Katie Valentine reports on the phenomenon:

Tony Fischbach is a wildlife biologist with the U.S. Geological Survey who’s a member of the Walrus Research Program in Anchorage, Alaska. He told ThinkProgress that when summer sea ice is at normal levels, only a small number of walrus will come to shore in Alaska — numbers typically in the tens or sometimes low hundreds of animals. This mass convergence of walrus — most of whom are females and calves — is a new phenomenon, he said.

Gwynn Guilford adds further context:

As it happens, the chunk of sea ice that caps the Arctic was, this year, the sixth-smallest on record.

“The walruses are telling us what the polar bears have told us and what many indigenous people have told us in the high Arctic,” Margaret Williams, managing director of the World Wildlife Fund’s Arctic program,told the AP, “and that is that the Arctic environment is changing extremely rapidly and it is time for the rest of the world to take notice and also to take action to address the root causes of climate change.”

Linda Qiu explains how living on land could hurt the walrus population:

For one, calves are particularly at risk of disease and from stampedes. Upon a disturbance, whether that’s a polar bear or a boat in the distance, walruses tend to rush to the water.

“The calves get trampled,” [Lori] Polasek [a marine biologist at the Alaska SeaLife Center] said.

In 2009, about a tenth of the walruses that hauled out died. This year, at least 36 walrus carcasses have been spotted, according to NOAA. That track record does not bode well for the species.