Tag Archives: hunting

Polar bears of W Hudson Bay utilizing a substantial patch of thick first year ice

There’s been no word as yet, either from tour operators or polar bear researchers, that Western Hudson Bay polar bears have come ashore for the summer/fall season. Andrew Derocher reported at the end of June that the bears tagged by his team were still on the ice and as I write this, has not yet reported them ashore.

That pattern is consistent with the presence of thick ice along the west coast of the Bay — from well north of Churchill to the south of Wapusk National Park — for the last few weeks. The weekly chart for 3 July 2017 below from the Canadian Ice Service shows that virtually all of the ice remaining is thick first year ice (>1.2m, dark green on this map):

Hudson Bay weekly ice stage of development 2017 July 3

By the 9 July, the extent of this patch of ice was somewhat reduced but still a very prominent feature over the Bay, suggesting that if adult seals are using this ice as a refuge while molting, some bears may still be attempting to hunt even though their success rate may not be very high:

Sea ice Canada 2017 July 9

Bottom line: As has been the pattern for more than a decade, 2017 will not go down in history as an especially early year for WHB polar bears coming off the ice for the summer/fall season but instead may be as late as last year, when lots of bears were reported off the ice by mid-July at Seal River (just north of Churchill), all in excellent condition.

It remains to be seen if the condition of bears will be as good this year as they were in 2016, given the late start to the season. But it does mean that the lack of trend in breakup dates since 2001 continues: breakup of the sea ice in WHB since 2001 has been about one week later than it was before 1998 (Castro de la Guardia 2017; Cherry et al. 2013; Lunn et al. 2016).

If some polar bear struggle to survive this year it will be due to the late freeze-up date last fall combined with challenging winter conditions over Hudson Bay, not because of an early breakup of the sea ice.

And while it is certainly true that the overall trend in time spent onshore by WHB polar bears since 1979 has increased by about three weeks, the lack of a continued trend since 2001 is not what was expected or predicted, especially given the marked decline in global sea ice levels that have made headlines since 2007 (Crockford 2017), and the predictions of how devastating such low levels of ice would be to polar bears in areas like Hudson Bay that have to deal with a total disappearance of sea ice in summer and early fall.

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Breakup of sea ice on track in Canada as critical feeding period for polar bears ends

Relative to recent years and potential impacts on polar bear health and survival in Canada, there is nothing alarming in the pattern or speed of sea ice breakup for 2017, either over Hudson Bay, the southern Beaufort, or the eastern high Arctic.

Sea ice Canada 2017 June 8

Last year at this time (see map below), there was more open water in Hudson Bay and in the Southern Beaufort yet the polar bears came ashore in fine shape that summer and there was no hue-and-cry of dying bears anywhere. Breakup this year is on track to be about 3 weeks earlier than it was in the 1980s, as it has been since at least 2001, a conclusion reached by polar bear specialists (Castro de la Guardia et al. 2017; Lunn et al. 2016), who examined sea ice breakup to 2015.

Sea ice extent Canada 2016 June 8 CIS

Here are critical words to remember (more details here) from biologist Martin Obbard and colleagues (2016:29) on the relationship between body condition and sea ice for Southern Hudson Bay (SH) polar bears, which apply equally well to bears in other regions:

Date of freeze-up had a stronger influence on subsequent body condition than date of break-up in our study. Though models with date of freeze-up were supported over models with other ice covariates, we acknowledge that lower variability in freeze-up dates than in ice duration or break-up dates could have influenced the model selection process. Nevertheless, we suggest that a stronger effect of date of freeze-up may be because even though break-up has advanced by up to 3-4 weeks in portions of Hudson Bay it still occurs no earlier than late June or early July so does not yet interfere with opportunities to feed on neonate ringed seal pups that are born in March-April in eastern Hudson Bay (Chambellant 2010). Therefore, losing days or weeks of hunting opportunities during June and July deprives polar bears of the opportunity to feed on adult seals, but does not deprive them of the critical spring period (Watts and Hansen 1987) when they are truly hyperphagic. No doubt, the loss of hunting opportunities to kill adult seals has a negative effect on body condition, but it appears that for bears in SH a forced extension of the fast in late fall has a greater negative effect on subsequent body condition.” [my bold]

In other words, by mid-June at least (maybe earlier), polar bears have largely finished their intensive feeding that’s so critical to their survival over the rest of the year.

That’s why the latest count of SH polar bears (Obbard et al. 2015) showed a stable population (and see this recent post on WHB polar population estimates). But freeze-up was late last year and that’s what will make the difference to polar bears over the coming year.

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Newfoundland conservation officers right to kill polar bear in hunting mode

Apparently, some locals were upset that a polar bear that refused to be scared away from a Newfoundland community over the weekend was shot as it advanced on conservation officers and a crowd of onlookers who refused to disperse (see updated report here on recent Newfoundland polar bear sightings, with annotated map).

Catalina map and bear shot location Nfld

Polar bear shot by wildlife officers near Catalina after being deemed public safety risk” (CBC 10 April 2017)

What these animal lovers may not realize is that Newfoundland in March and April is not a Churchill-like situation: polar bears are in strong hunting mode right now.

Polar bears in late winter and spring have an immense drive to kill and eat as much as possible. Even bears that look well fed will continue to kill and eat. Enticing smells attract them onshore as they investigate any food possibility (see list below).

Seriously, you don’t want that food possibility to be you.

Polar bears can go from watching to charging, in the blink of an eye. You can’t outrun one. Killing quickly is what they do and they are immensely strong. Polar bears generally go for a killing bite to the head. Things to think about when a polar bear is prowling your community…
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An El Niño year late start to freeze-up on Hudson Bay: bears gearing up to hunt

There is no serious ice on the west shore of Hudson Bay yet (as the map below shows) but the winds have just shifted – instead of coming from the south, they are now blowing in from the north.

Freeze-up and a resumption of seal hunting for Western and Southern Hudson Bay polar bears looks imminent. The 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).

sea-ice-extent-canada-2016-dec-5_cis

I’m going to let Kelsey Eliasson from PolarBearAlley, on shore at Churchill, convey the gist of the freeze-up situation on the Bay.

Recall that freeze-up was late in both 1998 and 1999 – during the height of that strong El Niño warmth as well as the year following. Continue reading

Fall Arctic ice growth often differs regionally: 2016 compared to other years

Arctic sea ice is spreading out quickly from its central basin summer refuge – according to this NSIDC Masie ice chart, it has already grown more than 2 mkm2 beyond the annual minimum reached in early September. Ice is already pushing south into the eastern Beaufort and the archipelago of Franz Josef Land in the Barents Sea.

masie-sea-ice-2016-oct-20-cropped-and-marked_polarbearscience

Over the next couple of weeks, shorefast ice will start forming along the coasts of North America and Eurasia (see the first bits off Alaska in the 21 October CIS map below), which will eventually meet the expanding Arctic Basin pack to fill the Basin and Canadian Arctic Archipelago with ice – as it has done for eons.

sea-ice-extent-canada-2016-oct-21_cis

The evidence from the last decade or so suggests that by the end of October, most of the Arctic north of the 79th parallel (see map below) will be filled with ice – although the Chukchi Sea (north of the Bering Strait) may not fill until sometime in November:

79-th-parallel-north_wikipedia

Polar bears usually resume hunting as soon as sea ice conditions permit in the fall, since it’s their last chance to top up their fat reserves before the dark and cold of winter when hunting may become next to impossible.

I’ve copied ice charts from the Masie archives for some previous years at 31 October below.

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Polar bear habitat this fall shaping up fast – more like 2010 than 2007

Arctic sea ice tied 2007 for extent at the September minimum less than 3 weeks ago but with the refreeze proceeding much faster than 2007, seals will soon be returning to the ice edge and polar bears will be back to feeding like they did in 2010.

sea-ice-at-28-sept_2016_vs-2007_2012_5-point-0_nsidc-interactive

Sea ice extent less than 5.0 mkm2 lasted less than 6 weeks (23 August – 28 September), according to NSIDC.

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Polar bears seldom catch seals they stalk in summer – it’s why they fast

This short BBC video shows why polar bears are so often unsuccessful in their summer hunts – adult bearded seals are the species most often available on the ice. These seals are not only predator-savvy but there are lots of escape routes in the melting ice, and this has always been so.

“Hungry polar bear surprises a seal – The Hunt: Episode 2 Preview – BBC One”

Melting ice in summer is not a new phenomenon (e.g. NASA photo below from mid-July 2016) – Thomas Grenfell and Gary Maykut described the process of melt pond development back in the 1970s:

“Melt ponds reach the maximum extent shortly after the disappearance of the snow, when they may cover upwards of 50% of the ice.”

sea-ice_melt-ponds_nasa-taken-13july2016_sm

Melting summer ice has always made it challenging for polar bears to catch seals, as this quote from Ian Stirling (1974) show, based on his work in the Central Canadian Arctic in the summer of 1973 (July and August):

There is a great abundance of natural holes in the ice during summer, anyone of which a seal could surface through.

This is still true in areas like the Southern Beaufort Sea today (e.g. Whiteman et al. 2015): the ice melts and in some areas, disappears completely in summer.

It’s why polar bears – unlike other species of bears in summer – depend on their stored fat to see them through until the ice reforms in the fall.

The meme “If there’s no ice, there’s no ice bear” is political-style rhetoric, not science.

[When polar bear scientists say “sea ice” or “ice” – they mean summer sea ice. Sea ice in winter and spring are not predicted to decline by 2100 to any appreciable degree and that has been true since sea ice predictions began]

Polar bears in Hudson Bay and Davis Strait routinely go 4-5 months without sea ice in the summer and have done since studies on them began. Yet, all of the polar bear subpopulations in Hudson Bay and Davis Strait are stable or increasing.

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