The Chukotka-Alaska population of polar bears in the Russian Arctic’s northeast

The Chukotka-Alaska population of polar bears in the Russian Arctic’s northeast

4 December 2014

The Chukotka-Alaska polar bear population (sub-population, according to the terminology of the World Conservation Union (IUCN) lives in the northeastern region of the Russian Arctic. Its habitat includes the entirety of the Chukchi Sea, the eastern part of the East Siberian Sea and the western part of the Beaufort Sea. As such, this polar bear population falls under the jurisdiction of Russia and the United States. 


The Chukotka-Alaska population is among the three polar bear populations inhabiting the Russian Arctic. The habitats of the Central Siberian population and the Barents Sea – Kara Sea population are centred in the Laptev Sea and the Barents Sea, respectively. Although the Kara Sea population is sometimes listed as a separate sub-population, there is no convincing scientific evidence for doing this. The Barents Sea population also falls under the jurisdiction of two countries – Russia and Norway.


The Chukotka-Alaska population is the least-studied polar bear population in Russia. Systematic data on it began to be collected in the early 1970s. Famous Russian polar zoologist Savva Uspensky pioneered this effort. Stanislav Belikov also spent many years studying the biology of hibernating polar bears on Wrangel Island.


Since 1990, we have been implementing a long-term project to study the behaviour and population ecology of polar bears at the Wrangel Island Reserve. This project aims to assess patterns of intra-population processes, including disruptions caused by global climate change. Long-term studies are essential in order to pinpoint specific changes. The long-term monitoring of basic population characteristics, including ground observations of intra-population processes, is an essential aspect of this project.


Wrangel Island, a state nature reserve, has gained broad international recognition as a polar bear “maternity ward.” Most fertile polar bears of the Chukotka-Alaska population gather on the island, as confirmed by ground observations and satellite photos. The latter were taken in the early 1990s and late 2000s by US teams. Virtually all female polar bears tagged with satellite transmitters off the Alaska coast were tracked to Wrangel and Herald Islands, as well as ice formations to the north of them, in late summer.


As with other polar bear populations in the Russian Arctic, the Chukotka-Alaska population has an open habitat, and nothing hampers the migration of polar bears along ice formations on sea. Despite long-term efforts to pinpoint polar bear dens serving as improvised “maternity wards” on Wrangel Island in the 1970s, 1980s and early 1990s and similar sporadic projects on the Chukotka coast, the precise numbers of this population were never determined. In fact, a methodologically precise assessment is impossible, considering the size of the population’s habitat, the extremely uneven distribution of polar bears and considerable seasonal fluctuations in their migration patterns along ice formations.


In 1992, Stanislav Belikov made approximate calculations for the 1980s and early 1990s using bear den data on Wrangel and Herald Islands, as well as best guesses of the population’s sex and age structure. He estimated the entire population at 2,000-5000 bears, with a high margin of error. Nevertheless, his work was used for official statistics in the Red Data Books of the USSR, the RSFSR and the Russian Federation. This estimate was repeatedly cited in various publications, with media  outlets mentioned reporting it as established fact without even indicating the time period it applies to.


This population peaked in the late 1980s and early 1990s, due to long-term polar bear conservation efforts in Russia and optimal ice conditions. On 1 January 1957, the Soviet Government banned the hunting of polar bears, and this ban remains effective to this day. However, the Arctic ice situation started deteriorating rapidly since 1990 to the detriment of polar bear habitats. This trend was accompanied by unprecedented poaching during the economic reform years of the 1990s. According to official expert estimates, confirmed by local hunters, about 70 to 300 polar bears were annually killed in Chukotka from the mid-1990s until the early 2000s. In addition, Alaskan natives continued to hunt bears of this population without restriction. Add to this steadily progressing global warming and shrinking ice formations, the main habitat for polar bears. The problem of declining ice cover has been especially pronounced in this region. All this has caused a number of negative trends.


There are several indicators of population decline among the core fertile group of the Chukotka-Alaska population. The number of bear dens serving as improvised “maternity wards” has decreased from an estimated 300-400 in the late 1980s and early 1990s to less than 60-70 in 2007-2012. Since the early 1990s, the number of bears reaching Wrangel Island during the melting of the ice formations that are their main habitats in the continental shelf zone has fallen by at least three to four times. The number of family groups with newborn cubs aged 1-12 months living on Wrangel Island every autumn has decreased five- to six-fold. In 2004-2012, the proportion of family groups with cubs born in the first and second autumns has dropped by over 66 percent, and cub losses over the same period exceed 75 percent of the total. In 2011-2013, malnourished bears accounted for an increasingly greater share of the summer-autumn polar bear population on Wrangel Island (8.1 percent in 2011, 11.3 percent in 2012, 6.5 percent in 2013).


This is a substantial increase on 2005-2010 (0.8-4.9 percent). The share of adult males also exceeded normal values. In 2011-2013, male bears accounted for an average of 22.3 percent (14-35 percent, to be more exact) of the entire population. For comparison’s sake, in 2004-2010, adult males accounted for an average of 13.6 percent (6.1-19.6 percent) of the entire population.


Some interesting statistics on the share of female polar bears have been obtained. In 2011-2013, the share of single females that can potentially mate and reproduce during any specific season was 12.9-16.7 percent, as compared to 9.3-10.4 percent in 2004-2010. This increase in the share of single females in the summer-autumn population (prior to hibernation) over the past three years correlates with a reduction in the proportion of family groups with newborn cubs. Most likely, this is linked with the loss of cubs during the first spring and summer of their lives. In 2013, only 11 females with newborn cubs aged 1-12 months were recorded as part of the summer-autumn population near Wrangel Island (including the island and ice formations in the adjacent waters), or just 6.5 percent of all bears recorded during the study (compared to 4.3 percent in 2012, 7.6 percent in 2011, and 9.3-15 percent in 2004-2010).


The share of cubs aged 1-12 months reached 8.9 percent in 2013, 6.1 percent in 2012 and 9.3 percent in 2011. This is considerably less than in 2004-2010, when their share varied from 13.2 percent to 24.1 percent.


Another alarming trend is the large share of single females that hibernate without having accumulated sufficient fat reserves. In 2004-2010, 25-33 percent of all observed single females were insufficiently nourished prior to hibernation. A striking 45.8 percent of female bears we observed in 2012 were undernourished, although their share dropped to just 14.3 percent throughout 2013. Obviously, this was related to better summer ice conditions.


Statistics on the demographic composition of the autumn polar bear population near Wrangel Island and its changes can be taken as characteristic for the entire population. In 2008-2011, US researchers tracked 14 females tagged with satellite transmitters in the southeastern part of the Chukchi Sea (United States Fish and Wildlife Service data). Ten of these females (71.4 percent) hibernated on Wrangel Island and two on Herald Island. Of 40 bears tracked for over 180 days, 23 (57.5 percent) entered Wrangel Island, demonstrating that polar bears from the entire Chukotka-Alaska population mass near Wrangel Island each autumn.


As has already been noted, it is methodologically impossible to accurately estimate the entire population because of its huge habitat and porousness (annual emigration and immigration), as well as due to the extremely uneven and fluid distribution of polar bears on ice formations. However, the defining feature of this population is that the most widely used ice formations in the continental shelf zone accumulate in the Russian Arctic near Wrangel Island – to the north and northwest of it and, in some years, even off the Chukotka coast – prior to complete melting in late summer. Therefore, when this ice cover melts on the continental shelf, most bears go the Russian coast and wait for the new ice to form. Long-term efforts to monitor this population have shown that it continues to shrink. In the early 1990s, many hundreds of polar bears entered Wrangel Island. Over the past few years, not more than 200-250 bears arrived there each year. In 2011-2013, about 160-170 bears were sighted on the island.


A calculation of this population’s approximate size for the past five years, based on data analysis regarding the size and demographic composition of the ground-based polar bear population and using the most optimistic indicators of the share of fertile females, indicates that the entire current population cannot exceed 1,300-1,500 bears. Supposing that less than two-thirds of all bears remain on the ice, and that only one-third of them come ashore, even this does not necessarily reflect the real situation. Available data shows that no more than 50 percent of polar bears remain on the ice prior to autumn and gravitate towards polar areas, and that at least half of the entire bear population comes onto Russian territory.


Therefore, an entire range of population indicators shows the negative impact of climate change and melting of ice formations on this population. It is important that the changing environment is adversely affecting even this population, which inhabits a region that abounds in the resources that polar bears need. It should be noted that the waters of the Chukchi Sea contain many food sources for polar bears. Before the ice melts, polar bears hunt successfully in this section of the Arctic and are well-nourished. The first malnourished animals are sighted in late summer and autumn, and cubs perish during that time period. But, even during these critical seasons, polar bears are able to find food on Wrangel Island and the Chukotka coast, including walrus breeding grounds, and dead walruses and whales that have been washed ashore.


Environmental changes aggravated by man-made factors pose the greatest threat to the survival of polar bears. Man-made threats, rather than global warming, pose a direct danger to this population. First of all, humans continue to kill bears, and this includes unrestricted indigenous hunting in Alaska. Natives killed 42 bears in 2011, 57 in 2012, and 23 in 2013. Add to this poaching in Chukotka. While the scale of poaching declined in the 1990s and the 2000s, local dwellers annually kill an estimated 35 bears. Moreover, bears that approach human communities continue to be shot. Polar bears may be able to survive global warming, as they already have many times in the history of their evolution, but they will have no chance if the struggle for survival is accompanied by their ongoing extermination by humans for whatever reason


Nikita Ovsyanikov, DSc (Biology), is an independent expert on polar bears and an Honoured Polar Explorer of Russia 

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