Bison becomes official national mammal of US

The bison has become the official national mammal of the United States under legislation signed into law by President Barack Obama on Monday.

Lawmakers spearheading the effort say the once nearly extinct icon deserves the elevated stature because of its economic and cultural significance in the nation's history.

Millions of bison once roamed the Great Plains. About 500,000 now live in the US but most of those have been crossbred with cattle, and are semi-domesticated. About 30,000 wild bison roam the country, with the largest population in Yellowstone National Park.