Robert Irwin holds back tears as he speaks about mother in rare solo interview

In a rare solo interview, Robert Irwin was holding back tears after he spoke about his mother Terri.

The 18-year-old described his mother as a 'wonder woman' and the 'force of nature' in an interview with ABC on its One Plus One programme on Thursday (29 September).

You can watch his heartwarming tribute to his mother below:

Robert lost his father Steve Irwin in 2006 when he was just two years old.

In the interview, Robert praised his single mother's strength, and discussed her choice not to sell Australia Zoo.

"She could have sold the zoo and just raised us. And we could have just squirrelled away and lived a little hidden life," Robert said.

Robert admitted his mother wanted to carry on the legacy of his father, but said walking away from the zoo wouldn't have been the 'wrong thing to do'.

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Robert continued: "She could see the legacy that he started and she said 'you know what, I'm making sure this is going to continue and grow and get bigger and better every single year'.

"Everyone saw dad as this larger-than-life character. Which he was in real life. 120 percent every single day. But mum is the one who kept it going, it's pretty special."

ABC News In-depth/ YouTube

Also in the interview, Robert reflected on his admiration for his mother Terri, and how she brought up him and his older sister Bindi.

He said: "I don't think I really fully understood, fully grasped what a powerful human being and brave human being she is, and was, until I really started to kind of step into adulthood.

"I realise now and only now what she has been through.

"I mean raising children, for mum to do that, without dad, to lose this sounding board and the person who you count on. I mean, the rug is just taken out from under you."

AJ Pics / Alamy Stock Photo

The 18-year-old conservationist also spoke on how his mother set some ground rules on the zoo.

He jokingly said the biggest one was that 'you can't feed crocs till you are 10 years old'.

Robert said that from the time he could talk, he was constantly asking about when he could feed crocodiles.

Steve Irwin died in September 2006 while filming at the Great Barrier Reef after being pierced in the chest by a stingray barb.

'The Crocodile Hunter' left such a legacy in his home country that there is now an annual Steve Irwin day on 15 November.