An exhaustive survey of the world's most southerly polar bears has found a significant drop in their numbers.
Scientists fear this could be the start of years of climate change finally taking its toll on a population whose health has been declining for a long time.
The study, published his week in the journal Arctic Science, found that the number of bears around southern Hudson Bay have declined about 17 per cent in the past five years.
The bears were previously thought to be stable, although they were getting thinner and fewer cubs were surviving.
The new estimate is based on an aerial survey deliberately designed to be compared to previous counts.
The number of bears in the region is now thought to have fallen from 943 to 780.
Lead author Martyn Obbard says it's too soon to say the population is collapsing.
But he urges caution in setting hunting quotas for the area.
