Posted onOctober 20, 2021|Comments Off on Most Chukchi Sea ice in 20 years means no walrus feasts for polar bears at famous Russian cliffs
After years of hype, including documentary over-reach by David Attenborough and his collaborators at WWF and Netflix, there has been relatively abundant ice in the Chukchi Sea this summer, particulary along the Russian coast and around Wrangel Island, which in recent years have been important summer refuge areas for polar bears and Pacific walrus.
This year, there has been nothing like the complete retreat of ice into the Arctic Basin as happened in 2007, 2012, and 2020. The chart below shows the ice extent at 11 October 2021:
Wrangel Island was surrounded by ice in 2000 and 2001, which made access to walrus haulouts on the island impossible (Kochnev 2004). Most of the walrus haulouts along the Chukotka coast were also ice-covered in September in those years, as were all of the western locations in 2021 – as the ice charts below show. The extra ice will have drastically affected the distribution of walrus this year, which in turn will have meant no walrus carcasses for polar bears to feast on as they have done for many years now.
Posted onApril 27, 2018|Comments Off on Polar bear habitat update early spring 2018
Spring in the Arctic is April-June (Pilfold et al. 2015). As late April is the peak of this critical spring feeding periodfor most polar bear populations, this is when sea ice conditions are also critical. This year, as has been true since 1979, that sea ice coverage is abundant across the Arctic for seals that are giving birth and mating at this time as well as for polar bears busy feeding on young seals and mating.
Below is a chart of sea ice at 25 April 2018, showing sea ice in all PBSG polar bear subpopulation regions:
Posted onFebruary 7, 2017|Comments Off on 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 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.
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.
Posted onJanuary 5, 2016|Comments Off on Tracking polar bears in the Beaufort Sea – one tagged bear left at year end 2015
I’ve combined the months of November and December for this post on USGS polar bear tracking in the Beaufort Sea because there’s not much to tell: there’s one tagged bear left and she’s going almost nowhere. Where’s the news in that?
Movements of 1 satellite-tagged polar bear female for the month of November, 2015; shown with sea ice coverage at 30 November 2015. This bear was tagged in the spring of 2015 in the Southern Beaufort Sea. See original image here and December movements below.
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; Derocher et al. 1992).
Polar bear cubs, like all bears, are born tiny and rather undeveloped (see Figs 1 and 2 below). Their eyes do not open until about one month after birth. By the time they are 63 days old (two long months after birth, see Toronto Zoo photo here ), their eyes are wide open and they are well furred. Keep in mind, for perspective, that domestic dogs are born after a 63 day gestation period and their eyes open at about 12 days. Continue reading
Comments Off on December is Polar Bear Nativity Month