Even with Inuit lives at stake, polar bear specialists make unsupported claims

The standoff between Inuit and polar bear specialists regarding the status of polar bears in Canada is not going to end until someone in authority demands to see the data scientists insist contradict Inuit knowledge.

Macleans to kill a polar bear headline 21 April 2019

An article in Maclean’s Magazine (15 April 2019), entitled “To Kill a Polar Bear”, explores some of the feelings and opinions of folks involved but fails to ask whether the data support the rhetoric advanced by scientists. Author Aaron Hutchins takes the scientists at their word, that seeing more bears than 20 years ago is all because of lack of sea ice. However, from what I’ve seen, he might as well trust a fox in a hen house.

Ian Stirling is quoted by Hutchins insisting that polar bears in Western Hudson Bay continue to suffer from the effects of declining sea ice, without mentioning that ice cover has been essentially static on Hudson Bay since at least 2001 (Castro de al Guardia et al. 2017; Lunn et al. 2016) and fall freeze up dates for the last two years were earlier than most years in the 1980s:

“This year saw the seventh-lowest Arctic sea ice levels since the National Snow and Ice Data Center first started gathering satellite data 40 years ago, with the long-term trend clearly downwards. And the negative effects on polar bears can be clearly seen in the science, says Stirling, pointing to the closely studied subpopulation along western Hudson Bay: “They’re losing body condition. Reproductive rates have dropped. Survival rates of young have plummeted. Every indication you would expect from a declining population is there.”

However, as I’ve pointed out previously (last year and in 2012), there are no recent data published that support these claims: the only information that exists is at least 25 years old. And the fact that no such data have been published suggests strongly that it either does not exist or does not show what Stirling claims it shows.

Yet, the government of Canada is willing to bet the lives of Inuit on their belief that polar bear specialists would never stretch the truth to qualify for government grants.

Years ago now, in an oft-cited paper, Stirling and Derocher (2012) claimed to summarize the evidence that climate warming was negatively impacting polar bear health and survival. Several life history parameters were considered crucial, particularly body condition.

Despite almost a dozen papers (and perhaps more) on various aspects of WH polar bear health and life history studies based on capture/recapture data published since 2004 (e.g. Castro de la Guardia 2017; Lunn et al. 2016; Pilfold et al. 2017), none have reported the body condition data that supposedly support the claim that sea ice loss is having a severe impact — and the same is true for litter size, proportion of independent yearlings, and cub survival 1

And as I discuss in my new book, The Polar Bear Catastrophe That Never Happened, poor body condition, lowered reproductive rates and much reduced cub survival was a hallmark of Western Hudson Bay polar bears in the 1980s and early 1990s – before declining sea ice was any kind of issue but when polar bear numbers were higher than they’d been in perhaps a century or more (Derocher 1991; Derocher and Stirling 1992, 1995; Ramsay and Stirling 1988).

Too many bears relative to the food supply seemed a logical explanation at the time. But before Stirling had time to investigate fully, he jumped on the climate change bandwagon and banged the climate drum so loudly that concerns about WH bears in the 1980s were forgottern. From that point forward, everything bad that has happened to polar bears in general – and Western Hudson Bay bears in particular – has been blamed on global warming (Stirling and Derocher 1993, 2012; Stirling et al. 1999).

On an issue so contentious yet essential for Inuit safety, to not demand that Stirling and colleagues provide the data to back up their claims borders on criminal. If journalists and the government will not demand to see the data, then Inuit must – for their own protection.

Footnotes

1. There has also been no published data available for size of WH litters or proportion of independent yearlings since 1998 based on capture/recapture studies (Stirling et al. 1999) — 20 years ago — and no additional data on cub survival since 1992 — 26 years ago (Derocher and Stirling 1995).

There has been some data on litter size and proportion of independent yearlings based on aerial surveys, which may be broadly comparable to capture/recapture study data. However, cub survival metrics cannot be determined from aerial survey data and while some claim cub survival is declining, no data to support it has been published.

  Martin Obbard and colleagues determined that in the 2000s, females in Southern Hudson Bay were on average about 31 kg lighter than they were in 1980s and males 45 kg lighter. However, the number of bears in the population did not decline over the same period (Obbard et al. 2015), which suggests that amount of weight loss is not biologically significant. A claim for a slight reduction in population size (17%) has since been made for the Southern Hudson Bay subpopulation (Obbard et al. 2018) but no coorelations with body condition and/or sea ice metrics were presented.

References

Derocher, A.E. 1991. Population dynamics and ecology of polar bears in western Hudson Bay. Ph.D. Thesis, Univ. Alberta, Edmonton.

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.

Abstract. Reproductive 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

Dyck, M., Campbell, M., Lee, D., Boulanger, J. and Hedman, D. 2017. 2016 Aerial survey of the Western Hudson Bay polar bear subpopulation. Final report, Nunavut Department of Environment, Wildlife Research Section, Iglolik, NU. http://www.gov.nu.ca/environnement/information/wildlife-research-reports#polarbear

Lunn, N.J., Servanty, S., Regehr, E.V., Converse, S.J., Richardson, E. and Stirling, I. 2016. Demography of an apex predator at the edge of its range – impacts of changing sea ice on polar bears in Hudson Bay. Ecological Applications, in press. DOI: 10.1890/15-1256

Obbard, M.E., Cattet, M.R.I., Howe, E.J., Middel, K.R., Newton, E.J., Kolenosky, G.B., Abraham, K.F. and Greenwood, C.J. 2016. Trends in body condition in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to changes in sea ice. Arctic Science, in press. 10.1139/AS-2015-0027

Obbard, M.E., Stapleton, S., Middel, K.R., Thibault, I., Brodeur, V. and Jutras, C. 2015. Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys. Polar Biology 38:1713-1725.

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

Stapleton S., Atkinson, S., Hedman, D., and Garshelis, D. 2014. Revisiting Western Hudson Bay: using aerial surveys to update polar bear abundance in a sentinel population. Biological Conservation 170: 38-47. http://www.sciencedirect.com/science/article/pii/S0006320713004618#

Stirling, I. and Derocher, A.E. 2012. Effects of climate warming on polar bears: a review of the evidence. Global Change Biology 18:2694-2706. doi:10.1111/j.1365-2486.2012.02753.x

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., Lunn, N.J. and Iacozza, J. 1999. Long-term trends in the population ecology of polar bears in Western Hudson Bay in relation to climate change. Arctic 52:294-306.
http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/935/960

Stirling, I. and Parkinson, C.L. 2006. Possible effects of climate warming on selected populations of polar bears (Ursus maritimus) in the Canadian Arctic. Arctic 59:261-275. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/issue/view/16.

Recent WH polar bear papers using capture data

Bechshoft, T., Derocher, A.E., Richardson, E., Lunn, N.J. and St. Louis, V.L. 2016. Hair mercury concentrations in Western Hudson Bay polar bear family groups. Environmental Science & Technology 50(10):5313-5319.

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/

Cherry, S.G., Derocher, A.E. and Lunn, N.J. 2016. Habitat-mediated timing of migration in polar bears: an individual perspective. Ecology and Evolution 6(14):5032-5042. https://doi.org/10.1002/ece3.2233 Open access.

Cherry, S.G., Derocher, A.E., Thiemann, G.W., Lunn, N.J. 2013. Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics. Journal of Animal Ecology 82:912-921. https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2656.12050

McCall, A.G., Derocher, A.E. and Lunn, N.J. 2015. Home range distribution of polar bears in western Hudson Bay. Polar Biology 38(3):343-355. https://doi.org/10.1007/s00300-014-1590-y

Lunn, N.J., Servanty, S., Regehr, E.V., Converse, S.J., Richardson, E. and Stirling, I. 2016. Demography of an apex predator at the edge of its range – impacts of changing sea ice on polar bears in Hudson Bay. Ecological Applications, in press. DOI: 10.1890/15-1256

Pilfold, N.W., McCall, A., Derocher, A.E., Lunn, N.J., and Richardson, E. 2017. Migratory response of polar bears to sea ice loss: to swim or not to swim. Ecography 40:189-199. https://doi.org/10.1111/ecog.02109

Sciullo, L, Thiemann, G.W., and Lunn, N.J. 2016. Comparative assessment of metrics for monitoring the body condition of polar bears in western Hudson Bay. Journal of Zoology 300: 45-58. doi:10.1111/jzo.12354

Towns, L., Derocher, A.E., Stirling, I., Lunn, N.J. and Hedman, D. 2009. Spatial and temporal patterns of problem polar bears in Churchill, Manitoba. Polar Biology 32(10):1529-1537. http://link.springer.com/article/10.1007%2Fs00300-009-0653-y [paywalled]

Viengkone, M., Derocher, A.E., Richardson, E.S., Malenfant, R.M., Miller, J.M., Obbard, M.E., Dyck, M.G., Lunn, N.J., Sahanatien, V. and Davis, C.S. 2016. Assessing polar bear (Ursus maritimus) population structure in the Hudson Bay region using SNPs. Ecology and Evolution 6: 8474-8484. DOI: 10.1002/ece3.2563

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