Reposted by Polar Bear Science
Published on December 17, 2020 |
In 1983, it was claimed that the Hudson Bay freeze was so late that polar bears did not leave shore until December 4th – a few weeks later than usual at the time. However, the fact that the sea ice maps show significant ice offshore weeks prior to that time suggests that something else was likely going on.
About three weeks ago, CBC News published an article (with video) from its archives for December 1, 1983 on the plight of the Churchill people who had previously suffered a death and severe blow from polar bears. That was thirty-seven years ago, long before the lack of sea ice was blamed for all the bad things that happened to polar bears in Western Hudson Bay. In fact, the problem seems to have more to do with the fact that the bears had a particularly hard spring that year and only came ashore in an “OK” state – and as a result, with the city. The dump became one of those for many bears strong draw that they were reluctant to walk when the sea ice formed off the coast.
From the archived CBC report:
Warm November meant no ice cream in Hudson Bay, and the bears got hungry (my bold)
Polar bears were widespread in the town of Churchill in northern Manitoba. but in November 1983 they got too close to comfort one another.
Knowlton Nash, host of CBC's The National, said people in town had "special reason" for fear of the polar bear's "annual invasion".
"In the past week, bears have attacked people directly on city streets twice," said Nash.
It was the first time in 15 years, and patrols went out every night to "scare off the bears."
Reporter Karen Webb, usually a Winnipeg correspondent, made the trip to Churchill and explained that the city was on a migration route for the bears.
"Usually the bears just walk around town and disappear in the first week of November," she said. "The only people they meet: the scientists and the gamekeepers who count them."
But it had been a warm year, and that meant the ice in Hudson Bay couldn't freeze solid"and that means they are hungry," explained Webb.
The food of their choice became anything they could "crawl" into the dump on the outskirts of the city.
Of course, we now have a better perspective on what happened in 1983, which was historically the worst fall season for polar bears in Western Hudson Bay on record – including the years after the sea ice began to melt a few weeks earlier and froze a little later was in the late nineties.
THE SEA ICE 1983
First, the graph below shows what the conditions were like in the second week of November 1985, when polar bears usually went into the ice (average date, November 16 according to Castro de la Guardia et al. 2017) – not the first week of November, like the aforementioned CBC reporter claimed.
Below is the same 1983 date showing some ice in front of Churchill but not much. So it is true that the ice cream was a little late:
What is interesting is that the CIS maps show that Churchill had some significant ice in the third week of November (below) – not quite as much as 1985, but just barely. However, it appears that polar bears eating at the Churchill dump weren't particularly keen on leaving (see comments below), much like bears in Belushya Guba in 2019.
By the first week of December, when it was said that all the bears were finally going to the ice (see quotes below), most of the bay was already covered in ice.
This is what Canadian researchers had to say about the Fall of 1983 at Churchill, as reported in the Polar Bear Specialist Group's 1985 report (Calvert et al. 1986: 19 and 24):
"1983 The polar bear control program started in late August and lasted through early December. Bear numbers in the Churchill area were extremely high for the last three weeks of the period. By December 4th, the sea ice had formed and most of the bears were gone. (Freezing date confirmed in Stirling et al. 1999: 29 using the old criteria of 50% ice cover over the entire WH region)
It took almost 300 man-days to answer 191 calls (76 in 1982) regarding polar bear problems. There were 84 calls from November 24th to December 1st. Only three incidents resulted in property damage totaling $ 1,050. However, two incidents resulted in personal injury and death. A Wisconsin photographer's arm was severely mutilated by a bear while on a tour to Cape Churchill. About two weeks later, a Churchill resident was killed by a bear near the burned ruins of the Churchill Hotel.
Problem bears were captured in the dump, in Churchill and at Camp Nanuk. Of a total of 41 problem bears that were caught live and placed in D-20, 19 were trapped in ducts (compared to 5 in 1982) and 22 in the wild (1 in 1982). Nine problem bears were moved north of Churchill by helicopter to make room in D-20.
In 1984 The Churchill polar bear control program season ran from September 1 to November 2, more than a month shorter than the 1983 season. 69 incidents were reported and 200 man-days were expended. There was a serious encounter – an abuse that seemed to have extenuating circumstances. "(My bold)
Polar bear researchers Ian Stirling and Malcolm Ramsay emphasized that the average weight of the pregnant women they met in 1983 was 37 kg lighter than in other years (Ramsay and Stirling 1988: 615). These authors stated:
"..The bears of all ages and sexes in the summer and fall of 1983 appeared to us to be in worse condition on average at the time of capture than at comparable seasons in the years before and after. Some qualitative behavioral observations confirmed this view. In the fall of 1983, Churchill town recorded higher numbers of bears feeding on its dump (Lunn & Stirling, 1985) than in the previous three years and a higher number of human incidents than any year in the past decade. Three boys of the year were abandoned by their mothers in the fall and found almost starved, which has not been seen in any other year. "(My bold)
In one extreme example, a woman they met with three boys of the year in November 1983 weighed only 99 kg. As thin as she was then, she survived, and the following July she was pregnant again, weighing a remarkable 410 kg.
Lunn and Stirling had this to say about polar bears eating at the Churchill dump in 1983:
"In 1983, more than a month earlier, bears were thrown in the dump (Late August compared to early October) and there was about twice as many (20 vs. 10-11) as in the last 2 years. "
In other words, after a bad spring feeding season in 1983, the bears came ashore leaner than usual – we'll probably never know why the bears didn't get as much food as they needed that year. This was clearly an issue that preoccupied Ian Stirling before he became concerned about global warming. However, we do know that the poor feeding options in 1983 were not due to a lack of summer ice, as the bears came ashore in August as usual. Getting ashore leaner than usual meant they got hungry sooner and many turned to the dump. After finding food there, they didn't seem in a hurry to leave at the first opportunity when sea ice surfaced – exactly what seems to have happened to the bears in Belushya Guba in 2019.
WHAT TO FREEZE THIS YEAR
At the end of November 2020 there was much more ice than "normal" over the central and southwestern Hudson Bay, which is indicated by the dark blue stripe in the following table:
Up to the development stage (ice thickness) 2/3 of the bay was ice-covered by the end of November 2020:
This year, some polar bears appeared to be hanging out on land as ice formed abundantly off the coast. They weren't feeding on the dump, so it wasn't like 1983. But the bears came ashore late this summer and in excellent condition (very fat) after what must have been a very good spring feeding season.
The bears were so fat that they were hardly a problem at Churchill, and many hung out well after ice was available for hunting. We know from the onshore webcams that WH bears were successfully hunting on the new ice near the coast as early as October 31st, but Derocher's tagged bears show that the last of them was not until almost a month later, towards the end of the year. left November.
I have no explanation. However, bears that hang ashore for about weeks longer than necessary in the fall are just as strange as the bears that stayed on the rapidly declining ice in August this year when there were few opportunities to catch seals.
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: Report on the 9th IUCN / SSC Polar Bear Specialist Group Meeting, August 9-11, 1985 in Edmonton, Canada. Anonymous (ed.). 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's perspective. Marine Ecology Progress Series 564: 225-233. http://www.int-res.com/abstracts/meps/v564/p225-233/
Lunn, N. J. and Stirling, I. 1985. The Importance of Complementary Foods for Polar Bears during Hudson Bay's ice-free season. Canadian Journal of Zoology 63: 2291-8. 2297
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., Lunn, N. J. and Iacozza, J. 1999. Long-term trends in polar bear population ecology in Western Hudson Bay related to climate change. Arctic 52:294-306. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/935/960 (open access)