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 Chimp 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 (300 kilometers) from Johannesburg, hospital officials said.

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.

The sanctuary was temporarily closed after the attack, said David Oosthuizen, the institute's executive director.

``The safety of our visitors and staff is paramount,'' he said. ``We have never had an incident like this, and we have closed the sanctuary to investigate how we can ensure it will not happen again.''

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. Cussons is the host of Animal Planet's ``Escape to Chimp Eden.''

Oberle's mother, Mary Flint of St. Louis, said her son has been in South Africa since May working with chimpanzees, which have been ``his passion'' since seventh grade, when he watched a film about Jane Goodall.

She said her son knew the risks of working with chimps and would not want them blamed for the attack.

``The last thing he would do is blame a chimp for this. He adored them,'' she said. ``Since he was a little boy he just loved them, and I just have faith that ... when all is said and done, he's going to go right back into it.''

The two chimpanzees were placed in their night enclosure after the attack and will be held there pending the investigation, Jay said.

Steve Ross, an ape expert at Chicago's Lincoln Park Zoo, said chimpanzees are ``naturally a fairly violent species, naturally aggressive, very interested in things like power and hierarchy.''

Even researchers who understand their power, ``sometimes just relax a little bit,'' Ross said. ``And you can never relax with these chimps. They are so unbelievably fast, strong, and they're always looking for an opportunity.''

Ross has worked to raise awareness, but says many chimpanzees are still bred and sold as pets in the United States. People who raise them from infancy often end up trying to place them in zoos when they become aggressive adolescents.

The Goodall institute opened the Chimpanzee Eden sanctuary in 2006 as a haven for chimpanzees, which are not native to South Africa, rescued from elsewhere in Africa. Some lost their parents to poachers in countries where they are hunted for their meat or to be sold as pets, and others were held in captivity in cruel conditions.

According to the sanctuary's website, one of the animals involved in the attack, a chimp named Amadeus, was orphaned in Angola and brought to South Africa in 1996, where he was kept at the Johannesburg Zoo until the sanctuary opened. The other, named Nikki, came from Liberia in 1996 and was among the first chimps at the sanctuary. Before arriving, he had been treated like a son by his owners, who dressed him in clothes, shaved his body and taught him to eat at a table using cutlery, the website said.

In the United States, a Connecticut woman, Charla Nash, was attacked in 2009 by a friend's chimpanzee that ripped off her nose, lips, eyelids and hands before being killed by police. The woman was blinded and has had a face transplant. Lawyers for Nash filed papers this week accusing state officials of failing to seize the animal before the mauling despite a warning that it was dangerous.

Claire Jones, spokeswoman for the Jane Goodall Institute, said in an email that Goodall would have no comment ``out of respect for the young man and his family.''

Goodall, a Cambridge University-trained ethnologist, began studying chimpanzees in Tanzania's Gombe National Park in 1960. Since 1994, her institute has been involved in conservation programs across Africa. The institute says its Tchimpounga Chimpanzee Rehabilitation Center in Congo is the largest chimpanzee sanctuary in Africa.
(AP)