2/8/2021 2:51:36 PM
Bear Tracker Update: Winter 2021
By Alysa McCall, Director of Conservation Outreach and Staff Scientist
Every year for ten years, the Polar Bears International Bear Tracker has followed a sampling of satellite-collared female polar bears in Western Hudson Bay. Scientists regularly download locations from the collars to see when and how polar bears use their sea ice home, and our tracker shares data on some of these bears through time-delayed weekly updates. Such knowledge is critical when it comes to better understanding what these animals need to thrive and how to protect their future.
Photo copyright Craig Taylor/Polar Bears International.
The Western Hudson Bay polar bears have been back on the sea ice for just over two months and, as usual, no two are doing the same thing. Even though the average sea ice extent across the Arctic was the third lowest in the satellite record, this population was lucky, with an on-time freeze-up this fall.
This was the third good ice year in a row for these bears, which means they have been generally healthy. Several back-to-back years of good ice and hunting is likely why we saw a mom with triplet cubs in the fall, something not seen for quite a while! However, even with a timely break-up and freeze-up in 2020, there is no doubt that the bears were ready to return to the ice to hunt seals after not having had a meal since July.
The fatter the fitter
Although the bears use different hunting strategies, all of them focus on trying to build up their fat reserves. The biggest feeding time of year is coming up: in the spring when seals start pupping, there is a fat smorgasbord for polar bears to indulge in. Until then, the bears are searching daily for a meal, hoping to eat a seal roughly once a week.
While searching for seals, polar bear moms teach their cubs how to seek and hunt. Hopefully, the yearlings are getting plenty of guidance, but the youngest cubs haven’t yet learned how to hunt and won’t be on the ice for about another two months— they are just a few weeks old!
Photo copyright Daniel J. Cox/Natural Exposures.
We assign cubs a birthday of January 1st, but most are born in December. The 2021 cub cohort is currently nursing and growing in their dens, getting ready to emerge with mom and head to the sea ice in February/March. Most mothers teach their cubs well, but both hunting success and cub survival depend at least partially on the year’s sea ice conditions.
We look forward to following these bears until the summer, hoping that they have a very fat and happy hunting year.
Updates on Individual Bear Tracker Bears
X33931, Vienna Zoo
This bear spent her summer north of Churchill, just south of the Nunavut border and only slightly inland. She then moved south to west of Wapusk National Park, one of the most famous denning regions for polar bears in the world. In fact, she is likely denning! Her collar is active, but she has been stationary since November near a known denning area. If she is in fact denning, her cub(s) will be approximately 4-6 weeks old now and still growing rapidly and getting used to their legs. We won’t expect her to move for about another month when she decides it’s time to leave her den and go hunt with her new family, but until then we will keep a close eye on her.
X33928, Munich Zoo, Tenya
This bear arrived on shore in late July, which hopefully meant she had a great and long hunting season. She then walked around in northern Wapusk National Park for a few weeks, probably trying to find a good place to hunker down with her family and conserve her energy for the coming months on land. As of mid-November, she was back on the sea ice heading up the west coast of Hudson Bay and then into the north-central portion of the bay. Recently, she made a large movement south and is (far) off the coast of Ontario for now. She is a real traveler so it will be interesting to see what Tenya does next!
X32444, Hannover Zoo, Hope
Hope stayed out as long as she could on the sea ice last season, not returning to shore until late July. Hopefully this means she snuck in some extra meals before the summer fast! She arrived onshore pretty close to where the Tundra Buggy Lodge sits fall, walked inland a little bit, and spent her summer just west of Wapusk National Park and still fairly near the coast. This meant that as soon as the sea ice formed in mid-November, she was in a good position to head out and start hunting seals right away. She then headed north of Churchill before veering east and up into the north-central region of Hudson Bay. She has since moved south but is still quite a way off the coast, no doubt packing in as many meals as possible.
X33110, Rostock Zoo, Vilma
After a couple years of varied movements across northern Hudson Bay, Vilma again spent her summer north of Churchill, Manitoba. As soon as the sea ice was back in mid-November, she beelined it onto the new sea ice and northward off the coast of Nunavut. Since then, she has hunted in circles in the same general region that she has seemed to prefer for the past couple years. Maybe her mother taught her this was a good area to find seals, or maybe there’s something she especially likes about the region. Either way, we can be sure that she is teaching her cubs hunt in this area when they go off on their own.
X19271, Canada Goose, Aurora
We have been tracking the now 22-year-old Aurora for a couple years and she seems like a true Western Hudson Bay bear. While we are seeing many other WHB polar bears make large movements into the north/central regions of Hudson Bay, Aurora seems to be confident hunting largely within her own subpopulation boundary in the west. This area is known to have seals, especially in the spring, so she is in a good place to eat a lot and get as fat as possible. This is ideal as she will likely be looking to mate this spring and have more cubs this winter. She is getting older, but hopefully has one or two more litters left in her lifetime. Things can’t be easy for her, but luckily she has her experience to rely on, which is invaluable to her and any cubs she gives birth to.