The study was able to mostly rule out the possibility that strandings are due to inbreeding, finding that stranded seals are just as genetically diverse as non-stranded seals.
"Genetics didn't seem to have an influence," Soulen said.
The snow-colored harp seals mate and give birth on sea ice, then mothers nurse and stay with their young. After that, the pups are on their own. The researchers hypothesize that in years with less ice, the ice that exists becomes crowded, and some seals are forced into the water before they've learned how to navigate or how and where to fish, Soulen said. This may lead them to follow groups of fish moving south, or allow them to become disoriented, she added.
Between 1991 and 2010, nearly 3,100 seals were stranded along the U.S. East Coast. Some of the seals washed ashore dead, while others, found to be sick or dehydrated, were treated and released, Soulen said. Over the past 30 years, sea ice cover in April - a prime time for seal pupping - declined by 8 percent in the Arctic, said Cecilia Bitz, a researcher at the University of Washington, who wasn't involved in the study.