Beeld reported that Eugene Cussons, managing director of Chimp Eden, said that an Mpumalanga tourism and parks board investigation had found that the chimps had reacted much like any threatened wild animal.

Andrew Oberle, 26, who is a post-graduate student in anthropology and primatology at the University of Texas, in San Antonio, in the United States, reportedly climbed through a fence surrounding their enclosure.

The animals became enraged and pulled him under a second fence, which was electrified.

Oberle reportedly lost parts of his fingers and toes, sustained several bone fractures and was bitten all over his body.

His mother Mary Flint, who would arrive in South Africa on Monday, told Beeld her son had been aware of the dangers.

"He's loved these animals since childhood. I hope, after all this, that he still will," she said.

Oberle was in a stable condition in the Nelspruit Mediclinic.