Polar bear habitat update – sea ice for hunting plentiful in all subpopulation regions

Preferred polar bear habitat is said to be 50% concentration or higher over continental shelves, which describes all but the fringes of sea ice extent today, including Hudson Bay, the Southern Beaufort, and the Barents Sea.

Preferred polar bear habitat 50pc concentration_May 8 2015_PolarBearScience

However, polar bears – excellent swimmers that they are – are quite capable of utilizing areas with 15-50% sea ice concentration if necessary (Durner et al. 2004; Rode et al. 2014:79), especially when prey are plentiful.  This would account for the fact that there are still sightings of polar bears in and around northern Newfoundland (see previous post here and photo below1), where ice concentration is in the 30-50% range.

Photo with this news story (7 May 2015): "(Update) Polar bear sighting in Croque"

Photo with this news story (7 May 2015): “(Update) Polar bear sighting in Croque”


Sea ice concentration in Canadian waters at 8 May 2015, below (click to enlarge): note the apparent patch of open water in the Southern Beaufort (western Arctic), discussed here, is a bit smaller this week.

Sea ice Canada 2015 May 8_CIS

Ice extent in the Beaufort Sea (below) is spot on “average” for this week (7 May), according to the Canadian Ice Service:

Beaufort Sea week of May 7 1968-2015 CIS

However, sea ice in Davis Strait (below) is still well above average for this week (as it has been for weeks) – click to enlarge:

Davis Strait same week May 7 1971-2015 CIS

The month-end summary for April provided by NSIDC had this to say:

“Ice extent remained below average in the Barents Sea, the Sea of Okhotsk, and the Bering Sea. Sea ice was slightly more extensive than average off Newfoundland, in the Davis Strait, and in the Labrador Sea. The Labrador Sea is an important breeding area for harp and hooded seals in early spring. More extensive ice in this region favors more seal cubs being fully weaned before the ice breaks up, increasing their chance of survival.” [my bold]

Harp and hooded seal cubs, of course, are what the polar bears in that area (part of the “Davis Strait” subpopulation, one of the most southerly-living bears in the world) are feasting on right now.

NSIDC ice extent map for 7 May 2015 below (click to enlarge):

Sea ice extent 2015 May 7 NSIDC

Although there is less ice than average in the Barents Sea, it still provides lots of polar bear hunting habitat. Close-up of Barents Sea and East Greenland ice conditions below (click to enlarge, courtesy Norwegian Ice Service):

Barents Sea ice plus East Greenland 2015 May 8_NIS

Footnote 1. The most recent sighting (full story here) is from Croque, on the northern peninsula of Newfoundland (Google map below):

Croque_newfoundland_PB sighting location May 7 2015

References
Durner, G.M., Amstrup, S.C., Neilson, R. and MacDonald, T. 2004. The use of sea ice habitat by female polar bears in the Beaufort Sea. US Geological Survey, Alaska Science Center, Anchorage, Alaska. OCS study, MMS 2004-014. Abstract here; Pdf here.

Rode, K.D., Regehr, E.V., Douglas, D., Durner, G., Derocher, A.E., Thiemann, G.W., and Budge, S. 2014. Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. Global Change Biology 20(1):76-88. http://onlinelibrary.wiley.com/doi/10.1111/gcb.12339/abstract

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