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 in Life History, Sea ice habitat
Tagged birth, breeding, ecotype, fast ice, feeding, morphotype, offshore ice, pack ice, polar bear, prey, productivity, pups, ringed seal, shorefast ice
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 extent less than 5.0 mkm2 lasted less than 6 weeks (23 August – 28 September), according to NSIDC.
Posted in Conservation Status
Tagged Barents Sea, Chukchi Sea, extent, feeding, freeze-up, habitat, Hudson Bay freeze-up, hunting, ice-free, polar bear, sea ice, seals, September ice minimum
A large polar bear population with lots of adult males – due to bans on hunting – means more survival pressure on young bears, especially young males. To blame more problems with young male bears on lack of sea ice due to global warming ignores the downside to the reality Norway asked for when it banned hunting more than 40 years ago.
More hungry young males coming ashore looking for food is one of the potential consequences of living with a large, healthy population of polar bears. Biologist Ian Stirling warned of such problems back in 1974.
UPDATE: added below 6 Oct. 2016, statistics of defense of life shootings of polar bears in Svalbard since 1973.
Svalbard area polar bear numbers have increased 42% since 2004 and more hungry young polar bears almost certainly mean more polar bear problems, as folks in Svalbard (see map and quotes below) have experienced this year.
Posted in Conservation Status, Life History, Polar bear attacks, Sea ice habitat
Tagged attack, competition, facts, feeding, global warming, human-polar bear conflicts, numbers, polar bear, population size, problem bears, sea ice, subadult males, Svalbard, young bears
The recent open water in the Southern Beaufort didn’t seem to change what polar bears were doing – bears tracked by USGS show them on the ice, likely trying to hunt. More ice edge means more hunting habitat at this time of year.
However, few hunts are likely successful at this time of year – because only older seals are on the ice and the broken ice makes escape so much easier for the seals (see previous post here). Fat bears on shore this summer (like the ones seen at Kaktovik in September) will tell us that they got enough to eat earlier in the season. Note that bears in good condition that appear at the whaling bone piles in September are there by choice (not stranding) and they got fat by feeding in the spring (March-May), not by picking at leftover whale scraps. Calories from terrestrial sources (for most bears) just reduce the amount of weight they lose over the summer.
More maps below. Continue reading
What a difference a bit of historical perspective can make to one’s attitude on the annual Arctic sea ice breakup.
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:
Compare to 2011, when there was also 0.1 mkm2 less overall than this year:
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.
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.
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.
Posted in Life History, Sea ice habitat
Tagged bearded seal, facts, feeding, harp seal, hunting, Labrador, polar bear, polynya, ringed seal, sea ice, Southern Beaufort, Svalbard