Beloved animal expert and zookeeper Jack Hanna has been diagnosed with dementia and will no longer be able to take part in public life, his family said Wednesday. In a statement posted to Hanna’s official Twitter account, his daughters shared the heartbreaking news that the 76-year-old’s illness “has progressed much faster in the last few months than any of us could have anticipated. Sadly, Dad is no longer able to participate in public life as he used to, where people all over the world watched, learned and laughed alongside him.” Hanna, who served as the director of the Columbus Zoo and Aquarium for several years, became a national celebrity thanks to his frequent media appearances over several decades. He became a regular on Good Morning America and Late Night With David Letterman, bringing fame to the Columbus Zoo and encouraging a deeper appreciation for wildlife. “While Dad's health has deteriorated quickly, we can assure you that his great sense of humor continues to shine through. And yes—he still wears his khakis at home,” his daughters said.