Washington ? Tens of thousands of walruses have come ashore in northwest Alaska because the sea ice they normally rest on has melted.

Walruses crowd the beach near Point Lay, Alaska, because the sea ice they normally rest on has melted.

Federal scientists say this massive move to shore by walruses is unusual in the United States. But it has happened at least twice before, in 2007 and 2009. In those years Arctic sea ice also was at or near record low levels.

The population of walruses stretches “for one mile or more. This is just packed shoulder-to-shoulder,” U.S. Geological Survey biologist Anthony Fischbach said. He estimated their number at tens of thousands.

Scientists with two federal agencies are most concerned about the one-ton female walruses stampeding and crushing each other and their smaller calves near Point Lay, Alaska, on the Chukchi Sea.

The federal government is in a year-long process to determine whether walruses should be put on the endangered species list.