The last Viking settlements may have vanished after walruses moved to safer shores to avoid being hunted for their ivory, a new study suggests.

Norse communities founded by Erik the Red flourished in Greenland for 500 years but then disappeared suddenly in the late 15th century leaving towns and villages abandoned.

Now scientists at Cambridge University think they have solved the mystery. The Norse economy relied so heavily on the ivory trade that when supply and demand slumped they had no other way to make a living and were forced to leave.

Researchers believe that centuries of hunting walrus may have led the animals to stop congregating in large groups, known as haulouts, on Greenland’s shores.