Nereus is a walrus that was found orphaned in Alaska, USA, in 2003. His mother either abandoned him, or was caught by predators. Alaskan marine biologists found him on his fifth day of living and transported him to The Alaska SeaLife Center. He was later transferred to the Indianapolis Zoo, where he was raised and taken care of by zoo trainer, Amanda Barnett.

When Nereus became a year old, he moved permanently to the walrus habitat where he has lived ever since.

In 2005, he was featured on the cover of Time magazine.

An episode of the Animal Planet series "Growing Up" chronicled the life and struggle of Nereus the walrus.