Celebrate moms and cubs on International Polar Bear Day
Today is International Polar Bear Day, a day founded nearly 20 years ago by Polar Bears International (PBI) to celebrate and learn about these most magnificent of predators.
Late February, when International Polar Bear Day takes place each year, is a time when most polar bears are out on the sea ice, braving the cold, dark Arctic winter as they search for seals. At this time of year, temperatures in the region can easily drop to minus 40 degrees, making life a challenge even for these hardy carnivores. But one group of polar bears spends winter relatively toasty and warm: mothers and newborn cubs are curled up in dens that the mothers have dug into snow drifts.
For the experts at PBI, learning as much as possible about how this denning behaviour is crucial, not only to fill in gaps in our knowledge about the species but also to know to what extent that behaviour is being affected by human activities from tourism to oil drilling and by climate change.
Adult polar bears are huge: the largest males can tip the scales at more than 1,700 pounds, although the average size is between 600 and 1,200 pounds with a length of 8-10 feet. Even their paws are massive, measuring up to 12 inches across. Yet, remarkably, these powerful predators start out tiny and helpless: blind, with a thin coat of very light fur, and weighing no more than a pound. They spend the first three or so months of their lives in the dens that their mothers have dug for them, nursing on fat-rich milk until they are big and strong enough to experience the outside world for the first time.
Since 2015 PBI has been conducting a study of polar bear dens on Svalbard, a Norwegian-governed archipelago east of Greenland. Each winter, while mothers and cubs are safely tucked away, PBI team members set up solar-powered cameras, designed to withstand the fierce Arctic conditions, that they point at the snowbanks in which bears are denning. And then they depart, and let the cameras do their work.
“When the family emerges from their snow den in spring, the cameras capture their activity,” explains Geoff York, PBI’s senior director of research and policy. “The footage allows us to assess the body condition of the moms and cubs. It also provides information on how families spend their time and how long they remain at the den site before heading to the sea ice to hunt seals.”
Reaching the denning sites can be a challenge, York explains.
“Because polar bears on Svalbard den on steep mountain slopes, sometimes the only way to reach them is by helicopter, landing a safe distance away,” he says. “After landing, we usually ski in with our equipment, but one year there was almost no snow, so we mostly hiked in from there, pulling the sled with our equipment.”
After they retrieve the footage, PBI experts log information such as the number of cubs (most polar bears give birth to two cubs, although one or three are also possible), the health and body condition of mothers and offspring, their behavior, and how much time they spend around the den before leaving for the sea ice to hunt seals.
Because polar bears tend to give birth once every three or so years, it takes several years of study until it is possible to start piecing together a reliable picture of denning behavior; but after almost a decade, PBI has found that moms on Svalbard emerge from their dens earlier than had previously been believed. They have also learned that before the whole family leaves the den, the mothers poke their heads out and check the surroundings for short periods of time, and that once she decides it is okay to leave, her cubs follow – but at first only on warm days.
“After the cubs begin emerging more often, and presumably start feeling more comfortable with their surroundings, they start to increase the distance from the den and their mother,” says York. (They will, however, remain with her until they are approximately two and a half years old.)
Unfortunately, sea ice loss due to climate change is impacting denning polar bears across the Arctic. Because bears need to be on the sea ice as long as possible to hunt, the fact that sea ice is on average melting earlier in spring and forming later in the fall means that bears have less time to eat and build up their strength, which is a particular challenge for pregnant females who must nurse their young while going without food entirely during the winter.
“In the Barents Sea—where sea ice loss is most dramatic—we are observing fewer maternal dens on Svalbard, as well as moms and cubs in poorer condition when they emerge from their dens,” York reveals.
PBI is continuing its den studies on Svalbard and expanding them to test a special kind of radar to see if it can detect dens with pinpoint accuracy – a vital piece of knowledge to protect them from human activity. In the meantime, even these experts continue to find themselves impressed by their subjects.
“In Svalbard, we are constantly surprised about where the bears choose to den,” says York. “To anyone who knows snowy mountains and the danger of steep slopes and avalanches, it’s amazing to see how frequently the bears perch themselves in fairly precarious places. For a cub coming out of the den for the first time, he’d better know how to use his brakes! It’s remarkable how polar bear moms have figured out how to den on these steep slopes and then lead their young cubs to the sea ice. The more I learn about polar bears, the more amazed I am.”
In honor of International Polar Bear Day, you can donate to help support Polar Bears International’s efforts to protect moms and cubs, along with their other conservation work on behalf of the world’s polar bears.
