Warming will cause polar bears to fast for longer

Global climate change particularly affects the Arctic, where the effect of the growth of the average temperatures is more evident than in the middle lane. This year reduced the area of ocean covered with ice, so polar bears have less places where they can hunt from the ice for their main prey — seals, reported in Nature Climate Change. This means that the fasting period is lengthened and bears to survive it becomes difficult. The authors predict that in the worst case due to that by 2100 almost all groups of polar bears will be endangered.

Polar bears (Ursus maritimus) are found only in the Arctic. Their population is divided into 19 groups depending on the characteristics of the terrain where they live. In the summer many of them as the ice melts, the bears hunt mainly from the ice (the seals) were deprived of regular opportunities to forage for food. Therefore, predators have few months to live on their own fat reserves. Given that in recent years, the Arctic is getting warmer, ice-free period gradually lengthened and it affects the lives of polar bears.

Peter Molnar (Péter Molnár) from the University of Toronto, together with colleagues from Canada and the United States decided to find out how the warming will affect the period of fasting polar bears, for some individuals it will affect in the first place and the condition of various groups of population will be in a few decades. The researchers used the Community Earth System Model (CESM) and recent data on the number of days without ice cover in different parts of the Arctic, to predict a term that bears different populations will have to spend without food. The researchers also took into account the volume of fat stores in young, adult males and females (and even then, whether the females feed the cubs): it is possible to determine on which day the fasting will begin to rise the probability to die from lack of nutrients.

For adult males the maximum period without food, after which begins to increase significantly the probability of death within 200 days for females without cubs — 255 days, for females with cubs, from 117 to 228 days for females with cubs of the previous year of birth — from 185 to 232 days. In all cases this refers to the animals mass, which is calculated as the average in the studies between 1989-1996 for animals from West of Hudson Bay, and the time may vary depending on the specific population. Reproduction, of course, is also broken (that is young grows less than the mortality of adults): for juveniles — after 117 days of fasting, to cubs the previous year of birth — after 185 days.

The calculations were made based on the fact that during fasting, all the animals move as little as possible to save energy. But if not, the threshold after which every day without food significantly reduces the survival of the bear will be even lower. In this case, even a small number of failed seasons with very low area of ice cover permanently undermine the strength of the beasts.

Depending on which scenario of future climate change was chosen by the researchers, the estimated fate of groups of populations of bears was different. At the worst, in case of significant greenhouse gas emissions, it turned out that by the year 2100 13 out of 19 of these groups, that is, 80 percent of all polar bears will be on the verge of extinction. Low impact climate change will have on populations on the Islands of Queen Elizabeth: there’s the largest “reserves” of ice. However, they 80 years will be difficult to maintain the number. Under more favorable scenario, with the reduction of greenhouse gas emissions, many populations have a chance to survive at least another hundred years, but their reproduction will be impaired. This is another argument in favor of the fact that with the current climate change is to actively deal.

In 2019 on the New Earth has recorded many cases yield the polar bears to people. According to the researchers of the Institute of problems of ecology and evolution (IPEE RAS), the reason for this is that the ice was up too late, and animals for a long time had nothing to eat. According to the alternative version, which in the course of the special Commission were not confirmed, the animals were attracted primarily landfills. Although they do provide a source of food for polar bears, scientists still felt that it was not the main reason for the appearance of predators in human settlements. Read more about problems with polar bears in then Arctic and adjacent territories you can read in the material “Between us is melting the ice”.

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