What a difference two weeks make! When the seasonal minimum Arctic sea ice extent occurs in September, polar bear doom-mongers always forget to tell you that within two months, sea ice will return to virtually all regions where polar bears have spent the summer on land, including Hudson Bay. Just as it did in 2007, when polar bears did not die by the thousands due to lack of fall sea ice, polar bear habitat is reforming.
This year, the seasonal minimum came on 23 September. Despite the fact that the US National Snow and Ice Data Center proclaimed that “unusual warmth” in the Arctic continued during October, over the last two weeks sea ice expanded from 6 mkm2 to 9 mkm2. At the current rate of ice growth documented by sea ice charts (see below), Arctic sea ice will be wide-spread by 23 November.
A recent study by Norwegian biologist Karen Lone and colleagues, who tagged 57 polar bear females with sensors around Svalbard, discovered that polar bears can dive to a maximum depth of 13.9m and can swim long distances across open water without rest. Contrary to previous claims, polar bears are excellent divers and their breath-holding ability did not seem to limit how deep they could dive.
From the abstract of the new paper by Lone and colleagues (Lone et al. 2018):
“Some bears undertook notable long-distance-swims. Dive depths up to 13.9 m were recorded, with dives ≥5 m being common. The considerable swimming and diving capacities of polar bears might provide them with tools to exploit aquatic environments previously not utilized.”
Compare the above statement to one made by Stirling and van Meurs (2015), after describing a 3 minute dive video-taped during an aquatic stalk of a bearded seal, also in the Svalbard area:
“…increased diving ability cannot evolve rapidly enough to compensate for the increasing difficulty of hunting seals because of the rapidly declining availability of sea ice during the open-water period resulting from climate warming.” [my bold]
These two papers really show the difference between using anecdotal accounts as if they were evidence of species-wide physical abilities and doing a scientific study on the physical ability of interest.
Posted in Advocacy, Life History, Sea ice habitat
Tagged continuous swims, depth, dive, harbour seals, polar bear, Spitsbergen, stalk, Stirling, Svalbard, swimming, underwater
A few polar bears have become stranded on small islands north of Svalbard since the local sea ice retreated — of which the bear that mauled a cruise ship guard last month was but one — and if return of the ice is as late as last year, those handful of bears are likely doomed to die of starvation. This is not due to climate change but rather bad judgment on the part of these few bears. They were not forced ashore: if they’d stayed on the ice like the rest of the population, they’d have likely been just fine.
Similar to the bear in northwestern Hudson Bay that fatally mauled a young father in early July, these bears were likely lured ashore by the prospect of masses of bird eggs present on island rookeries. But they overstayed their window of opportunity and the ice retreated without them.
Fledgling birds and bird eggs are not replacements for seals in a bear’s diet but when the season of easy seal kills winds down, as it does in late spring, easy-picking sea bird eggs may be enticing enough to lure a few bears ashore when they’d be better off on the ice.
That is not the fault of climate change.
Unlike bears in Hudson Bay and many other regions — including the Lancaster Sound area of Canada where the National Geographic “starving” bear was filmed last summer — these bears were not forced ashore by retreating ice: they chose to do so.
Posted in Life History, Polar bear attacks, Sea ice habitat
Tagged attack, Barents Sea, climate change, polar bear, Refuge, sea ice, stranded, summer, Svalbard
Less than a month after a fatal polar bear attack near Arviat, Western Hudson Bay, European media reported this morning that one of two German polar bear guards escorting a group of tourists on a shore visit in northern Svalbard was mauled on 28 July by a polar bear before the second guard could kill it.
The man was air-lifted to hospital in Longyearbyen with non-life-threatening head injuries. Whether the bear was fat or thin was not mentioned but a necropsy will be performed.
More details are likely to be available within the next few days. The guards and tourists were from the German cruise ship MS Bremen, which apparently is operating a live web cam. The group landed on the Sjuøyane Islands, the northernmost group of islands in the Svalbard archipelago (see the top of the black box on the map below).
UPDATE 28 July 2018 11:00 pm PT: The photo of the dead bear (above, provided by the Governor of Svalbard), shows the animal was in poor condition. See my comments below regarding sea ice coverage for the area: the bear had likely been on the islands since early May and if he was not in good condition when he left the ice, he would have been desperate by now. However, we still do not know if he was sick or injured, young or old. That information will come with time.
UPDATE 29 July 2018: The cruise ship line has released a statement on Facebook that includes further details about the attack, see below.
Last week, the Norwegian Polar Institute updated their online data collected for the Svalbard area to include 2017 and 2018 — fall sea ice data and spring polar bear data. Older data for comparison go back to 1993 for polar bears and 1979 for sea ice, showing little to no impact of the reduced ice present since 2016 in late spring through fall.
Here’s what the introduction says, in part [my bold]:
“…The polar bear habitat is changing rapidly, and the Polar Basin could be ice-free in summer within a few years. Gaining access to preferred denning areas and their favourite prey, ringed seals, depends on good sea ice conditions at the right time and place. The population probably increased considerably during the years after hunting was banned in 1973, and new knowledge indicates that the population hasn’t been reduced the last 10-15 years, in spite of a large reduction in available sea ice in the same period.”
See Aars et al. 2017 for details on the 2015 Svalbard polar bear population count, keeping in mind that the subpopulation region is called “Barents Sea” for a reason: only a few hundred individuals currently stick close to Svalbard year round while most Barents Sea bears inhabit the pack ice around Franz Josef Land to the east (Aars et al. 2009; Crockford 2017, 2018).
Posted in Advocacy, Conservation Status, Sea ice habitat
Tagged Barents Sea, body condition, decline, denning, Derocher, Franz Josef Land, litter size, mothers with cubs, polar bear, population, sea ice, Svalbard
Large margins of error in polar bear population estimates means the conservation status threshold of a 30% decline (real or predicted) used by the US Endangered Species Act and the IUCN Red List is probably not valid for this species.
Several recent subpopulation estimates have shown an increase between one estimate and another of greater than 30% yet deemed not to be statistically significant due to large margins of error. How can such estimates be used to assess whether population numbers have declined enough to warrant IUCN Red List or ESA protection?
What do polar bear population numbers mean for conservation status, if anything?
Posted in Conservation Status, Population
Tagged baffin bay, declining, Derocher, errors, ESA, estimate, facts, IUCN Red List, numbers, polar bear, population, science, significance, statistics, Svalbard, western hudson bay