Distance Sampling (Aerial Surveys)

Aerial surveys are a well-established method for deriving population estimates for ungulates, such as caribou and muskoxen; however, this approach has only recently been used to survey polar bears. To date, the size of four subpopulations of polar bears (Foxe Basin, Kane Basin, Southern Hudson Bay, and Western Hudson Bay) have been estimated by aerial survey.

During aerial surveys, transects are flown over polar bear habitat to detect individuals from the air along predefined transect lines.  In this manner, “samples” of polar bear density (bear/square unit) are taken.  The distance from each polar bear to the track line is determined by measurements from the air and used to create a “probability of detection”-function and calculate the area from the track line covered by the survey.  The line-transect methodology includes double observer teams which allow for estimation of observer efficiency.

No polar bears are handled or chased; the aircraft flies over individuals at an altitude of ~200-500 feet (~50-150 m). Information on number of cubs, condition of animals, and limited data on age- and sex-class can be collected, dependent on observer experience.