COLUMBUS, Ohio (WJW)– Beloved wildlife advocate and longtime Columbus Zoo director Jack Hanna has been diagnosed with dementia, his family announced on Wednesday.

His family said it’s believed the 74-year-old has Alzheimer’s disease. His condition progressed quickly over the last few months.

“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,” the letter said.

Hanna retired from the Columbus Zoo and Aquarium last year. He served as director of the from 1978 to 1992, before he became director emeritus. He’s authored 15 books and hosted three syndicated shows, including “Jack Hanna’s Animal Adventures.”

Over the years, he’s appeared on countless other shows, like “Good Morning America,” and “The Late Show with David Letterman,” and became a frequent resource for news outlets, like CNN and Fox News.

“A passion for wildlife conservation and education has been at the core of who our dad is and everything he has accomplished with the help of so many. He has spent his life connecting people and wildlife because he has always believed that having people see and experience animals is key to engaging them in more impactful conservation efforts,” the family’s letter said.

Governor Mike DeWine and his wife Fran released the following statement upon learning of Hanna’s diagnosis, ” Over the years, Fran and I have had the opportunity to take our kids and grandkids to the Columbus Zoo and Aquarium and The Wilds.  When we were there with Jack, we were so fortunate to experience his passion for animals and the natural world. Along with our fellow Ohioans, we wish Jack, Suzi, and their daughters our best as they navigate the challenges of this disease and will be keeping them in our prayers.”