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).

From a tweet posted by Derocher yesterday (27 November 2022), with a tracking map dated 25 November:

Freeze-up in Hudson Bay is slowing picking up & the polar bears we’re tracking are moving offshore. It’s a late freeze-up this year but hopefully the ice will form quickly now. Temperatures are forecast to drop this week & the bears can get serious about hunting seals again.

Note the collared bears well back from the coast on this map will be pregnant females that will stay ashore in maternity dens until their cubs are born around Christmas time (late December/early January). There are a couple ear-tagged bears (purple icons) that should be young bears or adult males that are still on land and far from shore: Derocher doesn’t explain but it’s possible these are young females with ear tags pregnant with their first litters.

Sea ice according to the Canadian Ice Service for 25 November (the same day as Derocher’s map), since the ice on his image is very difficult to see and which CIS says is ‘more than usual’ for this time of year:

To me, this goes beyond ‘advocating’ for animal conservation: it seems to be deliberate misinformation to support a narrative that has fallen apart. Derocher could prove me wrong if he and his colleagues simply updated their WH data (including official breakup and freeze-up dates since 2015, as well as dates when bears left the ice and left shore) but they continue to withhold.

Norwegian researchers post their data every year.

I dare Canadian polar bear specialists to do the same.


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/

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