Study predicts climate change impacts on polar bear litter size



Posted on 09 February 2011  | 
Polar bear cubs.
Polar bear (Ursus maritimus) cubs. Many toxins have been found to accumulate in the fat of polar bears and are passed from mother to cubs.
© NPIEnlarge
A new study, published in the Nature Communications journal, has predicted decreases in polar bear litter size due to loss of sea ice. The study reports that if sea ice in the west Hudson Bay decreases as anticipated, failure to reproduce could jeopardise polar bear population viability.

When little food is available, polar bears are known to rely on stores of energy for survival and reproduction. The reliance on energy stores in pregnant females however, limits the survival rates of their cubs. Using data obtainable under current conditions, the authors show 28% of pregnant females failed to reproduce due to energetic reasons during the 1990’s.

They then use predictive modelling to suggest that 40-73% of pregnant females could fail to reproduce in the same way if spring sea ice break-up occurs 1 month earlier than during the 1990’s and 55-100% if break-up occurs 2 months earlier.

The authors suggest that their finding may also apply to populations outside the western Hudson Bay area, however they caution that the expected time-line for declines in litter size may vary with different climate models’ predictions about sea ice loss.

Read the full article in the Nature Communications online journal.

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