JOHANNESBURG – Chimpanzees at a sanctuary founded by famed primatologist Jane Goodall pulled a Texas graduate student into their fenced-off enclosure, dragging him nearly a half-mile and biting his ear and hands.

Andrew F. Oberle was giving a lecture to a group of tourists at the Chimpanzee Eden sanctuary on Thursday when two chimpanzees grabbed his feet and pulled him under a fence into their enclosure, said Jeffrey Wicks of the Netcare911 emergency services company.

The 26-year-old anthropology student at the University of Texas at San Antonio suffered “multiple and severe bite wounds,” Wicks said.

He was in critical condition Friday after undergoing surgery at the Mediclinic hospital in Nelspruit, 180 miles from Johannesburg.

Oberle, who was doing research at the sanctuary, had crossed the first of two fences separating the chimpanzees from visitors and was standing close to the second fence, which is electrified, at the time of the attack, said Edwin Jay, chairman of the Jane Goodall Institute South Africa.

Oberle lost part of an ear and parts of his fingers in the attack, according to the South African newspaper Beeld. The sanctuary’s manager, Eugene Cussons, fired into the air to scare the chimps away from Oberle, then chased them back into their enclosure.