But that breeding ice is melting: Studies have projected that the Arctic’s ice may recede by as much as 20 percent by 2050, with summers being ice-free by 2037. A paper published last year in PLOS ONE found that ice cover in all harp seal breeding regions is declining by as much as 6 percent per decade. As a result, since 1991 over 3,000 harp seals have been stranded along the East Coast from Maine to North Carolina, the authors report. In 2011 alone, five seals turned up in North Carolina and Virginia.
Now, scientists at Duke University have expanded previous research on seal strandings and melting ice cover to take into account biologic factors: Is one of the sexes more vulnerable to strandings than the other? Are strandings compromising genetic diversity, producing less fit seals that are in turn more susceptible to strandings?
"This is one of the first studies in this region to analyze multiple factors: sea ice, demographics, and genetics, said Kristina Cammen, a doctoral student in ecology at Duke University and a co-author on the paper. "Previous studies have analyzed the effects of sea ice or genetics independently, but our study considered multiple factors at once."
Researchers collected skin samples from 106 harp seals that were either caught or found stranded on the United States’ East Coast between 1992 and 2010. DNA was then extracted and analyzed from those skins to test for genetic variability. The stranding rates were also broken down into different demographic categories, including age and sex.
The researchers found no strong correlation between strandings and genetic diversity.
"We have shown that the genetic diversity in the population seems to be high," said Dr. Soulen. "Further research with a larger sample size would be needed to definitively determine population diversity.