Posted on December 17, 2020 |
In 1983, it was claimed that freeze-up of Hudson Bay was so late that polar bears didn’t leave the shore until the 4th of December – several weeks later than had been usual at that time. However, the fact that sea ice charts show significant ice offshore weeks before that time suggests something else was probably going on.
About three weeks ago, CBC News republished an article (with video) from their 1983 archives for 1 December, about the plight of the people of Churchill who had already suffered one death and one serious mauling by polar bears. That was thirty-seven years ago, long before lack of sea ice was blamed for everything bad that happened to Western Hudson Bay polar bears. In fact, rather than a really late freeze-up, it appears the problem had more to do with the fact the bears had had an especially tough spring that year and arrived onshore in only ‘OK’ condition – and as a consequence, the town dump became such a strong attractant for many bears that they were reluctant to leave when the sea ice formed offshore.
From the CBC archived report:
Polar bears were a common enough sight in the northern Manitoba town of Churchill, but in November 1983 they were getting too close for comfort.
Knowlton Nash, host of CBC’s The National, explained that people in the town had “special reason” to fear the “annual invasion” by polar bears.
“Twice in the past week, bears have attacked people right on the streets of the town,” said Nash.
It was the first time that had happened in 15 years, and patrols were setting out nightly to “scare the bears off.”
Reporter Karen Webb, usually a Winnipeg correspondent, made the trip to Churchill and explained that the town sat on a migration route for the bears.
“Usually the bears just walk around the town and are gone by the first week of November,” she said. “The only people they encounter: the scientists and the game wardens who count them.”
But it had been a warm year, and that meant the ice couldn’t freeze solidly on Hudson Bay, preventing the bears from walking out to hunt for seal — “and that means they’re hungry,” explained Webb.
Their food of choice became whatever they could “scrounge” at the dump on the edge of town.
Of course, we now have a better perspective on what happened in 1983, which historically was the worst fall season for Western Hudson Bay polar bears since records began – including those years after sea ice starting melting a few weeks earlier and freezing a bit later in the late 1990s.
THE SEA ICE IN 1983
First, the chart below shows what conditions were like in 1985 in the second week of November, when polar bears usually took to the ice (average date, 16 November according to Castro de la Guardia et al. 2017) – not the first week in November, as the CBC reporter above claimed.
Below is the same date in 1983, showing a bit of ice off Churchill but not much, so it’s true that the ice was a bit late:
What’s interesting is that CIS charts show there was significant ice off Churchill by the third week of November (below) – not quite as much as in 1985 but close. However, it seems that polar bears feeding at the Churchill dump weren’t particularly interested in leaving (see comments below), similar to what happened with bears in Belushya Guba in 2019.
By the first week in December, when it was said all the bears finally left for the ice (see quotes below), most of the bay was already covered in ice.
PROBLEM BEARS IN 1983
This is what Canadian researchers had to say about the fall of 1983 in Churchill, reported in the 1985 Polar Bear Specialist Group report (Calvert et al. 1986:19 and 24):
“In 1983, the Polar Bear Control Programme began in late August and continued until early December. Bear numbers in the Churchill area were extremely high during the last three weeks of the period. By December 4, the sea ice had formed and most of the bears had left. [freeze-up date confirmed in Stirling et al. 1999:29, using the old criteria of 50% ice cover over the entire WH region]
Nearly 300 man-days were required to respond to 191 calls (76 in 1982) regarding polar bear problems. From November 24 – December I, 84 calls were received. Only three incidents resulted in property damage totalling $1050. However, two incidents resulted in personal injury and death. The arm of a photographer from Wisconsin was severely mangled by a bear during 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 at the garbage dump, in Churchill, and at Camp Nanuk. Of the total 41 problem bears live-captured and placed in D-20, 19 were culvert-trapped (compared to 5 in 1982) and 22 free-ranged (1 in 1982). Nine problem bears were moved north of Churchill by helicopter in order to make more room in D -20.
In 1984, the Polar Bear Control Programme season in Churchill was from 1 September to 2 November, more than a month shorter than the 1983 season. There were 69 reported incidents, and 200 man-days expended. There was one serious encounter – a mauling in which there appeared to be extenuating circumstances.” [my bold]
Polar bear researchers Ian Stirling and Malcolm Ramsay emphasized that the mean weight of pregnant females they enountered 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 the bears didn’t get as much to eat as they needed that year. This was clearly an issue that bothered Ian Stirling, before he moved on to worrying about global warminng. However, we know the poor feeding opportunities in 1983 wasn’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.
WH FREEZE-UP THIS YEAR
At the end of November 2020, there was much more ice than ‘normal’ over central and south-western Hudson Bay, indicated by the swath of dark blue in the chart below:
By stage of development (ice thickness), 2/3 of the bay was ice-covered by the end of November 2020:
This year, a number of polar bears seemed to hang around onshore when there was ample ice forming offshore. They were not feeding at the dump, so it wasn’t like 1983. But the bears did come ashore late and in excellent condition (very fat) this summer after what must have been a very good spring feeding season.
The bears were so fat they caused very little trouble around Churchill and many hung around well after there was ice available for hunting. We know from the onshore webcams that WH bears were successfully hunting on the new ice close to shore as early as 31 October but it appears from Derocher’s tagged bears that the last of them didn’t leave until almost a month later, near the end of November.
I don’t have an explanation. However, bears hanging around weeks longer than necessary onshore in the fall is as odd as the bears that stayed on the rapidly declining ice in August this year, when there would have been 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: 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/
Lunn, N.J. and Stirling, I. 1985. The significance of supplemental food to polar bears during the ice-free period of Hudson Bay. Canadian Journal of Zoology 63:2291-2297.
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 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 [open access]