12/5/2013 3:50:45 PM
Western Hudson Bay Polar Bear Survey
Ten minutes out of Churchill and our first wildlife encounter was a wolverine. An exciting all-time first for me! During the first week of November, I took part in an annual helicopter survey of the Western Hudson Bay polar bear population as a representative of Polar Bears International. On board and heading up the survey were Daryll Hedman and Vicki Trim of Manitoba Conservation and our pilot from Prairie Helicopters, Justin Seniuk.
Manitoba Conservation and PBI conduct the survey in late fall to obtain basic polar bear population data along western Hudson Bay. It takes place during a period immediately preceding winter ice development. Ice is an essential substrate for polar bears to successfully hunt ringed and bearded seals, their primary prey.
Before ice-up, waiting polar bears stack up along the Hudson Bay shore, anxiously awaiting freeze-up and facilitating aerial counts. The relative accessibility of these bears, combined with detailed knowledge resulting from long term studies by Environment Canada, provide an unparalleled opportunity to test whether a simple survey could provide a valid index of important population trends.
The first leg of our survey, and longest, began November 4. We flew east and south along the Hudson Bay shore to the Hayes River, stopping along the way to get helicopter fuel from drums cached at remote cabins. This section of the survey yielded the greatest numbers of bears with a large concentration at Cape Churchill. Along some stretches of shoreline, narrow patches of "pancake" ice were forming where we documented several "kill" sites where polar bears had caught seals.
South of Cape Churchill, we came across a large male and a smaller bear feeding on a fresh seal kill. As we approached, a female, with two spring cubs trailing well behind, moved in and also began to feed. Soon afterwards the cubs joined in, causing a moment of despair in the helicopter. Large males are known to kill cubs, and females with cubs typically steer well clear of adult males. We circled at a respectful distance to watch, all the while clicking away with telephoto lenses. At first, things seemed pretty peaceful but the female soon jumped all over the male, forcing him to back off. She pushed him backward, mouth to growling mouth, with occasional wicked swats for good measure. She drove him away twice, and photos suggest that as the cubs' bravery bolstered, they provided close back-up for mom. As we departed, the female, cubs and the other smaller bear were all settled on the seal kill and the big male was walking away.
We overnighted in a small comfortable Manitoba Renewable Resources cabin near the York Factory site (Hudson Bay Company) that was established in the late 1600s. Unfortunately, the weather was not conducive for flight the next day, but the company and food were excellent and the day passed quickly. The survey was completed over November 6 and 7, with flights ultimately covering all the Manitoba, shoreline from just south of the Ontario border to the Nunavut territorial border up north. I have never seen such a large number of bears over such a short period before and coupled with an incredible diversity of other wildlife made for one of those special life experiences.
As for the survey itself, the most important bear population data gathered during this survey are cub production and survival rates. Because young animals are among the first to suffer from reduced foraging opportunities, the proportion of dependent young (cubs and yearlings still traveling with their mother), is a key index of variation in productivity and survival from year to year. Although complete analyses of our data are yet to come, the proportion of dependent young observed in 2013 was consistent with the low proportions observed in recent years, and suggests continued poor survival of cubs during their first year of life.
Polar bear scientists from PBI and Manitoba Conservation are working to improve aerial polar bear survey methodology in an effort to ensure acquisition of consistent, cost effective, and comparable annual data on the status and trends of the western Hudson Bay polar bear population. It is hoped that refined survey techniques will not only aid in the conservation and management of the western Hudson Bay population, but will prove to be a reliable index of how polar bear populations respond to a warming climate, and may be applied to other areas where polar bears spend time ashore.