Polar bears in winter – a seasonal review of insights and research

Here are summaries of my “Polar bears in winter” series. It’s an interesting recap of what polar bears do over the unimaginably cold and dark months of an Arctic winter.

See original posts for fascinating photos, maps and references:

Polar bears in winter: insights from Behouden Huys, 1596-1597 January 6, 2013

While we don’t really know for sure what non-pregnant polar bears do during the depth of the Arctic winter, we have bits of evidence – some from modern hunters and polar bear researchers but also from Arctic explorers. One explorer in particular comes to mind: William Barents [Willem Barentsz] of Holland, who attempted to reach China via the Arctic Northeast Passage in the late 16th century.

On their third voyage (1596-1597), Barents and his crew were forced to spend the winter on the northern tip of Novaya Zemlya (latitude 760N, see Fig. 1) when their ship became trapped in the sea ice. Crew member Gerrit De Veer (1609) kept a journal account of the long, horrifying winter they spent on shore, in a shelter they built with materials salvaged from the ship. They called their winter home Behouden Huys (“the saved house”).

The Dutchmen were plagued by polar bears almost the entire time they were on Novaya Zemlya (see Fig. 2). De Veer’s notes on these encounters provide a unique perspective on polar bear activities over the Arctic winter – ironically, it is not the havoc the bears caused that provides the most important clue but rather, the timing of when they left Barents and his crew alone.

In summary, Barents and his crew saw or heard no bears from November 4 until January 31, almost exactly the period when the sun was below the horizon – with much activity both before and after. This hiatus of polar bear activity around Behouden Huys did not correlate with the period of most intense storms and cold. The experiences of these men – chronicled by De Veer more than 400 years ago – suggests that polar bears may spend the darkest part of the winter curled up in a sheltered spot rather than out and about looking for food.

Polar bears in winter: insights from modern research and Inuit hunters January 15, 2013

“The data collected by Ferguson and colleagues is less useful for addressing the question of whether polar bears use shelter dens during the darkest part of the winter because of the enormous range in latitude of their sample. However, they do confirm there were no winter dens used below 700 N and therefore, it appears that where the sun did not stay below the horizon for at least part of the winter, bears did not use winter shelter dens, regardless of storms or extreme cold.

I suggest, based on the limited modern and historical data, that the impression Gerrit De Veer had more than 400 years ago may be correct – that polar bears become inactive in the dark that affects regions above the Arctic Circle, even when the weather is not especially cold or stormy. Polar bears also spend time in shelter dens later in the winter in order to stay warm and save energy in foul weather.

So, while we certainly need more data on the activity of both sexes during the winter, it appears that De Veer’s observations provide an invaluable clue about what polar bears do over the long dark winter – his journal is more than an amazing story of Arctic survival. Since it is now illegal to disturb polar bears in their winter dens – even to study them – De Veer’s observations on polar bear activity over the Novaya Zemlya winter are all the more valuable.”

December is Polar Bear Nativity Month December 12, 2012

“Polar bears are generally out of sight at this time of year and will be for several more months. Pregnant females will be snug in maternity dens giving birth and all others will be out on the sea ice looking for seals to eat – if they can find them in the dark.

In most areas of the Arctic, December is when polar bear cubs are born, although in southern regions (like Western and Southern Hudson Bay), some may be born in late November and in the far, far north, a few may be born as late as early February.

The actual “date of birth” for polar bear cubs is often back-calculated from when they emerge with their mothers in the spring, because they are born well away from our prying eyes in the dark of the Arctic winter, deep with a snow or soil den dug for that purpose (see previous post here). So our knowledge of the “true” dates of birth in various regions is limited. We have some evidence from native Canadian hunters prior to 1968, when it was both legal and common practice in Canada for Inuit to hunt bears in their dens (Van de Velde et al. 2003), and from a few scientific research expeditions (Amstrup and Gardner 1994; Harington 1968; Ramsay and Stirling 1988).”

[See also Polar bear gives birth in Munich zoo, with photos and video January 8, 2014]

Polar bears in winter: starving bears and attacks on humans January 6, 2014

“Winter in the Arctic can be a tough time for polar bears. Between the cold, darkness and ever-thickening sea ice with fewer open leads, polar bears often find that seals are hard to come by.

So it should not be surprising to find out that polar bears are at their lowest body weight at the end of winter (Ramsay and Stirling 1988:613; Stirling 2002:68).

In other words, polar bears lose weight over the winter – not just during the ice-free summer period. That’s why the spring and early summer feeding period is so critical: gorging on young seals rebuilds the polar bears’ fat reserves lost over the winter and packs on even more fat to tide them over the late summer/early fall ice-free period.

The historic attacks of humans by polar bears on St. Lawrence Island are a reminder that these bears can be just as dangerous in winter, if not more so, than they are in the late summer and fall.

It’s possible that the data will show that serious predatory attacks by polar bears on humans (that result in death, near death and/or consumption), are more prevalent in late winter – when bears are at their leanest – than they are in the fall (when most bears are still in relatively good condition after their spring/summer feeding). However, we’ll have to wait and see what the final document on polar bear attacks looks like before we’ll know for sure.”

Polar bear winter: a spectacular Northern Lights video from Finland December 22, 2013.

“Yesterday, a short video clip of photographer Thomas Kast’s time-lapse Northern Lights video “Aurora – Queen of the Night” was posted at Alaska Dispatch, Time-lapse images show northern lights over Finland. There are no polar bears in the film but it is evocative of Arctic landscapes this time of year — when only the Northern Lights and the moon brighten the sky:

Thomas Kast’s four-minute time-lapse video “Aurora — Queen of the Night” is on show at Oulu’s Tietomaa planetarium. The short film was born during about 60 cold nights spent outdoors, mostly in the Oulu area.

Many think that vivid Aurora Borealis can only be seen in the far north, but Kast shows that it’s possible to view spectacular lights even within a city like Oulu, which is more than 125 miles south of the Arctic Circle. According to Kast, seeing and photographing them just requires patience.” [my bold]

 

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