Steep Decline in Western Hudson Bay Polar Bears

A new report by the government of Nunavut shows a steep decline in Western Hudson Bay polar bears, with numbers falling by 27 percent in the past five years. These bears, which represent one of 19 polar bear populations across the Arctic, are those that we see in the Churchill, Manitoba region. They’re considered some of the most vulnerable polar bears in the world due to the negative effects of sea ice loss.

Because their natural habitat is so remote, polar bears are difficult to count in the wild. However, a team of researchers led by Dr. Stephen Atkinson completed extensive aerial surveys of polar bears in the Western Hudson Bay region in 2011, 2016, and 2021. Importantly, the team used the same techniques for each survey, allowing direct comparisons across time. Their findings show that the estimated population in this region declined by 11 percent between 2011 and 2016, and by 27 percent between 2016 and 2021.

The 2021 estimate is 618 bears, roughly half the estimated 1987 population of 1,185. However, the 1987 estimate used a different technique, and direct comparisons should be interpreted with caution.

The 27 percent decline over the last five years was driven by fewer adult females and subadults (young bears and cubs) of both sexes, while the number of adult males changed little. These trends agree with long-held predictions by biologists that sea ice loss, and the resulting reduced opportunities to hunt seals, would first affect subadults (because they are still growing) and adult females (because they are producing and supporting cubs). These trends also agree with studies reporting links between warming temperatures, longer melt seasons in the Arctic, and polar bears becoming thinner.

Some of the recent decline of polar bears in Western Hudson Bay could also be driven by bears migrating to neighboring populations. For example, one study using genetic identification of polar bears in the adjacent Southern Hudson Bay population found that 22 percent of the sampled individuals were originally identified in Western Hudson Bay. However, most of the bears moving between populations were adult males, which are not declining in Western Hudson Bay. Also, relatively few bears were observed in the border regions between populations during aerial surveys.

The ongoing, apparent decline in the estimated number of polar bears in Western Hudson Bay—from 949 in 2011 to 618 in 2021—is consistent with everything that is known about their biology. Polar bears have evolved to be specialized predators of the Arctic sea ice. Unless climate-change-induced ice loss is halted, reductions of this habitat will ultimately drive this species to extinction.

The report’s findings underscore the importance of our efforts to address both long- and short-terms threats to the bears: First, continuing to work with others to address the overarching threat of climate change—protecting the polar bears’ future and our own—and, second, doing all we can to ensure healthy populations in the short term. This includes efforts to protect moms and cubs during the denning period and projects to reduce conflict between polar bears and people, a growing problem as the Arctic warms and more polar bears are spending more time onshore. 

Dr. John Whiteman is Chief Research Scientist at Polar Bears International and an Assistant Professor of Biology at Old Dominion University in Norfolk, Virginia.