Pacific walrus are gathering on the northwest coast of Alaska and the U.S. Fish and Wildlife Service has begun procedures to keep airplanes out of the area.
The agency says it’s also urging nearby residents to avoid actions that could cause stampedes.
The World Wildlife Fund estimates 2,000 to 4,000 walrus are on a beach near Point Lay, an Inupiat Eskimo community 700 miles northwest of Anchorage.
Female walrus and their young each summer rest on the edge of sea ice. The edge moves north as ice melts.
With climate warming, sea ice in recent years has melted far beyond shallow Chukchi Sea waters where walrus can dive for clams. Instead of riding the ice, they gather on shore.
More than 20,000 animals were counted in 2011.