Petition Congress to Investigate USGS Polar Bear Research Methods

 More Research Finds Polar Bears’ Condition Unaffected by Reduced Summer Sea Ice.

Reasons to Petition Congress to Investigate USGS’ Dubious Polar Bear Claims

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Although the Inuit steadfastly claim it is “the time of the most polar bears”, the most recent IUCN polar bear assessment predicts a 30% drop in the global polar bear population by mid‑century by assuming a linear correlation between summer sea ice melt and polar bear survival. They suggest bears “require sea ice to hunt” and thus predict less sea ice will prevent access to their preferred prey. However polar bear ecology and observations contradict that simplistic assertion. As listed below the current alarming predictions are due to extremely biased models and critical sins of omission presented in USGS publications, which ultimately misguide conservation efforts and the public’s understanding of the effects of climate change. Please petition congress to promote more reliable polar bear population studies and sign the petition here:

1)   Greater than eighty percent of most polar bears’ annual stored fat is accumulated during the ringed seal pupping season that stretches from late March to the first week of May. Well‑documented observations (Stirling 2002, Harwood 2012, Chambellant 2012) report that cycles of heavy springtime sea ice have drastically reduced ringed seal reproduction. Heavy springtime ice is likely the greatest cause of polar bear nutritional deprivations, yet not one USGS model incorporates sea ice conditions during this critical time.

2)   In areas like the Chukchi Sea that have experienced some of the greatest reductions in summer sea ice, there has been no reduction in polar bear body condition and some improvement (Rode 2014), contradicting USGS models driven by the hypothesis that less summer sea ice leads to nutritional deprivation.

3)   All USGS models incorporate measures of minimal summer sea ice area in September despite the fact that ringed seals leave the ice in June, after pupping and molting, and swim in distant open waters. During this time less summer ice has little effect on the accessibility of seals.

4)   USGS models assume more open water is detrimental to polar bears. But all published ecological studies (i.e. Harwood 2012, Chambellant 2012) show that ringed seal body condition, and thus seal reproductive outputs, decline when sea ice is slow to clear in the spring. It is longer periods of sea ice that cause lower ringed seal body condition and reproductive fitness that ultimately reduces the polar bears’ prey availability.

5)   The IUCN’s assessment predicting a 30% decline in the global polar bear population is driven largely by the USGS’ models suggesting unique declining polar bear population in Southern Beaufort Sea’s. USGS models:

a.     -calculated unrealistic bear survivorship estimates (0.77 here) during 2005 and 2006 based on mark and recapture models, that were unrealistic compared to known survivorship calculations of radio-collared bears (0.969 here) and survivorship estimates in 2002 to 2004. Only by uncritically embracing unrealistically low survivorship, USGS models created a dramatic drop in estimated abundance.

b.     -blamed less summer ice and global warming for re‑capturing fewer bears, despite observations that heavy springtime sea ice had reduced seal ovulation rates to 30% in 2005 (Harwood 2012), the year models determined the lowest survivor rate for adult bears.

c.      -ignored the 70% reduction in seal pups in 2005 due to heavy springtime ice that forced polar bears to increasingly hunt outside the USGS’ study area and making marked bears unavailable for re‑capture. As discussed here and here, the lack of recaptures due to temporary emigration is easily mistaken as a bear’s death.  The USGS dismissed their own observations of increased transiency. And despite acknowledging an increased number of radio-collared bears outside the study area in 2005 and 2006, USGS modelers suggested that instead of searching elsewhere, bears just died, resulting in a dramatic population decline without the bodies to prove it.

d.     -never published calculations of biological survival for known radio‑collared bears (10% of their study). Biological survival calculations provide a constraint on the reliability of estimated apparent survival from mark and recapture models. Previous research demonstrated that modeled apparent survival dramatically underestimates true biological survival.

Additional Supporting Evidence for Petitioning a USGS investigation

Whether or not reduced Arctic sea ice is the result of natural variability or rising CO₂, reduced sea ice benefits the Arctic ecosystem. As discussed in Why Less Summer Ice Increases Polar Bear Populations, evidence and theory unequivocally demonstrates that less ice allows more sunshine for plankton to photosynthesize, causing marine productivity to increase 30% this decade (i.e. Arrigo 2015). Increased marine productivity then reverberates throughout the entire Arctic food chain benefitting cod that are fed on by seals that are fed on by bears. Furthermore all observations have determined that thinner sea ice benefits ringed seals, the polar bears main prey item. Contrary to alarming assertions, less sea ice has generated a more robust food chain!

In a recently published United States Geological Survey (USGS) article, Rode et al (2015) Increased Land Use by Chukchi Sea Polar Bears in Relation to Changing Sea Ice Conditions, researchers tracked radio-collared bears in the Chukchi Sea region and analyzed how much time bears spent on land versus sea ice for the months of August to October. Then they compared that behavior between the 1986–1995 period to 2008–2013. As should be expected with less sea ice, bears naturally spent more time on land. However despite theoretical assertions that less sea ice causes polar bears to suffer “nutritional deprivation”, these researchers observed that a 

“lack of a change in the body condition and reproduction of Chukchi Sea polar bears during the time period of this study suggest that Chukchi Sea polar bears either come onshore with sufficient body fat or they are finding sufficient food resources on land (marine or terrestrial) to offset increased durations on land.” 

This confirmed an earlier study during that same time period concluding, “body condition was maintained or improved when sea ice declined”. 

In 2007 the 2^nd greatest decrease in Arctic sea ice was observed in the waters surrounding Wrangel Island in the Chukchi Sea. That summer researchers likewise observed greater numbers of polar bears on the island. However again contradicting the “less‑ice‑means‑starving‑bears” theory, there were no signs of increased nutritional stress. Quite the opposite! Researchers determined that only less than 5% of the Wrangel Island bears were skinny or very skinny and that compared very favorably to their previous designations of the 7 to 15% skinny bears observed in years with heavier ice. Furthermore researchers determined that not only did 29% of all bears look “normal”, the remaining 66% were fat or very fat.  Those polar bear experts wrote, 

“Under certain circumstances, such as were observed on Wrangel Island in 2007, resources available in coastal ecosystems may be so abundant that polar bears are able to feed on them more successfully than while hunting on the sea ice.”

Wrangel Island equally illustrates Rode (2015)’s alternative explanation for finding healthy polar bears on land: bears can find sufficient food resources on land to supplement their diet after ringed seals leave the ice.” In the essay Has David Attenborough Become A Propaganda Mouthpiece Promoting Climate Fear?  I provided links to published accounts from past centuries and earlier BBC videos demonstrating that polar bears throughout the Chukchi Sea commonly hunt walrus on land; a fact that Attenborough distorted into a cinematic illusion misrepresenting a natural behavior as a function of catastrophic climate change. There is a long list of observations of bears on land actively hunting walruses, reindeer and fish, foraging on berries or scavenging whale carcasses. Although there has been a hypothetical debate on whether or not such supplemental diets could provide the appropriate calories to maintain polar bears’ body condition, based on observations, most bears are doing just fine during years with reduced sea ice.

So why is it suggested that less sea ice reduces polar bears access to food? The short answer is the politics of the “climate wars”. For centuries walruses and polar bears have been observed on land despite much heavier Arctic sea ice during the Little Ice Age. However in the past decade there is a widespread attempt in the media to characterize observations of walruses and bears on land as a “perversion” caused by less sea ice from rising CO2. Skinny injured bears absurdly become media icons of climate change. Yet there is a multitude of peer-reviewed evidence (i.e. McKay 2008,  Fisher 2006) that bears and walruses are well adapted to thrive in the extensive periods of reduced Arctic sea ice that were much less than today and persisted throughout the last 10,000 years of the Holocene.

Nearly every alarmist publication that asserts less sea ice causes polar bears to suffer from nutritional stress references as “proof” a 1999 paper by Ian Stirling showing body condition of bears in the western Hudson Bay declined from the 1980s to 1997. However, as seen in the graph below, since 1997 western Hudson Bay polar bears’ body condition has been improving surpassing levels observed in the1980s despite, or because of, years of reduced sea ice. The unpublished improvements of polar bear body condition during the 2000s corresponds well with published reports that since the heavy ice years of the early 1990s reduced ringed seal body condition and reproduction, ringed seal pups tripled during subsequent lighter ice years of the 2000s.  However Nicholas Lunn of Environment Canada, has yet to publish that data, while Lunn and other PBSG researchers continue to reference only older zombie pre‑1997 data in assessments as recently as 2014. Publication bias that fails to report positive changes has been a disturbing phenomenon observed elsewhere by authors making catastrophic climate assertions (here and here). Dr. Susan Crockford has also highlighted Lunn’s penchant for deceptive reporting here as he attempts to downplay a recent survey that reports increasing bear populations in the Hudson Bay area.

The recent assessment submitted to the International Union for the Conservation of Nature argued a “reduction in mean global population size greater than 30%” by mid‑century. In contrast all polar bear populations have increased after imposing hunting regulation in the late 60s and 70s. Despite a decadal trend of declining sea ice only 3 of 19 populations are now reported to be declining and uniquely only the Southern Beaufort Sea population is attributed to climate change. The Baffin Bay population has declined due to increased hunting by Greenlanders, and declines in the Kane Basin are attributed to low seal populations due to thick multiyear ice. Of the 7 sub‑populations for which there was comparative data presented in the IUCN’s report, four sub‑populations (Foxe Basin, Gulf of Boothia, Davis Strait, Northern Beaufort) have shown increasing populations. Two subpopulations (Western and Southern Hudson Bay) have shown no significant population change (Stapelton 2014).

Only the Southern Beaufort Sea population suggests a dramatic loss of polar bears, yet before the heavy springtime ice in 2005 there was little sign of reduced body condition. A 2007 USGS study reported that between 1982 and 2006, 95% of the bears in the Beaufort Sea region, exhibited body conditions that were stable or improving. Adult female bears that represented about 34% of all captures exhibited improved body condition. All other categories of bears showed no trend in body condition except for sub-adult males that comprised a mere 5% of the individuals examined. Stable and/or improving body condition again is evidence that the lack of summer sea ice has no detrimental effect on the body condition of polar bears. Nonetheless a co-author of that 2007 study, USGS’ Eric Regehr, used the same data to proclaim in a 2010 paper, “evidence suggests that polar bears in the southern Beaufort Sea are under increasing nutritional stress. From 1982 to 2006, body size and body condition for most sex and age classes were positively correlated with the availability of sea ice habitat, and exhibited a statistically significant decline during this period.” 

It is well documented that the Arctic undergoes periodic events producing heavy springtime sea ice that reduces local ringed seal populations in various locations. Ian Stirling co-authored a paper reporting, “heavy ice reduces the availability of low consolidated ridges and refrozen leads with accompanying snowdrifts typically used by ringed seals for birth and haul-out lairs.” He observed in 2005 and 2006, “Hunting success of polar bears (Ursus maritimus) seeking seals was low despite extensive searching for prey.” The most recent paper by USGS researchers Bromaghin 2014 (and discussed here) acknowledges the decline in seal reproduction, yet they never acknowledge that it was a result of a cyclic increase in thick spring ice. As spring ice conditions have now returned to normal, seal ovulation rates also returned to normal, approaching 100%, and the Southern Beaufort bear population is now increasing.  Yet because the USGS researchers continue to assert population declines are due to less summer ice and CO2 climate change, they conclude, 

“For reasons that are not clear, survival of adults and cubs began to improve in 2007.”  

But the reasons are not unknown! The USGS simply refuses to acknowledge global warming and lost summer sea ice has not produced any catastrophic change for polar in the recent past. And the prediction of a 30% decline is a myth that they choose to perpetuate.

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Polar Bears Endangered? Are Some Researchers Hiding Evidence?

PolarBeargate? Are Some Researchers Hiding Evidence? 

Suggesting impending climate doom, headlines have been trumpeting polar bears are “barely surviving” and “bears are disappearing” prompted by a press release hyping the paper Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline (hereafter Bromaghin 2014), which based on an ongoing US Geological Survey (USGS) study. Dr. Susan Crockford rightfully criticized the media’s fear mongering and failure to mention increasing bear abundance since 2008. She also pointed out that modelers have consistently failed to account for the negative impacts of heavy springtime ice here.

I want to reinforce Crockford’s posts, plus argue the problem is much worse than she suggested. Bromaghin 2014’s purported 25 to 50% population decline is simply not real. The unprecedented decline is a statistical illusion generated by the unrealistic modeling of polar bear survival from 2003 to 2007.  The highly unlikely estimates of low survival were made possible only by ignoring the documented effect of cycles of heavy springtime sea ice which forces bears to hunt outside the researchers’ study area. Although several of Bromaghin’s co-authors had previously published about negative impacts of heavy springtime ice, they oddly chose to never incorporate that evidence into the USGS models. The following demonstrates how the statistical illusion of “disappearing polar bears” was generated and I urge you to forward your concerns about USGS fear-mongering via subjective modeling to your congressmen and push them to fully investigate these USGS’ polar bear studies.

Perhaps polar bear researchers are just victims of confirmation bias. Co-authors of Bromaghin 2014 have long tied their authority, fame and fortune to predictions of impending polar bear extinctions due to lost summer sea ice.  In a 2008 Dr. Andrew Derocher predicted, “It's clear from the research that's been done by myself and colleagues around the world that we're projecting that, by the middle of this century, two-thirds of the polar bears will be gone from their current populations”. Dr Steve Amstrup, chief scientist for Polar Bear International and the USGS researcher that initiated the Beaufort Sea studies, previously published “Declines in ice habitat were the overriding factors determining all model outcomes. Our modeling suggests that realization of the sea ice future which is currently projected, would mean loss of ≈ 2/3 of the world’s current polar bear population by mid-century.”¹Furthermore the USGS’ political reputation is on the line because their studies led to the listing of polar bears as “threatened” due to decreasing summer ice they attributed to CO2 warming. But why do USGS model estimates differ from Inuit experts and the Nunavut government who have steadfastly claimed it is the time of the most polar bears. And why does the USGS’ models differ from numerous surveys (i.e here and here) that support the Inuit claims?

There are 2 major flaws in USGS models:

1)   USGS Polar bear researchers tirelessly point to hypothesized stress due to lost summer sea ice, yet they completely ignore much more critical cycles of heavy springtime ice. As previously documented by Bromaghin’s co-authors, the condition of springtime sea ice determines the abundance and/or accessibility of ringed seal pups. Eighty percent or more of the bears’ annual stored fat is accumulated during the ringed seal pupping season that stretches from late March to the first week of May. At that time female bears emerge from their maternity dens to feast on ringed seal pups, and accordingly USGS mark and recapture studies focus virtually all their efforts during the month of April. Yet not one model has incorporated known changes sea ice during that same period. Is that data purposefully omitted because heavy spring time ice does not support their CO2-driven extinction scenarios?

2)   Furthermore heavy springtime ice forces movement outside the study area because it prevents local access to seal pups. Any movement outside the study area prevents subsequent recapture and can erroneously cause models to assume emigrant bears are dead. That false assumption creates lower survival estimates which then dramatically lower population estimates. Misinterpreting a temporary or permanent exodus away from a stressful local environment was the same critical error that led to bogus extinction claims for the Emperor Penguins.  Coincidently one modeler, Hal Caswell, created both models falsely suggesting Emperor Penguins and Polar Bears are both on the verge of extinction.

Why Spring Ice Conditions Are More Critical than Summer Ice.

South Beaufort Sea bears increase their body weight primarily by binging on ringed seal pups, and the bears’ springtime weight gains are huge. Researchers reported capturing a 17-year-old female, with three cubs-of-the-year, in November 1983 when she weighed just 218 lbs. Her weight would have continued to drop, as it does for all bears, throughout the icy winter. Weights do not increase until seal pups become available in late March and April. But after gorging on seal pups, she was recaptured in July and weighed 903 lbs, a four-fold weight change in just 4 months. ² (her picture is below). The ability to rapidly gain weight, hyperphagia, evolved as a crucial survival strategy to take advantage of abundant but temporary food sources. Springtime ice conditions govern their access to the fleeting availability of ringed seal pups.

Fat Polar Bear

In 2001, Bromaghin 2014 co-author Stirling described the negative impacts of heavy rafted springtime ice. 

“In the eastern Beaufort Sea, in years during and following heavy ice conditions in spring, we found a marked reduction in production of ringed seal pups and consequently in the natality of polar bears.” 

Stirling noted it took about 3 years for both seal and bear populations to rebound. Stirling also reported the South Beaufort Sea undergoes ~10-year cycles of such heavy ice, and those stressful cycle had been observed in the 70s, 80s and 90s. ⁵ The most recent cycle of heavy ice is well documented and occurred precisely when bears increasingly exited the study area from 2003 to 2007.

In 2008, Bromaghin 2014 co-authors Stirling, Richardson, Thiemann, and Derocher published Unusual Predation Attempts of Polar Bears on Ringed Seals in the Southern Beaufort Sea: Possible Significance of Changing Spring Ice Conditions. ¹⁰ Those researchers had observed that “unusually rough and rafted sea ice extended for several tens of kilometers offshore in the southeastern Beaufort Sea from about Atkinson Point to the Alaska border during the seals’ breeding season from 2003 through 2006”, precisely when their models calculated low survival and a rapid decline in the polar bear population.

Those researchers reported 

“heavy ice reduces the availability of low consolidated ridges and refrozen leads with accompanying snowdrifts typically used by ringed seals for birth and haul-out lairs.” And they observed, “Hunting success of polar bears (Ursus maritimus) seeking seals was low despite extensive searching for prey. It is unknown whether seals were less abundant in comparison to other years or less accessible because they maintained breathing holes below rafted ice rather than snowdrifts, or whether some other factor was involved.“ 

(Forcing bears to claw through rafted ice gives the seals ample time to escape.) Polar bears never defend territories. Instead polar bears are highly mobile. Dependent upon seal pups for most of their annual energy supply, a supply that varies annually, bears simply migrate to regions with greater seal abundance.

After giving birth and completing their annual molt by late June, most ringed seals migrate out to sea to fatten and are no longer available to the bears. After late June the amount of sea ice is no longer important habitat for ringed seals.So any correlations with summer sea ice extent from August to November have a relatively insignificant impact on survival. In fact, more open water benefits seals. In a previous essay, Why Less Summer Ice Increases Polar Bear Populations, I explained why ringed seals avoid thick multi-year ice, and why more open water later in the season benefits the whole food web. Bromaghin 2014’s co-author Stirling previously co-authored a paper reporting ringed seals must feed intensively in the open waters of summer in order to store the fat needed to survive the winter, and that seals suffer when sea ice is slow to break up. ⁴

He pointed out that in 1992 when breakup of sea ice was delayed by 25 days,the body condition of all ringed seals declined resulting in declining body condition of bears. To supplement their diet, bears will feed on a wide array of alternative items from whale carcasses, walruses to geese eggs. Despite the 2^ndlowest extent of Arctic summer ice in 2007, researchers on Wrangel Island reported fatter bears than they had previously documented.⁶ All the evidence suggests summer ice is far less critical than the condition of springtime ice. So is the erroneous focus on summer ice conditions merely driven by researchers predictions that rising CO2 will cause widespread polar bear extinctions in 30 years?

 Movement Lowers Survival Estimates which Lowers Population Estimates

Bromaghin 2014 authors acknowledged that the observed movement could bias model results, but simply dismissed the observed transiency of wandering bears writing, 

“The analyses of movement data suggested that Markovian dependency in the probability of being available for capture between consecutive years remains a potential source of bias. However, we view these results with some caution because of the small sample sizes and prior evidence that bears prefer ice in waters over the narrow continental shelf. Further, there is no reason to suspect behavior leading to non-random movement during the spring capture season changed during the investigation.” 

But their dismissal is nothing less than dishonest. Bromaghin 2014 authors had indeed observed that heavy springtime ice resulted inreduced hunting success and reduced body condition and would force bears to hunt elsewhere.

Bromaghin 2014 authors were denying their own evidence. A subset of bears had been radio-collared in order to track their movements. Between 2001-2003 when their study area experienced normal springtime ice conditions, researchers estimated high survival probability and high abundance, and only 24% of the radio-collared females had wandered outside their study area making them unavailable for recapture. In contrast during the years of heavy springtime ice between 2004 and 2006 researchers estimated unprecedented low survival, low abundance and observed an increased number of collared females outside the study area doubling to 47% in 2005 and 36% in 2006. ^7,9 Yet Bromaghin 2014 argue  “there is no reason to suspect behavior leading to non-random movement during the spring capture season changed during the investigation.”

A previous study by Amstrup had mapped the range over which radio-collared bears travelled each year. From his 3 examples illustrated below it is clear that polar bears are not always found in the same place each year. Furthermore in accordance with the changing availability of seal pups due to cycles of heavy springtime ice, he reported polar bears exhibited their lowest fidelity to any given area during the spring pupping season. Finally Amstrup’s map shows bears naturally wander outside the boundaries of the study areas searching for food. Because researchers restricted their search efforts to the east of Barrow Alaska, bears moving in and out of the Chukchi sea area have a far less recapture probabilities. Likewise bears that wander between Alaska and Canada will have different recapture probabilities because different amounts of effort were expended in each country.

Polar Bear movement out of study area

Due to movement of bears in and out of the Chukchi Sea region, Amstrup had determined those movements heavily biased previous survival and abundance estimates. ^{8, 12} Bromaghin 2014 also report that the Chukchi Sea region is more productive than the Beaufort Sea. So it is highly likely that bears migrate between the Beaufort Sea study area and the Chukchi Sea in response to varying periods of localized heavy springtime ice and seal pup availability. So why does Bromaghin 2014 dismiss observed movement bias by arguing  “there is no reason to suspect behavior leading to non-random movement during the spring capture season changed during the investigation” and contrary to their own evidence suggest bears would remain in the more productive Chukchi Sea region. 

In 2001 Amstrup had previously estimated survival rates of South Beaufort bears as 96.2% and natural survival rates were 99.6% and a population could be more than 2500 bears in 1998. ³  Amstrup reported “polar bears compensate for a low reproductive rate with the potential for long life” (i.e high survival). Because movements of bears into and out of his study area had greatly biased his results he warned, “models that predict rapid increases or decreases in population size would not mirror reality.” Curiouser and curiouser he no longer heeds his own advice. Amstrup and his colleaguessuddenly embraced the unprecedented low survival rates of 77%, and a rapid 25 to 50% decline in the population between 2004 and 2008 as seen in their graph of estimated abundance.

South Beaufort Sea Polar Bear population estimates

In order for their model to generate that unprecedented low survival rate of 77%, (despite no observed change in the trend of body condition for 95% of Beaufort Sea bears) ¹¹ modelers had to dismiss the observed movements outside their study area. Once Bromaghin’s authors had dismissed the significance of springtime movement, their models would interpret a lack of recaptures as an indicator of dead bears which then produced the illusion of a rapidly declining polar bear population.

Below is a table illustrating the simplified effects of historical survival estimates on abundance calculations (assuming no additions from new births and immigration). The numbers listed in the gray columns on the left are the USGS study’s actual number of bears captured annually, and the number of that total capture that were previously marked bears. As the study progressed and newly captured bears are marked, the pool of marked bears increases.  If the study area was a closed system, we would expect each year’s total number of captures to consist of an increasingly higher percentage of marked bears once the pool of marked bears was large enough. But each year the number of previously marked bears made up only ~50% of the total captures, suggesting a larger population was more likely than what was currently estimated, and that the length of this study was not yet long enough.

In the simplest models, abundance is determined by dividing the total number of bears captured each year by the percentage of captured marked bears from the pool of previously marked bears. (Read How science Counts Bears for a further discussion of mark and recapture studies) However the size of the pool of marked bears depends upon the bears’ survival probability. To illustrate, for each year I generated 3 different pools according to different historical survival estimates. The resulting change in abundance calculated from those 3 different survival probabilities are highlighted in yellow.

How survival estimates alter polar bear population estimates

 

If researchers assumed 100% survival, which is close to Amstrup’s 99.6% in his original study, (but with no additions from birth or immigration) then Bromaghin’s data would estimate a 2010 growing population of 2,255 bears. An estimate that is remarkably similar to Amstrup’s 1998 estimate of ~2500 bears. 

If the researchers assumed Amstrup’s 96% survival, a lower survival estimate due to the impact of hunting, then the 2010 abundance would be calculated at 1865 bears. Again remarkably close to Amstrup’s suggested abundance of 1800 for a hunted population.

In the 2006 USGS analyses, ⁷ the authors interpreted fewer recaptures as an averaged lower survival rate of 92%.  A 92% survival rate would produce a stable 2010 population estimate of 1664 bears, which is also 70% higher than Bromaghin’s results.  

The only way to generate a tragically declining bear population was to employ much lower survival estimates. And as evidenced by their graph below, that is just what they did for the period of heavy springtime ice with low seal availability and much greater movement out of the study area. When the springtime ice returned to normal so did the bears, and their estimated survival rates likewise returned to the expected high ~95%. The huge error bars in Bromaghin’s survival probabilities (see graph below) during those heavy ice years, illustrates the great uncertainty regards the actual fate of marked bears that were never recaptured.

Lower survival Polar Bear survival during heavy springtime ice

So we must question why these polar bear researchers ignored their co-author’s earlier warning, “models that predict rapid increases or decreases in population size would not mirror reality.” 

Were polar bear researchers blinded by climate change beliefs, or acting dishonestly?

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Literature Cited

1. Amstrup (2007) Forecasting the Range-wide Status of Polar Bears at Selected Times in the 21st Century  USGS Science Strategy to Support U.S. Fish and Wildlife Service Polar Bear  Listing Decision

2. Ramsay, M, and Stirling, I. (1988) Reproductive biology and ecology of female polar bears (Ursus maritimus). Journal of Zoology (London) Series A 214:601–634.

3. Amstrup, S. et al. (2001) Polar Bears in the Beaufort Sea: A 30-YearMark–Recapture Case History. Journal of Agricultural, Biological, and Environmental Statistics, Volume  6, Number 2, Pages 221–234

4. Chambellant, M. et al. (2012) Temporal variations in Hudson Bay ringed seal (Phoca hispida) life-history parameters in relation to environment.Journal of Mammalogy, vol. 93, p.267-281

5. Stirling, I. (2002)Polar Bears and Seals in the Eastern Beaufort Sea and Amundsen Gulf: A Synthesis of Population Trends and Ecological Relationships over Three Decades. Arctic, vol. 55, p. 59-76

6. Ovsyanikov N.G., and Menyushina I.E. (2008) Specifics of Polar Bears Surviving an Ice Free Season on Wrangel Island in 2007. Marine Mammals of the Holarctic. Odessa, pp. 407-412.

7. Regehr et al 2006, Polar bear population status in the southern Beaufort Sea: U.S.  Geological Survey Open-File Report 2006

8. Amstrup et al (2000) Movements and distribution of polar bears in the Beaufort Sea. Can. J. Zool. Vol. 78, 2000

 9.  Regehr, E., et al. (2010) Survival and breeding of polar bears in the southern Beaufort Sea in relation to sea ice. Journal of Animal Ecology 2010, 79, 117–127

10. Stirling, I. et al. (2008) Unusual Predation Attempts of Polar Bears on Ringed Seals in the Southern Beaufort Sea: Possible Significance of Changing Spring Ice Conditions.  Arctic, vol 61, p. 14-22.

 11. Rode, K. et al. (2007) Polar Bears in the Southern Beaufort Sea III: Stature, Mass, and Cub Recruitment in Relationship to Time and Sea Ice Extent Between 1982 and 2006. USGS Alaska Science Center, Anchorage, Administrative Report.

 12. Amstrup, S.  and Durner, G. (1995) Survival rates of radio-collared female polar bears and their dependent young. Canadian Journal of Zoology, vol. 73. P. 1312?1322.