Britain's Guardian newspaper said Bob Irwin has been unhappy with the way Steve Irwin's wife Terri Irwin has been commercializing the family business, which Bob Irwin started as a reptile park in the 1970s.
In a statement issued to Australia's Sunday Telegraph, Bob Irwin said it was a "difficult decision" to leave the zoo but added he planned to "continue Steve's dream" at a property he recently acquired in another part of Queensland.
"You may rest assured that Judy (his partner) and I will continue Steve's dream, with the passion and commitment he would expect," Bob Iwin said in the statement. "Steve's ultimate passion, even from a young boy, was always for the conservation of Australian wildlife and its habitat."
The Guardian reported John Stainton, Steve Irwin's longtime business partner who is now guiding 9-year-old Bindi Irwin's career, said he wasn't aware of a rift between Bob Irwin and Terri Irwin.