Bindi Irwin has revealed a little known fact about her father, Steve Irwin, in a wide-ranging conversation about her grief, childhood memories and her own struggles with chronic illness.

Speaking to Sarah Grynberg on a new episode of the A Life of Greatness podcast on Tuesday, the 26-year-old said the late Crocodile Hunter ‘never slept’.

The beloved conservationist died on September 4, 2006 after being pierced in the chest with a sting-ray barb while filming in the Great Barrier Reef.

At the time, his beloved children Bindi and Robert were just eight and two years old.

Describing their childhood as ‘a whirlwind’, Bindi said she thinks she and her brother Robert grew up in ‘a hurricane of adventure and wonder because of dad’.

As an example, she said Steve would always start his days at two o’clock in the morning.

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Bindi Irwin has revealed a little known fact about her father, Steve Irwin, both pictured

‘He had terrible insomnia. I mean, he just never slept,’ she said.

Insomnia is the most common sleep disorder in adults, which the Australasian Sleep Association defines as someone self-reporting difficulties in falling asleep, maintaining sleep and/or waking too early on at least three nights a week.

Acute insomnia, which lasts less than three months, affects up to 30-50 per cent of Australians at any given time.

This usually has an obvious underlying cause, related to work, family, stress or jetlag.

Chronic insomnia, which lasts for a longer period of time and can develop due to underlying psychological or behavioural patterns, affects 10 to 15 per cent of adults.

‘A couple weeks ago, we were going through some of his things because we were cleaning out one of our old cupboards in an office [at Australia Zoo], because we were renovating our offices,’ Bindi said.

She stumbled upon an overwhelming trove of her late father’s scientific research ‘hidden in the back of the cupboards’.

The discovery unlocked childhood memories about how Steve would put in a day’s work well before sunrise.

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‘He had terrible insomnia. I mean, he just never slept,’ she said

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In a surprising new revelation, Bindi said her father would always begin his days at 2am

‘We were going through his cupboards. And people may not realise that he had such a scientific mind,’ she said.

‘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.’

‘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.’

Bindi said Steve preferred to spend the hours before dawn ‘researching and studying’ in peace and quiet when ‘the world is dark’.

‘And that’s where these these journals came from.’

It’s because of those efforts, she added, that Australia Zoo has the largest study of crocodilians in the world.

‘It is unbelievable how much time and effort he spent just researching every facet of the information that people shared with him.’

Most people, Bindi said, saw her TV star dad as ‘who he was on their TV screens… this passionate, wild human being’.

‘But I really wish people could have also seen his scientific mind, which was second to none.’

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Elsewhere in the conversation, she shared another heartbreaking revelation. Pictured with her daughter Grace at Australia Zoo

Elsewhere in the conversation, she shared another heartbreaking revelation.

Part of the reason Bindi wrote a speech for her dad’s funeral was because she feared forgetting about him.

‘I remember when I was little and dad had just died, every adult that I saw would say to me: “Time heals all wounds.”

‘And I remember thinking, as an eight-year-old: “What in the heck does that mean?” Why do people keep telling me like, one day I’ll forget about this?

‘It actually made me a little bit scared,’ she said.

Now Bindi knows ‘that information is wrong’.

‘So firstly, don’t say that to an eight-year-old. Time changes your grief. Time changes things and your perspective and everything,’ she continued.

‘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.’