One of the most emblematic images of the climate crisis is that of a starving and malnourished polar bear photographed on the Svalbard archipelago, which traveled around the world in 2015. If we take into account that these animals depend on the arctic sea icewhich is rapidly disappearing due to global warming, the concern is more than justified.
Inside Greenland There’s a team of scientists that spent years, commissioned by the island’s government, documenting a hitherto unknown subpopulation of polar bears that live in the southeastern part of the archipelago and that only have access to sea ice for four months, between February and late May.
What is surprising about these animals is that they survive with limited access to this type of ice and hunt in the fresh water that flows into the ocean from Greenland’s glaciers. They are the most genetically isolated population of polar bears on the planet.
As a preliminary stage of the fieldwork, the researchers spent two years collecting information from hunters who participated in all stages of the study, contributing their experience and providing samples for genetic analysis.
“Assessing the status of the polar bears In this territory, we started by asking hunters to send us a tooth and the tip of the tongue of each hunted bear. The tooth to calculate age and the tongue for genetic analysis. We have received these samples since 2011 and they are part of the data analyzed in the study published in Science”, points out the SINC Fernando UgarteMexican biologist from the Greenland Institute of Natural Resources, who moved to Greenland in 2005.
A family group of polar bears, consisting of an adult female (left) and two cubs, cross glacier ice in southeastern Greenland in September 2016. / NASA OMG
The study is part of a broader project to advise the country’s government on the conservation and sustainable use of polar bears in the east of the island. “This is important because people who depend on hunting these bears for their livelihood, and because bears are also affected by pollutants that come from industrialized countries and because of global warming”, argues the scientist.
The population is not new, as Greenland hunters knew they existed. What is new is that scientists are now aware that there are two separate populations in eastern Greenland, not one as was previously believed. That is, there are six populations in the country, not five, and 20 in the world, instead of 19.
“We knew there were some bears in the area from historical records and indigenous knowledge. We just didn’t know how special they were,” says lead author Kristin Laidrepolar researcher at the Applied Physics Laboratory at the University of Washington (USA).
Sea ice provides the platform that most of the Arctic’s roughly 26,000 polar bears use to hunt seals. However, these southeastern Greenland bears have adapted their survival to a different strategy: they hunt seals among chunks of freshwater ice that break off from the Greenland ice sheet.
The fuel barrels were tied with a longline, shown here in March 2015, and deposited at strategic points for the helicopter to reach polar bears in southeastern Greenland./ Fernando Ugarte
Multi-year follow-up under extreme conditions
The second stage of the assessment was a study of local knowledge, which they did in late 2014 and early 2015. They contacted the hunters who reported the most bears in the five years between 2009 and 2013 and asked a number of questions about the weather. , animals and hunting.
“This study was fundamental to confirm that in fact there were many changes and to plan the next phases of the evaluation. We published the results of the interviews in 2018”, explains the researcher.
The penultimate phase consisted of sedated polar bears to take biological samples, brand them with tattoos and equip them with radio transmitting collars. There were six seasons of fieldwork, between 2015 and 2022 – not counting 2019 and 2020, when they could not go to the field because of covid-19. This remote region has been little studied due to its unpredictable climate, rugged mountains and heavy snowfall. Part of the collected results were analyzed in the study.
“The last part of the investigation will be done next year. It will consist of using all the data from the collars and the information from the hunters to carry out an aerial census and find out how many polar bears there are”, adds Ugarte.
More genetically different than any other
Another conclusion of the research is that the genetic difference between this group of bears and their closest genetic neighbor is greater than that observed in any of the 19 previously known polar bear populations.
“We isolated several different types of genetic data from some bears and compared them to other subpopulations around the world. In doing so, we find that they are more different from their larger populations. geographically close, than any other pair of populations with each other. It was a really surprising genetic isolation, which suggested a long-term separation”, he tells SINC. Beth Shapiromolecular biologist at the University of California and director of evolutionary genomics at the Institute of Genomics at that institution.
The low genetic diversity of the population is also what indicates that they have been a small population since they were isolated. Polar bears in general don’t have a lot of genetic diversity, but they tend to increase along with population size.
“We can use the amount of diversity that we observe in this population and how it is divided between individuals and between populations to piece together its story. In this case, we saw that the population was isolated and different from other bears, and it was also small for at least several hundred years,” says Shapiro.
In future studies, they hope to link the fixed genetic differences of this group, distinguishing it from the others, with functional adaptations to its unique environment.
“In my opinion, this is the most important part of the job. There is a population of polar bears that has not been described before, that does not mix with other populations and that is genetically different, has different behavior and also different biological parameters”, emphasizes Ugarte.
What they still don’t know is whether the differences with other populations are due to genes or of learned cultural patterns. “More studies will need to be done, but I suspect that what polar bears learn from their mothers and from their own experience plays a very important role in how they adapt to different circumstances,” he continues.
The researchers believe that part of the reason the population is so isolated is that they are surrounded: by the mountain peaks and enormous ice sheet of Greenland to the west, the open waters of the Denmark Strait to the east and the rapid coastal current of East Greenland, which poses a danger on the high seas.
The dots on the map on the left show the locations where the Greenland polar bear samples were collected. The map on the right shows the 19 current subpopulations of polar bears, with colored dots indicating the location of other samples used in the analysis. /Science
Bears that live among icebergs and freshwater ice
The ecosystem where they live are fjords where the sea only freezes for about four months a year, but there is ice the rest of the year from icebergs and chunks of ice coming out of glaciers at the bottom of the fjords, connected to the Greenland ice sheet.
“The captures we made for put on transmitter necklaces It was in April, when the fjords were frozen, so the bears hunted in the usual way looking for seals in the dens where you have your pups or in the holes they make in the ice to breathe. I would like to know how they hunt in the summer. I imagine they take advantage of the pieces of ice where they leave to rest”, reveals Ugarte.
But one of the peculiar things they saw is that these bears travel between fjords taking shortcuts through the mountains and gliding in a kind of slide down the slopes. “From the helicopter we could follow the tracks of their paws and then the long marks left when they glided while lying in the snow”, he describes.
Polar Bear / Pixabay
Very few places have these conditions.
O satellite tracking of adult females shows that, unlike most other polar bears that travel far beyond the sea ice to hunt, bears in southeastern Greenland are at home.
Furthermore, half of 27 bears tracked they accidentally floated an average of 120 miles south on small blocks of ice, caught in the East Greenland Coastal Stream, but then jumped off and walked back north over land to their fjord of origin.
While this work offers hopeful insight into polar bears that could live longer than previously expected in places with glacial ice, unfortunately these areas are sparse compared to their entire current habitat. “Greenland comes to mind, Svalbard and parts of the Canadian Arctic”, adds the scientist.
Therefore, extrapolation of these findings is not possible because the glacial ice that sustains bears in southeastern Greenland is not available in most parts of the Arctic. However, it is good news for these bear populations that they have managed to adapt. In a way, they provide insights into how the country’s bears might behave in future climate scenarios.
It will be the government of Greenland that will decide any protection and management measures for these groups. Likewise, it will be International Union for the Conservation of Naturewhich helps monitor protected species, which determines whether Southeast bears are internationally recognized as a separate population, the 20th in the world.
Reference:
“Glacial ice supports a distinct and undocumented subpopulation of polar bears that persists in late 21st century sea ice conditions.” Science