, that earlier inferences were entirely misleading,” says Webb Miller of Penn State.

Hybridization between the two species has continued to this day. As Arctic sea ice upon which they live recedes ever more and polar bears become forced to spend increasingly more time on land, this trend is set to intensify.

“Recently, wild hybrids and even second-generation offspring have been documented in the Northern Beaufort Sea of Arctic Canada where the ranges of brown bears and [polar bears] appear to overlap, perhaps as a recent response to climatic changes,”  the researchers write.

The findings were presented in the journal PNAS.


Climate change causes animals to shrink

Global warming has significant consequences to Earth’s ecosystems, each effect triggering another one in a slew of chain reactions. Frighting enough, rising temperatures and changed global weather patterns has caused certain types of plants and animals to become smaller, claims a new study published Monday in the journal Nature Climate Change.

Warmer and drier weather causes plants and animals to reach smaller sizes,  which frankly it wouldn’t be that much of a problem if every organism on earth would shrink at the same rate. Unfortunately, this is not the case since some species get smaller in size with each passing generation, while others remain the same, which in terms puts the entire world ecosystem out of balance. Over the past century animals including toads, tortoises, blue tits, Soay sheep and red deer have all started to reduce in size, scientists claim in the study.

“The consequences of shrinkage are not yet fully understood, but could be far-reaching for biodiversity and humans alike,” said Dr David Bickford and Jennifer Sheridan of the National University of Singapore.

“Because recent climate change may be faster than past historical changes in climate, many organisms may not respond or adapt quickly enough. This implies that species may go extinct because of climate change.”

Climate change is a cyclic phenomena, and though out its history the Earth has went through numerous such disruptions. Fossil evidence dating from the Palaeocene-Eocene (55 million years ago), for instance, shows that around that time the average world temperature rose between 3-7% , which in term lead to the shrinkage of invertebrates, including beetles, bees and spiders,  by 50 to 75 percent.

In the past century, the Earth has warmed by 1C, while some climate experts  predict 7C of warming by 2100. Past experimental research implies that for every 1C added in temperature, a variety of plants lose between 3-17% in size, while fish shrink by 6-22%.

Cold-blooded animals, the majority here on Earth, are most vulnerable in the face of global warming, since it causes their metabolic rate to increase. Amphibians, particularly, are at an even greater risk because of their already small size. Thus, they need more food to maintain their size, otherwise they’ll shrink. As for warm-blooded animals, they’re organism allows them to better conserve their body heat, so the colder the climate, the bigger the animals there, generally speaking. Lower levels of sea ice, directly correlated to an increase of temperature in the region,  have resulted, however, in polar bears getting smaller.

“Continued global warming is likely to favor smaller individuals, and we predict that organism size will continue to decrease over the century,” Sheridan and Bickford write.

It’s evident there’s an imbalanced ecosystem in play at the moment, which will only get worse. For humans, changes in organism size could have a direct effect on our food supply, for instance, through crops and fisheries.

“The worst-case scenarios … are that food crops and animals will shrink enough to have real implications for food security,” Bickford told Reuters. “Impacts could range from food resources becoming more limited… to wholesale biodiversity loss and eventual catastrophic cascades of ecosystem services… We have not seen large-scale effects yet, but as temperatures change even more, these changes in body size might become much more pronounced — even having impacts for food security.”


The fight for survival – a single bear vs a colony

As we enjoy our peace and quiet (or at least we should be), we shouldn’t forget that how the society we’ve built leads to an ever fiercer fight for survival. Here’s a movie that really touched me, with an ending you don’t (thankfully) see every day.