LOGGING of tropical forests in the central African country of Gabon appears to have touched off a savage territorial war among chimpanzees in which four of every five chimps die, says a field biologist for the Wildlife Conservation Society.

With an estimated 50,000 chimpanzees, Gabon has until lately accounted for a third to a half of a total African chimp population estimated at 100,000 to 150,000. But the chimpanzee wars have apparently reduced the Gabonese population to about 30,000, and it could ultimately fall to 10,000 if most of the country is logged as now planned, said the biologist, Dr. Lee White. The fear is that the central African subspecies of which the Gabon chimps are members might become endangered, as are two other subspecies in western and eastern Africa.

The findings from Gabon are especially startling because the logging is selective, intended to minimize damage to the habitat of chimpanzees and other animals. No more than 10 percent of the trees in a given tract are cut, Dr. White said at a briefing last week in New York sponsored by the society, which has its headquarters at the Bronx Zoo. Nor is there any hunting in the area studied by Dr. White. And no other large animals like elephants or gorillas appear to have suffered.

But chimps, the animals most closely related to humans, are known to be highly jealous of territory, patrolling and defending borders constantly. Even without logging, violent clashes are known to erupt in which chimps kill each other with their bare hands and feet. In at least two documented cases, large communities of chimpanzees have systematically hunted down smaller ones and killed all members.