Over the next several decades, the bears learned to hunt and forage for themselves from non-human food sources, and their population slowly grew. On March 22, 2007, the grizzly bear was taken off the endangered species list. In the years since it was listed as a threatened species, the Yellowstone grizzly bear population has increased from 136 to more than 500 by 2007, and at least 640 by 2017. "The grizzly is a large predator that requires a great deal of space, and conserving such animals is a challenge in today's world," Deputy Interior Secretary Lynn Scarlett said in announcing the decision. "I believe all Americans should be proud that, as a nation, we had the will and the ability to protect and restore this symbol of the wild."