Tag Archives: hunting

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.

Continue reading

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.

Continue reading

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.

Continue reading

Critical spring feeding for polar bears is over – sea ice levels are now irrelevant

Polar bears in virtually all regions will now have finished their intensive spring feeding, which means sea ice levels are no longer an issue. A few additional seals won’t make much difference to a bear’s condition at this point.

Relative importance of seasons polar bear graphic_PolarBearScience_June2016

The only seals available on the ice for polar bears to hunt in early July are predator-savvy adults and subadults but since the condition of the sea ice makes escape so much easier for the seals, most bears that continue to hunt are unsuccessful – and that’s been true since the 1970s. So much for the public hand-wringing over the loss of summer sea ice on behalf of polar bear survival! Continue reading

Polar bear habitat update end of April 2016: Plenty of sea ice for feeding

So, here we are near the end of the first month of the Arctic spring and there is still more ice than usual off Labrador and conditions in the Barents Sea are improving daily. The fear-mongers can blather all they like about the potential risks of bears swimming in summer – but spring is the critical season as far as sea ice is concerned for polar bears and all polar bear biologists know it. Polar bears consume 2/3 of all the food they need for the year during April-June and so far, ice conditions are looking just fine.

Cambridge Bay_we re OK_from Joe Prins

There is enough ice where there needs to be ice for polar bears to gorge themselves on new-born ringed and bearded seals – and that’s really all that matters. More ice off Labrador means more hunting ground for the Davis Strait polar bears that depend on the tens of thousands of young harp seals born this year off the Front.

Harp seal pup_DFO Newfoundland
Continue reading

W Hudson Bay polar bears now on the ice hunting but killer whales could be trapped

According to reports from folks on the ground in Western Hudson Bay, most polar bears were out on the ice resuming seal hunting by the 20th or 21st November at the latest (some got started quite a bit earlier). That’s less than 2 weeks later than the average date in the 1980s (which was November 8).

Sea ice Canada 25 Nov 2015_with Churchill

However, the rather odd pattern of freeze-up this year may not be good news for any killer whales still remaining in Hudson Bay – their access to the open ocean is already virtually blocked by ice.

UPDATE 26 November 2015: What a difference a day makes! Look at the spectacular ice development overnight along the west coast of Hudson Bay and in the central portion of the bay since yesterday (below).

Canadian Arctic Nov 26 2015_CIS

Continue reading

Polar bear habitat update – Arctic sea ice today covers same area as it did on June 30

Arctic refreeze is well underway. Less than half way through the Arctic autumn (Oct-Dec), polar bear habitat on 11 November 2015 covered the same total area as it did on the last day of Arctic spring (April-June); it’s just distributed differently.

polar_bear_usfws_no date_sm

Yesterday, courtesy NSIDC Masie

masie_all_zoom_4km_2015 Nov 11

Here is what 30 June 2015 ice extent looked like, with the same amount of ice coverage:

masie_all_zoom_v01_2015181_4km

For the week of 12 November, Hudson Bay sea ice development is well underway, with more ice in the north than there has been in many years; Davis Strait ice is the highest this week since 1999 and Baffin Bay ice coverage is above average. Foxe Basin and the Beaufort Sea are both approaching maximum coverage, which means bears there will be back out on the ice hunting. Chukchi Sea ice has finally surrounded Wrangel Island but the Svalbard Archipelago in the Barents Sea is still ice-free. More ice maps and charts below.
Continue reading

2015 may be the earliest in many years that W. Hudson Bay polar bears head for the sea ice

Great news for Western Hudson Bay polar bears! Following up from sea ice conditions last week, CIS maps show ice forming all along western Hudson Bay – not a huge amount, but the beginning of the end of the ice-free season, which recently has not occurred until mid-November (Cherry et al. 2013).

Canadian Arctic Oct 29 2015_CIS

There is above-average sea ice coverage in Foxe Basin and Davis Strait, and only slightly below average coverage in the Beaufort Sea (see graphs below). Polar bear habitat is shaping up very nicely indeed across Canada and the US this year.
Continue reading

Summer polar bear habitat then & now – little impact from 2007 record-breaking sea ice low

Sea ice looks low for this time of year but how does it compare to 2007, when summer ice habitat for polar bears hit a record-breaking low?  What can the impact of 2007 ice levels on polar bears tell us about what to expect this year?

Sea ice at 2015 Aug 8 vs pb status map_Aug 9 2015 sm

By this date in 2007 (8 August, Day 220, NSIDC Masie map below), there was almost 1 million km2 less ice than there is this year (map above). However, look which polar bear subpopulations not only survived, but thrived, through the 2007 low ice summer: Chukchi Sea, Southern Beaufort, Barents Sea, Davis Strait, Foxe Basin, Western Hudson Bay, and Southern Hudson Bay. That’s all of the subpopulations for which we have recent data.

There is more than a month left in the melt season, of course. However, while 2012 finished with a lower minimum ice extent due to a massive mid-August storm that broke up a lot of ice (Simmonds and Rudeva 2012), by the end of the first week of August (i.e, the 8th), there was more  ice in 2012 than in 2007 and a bit less than this year (2012, 6.3 mkm2; 2007, 5.6 mkm2; 2015, 6.5 mkm2).

This means if less summer ice for a longer period of time impacts polar bear health and survival, conditions in 2007 should have had a noticeable impact on polar bears around the world. They didn’t. That suggests even if this September sea ice minimum is as low as 2007, it won’t have any negative impact on polar bear health or survival. The most profoundly negative documented impacts have come from thick sea ice in spring or  suboptimal spring snow levels (Crockford 2015) and the evidence shows that variation in the extent of summer ice is simply irrelevant to polar bears.

Sea ice at 2007 Aug 8_polarbearscience
Continue reading