Sea ice development in eastern Svalbard this fall is lagging well behind the rest of the Arctic. Several polar bear researchers (e.g., Andrew Derocher here and here) have recently been raising the alarm that this might be devastating for Barents Sea females looking for suitable denning sites.
The implication is that pregnant polar bear females are inflexible – so fixated on one location to give birth that they are unable or unwilling to choose an alternative if conditions preclude using their preferred location this year. However, the available facts do not support such a pessimistic attitude.
Posted in Life History, Sea ice habitat
Tagged Aars, Barents Sea, dens, Derocher, flexibility, Franz Josef Land, Hopen Island, Kong Karls Land, nearshore, pelagic, philopatry, polar bear, polar bear facts, pregnant females, sea ice, Svalbard
It’s just past the height of fall in the Arctic (Oct-Dec) and polar bear habitat is expanding day by day: according to NSIDC Masie ice charts, the ice has now surpassed 11 mkm2 in extent. Fall is the second most important feeding period for polar bears after spring.
Only the Barents and Kara Seas (north of Norway and western Russia) are short of ice right now, similar to conditions seen in the fall of 2013. Last fall (2014), conditions were much better and as a consequence, researchers saw a lot of females with healthy cubs in the spring of 2015.
Posted in Life History, Sea ice habitat
Tagged AMO, Barents Sea, Davis Strait, denning, fall feeding, Hudson Bay, polar bear, pregnant females, sea ice, spring feeding
Oddly, it seems some people expect polar bears to sit around and suffer (or die) when local conditions deteriorate, rather than move elsewhere.
While there are perhaps a few places where moving is not really an option over the short term, over the long term (more than one season) polar bears are free to shift to another locale if ice conditions change (either too much ice or too little).
An announcement by the WWF last week (10 April) caught my eye, as it talked about bears moving from one area to another because of changing ice conditions — as if this was surprising, extraordinary and newsworthy. That said, at least they weren’t suggesting the bears are all going to die because of declining ice, which is a huge improvement.
See what you think of this part of the press release (below), in the context of what we know about the movement of bears between regions:
Posted in Conservation Status, Life History, Sea ice habitat
Tagged adaptation, AMO, Amstrup, Barents Sea, dens, Franz Josef Land, Kara Sea, Mauritzen, polar bear, polar bear resilience, pregnant females, satellite radio collars, spring ice conditions, Svalbard, WWF
So far, I’ve not discussed the Barents Sea subpopulation in very much detail, except in comparison to other groups. For example, the Barents is considered to be the same type of sea ice “ecoregion” as the Chukchi Sea and the Southern Beaufort (discussed here). Previous studies on the Barents Sea polar bear population (Derocher 2005) indicate it may have recovered from extreme levels of overhunting (discussed here) and had stabilized, or was increasing very slowly, as early as 2002 (discussed here) — similar to what has happened in Davis Strait (discussed here).
Figure 1. Polar bear subpopulations, with the Barents Sea region highlighted; map courtesy the IUCN Polar Bear Specialist Group (PBSG), extra labels added.
The most recent Barents Sea population estimate was done in 2004 (2,650; range ~1900-3600), based on an aerial survey (Aars et al. 2009). Aerial surveys are the only practical method of establishing population counts in regions like this where many bears never set foot on land. The previous estimate for the Barents (1982) was “2,000-5,000” but its accuracy was considered “poor” (discussed here).
The IUCN Polar Bear Specialist Group (PBSG), in their most recent report, lists the Barents Sea population as “data deficient” for status, current trend and estimated risk of decline within 10 years (Obbard et al. 2010:62, Table 1) and the “notes” for this entry say:
“Population estimate is based on a new aerial survey. There was likely an increase in the subpopulation size after 1973 until recently. Current growth trend is unknown.”
This 2004 estimate is now almost a decade old and potentially no longer an accurate representation of what’s happening in the Barents Sea. The most up-to-date information has not yet been published but it is available online. It’s eye-opening to say the least, if only that it appears to be yet another example of a polar bear population that is so far not showing signs of being harmed by sea ice declines, as I’ve discussed before (here).
[Update October 15, 2013: I’ve simplified the text discussion and figure regarding the Aars and Andersen denning study from the original posted]
Posted in Conservation Status, Life History, Population, Sea ice habitat
Tagged aerial survey, Barents Sea, body condition, Derocher, ecoregrions, Environmental Monitoring of Svalbard and Jan Mayen, Jon Aars, litter size, Magnus Andersen, maternity dens, Mauritzen, MOSJ, number of cubs, Olga Pavlova, population size, pregnant females, reproduction, sea ice, Sebastian Gerland, Svalbard