Where were the starving W. Hudson Bay polar bears in 2020 if the population had declined by 2021?

From Polar Bear Science

Dr. Susan Crockfore

Polar bears are supposed to starve before they die, the experts said. They said only a few years ago that dead or emaciated individuals onshore were evidence that many polar bears would soon be dying of starvation out on the sea ice. So, if the Western Hudson Bay (WH) subpopulation had indeed dropped by 27% by late summer 2021 as researchers claimed, where are all the photos of starving bears in the fall of 2020, the year before the count? The photo below of a thin female and cub was taken in late fall of 2021 (the year of the count) by a stationary web cam. In other words, some bears came off the ice without an optimal amount of fat because of poor hunting conditions over the winter but they were still alive. We know that 2020 had the shortest ice-free season in at least 20 years (and no similar images were captured), so bears went into the winter of 2020/2021 in good condition. Ditto for 2017-2019. In contrast to 2021, in 2016 (the year of the previous survey that also indicated a declining population size), bears reportedly came off the ice in good condition.

All I’ve seen are photos of fat bears and fat cubseven a triplet litter in fall 2020. The shore of WH near Churchill should have been abounding with starving bears in 2020 (and in 2015), if the experts were right about starving bears preceding a population decline. More importantly, where are the studies on food-deprived bears onshore, as were done in the 1980s when WH bears were emaciated and cub survival poor (e.g. Ramsay et al. 1988)? WH bears are being used exclusively to model an implausibly pessimistic future for polar bears across the entire Arctic (Molnar et al. 2010; 2020), which means lack of good science for WH polar bears has big consequences. Covid restrictions in two of those ten years don’t excuse lack of study on this phenomenon.

Condition of bears since 2017

If adult females with cubs and young bears on their own for the first time actually starved to death over the winter of 2020/2021–accounting for a 27% decline in numbers documented in the fall of 2021–at least a few of those bears should have been come ashore in the summer of 2020 in poor condition. As a result of not eating over the summer months, those bears should have been skin and bones by late October/early November 2020 and died over the winter of 2020/2021.

Yet as far as I know, not a single photo of a lean or truly starving polar bear was shared on social media by locals or captured on the Explore.org stationary or buggy-mounted web cams in 2020 (which weren’t affected by Covid restrictions in 2020). There was certainly nothing in the media or shared by Polar Bears International. If I’ve missed any, please let me know.

The two lean bears below (probably youngsters) were photographed be the Explore webcam on 26 November 2021 just as ice formation had begun that fall. The photos of these bears, and of the thin female with cub above, indicate that some bears came off the ice that summer in less-than-ideal condition but were still alive. It’s what we should have seen in 2020 (and in years before that) but didn’t.

By 2022, Andrew Derocher said the bears his team out tagging bears in April were in good condition (by “past years”, he meant many years past, not the recent past, since he said bears were in good condition in 2019).

Although researchers weren’t out in fall 2020 because of Covid restrictions, the Tundra buggies of Frontiers North were out watching and photographing the bears even if they weren’t taking tourists (see photo below, taken 4 November 2020). Very good sea ice conditions in 2020 (late breakup, early freeze-up compared to early 2000s) and photos of fat bears taken by the webcams suggest the animals did very well that year.

More photos of fat bears below, most from the fall of 2020 and one from 2017, captured by stationary Explore.org web cams or those mounted on Tundra buggies (which I have monitored since 2017).

Below, bears on a fresh seal kill, 5 November 2020:

Below, female and yearly cubs on a seal kill, 31 October 2020:

Below, female with triplet litter, 15 September 2020:

Below, female with two cubs in good condition, 24 August 2020:

Below, big male in excellent condition, 10 November 2017:

The purported 27% population decline between 2017 and September 2021 would have required a large number of bears to have died very quickly of starvation over the spring of 2021, even though they were in good shape beforehand. That premise is hard to swallow without some kind of corroborating evidence.

That leads to an even bigger question. How does a population of polar bears supposedly decline by 40% over 10 years–from about 1030 in 2011 to about 618 in 2021–without significant numbers of bears in poor or very poor condition being documented in the years immediately before the counts were done, especially for the most-studied–and probably the most photographed–subpopulation in the world?

What happened in the 1980s?

In the 1980s, when it was known from yearly detailed studies that WH polar bears were really struggling (Calvert et al. 1986:19,24; Ramsay et al. 1988), polar bear specialists Ian Stirling and Andrew Derocher suggested that there might be too many bears in Hudson Bay (i.e., more bears than food to eat). Alternatively, it was suggested that something might have happened out on the ice during the winter that made it difficult for the bears to find ringed seals, their primary prey, although lack of data meant the possibility could not be confirmed (Derocher and Stirling 1992, 1995).

There was no apparent population decline in WH during the 1980s (1983-1990) as there had been in the Southern Beaufort between 1974 and 1976, when thick spring ice drove seals out of the region and left many bears to starve or move elsewhere themselves (Burns et al. 1975; Lentfer 1976:187, 192; Stirling 2002; Stirling et al. 1975a, 1975b, 1980, 1982, 1993, 2008), because compared to everywhere else, WH bears overall had been doing exceptionally well even when some bears were clearly starving (Stirling and Lunn 1997).

Regardless of the cause, the result for several years during the 1980s, some WH bears were in poor condition during the summer but no population decline occurred. These starving bears were impossible to ignore, as the details below show.

1983

Polar bear researchers Ian Stirling and Malcolm Ramsay emphasized that the mean weight of pregnant females they encountered in 1983 was 37kgs lighter than in other years (Ramsay and Stirling 1988:615). These authors stated:

“...bears of all age and sex classes in the summer and autumn of 1983 appeared to us, at the time of capture, to be, on average, in poorer condition than at equivalent seasons in the years previous and subsequent. Some qualitative behavioural observations corroborated this view. During autumn, 1983, the town of Churchill recorded a larger number of bears feeding at its dump (Lunn & Stirling, 1985) than in the previous three years and a higher number of human-bear incidents than in any year of the previous decade. Three cubs-of-the-year were found abandoned by their mothers in autumn and near starvation, something seen in no other year.” [my bold]

In one extreme example, a female they encountered with three cubs-of-the year in November 1983 weighed only 99 kg (218 lb). As thin as she was then, she survived and by the following July she was pregnant again and weighed a remarkable 410 kg (904 lb).

Lunn and Stirling had this to say about polar bears feeding at the Churchill dump in 1983:

In 1983, bears came into the dump more than a month earlier (late August compared with early October) and there were about twice as many (20 vs. 10-11) as in the previous 2 years.”

In other words, in 1983 the bears arrived onshore in WH leaner than usual after a poor spring feeding season–we probably won’t ever know why but it could have been thicker-than-usual sea ice or deeper-than-usual snow pack over the ice that year. This was clearly an issue that bothered Ian Stirling, before he moved on to worrying about global warming.

However, we know the poor feeding opportunities in 1983 weren’t due to lack of summer ice because the bears came ashore in August as usual. Coming ashore leaner than usual meant they got hungry earlier and many turned to the dump. Having found food there, it appears they were not in any hurry to leave at the first opportunity when sea ice appeared – exactly what seems to have happened with the bears at Belushya Guba in 2019.

1989

From Derocher and Stirling (1992:1153):

The proportion of females with yearlings varied annually between 6% and 25% of all adult females sampled over the study, but did not demonstrate any trend. The low proportion of females with yearlings in 1990 appeared to be due to very low survival in the cohort of cubs from 1989.”

What was happening with sea ice in 1989 in WH? Breakup was a bit early in 1989 but not especially so, and the date of freeze-up was about average (Castro de la Guardia et al. 2017). As a consequence, like a recent decline in proportion of females with yearlings cubs documented in Southern Hudson Bay (Obbard et al. 2018)–as well as the purported 2017-2021 decline in WH numbers–a decline in the length of the ice-free season could not have caused the low survival of WH cubs in 1989.

Average weights of females in the fall declined from about 230 kg (1965-1982) to about 190 kg (1983-1990)(Derocher and Stirling 1992:1154), but there was no apparent population decline.  The authors state later in that paper:

Typically, density dependence in large mammals is expressed by changes in juvenile survival, birthrate, age of first reproduction, and body size, all of which have been documented in this study. Invoking an argument of density-dependent changes is difficult to support without accurate population estimates, and other explanations for the observed patterns in our study cannot be dismissed as alternatives. For example, climatic fluctuations and variation in ice conditions could impact polar bear populations by increasing or decreasing the availability of prey. The observed decreases in reproduction and weight could be a function of a reduction in the seal population or their availability to polar bears.

Variation in the abundance of a prey base is usually reflected in changes in weight and subsequently in reproduction of predators. For example, the weights and reproductive output of polar bears in the Beaufort Sea decreased markedly following a decline in ringed and bearded seal populations.

In contrast to the Beaufort Sea studies, where the decline in body size and reproduction was sudden and then evident for only 2 or 3 years, the trend in the western Hudson Bay population has been of much longer duration. [my bold]

Conclusion

On the two notable occasions when starving polar bears were studied (1974-76 in the Southern Beaufort Sea, and the 1980s in Western Hudson Bay), lack of summer sea ice was not the cause and in only one case (the SB example) did significant numbers of starving bears result in a documented population decline.

However, on both previous occasions, bears in poor condition were noted by researchers in studies dedicated to documenting the phenomenon. If a polar bear population decline of 40% between 2011 and 2021 indeed occurred in WH because of starvation caused by climate change, where is the evidence? Why has there not been a single scientific study documenting bears in poor condition onshore during the summer and fall over the last 10 years (2020–and perhaps 2021–excepted, due to Covid restrictions)?

The stakes for polar bear researchers couldn’t be higher. This makes it all the more significant that they have provided no actual evidence that WH bears are indeed starving to death in sufficient numbers to substantiate a 40% decline over 10 years. If the claimed population decline of 2011-2021 is real and not an artifact of some other phenomenon (like females moving north of Churchill to have their cubs), we should have been seeing numerous photos of starving bears in the summer/fall of 2016 and 2020 at the very least, as well as a peer-reviewed paper or two describing the situation. So far, neither has been presented and there is still no publicly-available copy of the 2021 population count report.

References

Burns, J. J., Fay, F. H., and Shapiro, L.H. 1975. The relationships of marine mammal distributions, densities, and activities to sea ice conditions (Quarterly report for quarter ending September 30, 1975, projects #248 and 249), pp. 77-78 in Environmental Assessment of the Alaskan Continental Shelf, Principal Investiagors’ Reports. July-September 1975, Volume 1. NOAA, Environmental Research Laboratories, Boulder Colorado. pdf here.

Calvert, W., Stirling, I., Schweinsburg, R.E., Lee, L.J., Kolenosky, G.B., Shoesmith, M., Smith, B., Crete, M. and Luttich, S. 1986. Polar bear management in Canada 1982-84. In: Polar Bears: Proceedings of the 9th meeting of the Polar Bear Specialists Group IUCN/SSC, 9-11 August, 1985, Edmonton, Canada. Anonymous (eds). Gland, Switzerland and Cambridge UK, IUCN. http://pbsg.npolar.no/en/meetings/ pg. 19-34.

Castro de la Guardia, L., Myers, P.G., Derocher, A.E., Lunn, N.J., Terwisscha van Scheltinga, A.D. 2017. Sea ice cycle in western Hudson Bay, Canada, from a polar bear perspective. Marine Ecology Progress Series 564: 225–233. http://www.int-res.com/abstracts/meps/v564/p225-233/

Derocher, A.E. and Stirling, I. 1992. The population dynamics of polar bears in western Hudson Bay. pg. 1150-1159 in D. R. McCullough and R. H. Barrett, eds. Wildlife 2001: Populations. Elsevier Sci. Publ., London, U.K.

AbstractReproductive output of polar bears in western Hudson Bay declined through the 1980’s from higher levels in the 1960’s and 1970’s. Age of first reproduction increased slightly and the rate of litter production declined from 0.45 to 0.35 litters/female/year over the study, indicating that the reproductive interval had increased. Recruitment of cubs to autumn decreased from 0.71 to 0.53 cubs/female/year. Cub mortality increased from the early to late 1980’s. Litter size did not show any significant trend or significant annual variation due to an increase in loss of the whole litter. Mean body weights of females with cubs in the spring and autumn declined significantly. Weights of cubs in the spring did not decline, although weights of both female and male cubs declined over the study. The population is approximately 60% female, possibly due to the sex-biased harvest. Although estimates of population size are not available from the whole period over which we have weight and reproductive data, the changes in reproduction, weight, and cub mortality are consistent with the predictions of a densitydependent response to increasing population size. [my bold]

Derocher, A.E. and Stirling, I. 1995. Temporal variation in reproduction and body mass of polar bears in western Hudson Bay. Canadian Journal of Zoology 73:1657-1665. http://www.nrcresearchpress.com/doi/abs/10.1139/z95-197

Lentfer 1976. Polar bear management and research in Alaska 1974-76. Pg. 187-197 in [Anonymous]. Polar Bears: Proceedings of the 6th meeting of the Polar Bear Specialists Group IUCN/SSC, 7 December, 1976, Morges, Switzerland. Gland, Switzerland and Cambridge UK, IUCN. http://pbsg.npolar.no/en/meetings/

Molnár, P.K., Bitz, C.M., Holland, M.M., Kay, J.E., Penk, S.R. and Amstrup, S.C. 2020. Fasting season length sets temporal limits for global polar bear persistence. Nature Climate Change 10:732-738.  https://doi.org/10.1038/s41558-020-0818-9

Molnar, P.K., Derocher, A.E., Theimann, G., and Lewis, M.A. 2010. Predicting survival, reproduction and abundance of polar bears under climate change. Biological Conservation 143:1612-1622. http://www.math.ualberta.ca/~mlewis/Publications%202010/Molnar-Derocher-Thiemann-Lewis.pdf

Obbard, M.E., Stapleton, S., Szor, G., Middel, K.R., Jutras, C. and Dyck, M. 2018. Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys. Arctic Science https://doi.org/10.1139/AS-2018-0004

Ramsay, M.A. and Stirling, I. 1988. Reproductive biology and ecology of female polar bears (Ursus maritimus). Journal of Zoology London 214:601-624. http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.1988.tb03762.x/abstract

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 55 (Suppl. 1):59-76. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/issue/view/42

Stirling, I. and Lunn, N.J. 1997. Environmental fluctuations in arctic marine ecosystems as reflected by variability in reproduction of polar bears and ringed seals. In Ecology of Arctic Environments, Woodin, S.J. and Marquiss, M. (eds), pg. 167-181. Blackwell Science, UK.

Stirling, I., Andriashek, D., and Calvert, W. 1993. Habitat preferences of polar bears in the western Canadian Arctic in late winter and spring. Polar Record 29:13-24. http://tinyurl.com/qxt33wj

Stirling, I., Andriashek, D., Latour, P.B. and Calvert, W. 1975a. Distribution and abundance of polar bears in the Eastern Beaufort Sea. Beaufort Sea Tech. Report #2, Dept. Environment, Victoria, B.C.

Stirling, I., Archibald, R. and DeMaster, D. 1975b. Distribution and abundance of seals in the Eastern Beaufort Sea. Beaufort Sea Tech. Report #1, Dept. Environment, Victoria, B.C.

Stirling, I, Kingsley, M. and Calvert, W. 1982. The distribution and abundance of seals in the eastern Beaufort Sea, 1974–79. Canadian Wildlife Service Occasional Paper 47. Edmonton.

Stirling, I., Richardson, E., Thiemann, G.W. and Derocher, A.E. 2008. Unusual predation attempts of polar bears on ringed seals in the southern Beaufort Sea: possible significance of changing spring ice conditions. Arctic 61:14-22. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/3/3

Stirling, I., Schweinsburg, R.E., Kolenasky, G.B., Juniper, I., Robertson, R.J., and Luttich, S. 1980. Proceedings of the 7th meeting of the Polar Bear Specialists Group IUCN/SSC, 30 January-1 February, 1979, Copenhagen, Denmark. Gland, Switzerland and Cambridge UK, IUCN., pg. 45-53.http://pbsg.npolar.no/en/meetings/ pdf of except here.

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January 5, 2023 at 08:43PM

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