New Field Study Observations Prove Polar Bears Are Thriving

Written by Dr Susan Crockford on February 27, 2023. Posted in Current News

There is irrefutable evidence from Barents and Chukchi Sea subpopulations, among others, that polar bears are fat and reproducing well despite marked declines in summer sea ice over the last two decades

These indicators of physical and reproductive health, in any species, are signs of thriving populations.

However, these facts negate the premise that polar bears require abundant summer sea ice to flourish, and that creates a problem for polar bear specialists who continue to make that claim (Amstrup et al. 2007; Crockford 2017, 2019).

In other words, the assessment that polar bears are currently thriving is not based solely on estimates of a slight increase in global population size but on published data gathered from field studies on the bears’ physical and reproductive health.

Oddly, biologists repeatedly turn to data from Western Hudson Bay to drive home to the public their preferred message that polar bear health and abundance are being negatively affected by recent summer sea ice declines.

However, they fail to mention that robust field data from many other regions, including the Barents and Chukchi Seas, support the opposite conclusion.

Moreover, wherever possible, they mumble under their breath (or leave out entirely) the fact that poor ice conditions could not be blamed for a 27 percent decline in polar bear numbers in Western Hudson Bay since 2016 — because their own data showed sea ice conditions had been strong!

Population numbers

Polar bear specialists refuse to update their 2015 global population estimate of 26,000 to reflect recent subpopulation survey results but when those data are taken into account (e.g. Conn et al. 2021; Dyck et al. 2021, 2022; Matishov et al. 2014), the average global population estimate comes to about 32,000 with a wide range of potential error.

Although this modest increase is not statistically significant, it would likely take a 50 percent increase over that 26,000 estimate to meet that benchmark, considering that a recent 42 percent increase in Svalbard polar bear abundance was deemed statistically insignificant (Aars et al. 2017).

Although a case has been made that global numbers may indeed be as high as 39,000 (Crockford 2019), that’s not why polar bears are said to be thriving.

Barents Sea/Svalbard

Spring research in Svalbard, Norway in 2022 showed body condition of male polar bears was stable and the number of females with cubs (both cubs-of-the-year and one-year old cubs) were up compared to many previous years.

While many bears have abandoned the Svalbard region for less volatile ice conditions in the eastern Barents Sea around Franz Josef Land, the 300 or so that remain are still doing well (Aars 2015, 2018, 2022; Aars et al. 2017; Anderson et al. 2012; Haavik 2022), despite having lost 5-6 times as much summer ice as Western Hudson Bay (Lippold et al. 2019:988; Regehr et al. 2016).

The graph below shows that the number of females with cubs-of-the-year (blue dots) and one-year-old cubs (red dots) were both up slightly in 2022, although overall, neither metric had a significant trend (declining or increasing) over time:

Body condition of adult male bears shown below was down a bit in 2022 but not significantly, and 2019 saw bears in the best condition since 1995 (2020 data is missing):

Body condition of females is not presented in the annual records posted by Norwegian researchers but Jon Aars stated in 2022 that females were in excellent condition, continuing the trend documented in a 2019 published study (Lippold et al. 2019).

“Unexpectedly, body condition of female polar bears from the Barents Sea has increased after 2005, although sea ice has retreated by ∼50 percent since the late 1990s in the area, and the length of the ice-free season has increased by over 20 weeks between 1979 and 2013.

These changes are also accompanied by winter sea ice retreat that is especially pronounced in the Barents Sea compared to other Arctic areas” [Lippold et al. 2019:988, my bold]

Chukchi Sea

An aerial survey of the Chukchi Sea in 2016 generated a population estimate of 5,444 (range 3,636–8,152), about 2,500 greater than a previous survey (Conn et al. 2021; Regehr et al. 2018).

Field studies found Chukchi Sea bears have been in excellent condition and reproducing well, and are not spending more time on land during the summer than they did during the 1980s (Rode et al. 2014, 2018, 2021, 2022; Wilson et al. 2016).

Reports in early 2022 that polar bears have been moving from Alaska to Russia in a ‘mass exodus’ may describe a real phenomenon that reflects the excellent feeding conditions for bears in the Chukchi Sea compared to Alaska, fueled by continued increases in primary productivity made possible by less summer sea ice (Frey et al. 2022).

The Chukchi Sea has lost as much summer sea ice since 1979 as Western Hudson Bay (Regehr et al. 2016).

“Chukchi bears remain larger and fatter and have not seen downward trends in cub production and survival, according to new preliminary information on the health and numbers of bears.” [The Province, interview with Eric Regehr, 2018, my bold]

Other Thriving Subpopulations

Davis Strait: Results from the 2017–2018 survey revealed most bears were fatter than they had been in 2005–2007, with good cub survival; the authors found no relationship between bear survival and summer sea ice conditions, including number of ice-free days (Dyck et al. 2022).

M’Clintock Channel: Dyck et al. 2021 found that by 2014-2016, this subpopulation in the central Canadian Arctic had increased in abundance and body condition of bears had improved since the previous study, likely due to increased biological productivity.

Kane Basin: Field work by polar bear specialist Kirstin Laidre and colleagues (2020) found that numbers had not only increased significantly (from about 224 to 357, a 59% increase) but that bears were in excellent condition and reproducing well.

“Our study provides evidence for range expansion, improved body condition, and stable reproductive performance in the KB polar bear subpopulation. These changes, together with a likely increasing subpopulation abundance, may reflect the shift from thick, multiyear ice to thinner, seasonal ice with higher biological productivity.” [Laidre et al. 2020: abstract, my bold]

Gulf of Boothia: Local Inuit insist polar bears are physically “robust” and abundant; a recent survey conducted by biologists concluded the population was stable but noted improved body condition since the previous study. High survival of adult females and cubs indicated “healthy reproduction” despite the region having the highest known density of bears anywhere in the Arctic (8.9 bears per 1,000km2) (Dyck et al. 2023).

Southeast Greenland: Researchers Kristin Laidre and colleagues discovered a previously unknown subpopulation of about 234 polar bears living in SE Greenland (below 64 degrees N) that are genetically distinct and geographically isolated from East Greenland bears to the north. Photos provided by the authors show fat bears at the end of summer (see one above) and they state:

“Adult female body mass, an important determinant of cub production and survival, was lower in Southeast Greenland than in several other subpopulations but was similar to that of Northeast Greenland bears and the Barents Sea subpopulation, both of which use glacial fjords.” [Laidre et al. 2022: 1334, my bold]

Western Hudson Bay

Not thriving but not due to lack of sea ice. Far from being representative of all subpopulations, it is an anomaly.

A Western Hudson Bay survey conducted in 2021 revealed a 27 percent decline in polar bear abundance over the previous five years but the information released to the media in late December 2022 (still no report publicly available) admits that reduced summer sea ice conditions could not be responsible for this population decline because sea ice conditions had been “moderately good” for four out of five years.

This is surely an understatement, as another study found no temporal trend in sea ice or departure dates of polar bears from shore between 1991 and 2020 (Miller et al. 2022) and in several years, preliminary information on departure dates suggest they were as early as they had been in the 1980s.

No details about the body condition of WH bears were released to the media to substantiate the implication that large numbers of bears could have starved to death between 2017 and 2021.

Conclusion

Polar bears in most studied subpopuatlions that have been recently assessed (seven so far) are in good or excellent body condition and reproducing well.

These are known indicators of a thriving species.

The evidence to date shows that declines in summer sea ice have not been detrimental to polar bear health and survival. On the contrary, in virtually all areas, much less sea ice has been beneficial: the opposite of what polar bear models predicted would happen.

Thriving subpopulations prove there is no “immediate existential threat to the entire species,” as the chief research scientist from activist organization Polar Bears International would have the public believe:

“It is both simultaneously true to point to part of recent history and say there’s a conservation success story here, and that should rightfully be celebrated, and to also say there’s an immediate existential threat to the entire species right now,” said John Whiteman, chief research scientist for Polar Bears International. [2 December 2022, It’s misleading to claim that polar bears are ‘thriving’ because of ‘increasing population’, my bold]

See more here polarbearscience

Some bold emphasis added

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