The body condition of polar bears may be an important indicator of changing climate, as the time when the sea ice is frozen has declined with rising temperatures. Polar bears consume large amounts of seal blubber, which must sustain them during the ice-free period until the ocean freezes again.

 

Recent studies indicate that polar bears in Western Hudson Bay are coming off the sea ice in poorer body condition as the annual ice-free period has increased, but these data required the capture of bears on land. Using a body condition index (BCI) developed using photos taken from field research, and facial recognition software (Whiskerprint) developed to identify individuals, we monitored annual variation in polar bear body condition over the past 25 years non-invasively. We also investigated the relationship between body condition and the date sea ice breakup. Our body condition index differed significantly between males and females, so our analysis used sex as a fixed factor.

 

Our data show a pattern of a decrease in body condition in both sexes over the past 25 years, similar to the pattern found in live-captured polar bears earlier in the season. Our non-invasive methods complement the use of more invasive methods to estimate body condition, but they can be used in periods when invasive estimates are not possible, such as during times of peak tourism or in conditions not conducive to direct estimates.