Andrew F. Oberle, 26, remains hospitalized. He was seriously injured Thursday when two chimpanzees pulled him under a fence. Oberle is a University of Texas at San Antonio anthropology graduate student.
Carl Oberle described chimps as his nephew's "passion" and says he knew each animal by its "name and face."
A conservationist who runs the sanctuary says investigators will have to wait until Oberle is well enough to provide details to try to determine what prompted the attack.
The Associated Press contributed to this report. All rights reserved.