Steve Irwin suffered from a hidden health condition which saw him 'start his day at 2am', his daughter Bindi has revealed.
His eldest child explained that the late and great Crocodile Hunter would get a 'full day's work' done before the rest of the world had woken up due to his condition.
So at least there was something of a silver lining for Steve in the midst of his private struggle.
The 44-year-old passed away on 4 September, 2006, after being pierced in the chest by a stingray while snorkelling at Batt Reef, Australia.
His beloved children Bindi, 26, and Robert, 21, have both followed in their father's footsteps and became keen conservationists who are now at the helm of Australia Zoo, just like Steve was.
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It's been nearly two decades since the star's death, but Bindi admitted the family were still 'going through some of his things' during an appearance on Sarah Grynberg's podcast, A Life of Greatness.
The TV star - who had her own wildlife documentary series titled Bindi the Jungle Girl when she was just nine years old - also opened up about her dad's life and legacy during the interview on Monday (3 February).
She explained that her and Robert's childhood were a 'hurricane of adventure and wonder because of dad'... but it was a bit of a 'whirlwind' too.
That's because Steve wasn't operating on the same time as the majority of people in his native Australia, as according to Bindi, he 'never slept'.
The mother-of-one, who welcomed her 'miracle' baby back in March 2021, explained: "He had terrible insomnia."
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"I mean, he just never slept," Bindi added. "Dad would wake up at 2am in the morning. I swear to you, his day would start at 2am.
"And by the time everyone else's workday has started, he'd put in a full day's work."
Steve wasn't alone on his insomnia journey, though, as it is the most common sleep disorder in adults.
It causes sufferers to have trouble with falling asleep, staying asleep or waking up to early, and it is classified as chronic if it lasts for three months or longer, according to the NHS.
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The most common causes of insomnia are stress, anxiety or depression, noise, the temperature of a room, uncomfortable beds, jet lag and shift work.
Bindi explained that her father made the most of being unable to sleep by compiling a treasure trove of scientific research - which has been 'hidden in the back of the cupboards' for the last 19 years.
She explained that the Irwins had headed to the zoo to clear out some offices which are going to be renovated when she stumbled upon some of Steve's old work.
"We were going through his cupboards," Bindi said. "And people may not realise that he had such a scientific mind.
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"I was looking through his journals and he would just write down, I mean, thousands - it's not an exaggeration - but thousands of pages worth of information and facts and studies and findings."
According to Bindi, Steve's tendency to burn the midnight oil is the reason why Australia Zoo has the largest study of crocodilians in the world.
She explained that her dad enjoyed 'researching and studying' in the hours before dawn, when the 'world [was] dark', adding: "And that's where these these journals came from.
"It is unbelievable how much time and effort he spent just researching every facet of the information that people shared with him."
The Dancing with the Stars winner said that although Steve was known to the world as a 'passionate, wild human being', she wishes that everyone also appreciated his 'scientific mind', as it was 'second to none'.
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Bindi also admitted that her feelings about losing her dad have changed a lot as she has grown up, as she was just eight years old when it happened.
"Time changes your grief," she said. "Time changes things and your perspective and everything. But I know firsthand that the grief and the sadness and the feeling of loss from losing dad.
"That feeling is just a part of me. It's like a scar on your heart."
Topics: Celebrity, Bindi Irwin, Steve Irwin, Health, Sleep
Olivia Burke