Tag Archives: western hudson bay

Polar bear numbers, margins of error, & consequences for conservation status

Large margins of error in polar bear population estimates means the conservation status threshold of a 30% decline (real or predicted) used by the US Endangered Species Act and the IUCN Red List is probably not valid for this species.

Polar_Bear_Biologist_USFWS_working_with_a_Bear_Oct 24 2001 Amstrup photo

Several recent subpopulation estimates have shown an increase between one estimate and another of greater than 30% yet deemed not to be statistacally significant due to large margins of error. How can such estimates be used to assess whether population numbers have declined enough to warrant IUCN Red List or ESA protection?

What do polar bear population numbers mean for conservation status, if anything?

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W Hudson Bay polar bear season wrap-up: problem bear stats & sea ice vs. 2016

This year, due to an early freeze-up of the sea ice, many polar bears left the Western Hudson Bay area (including Churchill) the week of November 6-12. However, the folks who produce Churchill’s problem polar bear statistics did not generate a report for that week, so we are left with assessing the final freeze-up situation based on the previous report (see it here) and the one they have just released for the week of 13-19 November (below), the 18th week of the season (which began July 10):

Churchill Polar bear alert report Nov 13-19_Nov 20 released

The “quiet” week was almost certainly due to the fact that very few bears were still around, having left the previous week.

While it is apparently true that a south wind briefly blew ice away from the area around the town of Churchill, most bears had left by that point and there was plenty of ice to the north and southeast for bears that had congregated outside the town to wait for the ice to form.

Churchill sits on a point of land (see map below) that makes new ice vulnerable to winds from the south but this year impact was small: the north winds returned within a few days and so did the ice.

Hudson Bay weekly ice stage of development 2017 Nov 20

By this week there were still a few stragglers that hadn’t left shore but most of these were mothers with cubs, as well as young bears living on their own, who often hold back to avoid dangerous encounters with adult males at the ice edge.

A few adult males that were still in excellent condition after 4 months ashore without food seemed in no particular hurry to resume hunting. In part, this may have been due to the rather foul weather prevalent since the first week of November (with howling winds, low temperatures and blowing snow much of the time).

You can see in the chart below just how much more ice there was for the week of 20 November compared to average — all those dark and light blue areas along the west coast of Hudson Bay (and east of Baffin Bay) indicate more ice than usual. Even Southern Hudson Bay has enough shore ice for bears to resume hunting. Foxe Basin (to the north of Hudson Bay) has less ice than usual (red and pink) but there is still enough ice for polar bears there to begin their fall hunting, as the chart above makes very clear.

Hudson Bay weekly departure from normal 2017 Nov 20

Freeze-up and bear movement offshore were about three weeks earlier this year in Western Hudson Bay compared to 2016, which made a huge difference to the number of problem bears in Churchill, see below.

UPDATE 23 November 2017: CIS ice chart for today showing the ice forming in the northwest sector of Hudson Bay

Sea ice Canada 2017 Nov 23

UPDATE 27 November 2017: Final problem polar bear report copied below, issued by the town of Churchill. As noted above, the fact that some bears remained onshore into last week was a very local anomaly not experienced over the rest of the region.

churchill-pb-reports_week-19_20-26-nov-2017_last-of-the-season.jpg

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Experts talk of their bleak future, W Hudson Bay polar bears get earliest freezeup in decades

It seems that Churchill residents and visitors woke up this morning to find most local polar bears had left to go hunting — on the sea ice that supposedly doesn’t exist. Right in the middle of the Polar Bear Week campaign devised by Polar Bears International to drum up donation dollars and public sympathy for polar bear conservation!

Polar bear on the sea ice_Churchill_8 Nov 2017_Explore dot org cam my photo 2Frigid temperatures and north winds last night helped the process along, but this early freeze-up has been in the works for almost a week. From what I can ascertain, it appeared the only bears around onshore today were a mother with her young cub moving out towards the ice (females with cubs are usually the last to move offshore, probably to reduce the risk of encounters with adult males who might kill the cubs).

Tundra Buggy cams at Explore.org have been showing markedly fewer bears today and those that have been seen were on the ice (see above and below) or heading out to it.

The chart below is for yesterday (7 November), before the cold and north winds hit the region. It shows the concentration of ice that’s >15 cm thick.

Hudson Bay North 2017 concentration Nov 7

The chart for 8 November is below, after the storm.

Hudson Bay North daily ice concentration 2017_Nov 8

This is ice thick and extensive enough for polar bears to go hunting. Some bears almost certainly left shore yesterday, with the rest following quickly on their heals today. There are sure to be some stragglers left ashore that will leave over the next few days but the fact remains: there is sea ice to be had for those polar bear willing to start hunting.

Watch polar bear on the WHB sea ice below (screen caps below – and one above – were taken the afternoon of 8 November, from the Tundra Buggy Cam live feed near Churchill).

Polar bear on the sea ice_Churchill_8 Nov 2017_Explore dot org cam my photo 3

Keep in mind that in the 1980s, bears left for the ice on 8 November, on average. That means we’re back to a 1980s freeze-up scenario, at least for this year.

Funny how no one bothered to mention the potential for an early freeze-up to the media last week, when scientist were so eager to talk about the imminent demise of WHB bears. And funny that Polar Bears International hasn’t tweeted a word today about the famous Churchill bears having enough sea ice to go hunting, smack in the middle of Polar Bear Week.

Yes, the “Save Our Sea Ice” PBI rallying cry sounds a bit hollow with sea ice as far as the eye can see off Churchill today. But will anyone in the mainstream media point out the irony?

See charts below for years back to 2004, on this date (2005 missing for some reason), to compare to the above 8 November image (2004 is as far back as the archive goes).

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Problem bear report for Churchill might be second-last one this year

Good news for Western Hudson Bay polar bears that have been getting into trouble in Churchill, Manitoba: the seasons looks to be almost over.  Only a few more days of “Polar Bear Week” likely remain, as sea ice will build along the shoreline in response to severe cold and the north winds expected later today.

Churchill PB reports_week 17_30 Oct- Nov 5_2017_week 10 and 13 missing

This morning near Churchill, from one of the tundra buggies, post at Explore.org:

Churchill on 7 Nov 2017_Explore dot org

Churchill weather 2017 Nov 7

Sea ice at 7 November, will be updated so check back:

Sea ice Canada 2017 Nov 7

Ice forming all the way into James Bay (Southern Hudson Bay), as shown by the daily ice concentration charts for 7 November 2017 (Northern and Southern Hudson Bay) of ice thicker than 15 cm:

Hudson Bay North daily ice concentration 2017_Nov 7

Hudson Bay South daily ice concentration 2017_Nov 7 greater than 15 cm

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Scientists and media continue to spread misinformation about polar bears & walrus

“Lies” might be a better word to characterize the misinformation that scientists and the media have been busy spreading to the public over the last few weeks. The information is either known to be false (by scientists whose job it is to relay facts honestly) or is easily shown to be false (by journalists whose job it is to fact-check their stories).

Churchill polar bear and walrus 2017

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Early freeze-up in progress on Hudson Bay – what a difference a year makes

In contrast to 2016, when freeze-up along Western Hudson Bay was about as late as its ever been (early December), ice is already forming along the shore of northern Hudson Bay. There is much more ice than usual for this date, indicated by the dark blue in the latest weekly ice chart below:

Hudson Bay weekly departure from normal 2017 Oct 30

The ice is still thin, as the chart below indicates, but that’s how freeze-up starts. As long as strong winds don’t blow the ice away (as it sometimes does at this stage), the ice gets thicker day by day — and advances further and further off shore. Polar bears get out on the ice as soon as they are physically able, when the ice is about 3-4 inches thick (about 10 cm) or less.

Hudson Bay North daily ice stage of development 2017_Nov 1

Below is a video of a bear traversing that thin ice yesterday (1 November 2017), near Churchill. Is this a portend of a freeze-up date as early as occurred in the 1980s?
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Breaking: 2016 W. Hudson Bay polar bear survey shows the population is still stable

A just-released report on the most recent (2016) survey shows Western Hudson Bay polar bear numbers were still stable despite predictions that this subpopulation would be wiped out completely (reduced to zero) due to low Arctic sea ice.

Churchill_Polar_Bear_2004-11-15 Wikipedia

The authors of the report on the August 2016 aerial survey of the Western Hudson Bay polar bear subpopulation (Dyck et al. 2017) state clearly that the only trends they could find were that the number of adult males increased somewhat over 2011 estimates and the number of females either declined or remained stable. The overall population estimate was a bit lower (11% less) compared to the 2011 survey but the difference is not statistically significant. Therefore, the population status must be stable.

2011 estimate: 949 bears (using comparable data, range 618-1280), litter size 1.43

2016 estimate: 842 bears (using comparable data, range 562-1121), litter size 1.63

[cf. Foxe Basin [stable], from 2009-2010 survey (Stapleton et al. 2016) litter size was 1.54]

An 11% decline in WH numbers since 2011 is most definitely NOT the decline to ZERO (extirpation) we were told to expect with Arctic sea ice as low as it has been since 2007 (Crockford 2017, see list of annual minimum extents 2007-2017 here).

Note: The percentage decline from 2011 to 2016 for Western Hudson Bay polar bears is 11%, NOT 18% as claimed recently by Andrew Derocher on twitter: it is not appropriate to compare the official 2011 estimate of 1030 (Stapleton 2014) to the 2016 estimate of 842 because the methods used to generate the estimates were different (Dyck et al. 2017). The authors of the report state that the estimate for 2011 that’s comparable to 2016 is 949.

An 11% decline from 1030 would be 917 bears, a statistically insignificant decline that is also biologically insignificant and therefore, so slight as to indicate a stable population.

Predicted sea ice at 2050 and 2080 shown below (see Crockford 2017 for details):

Crockford 2017 sea ice graphic

Quotes, map, and table from the Dyck et al. 2017 report (pdf here) are copied below.

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