Tag Archives: prey

Svalbard polar bears thrive in part due to ringed seal pups in the spring pack ice

Few people know that Arctic ringed seals (Phoca hispida, aka Pusa hispida) give birth and breed in the offshore pack ice in the spring, as it is seldom mentioned by either seal or polar bear specialists.

While it is true that some ringed seals give birth in stable shorefast ice close to shore, many others give birth well offshore in thick pack ice – where polar bears also live and hunt in the spring but where few Arctic scientists ever venture – and the existence of pack ice breeding ringed seals is one of the reasons that polar bears are such a resilient species.

ringed-seal-in-snow-cave_b-kelly-wikipedia

Ringed seal pup in a snow cave, B. Kelly photo (Wikipedia).

As a consequence, despite fears expressed by Ian Stirling, low shorefast ice and associated snow around Svalbard this winter (and any time in the past) is not necessarily a hindrance to polar bear survival because there are ringed seal pups available out in the surrounding pack ice – where bearded seals also give birth.

Of course, ringed seals pups are also available to Svalbard polar bears in the shorefast ice in the Franz Josef Land archipelago to the east (see map below) but it is the pups born in the offshore pack ice that are of interest here. The existence of pack ice breeding ringed seals may be why Norwegian biologists do not currently monitor ringed seals in the Barents Sea, despite many years of poor ice conditions around Svalbard in spring – this simply is not a species of concern.

barents-sea-ice-2017-feb-6_nis

The fact that distinct ringed seal ecotypes (or habitat-specific morphotypes) exist in the Arctic – one that gives birth and breeds in shorefast ice and another that gives birth and breeds in offshore pack ice, perhaps driven by competition for limited shorefast ice habitat – is a phenomenon a colleague and I discussed in a peer-reviewed book chapter published several years ago. Have a look at the excerpt below and see what you think.

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Most polar bears easily deterred this time of year, lucky Labrador boaters discover

A polar bear female accompanied by a cub recently attempted to board a small sailboat anchored in a remote harbour off central Labrador – giving the two American boaters below deck a mighty big surprise.

Labrador polar bear encounter Torngat boat_CBC 30 Aug 2016

‘He said ‘it’s a bear, it’s right on the boat, make some noise.'” – Nancy Zydler

The encounter occurred south of the same national park where a much-publicized attack occurred in July 2013 (see previous posts here and here) but had a happier ending. See more below from a CBC report released this morning (based on a radio interview) and some ecological context for the sighting not mentioned by the reporter.
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Narwhal and beluga ice entrapment is natural – not caused by global warming

A part-time Arctic researcher eager for media attention suggested earlier today that the ice entrapment of narwhals in 2008 and again in 2015 at Pond Inlet (that made headlines around the world) was the result of “sudden changes in temperature” caused by climate change. This grossly misleading claim ignores the facts: ice entrapment of narwhals is an entirely natural feature of the Arctic that has been known about for hundreds of years.

Narwhals_at risk from climate change_CBC 13 Aug 2016 headline

Narwhals: the ‘giant unicorn of the sea’ at risk from climate change” (CBC, 13 August 2016), a print version of a CBC Radio interview with Clint Wright that aired 8 August 2016. Wright is the general manager at the Vancouver Aquarium and apparently has “joined a team of researchers to tag and study” narwhals for several years – but does not seem to know much about the history or circumstances of natural ice entrapment.

Ice entrapment of small whales is nothing new. The first formally documented incident – in English – occurred in 1915 (Porsild 1918) and the phenomenon has probably occurred as long as there has been ice in the Arctic (millions of years).

Animals routinely become trapped in a few specific areas due to local geography: when ice that forms in the north moves south quickly, it blocks the entrances to inlets or coastal bays that still have open water. The presence of the pack ice causes nearby  temperatures to drop quickly. Rapid development of ice on the bay proceeds from the mouth toward the head of the bay. Any whales present cannot escape to open water and will eventually die or be eaten.

Pond Inlet at the north end of Baffin Island is one such place but Disko Bay in western Greenland is another. In fact, Pond Inlet and Disko Bay are almost identical in geographic layout even though they lie on opposite sides of Baffin Bay, so it’s not surprising that both are locations of repeated entrapment events.

Three highly informative journal articles on the phenomenon of ice entrapment of narwhals and beluga are open access documents that reveal some fascinating details of such incidents, including polar bear predation on trapped whales. h/t T. Nelson 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

More polar bear habitat in Hudson Bay region at mid-May than in 2006 & 2011

What a difference a bit of historical perspective can make to one’s attitude on the annual Arctic sea ice breakup.

masie_all_r10_v01_2016137_4km

The usual recent pattern (since 1979) has been for breakup to begin on the east side. However, this year and last (below), it has begun in the NW (as it did in 1990 and a few other years).

Not all of the open water is due to melt, of course. As I discussed last week in relation to the Southern Beaufort Sea, winds and prevailing currents at this time of year start to fracture the ice and move it around well before much significant melt has begun.

Compare 2016 (above) to 2006 (below), when there was 0.1 mkm2 less overall – with much less ice in Hudson Strait and in the east of Hudson Bay than this year:
masie_all_r10_v01_2006136_4km

Compare to 2011, when there was also 0.1 mkm2 less overall than this year:
masie_all_r10_v01_2011136_4km

It’s important to keep in mind that the intensive feeding season for polar bears is drawing to a close – within another two weeks, most young-of-the-year seals will be in the water feeding and inaccessible to bears.

The only seals on the ice during June and July are predator-savvy adults and subadults that have hauled out to moult and for these seals the rapidly disintegrating ice creates many escape routes. That means that as long as the ice breakup sequence allows polar bears to get their fill of young seals before the end of May, even during early breakup years most bears should be fat enough to survive the coming summer and winter fasts (see more here). So we should expect to see some bears coming ashore within the next two weeks.

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Harp seal: most abundant Arctic seal is an undervalued polar bear prey species

The harp seal is the most abundant seal species in the northern hemisphere (estimated to number more than 9 million animals – that’s more harps than ringed seals) but are found only in the North Atlantic. Partly because they give birth on mobile pack ice, harps have their pups earlier in the season than all other Arctic seals, which means that in some regions, they are a critical food source for polar bears that have eaten little over the winter months.

Harp seal pup_DFO Newfoundland

Although young ringed seals are considered the primary prey of polar bears throughout the Arctic, young harp seals undoubtedly represent an increasingly important resource for populations of Davis Strait, East Greenland and Kara Sea bears.

Most of the harp seals in the NW Atlantic/Atlantic Canada (about 80% of them) have their pups off Newfoundland and Labrador, an area known as the “Front” (the location of my polar bear attack novel, EATEN: special deals all this week). Harps seals at the Front now provide a huge prey base for polar bears of the large (and possibly still growing) Davis Strait subpopulation (photo below courtesy DFO Canada).

There are an estimated 7.4 million harps in Atlantic Canada today (range 6.5-8.3m), an exponential increase over the early 1980s, when perhaps only half a million so remained.  Pagophilus groenlandicus was assigned a conservation status of ‘Least Concern’ by the IUCN Red List in June last year (Kovacs 2015), when it was estimated that the global population size of the harp seal was greater than 9 million animals and probably growing1, 2 due to reduced human hunting:

“…harp seals have been harvested for thousands of years but currently the population is large and the number of animals harvested is declining.” [my bold]

Photographers and animial rights activists love cute, fluffy harp seal pups and rarely mention the carnage that goes on in spring as polar bears devour the naive youngsters. See the video below (from 2008), for an example of the cuteness factor.

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Human sees cute – polar bear sees dinner

Newborn harp seals are food for Davis Strait, East Greenland and Kara Sea polar bears but wildlife photographers see only cute furry babies with big eyes and trusting natures.

Harp sea newborn_wikipedia

See these photos taken some unknown spring (early March) in the Gulf of St. Lawrence, Canada (published 29 December 2015 by Mailonline): the pups are kind of skinny when first born but fatten up quickly on fat-rich milk from their attentive mothers. Ask yourself: does this photographer know that the fattest of these baby seals he oh’s and ah’s over in his commentary are just what polar bears depend on for their existence – and that the bears will eat as many of them as they can catch, peeling them like bananas so that they can eat the skin and fat first?

The title of the piece is: “Eye-eye! Cheeky seal cubs just a few days old wink and pose for the camera as they wait for their mother to feed them:

  • The young Harp seal pups had never seen humans before the pictures were taken
  • They were photographed in their habitat of Madeleine Island in Quebec, Canada
  • Harp seals are solitary animals except during breeding season, when they congregate in their thousands

“These seal-ebrities from Canada are pictured striking hilarious poses that even Cara Delevingne would be proud of.

The three Harp seal pups – just days old – were passing time while they waited for their mother to return from hunting.

One pup looked straight to the camera with a cheeky wink, while another lay on its back looking longingly at the lens.

The impressive poses were captured by photographer Gunther Riehle, who was lucky enough to get just feet away from the baby seals on Madeleine Island in Quebec.”

See the photos here. Harp seal and hooded seal distribution and breeding areas in the Eastern Arctic (from DFO Canada).

Harp and hooded seal pupping areas and distribution_Stenson 2014 fig 1

More polar bear seal prey info here. See potential consequences of lots of polar bears depending on abundant harp seals north of Newfoundland in my novel, EATEN.