And the proposed coastal refuge won’t protect the denning areas of the majority of Southern Beaufort Sea polar bears, because most females den out on the sea ice, not on land.
The folks at Polar Bears International (PBI) are crowing with delight at the announcement today that US President Obama has recommended that congress approve plans to implement a proposed an Arctic wildlife refuge area that would include the Arctic coastal plain [see links below, including Obama video].
And in doing so, they mislead the public about how many polar bears use this region of coastal Alaska — as do the US Fish and Wildlife Service on their Refuge website.
The PBI news flash, entitled “News to Celebrate: Obama Recommends Protection for Key Polar Bear Dennning Area,” includes this misleading statement:
“Today, the White House recommended that this remarkable place be granted protection as a wilderness area. This is important news for polar bears because the coastal plain provides the bears with vital on-land denning sites.
“The coastal plain of the Arctic National Wildlife Refuge historically has the highest number of polar bear maternal dens in Alaska,” says Geoff York, PBI’s senior director of conservation.
“In recent years, these shorelines have also seen increased numbers of polar bears resting in the summer as they wait for sea ice to return in the fall.”
Those statements are at best only partially true. In fact, only a small percentage of all Alaskan polar bear females make their dens on land (most den on the sea ice). In fact, the bears that den onshore in that region are the ones most at risk from decadal bouts of thick spring ice. And the most recent study published (2007) showed that, on average, only ~4% of all Southern Beaufort bears spent time on shore in the summer (the maximum was 8%).[see details below]
As for more recent years, see my posts following the USGS “Tracking polar bears in the Beaufort Sea” program (start 2013 here, “Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice” [copied below] with recent updates every month, other recent summer ones here and here): see for yourself where the females go, other years and months here. Most females stay on the sea ice all year, although a few do go ashore.My conclusion: Whatever good an Arctic National Wildlife Refuge might do for terrestrial mammals and other creatures in Northeastern Alaska, it would not offer any real protection for Southern Beaufort polar bears — because so few females make their dens onshore and because the greatest threat to the health and survival of polar bears on that stretch of coast is the naturally-caused bouts of thick spring ice that occur every decade. I fail to see how this region can be seriously considered ‘critical habitat’ for Southern Beaufort polar bears.
“Southern Beaufort Sea polar bear subpopulation is the only one in which a significant proportion of the pregnant females are known to have had maternity dens on the stable multiyear ice floes in drifting pack ice.” [my bold]
Below is a copy of a previous post where I discussed the issue of sea ice vs. onshore denning, from a study by Fischbach and colleagues (2007) who said they found evidence that the proportion of bears they followed with satellite collars who made their dens on the sea ice declined from 62% in 1985-1994 to 36% in 1998-2004. Here is what I said:
“However, the radio-collars used to track pregnant females in this study [Fischbach et al. 2007] were attached to the bears in the fall, within helicopter range of coastal research bases (pg. 1398), suggesting the near-certainty that both samples were biased towards bears that chose to den on land – because of the location where the bears were captured.
In other words, more bears in both periods may have been captured on or near land in the fall than was representative for the entire population (many bears would have been offshore on the sea ice). This method of capture would have increased the number of bears in each of the samples that, a few months later, chose to den on land.
The authors say they accounted for this potential bias in the model that was used to analyzed patterns in denning location, but I take this statement to mean there was no bias between years.
The Fischbach et al. study actually determined the den locations of bears that remained near the coast in the fall each year – it could not estimate the proportion of all bears in the Southern Beaufort Sea that make their dens on land vs. sea ice because it did not sample bears that were offshore during the fall.
The Fischbach et al. study sampled only 124 dens occupied by 89 bears that were near shore in the fall, sampled over 20 years, out of a population estimated to have been 1,800 in 1993 (Wiig et al. 1995) and 1,200 (range 1,000-2,000, a preliminary estimate) in 2006 (Aars et al. 2006), now considered to be 1,526 (Obbard et al. 2011).
The point is, there were almost certainly many female polar bears that were denning in the pack ice but never came to land in the fall and therefore, could not be counted by this survey.
What is even more interesting is that in a separate study in the same general area, conducted between 2000 and 2005, Schliebe et al. (2008:1005) found that an average of 3.7% (three point seven, not a typo) of all polar bears (out of an estimated 1,526 bears) spent time on land in fall (mid-September to end of October).
That’s 56 bears, per year, on land in the fall – out of 1,526 or so bears. That suggests that most pregnant females in the Southern Beaufort made their dens in the pack ice and never came to land in fall at all.
Previously, Amstrup and Gardner (1994:8) stated:
“Contrary to previous hypotheses (Stirling and Andriashek 1992), substantial polar bear denning occurs in the Beaufort Sea region of northern Alaska and adjacent Canada. Bears that den on pack ice are subject to risks not encountered by bears that den on land. Unstable, moving ice caused early abandonment of dens and, apparently, loss of cubs. However, the persistence of pack-ice denning indicated that those risks are not overwhelming.” [my bold]
References and Announcement Links
Volume 1, Chapter 4, pg 117 [“Affected Environment” with relevant polar bear description] download from this link (~25MB)
US Fish & Wildlife Arctic National Wildlife Refuge http://www.fws.gov/refuge/arctic/
Washington Post report January 25, 2015
Aars, J., Lunn, N. J. and Derocher, A.E. 2006. Polar Bears: Proceedings of the 14th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, 20-24 June 2005, Seattle, Washington, USA. Occasional Paper of the IUCN Species Survival Commission 32. IUCN, Gland (Switzerland) and Cambridge (UK). http://pbsg.npolar.no/en/meetings/
Amstrup, S.C. and Gardner, C. 1994. Polar bear maternity denning in the Beaufort Sea. The Journal of Wildlife Management 58:1-10.
Ferguson, S. H., Taylor, M. K., and F. Messier 2000. Influence of sea ice dynamics on habitat selection by polar bears. Ecology 81:761-772.
Fischbach, A. S., Amstrup, S. C., and D. C. Douglas 2007. Landward and eastward shift of Alaskan polar bear denning associated with recent sea ice changes. Polar Biology 30:1395-1405. http://link.springer.com/article/10.1007/s00300-007-0300-4
Obbard, M.E., Theimann, G.W., Peacock, E. and DeBryn, T.D. (eds.) 2010. Polar Bears: Proceedings of the 15th meeting of the Polar Bear Specialists Group IUCN/SSC, 29 June-3 July, 2009, Copenhagen, Denmark. Gland, Switzerland and Cambridge UK, IUCN. http://pbsg.npolar.no/en/meetings/
Mauritzen, M., Derocher, A.E. and Wiig, Ø. 2001. Space-use strategies of female polar bears in a dynamic sea ice habitat. Canadian Journal of Zoology 79:1704-1713. http://www.nrcresearchpress.com/doi/abs/10.1139/z01-126#.U0spVlda9lo
Schliebe, S., Rode, K.D., Gleason, J.S., Wilder, J., Proffitt, K., Evans, T.J., and S. Miller. 2008. Effects of sea ice extent and food availability on spatial and temporal distribution of polar bears during the fall open-water period in the southern Beaufort Sea. Polar Biology 31:999-1010. http://link.springer.com/article/10.1007/s00300-008-0439-7
Stirling, I. and Derocher, A.E. 2012. Effects of climate warming on polar bears: a review of the evidence. Global Change Biology 18:2694-2706.
Stirling, I. and Andriashek, D. 1992. Terrestrial maternity denning of polar bears in the eastern Beaufort Sea area. Arctic 45:363-366. http://arctic.journalhosting.ucalgary.ca/arctic/index.php/arctic/article/view/1415