Diminishing Sea Ice Having Impact on Seal Pup Populations
06.01.2012 - Ice & Snow, Flora & Fauna, Arctic
Thinning sea ice cover in the North Atlantic is diminishing harp seal breeding grounds and having an impact on the survival rate of seal pups, according to a study published in the online journal PLoS ONE.
Lead author David Johnston from Duke University said that mortality rates for seal pups in eastern Canada are dramatic. Looking at satellite images of winter sea ice from 1992 to 2010 in the Gulf of St. Lawrence – a traditional breeding ground for harp seals – and comparing them with data on dead seal pup strandings and recorded strengths of the North Atlantic Oscillation (NAO – which influences winter weather and sea ice formation in the region), Johnston and his team found that seal pup mortality rates were higher in years with lower sea ice.
Every February and March, female harp seals look for the thickest, oldest ice packs in sub-Arctic waters to giver birth to and nurse their pups until they are old enough to swim and hunt on their own. However entire year-classes may be disappearing due to thinning sea ice and an earlier onset of the sea ice melt season.
The species has been able to adapt to the earlier onset of sea ice melt by developing an unusually short 12-day nursing period. Yet while harp seals can adapt to natural short-term climate variability, research is suggesting that they may not be able to cope with the additional stressors of long-term climate change and human influences such as hunting. Sea ice cover in harp seal breeding grounds is declining by up to 6% per decade.