Zoologist Jack Hanna has retired from public life following a dementia diagnosis. 1 / 7
The animal activist is beloved the world over. 2 / 7
"He will no longer be able to participate in public life," his family said in a statement. 3 / 7
Hanna became famous for his appearances with live animals of The Late Show with David Letterman. 4 / 7
He went on to host multiple television shows. 5 / 7
And wrote a large collection of books promoting animal education. 6 / 7
Hanna's leadership at the Columbus Zoo made the establishment one of the best in the country. 7 / 7