Tag Archives: fall feeding

Polar bear specialist calls Hudson Bay freeze-up ‘late’ yet bears were moving offshore 2 weeks ago

Predictably, polar bear specialist Andrew Derocher has finally posted a tracking map of the Western Hudson Bay bears his team has fitted with collars and eartags–two weeks after bears were released from Churchill’s polar bear jail, which is the local signal that there is enough sea ice for bears to leave shore. As I reported two weeks ago, release of jailed bears happened this year on 10 November. And as I predicted in that post, by waiting so long after that event to post his map, Derocher can make it seem to his naive followers on Twitter that the bears are just starting to leave now (the last map he posted was on 11 November, when none of his bears had moved). He reinforces this by calling WH freeze-up “late”, when by all objective measures (including local informants reporting bears on the ice) it was as early as it had been in the 1980s (Castro de la Guardia et al. 2017).

Recall that fall is the second-most important feeding season for polar bears, due to the fact that seals are strongly attracted to newly-forming sea ice. It’s their chance to regain some or all of the weight lost over the summer, before the long winter fast begins (while bears indeed hunt when they can, they are not often successful during the depths of the Arctic winter: most bears are at their lowest weight by March).

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Late freeze-up for W. Hudson Bay polar bears at odds with ice conditions elsewhere

Sea ice is finally starting to form along the western shore of Hudson Bay, lagging well behind ice formation in the rest of the Arctic. Oddly, however, last year it was just the opposite: some WH bears were able to start hunting as early as 31 October (see photo below) while ice formation lagged behind in the Chukchi and Barents Seas.

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Chukchi Sea ice that didn’t melt this summer is now 2+m thick between Wrangel Island and the shore

Thick multiyear ice between Wrangel Island and the shore is now more than 2m thick, potentially impacting fall feeding for bears that routinely summer on Wrangel or the north coast of Chukotka.

Rapidly-forming sea ice in the Laptev and East Siberian Seas this fall – generated by cold winds from Siberia in late October despite warmer than ususal temperatures earlier in the month – has trapped a number of Russian ships that are being rescued by ice-breakers (below), according to a report in the Barents Observer earlier this week.

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Polar bear habit update – day 333 Arctic sea ice hits 11.1 mkm2

It’s just past the height of fall in the Arctic (Oct-Dec) and polar bear habitat is expanding day by day: according to NSIDC Masie ice charts, the ice has now surpassed 11 mkm2 in extent. Fall is the second most important feeding period for polar bears after spring.

masie_all_zoom_4km 2015 day 333_Nov 29

Only the Barents and Kara Seas (north of Norway and western Russia) are short of ice right now, similar to conditions seen in the fall of 2013. Last fall (2014), conditions were much better and as a consequence, researchers saw a lot of females with healthy cubs in the spring of 2015.

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