4/26/2021 7:21:11 PM
Spring Bear Tracker Update
By Alysa McCall, Director of Conservation Outreach
Polar Bears International works with researchers to track a subset of collared female polar bears from the Western and Southern Hudson Bay populations on our Bear Tracker. It’s always interesting to see what bears are up to on the sea ice, but especially during the spring.
Spring feasting season
By now, mothers who gave birth over the winter have emerged with their new cubs and are back on the sea ice. It’s perfect timing, as seals are giving birth to their own pups, which are naïve enough to be easy prey and fatty enough to be a hearty meal: a great trade-off for hungry polar bears. In fact, the eating is so good right now that polar bears are entering “hyperphagia,” where the bears gorge themselves on thousands upon thousands of calories in a short period of time. In the spring months, polar bears gain much of the body fat that they will rely on throughout the summer and fall, a time period when they are forced ashore, away from their seal prey.
For a polar bear, spring is the time to pack on the pounds. Photo © Craig Taylor/Polar Bears International.
This is also a great time for moms to teach their cubs how to hunt. New cubs will not be much help hunting yet as they are still tiny and learning how to navigate the ice. Cubs born last year, now called yearlings, are probably helping mom to hunt more often, refining their skills and getting stronger. The older two-year-old cubs can now hunt to some extent on their own and will be weaned this spring, after which they will head out on their own for the first time, using everything they learned from mom.
Furthermore, polar bears mate at this time of year, with males finding partners by following eligible females’ stinky footprints across miles of sea ice. Females who mate successfully will need to pack on hundreds of pounds, potentially doubling or even tripling their body weights, to successfully sustain a pregnancy, give birth, and nurse cubs through long months in a den—up to eight months without food!
Just how much weight they can gain is linked to when the sea ice breaks up this June or July: later break-up means more hunting opportunities, more food, and better body condition. Polar bear body condition can vary based on age, size, hunting ability, luck, and cubs, but sea ice condition is a driving factor which also influences hunting success and cub survival.
Summer ice break-up
Hudson Bay freeze-up was on time this year, and the conditions are mostly normal within Hudson Bay right now. The Arctic sea ice extent for March 2021 was the ninth lowest in the satellite record. Hopefully, this means we will not see an early sea ice break-up this summer. We will post an update when the bears start arriving back on land, likely sometime in July. You may even be able to see some of the migration on our Cape Cams located on the Cape Churchill tower. After traveling hundreds upon hundreds of miles this winter we hope to see them back on land looking fat and healthy. Until then, we will watch them on the Bear Tracker and wonder why they move where they do, and how they are being impacted by their changing sea ice habitat.
The key to protecting Arctic sea ice is society moving toward sustainable energy and embracing community solutions to lower carbon emissions. Protecting sea ice means protecting polar bears, people, and our entire planet.
Update on Individual Bear Tracker Bears
X33931, Hope Vienna, Vienna Zoo
How exciting! Hope exited her den in the first weeks of March, likely with a new cub or two in tow! She would have hung out at her den site for at least a few days to let her cub(s) exercise their little legs. Once she decided it was time to eat, though, this new family was off to the sea ice! On March 12th Hope started her travel, heading northeast toward the coast and through the northern part of Wapusk National Park. By March 15th this new family was on the sea ice and hasn’t slowed down since. They have been zig-zagging north of the national park, never going too far out in the bay because mom can’t risk the safety of her cubs when it comes to long trips and possible swims. In the past few days, Hope and cub(s) headed east into the bay, but we expect they will circle back again soon. We hope this family is finding lots of seals to eat—mom must be hungry after her eight months on land!
X33928, Munich Zoo, Tenya
Since our last update, Tenya moved west toward the coast and stayed close to land near the Manitoba/Ontario border. She didn’t stay for long though, swinging back out in the bay and looping around in the area she seems to prefer. There must be pretty good hunting here for her because she is a regular. At the time she was collared, Tenya had a young cub with her. This cub is now old enough to be weaned and head out on its own, which means Tenya may be looking for a mate right now. Her feet will be releasing a pheromone, allowing males to track her movements out on the sea ice by scent. She is currently still in the western part of the bay, her preferred area, and will need to gain lots of fat if she hopes to sustain a pregnancy over the long fall and winter. Good luck, Tenya!
X32444, Hannover Zoo, Hope
Hope has been on the move! Since our last update, she stayed off the coast of Manitoba for a while, hanging out in one small area for a week or two at a time. There must be good seal hunting there. Hope has since moved north, making larger treks until she seems to stop in one area for days at a time, probably for food and maybe a bit of rest. In April, Hope started moving again and is now off the coast of Nunavut. When Hope was collared, she had two young cubs with her. These cubs are now old enough to be weaned and head out on their own, meaning Hope is looking for a mate right now. Her feet will be releasing a pheromone allowing males to track her movements out on the sea ice by scent. She will need to gain lots of fat if she hopes to sustain a pregnancy over the long fall and winter. Hopefully break-up is on time or delayed this summer to give her lots of extra time to hunt seals and consume critical calories.
X33110, Rostock Zoo, Vilma
Vilma has given researchers many years of data by now, significantly helping us better understand female polar bears in Hudson Bay. She was first collared in 2013, and then again in 2019. Her collar will be dropping off soon, and we are so grateful for what she has taught us and continues to teach us about her species. Since our last update, Vilma has been concentrating her movements in her preferred home range, a region off the coast of the Manitoba/Nunavut border that may be a good region in which to hunt seals. Vilma had two young cubs when she was collared; these cubs are now old enough to be weaned and head out on their own, meaning Vilma will be looking for a mate this spring. Males will find her on the sea ice by following her footprints which are scented with a pheromone, allowing her to be followed across the shifting sea ice. Vilma must gain lots of fat (hundreds of pounds!) to have a successful pregnancy, give birth, and nurse cubs this fall and winter. Good luck, Vilma!
X19271, Canada Goose, Aurora
Aurora had one cub when she was collared. That cub is now about 2.5 years old and ready to be weaned. In the last couple of years, Aurora’s cub will have learned all it can from its mom: how to hunt, how to navigate sea ice, how to avoid threats, and when to migrate. Hopefully this bear (now considered a subadult) learned well from mom, since it is now on its own to hunt alone for the first time. Happily, though, this weaning period coincides with the time of year that seals are pupping, meaning there is lots of easy prey for all polar bears to gorge on. At the same time, the now-single Aurora will be ready to mate and start a family cycle over again. She is 22 now: still young enough to have a successful pregnancy but old enough to have lots of experience with raising cubs. She will need to gain hundreds of pounds of fat in the next few months in order to successfully give birth and raise a new cub or two. Hopefully, the sea ice breaks up late this year to allow extra time to hunt.