Abstract
After being defeated by other males, three alpha male chimpanzees in the Mahale Mountains National Park, Tanzania, became peripheral, spending much of their time alone. A very similar life style was observed when a male was left alone after all the other chimpanzees of his unit-group emigrated or disappeared. Observational evidence suggested that these males remained within the ranges of their original groups, only sometimes forming associations mostly with the familiar females and their offspring and rearely with the familiar males, but never with any strange chimpanzees. It seems that female chimpanzees tend to choose a larger group into which they immigrate. It also seems impossible for adult male chimpanzees to join another social network already established among other unrelated adult males. These factors force such males to remain within their familiar ranges as lone chimpanzees.
