Rhino calf lulled to sleep by Aussie zookeeper's serenade

A South Australian zoo keeper has told 9NEWS the story behind a touching video of him serenading a rhinoceros calf to sleep with his guitar.

The calf was abandoned by her mother and arrived at the Wild Rhino Sanctuary in South Africa when she was just one day old.

Staff called her 'Pepper', and she wouldn't settle.

Mark Mills, a keeper at Monarto Zoo in South Australia, decided to try an acoustic approach while on placement at the sanctuary.

"I then went and got the guitar out and played a few chords off and she seemed to like that. So I then played for her again and she seemed to settle in and fall asleep," he said.

The video has proved popular online, receiving hundreds of thousands of hits.

"It exceeded my expectations. It's a bit strange having it go that big, that quickly," Mr Mills said.

Despite his newfound fame, Mr Mills remains modest about his musical ability.

"It might've got sick of that same song though over and over again," he joked.

The ungulate keeper said he was motivated to do the placement in South Africa to help conservation efforts.

"Seeing the poaching numbers go so high in the past few years is quite close to my heart," he said.

"I was keen to head across there and work in some way towards rhino conservation, and I think I did that."

Mr Mills returned to his regular job today, after arriving back in Adelaide on Monday.