Lancaster Sound – a rarely-mentioned region with a large polar bear population

The polar bear subpopulation designated as Lancaster Sound lies at the eastern entrance to the Northwest Passage in the Canadian High Arctic (Fig.1). We rarely hear about it but this region has one of the largest polar bear populations anywhere in the Arctic – only the Barents Sea and Foxe Basin have higher estimated population sizes.

Figure 1. Lancaster Sound, magenta. Map courtesy Polar Bear Specialist Group, additional labels added.

Figure 1. Polar bear subpopulations with Lancaster Sound marked. Map courtesy IUCN Polar Bear Specialist Group, additional labels added.

Lancaster Sound includes the communities of Arctic Bay on northwestern Baffin Island and Resolute Bay on Cornwallis Island. Devon Island, which lies on the northern boundary, has no permanent communities, although two research stations are present (see here and here). A more detailed map showing the exact boundaries is available in Vongraven and Peacock (2011).

The eastern portion of Lancaster Sound is generally clear of ice by late summer (hence the Northwest Passage) but the western third of the region not only retains pack ice later in the season but some multiyear ice remains throughout the year.

The proximity of Lancaster Sound to Baffin Bay and the eastern Northwest Passage (Fig.2) undoubtedly exposed polar bears there to hunting by European whalers during the 1800s and early 1900s (see previous post here, especially Fig. 5), from which the population appears to have recovered.

On the other hand, the proximity of Lancaster Sound to oil and gas reserves further north in the High Arctic generated much-needed funds for polar bear biologists in the mid-to-late 1970s to collect essential baseline data for the entire region (Schweinsburg et al. 1982; Stirling et al. 1979, 1984; Stirling and Latour 1978).

Figure 2. The main Northwest Passage route starts at Lancaster Sound and runs east through Parry Channel because these waterways routinely clear of ice in late summer. The approximate boundary of the Lancaster Sound polar bear subpopulation (area ~490,000 km2) is marked in yellow; POW is Prince of Wales Island. Map from Wikipedia, labels added.

Figure 2. The main Northwest Passage route starts at Lancaster Sound and runs east through Parry Channel because these waterways routinely clear of ice in late summer. The approximate boundary of the Lancaster Sound polar bear subpopulation is marked in yellow; POW is Prince of Wales Island. Map from Wikipedia, labels added. Click to enlarge.

The latest population surveys in Lancaster Sound were conducted from 1995 to 1997 (Taylor et al. 2008) and in 1998 an estimate of 2,541 ± 391 bears was generated. This 1998 estimate appeared to be a significant increase over the previous estimate (1977) of “at least” 1,700 bears (Stirling et al. 1984:214; Lunn et al. 2002).

This puts Lancaster Sound amongst the most populous polar bear regions known in the Arctic, although it is one of the smaller regions in geographic area.

To show you how it compares, I’ve listed below all of the subpopulations that had 2,000 bears or more at last count (Obbard et al. 2010; Stapleton et al. 2012), with their most recent estimate, range and date of the estimate, plus the approximate area in square kilometers (from Vongraven and Peacock 2011):

Barents Sea                2,650 (1,900-3,600:2004), area ~1.69 million km2

Foxe Basin                 2,580 (2,100-3,200:2010), area ~1.18 million km2

Lancaster Sound       2,541 (1,759-3,323:1998), area ~0.49 million km2

Davis Strait                2,142 (1,811-2,534:2007), area ~2.62 million km2

Baffin Bay                 2,074 (1,544-2,604:1998), area ~ 1.08 million km2

In addition, Rode and colleagues (2013) assumed in their recent study that the Chukchi Sea region (area ~1.84 million km2) supported at least 2,000 bears, although a formal count has not been undertaken.

Status, current trend and risk of decline
Due to the fact that the Lancaster Sound data was more than 10 years old by the time the last IUCN Polar Bear Specialist Group (PBSG) assessment was made in 2009 (Obbard et al. 2010:48, 64), its “status” was listed as data deficient.

However, the “current trend” for this subpopulation was appraised as declining and the “estimated risk of future decline within 10 years” was declared to be “high” – both based on concerns of over-hunting. The PBSG say, regarding the traditional harvest, that  “a highly skewed harvest towards males exacerbates the risk of decline.” However, that pattern seems to be resolving, since they also say that “in 2008/09, the harvest was 39% female.”

In other words, while the large Lancaster Sound polar bear population was recently classified as having a “declining” trend by the PBSG and a “high risk” of decline over the next 10 years, this assessment was based on concerns of over-harvest, not sea ice declines blamed on global warming. In fact, changes in sea ice cover and/or breakup dates were not even mentioned in the PBSG evaluation for Lancaster Sound.

References
Lunn, N.J., Schliebe, S., and Born, E.W. (eds.). 2002. Polar Bears: Proceedings of the 13th working meeting of the IUCN/SSC Polar Bear Specialists Group, 23-28 June , 2001, Nuuk, Greenland. Gland, Switzerland and Cambridge UK, IUCN. http://pbsg.npolar.no/en/meetings/

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/

Rode, K.D., Regehr, E.V., Douglas, D., Durner, G., Derocher, A.E., Thiemann, G.W., and Budge, S. 2013 (accepted). Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. Global Change Biology. http://onlinelibrary.wiley.com/doi/10.1111/gcb.12339/abstract

Schweinsburg, R.E., Lee, L.J. and Latour, P.B. 1982. Distribution, movement and abundance of polar bears in Lancaster Sound, Northwest Territories. Arctic 35:159-169. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/2316

Stapleton, S., Peacock, E., and Garshelis, D. 2012. Foxe Basin polar bear aerial survey. Nunavut Wildlife Research Trust, Government of Nunavut, Igloolik.

Stirling, I., Calvert, W., and Andriashek, D. 1984. Polar bear ecology and environmental considerations in the Canadian High Arctic. Pg. 201-222. In Olson, R., Geddes, F. and Hastings, R. (eds.). Northern Ecology and Resource Management. University of Alberta Press, Edmonton.

Stirling, I. and Latour, P. 1978. Comparative hunting abilities of polar bear cubs of different ages. Canadian Journal of Zoology 56:1768-1722. http://www.nrcresearchpress.com/doi/abs/10.1139/z78-242#.UmNABRDkSUk

Stirling, I., Schweinsburg, R.E., Kolenosky, G.B., Juniper, I., Robertson, R.J., and Luttich, S. 1980. Research on polar bears in Canada 1976-1978. Pg. 45-66 in [Anonymous]. Polar Bears: Proceedings of the 7th meeting of the Polar Bear Specialists Group IUCN/SSC, 30 January-1 February, 1979, Copenhagen, Denmark. Gland, Switzerland and Cambridge UK, IUCN. http://pbsg.npolar.no/en/meetings/

Taylor , M.K., Laake, J., McLoughlin, P.D., Cluff, H.D., and Messier, F. 2008. Mark-recapture and stochastic population models for polar bears of the High Arctic. Arctic 61:143-152. http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/19

Vongraven, D. and Peacock E. 2011. Development of a pan-Arctic monitoring plan for polar bears: background paper. Circumpolar Biodiversity Monitoring Programme, CAFF Monitoring Series Report No. 1, CAFF International Secretariat, Akureyri, Iceland. Available at http://www.caff.is/publications/view_category/23-all-monitoring-documents

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