In January 1999, the Max Planck Institute for Evolutionary Anthropology hosted a conference in Leipzig, Germany, to celebrate more than three decades of research on wild mountain gorillas at the Karisoke Research Center. To be more specific, it was 32 years and 9 months since Dian Fossey had set up camp in the Rwandan sector of the Virunga Volcanoes (see Figure 1). On September 24, 1967, using a marriage of Karisimbi and Visoke, the names of the two closest volcanoes, Fossey christened her site Karisoke. She could not have known that this would be her home for the rest of her life, or that the tent she pitched at 3000 m in that wet, montane forest would become one of the longest-running research sites in field primatology. Many of the direct descendants of the mountain gorillas she first contacted in 1967 are still being observed today.

Cambridge University Press

Figure 1. Map of the Virunga Volcano region.

a chronicle of the development of behavioral and ecological research, intertwined with the growth of conservation efforts to save mountain gorillas. It has been played out against a backdrop of political instability and, over the past decade, devastating war.

The intellectual setting
By 1967, primatology and anthropology were ripe for a long-term study of gorillas. It was four years after the publication of George Schaller's classic work, The Mountain Gorilla, a landmark study of remarkable detail that described the basics of the subspecies' social organization, life history, and ecology. While western science had been aware of, and intrigued by, the gorilla since its discovery in Gabon in 1847, Schaller's work was based on more direct observations of wild gorillas and provided far more information than had ever been gathered before on any of the three gorilla subspecies.

	Gorilla taxonomy
	Currently three subspecies of gorilla are recognized. Western lowland gorillas (gorilla gorilla gorilla) are the most widely distributed, with populations totaling approximately 110,000 gorillas occurring in Gabon, Democratic Republic of Congo (formerly Zaire), Congo, Cameroon, Equatorial Guinea, and Central African Republic (Harcourt, 1996). Eastern lowland gorillas (G. g. graueri) are found only in the Democratic Republic of Congo with approximately 17,000 gorillas being found in several isolated populations. Mountain gorillas (G. g. beringei) number only approximately 600 individuals divided into two populations, the Virunga Volcanoes of Rwanda, Uganda, and Democratic Republic of Congo, and Bwindi Impenetrable National Park, Uganda. At a meeting held in February 2000, members of the IUCN/SSC Primate Specialist Group proposed a revised consensus taxonomy for gorillas. This proposed classification describes two species and four subspecies of gorillas. Western gorillas are divided into two subspecies, the western lowland gorilla (G. g. gorilla) and the Cross River gorilla (G. g. diehli). The Cross River gorilla, found in at least five small subpopulations in Nigeria, is critically endangered with approximately only 150-200 individuals remaining. The other species of gorilla, eastern gorilla, is divided into mountain gorillas (G. beringei beringei) and Grauer's gorilla (G. b. graueri). There is debate as to whether mountain gorillas should be further split into two subspecies by raising the Bwindi Impenetrable gorilla population to the level of subspecies. Limited morphological and ecological comparisons between the Virunga and Bwindi gorillas suggest that they should not be considered the same subspecies, but genetic evidence indicates that that there is no difference between the two populations. Further research on both populations, but particularly the Bwindi gorillas, is necessary to resolve this issue.

Primatologists at the time were recognizing the value of long-term observations of known individuals, thanks to naturalistic studies of Japanese macaques and rhesus monkeys, initiated in the 1950s and early 1960s. During the same period, anthropologists were beginning to use the behavior of living primates as a window into our hominid past. Baboons, by virtue of living in a habitat which was thought to be the one in which early hominids evolved, became a favorite species for modeling the behavior of our ancestors (Washburn & DeVore, Social behaviour of baboons and early man. In The Social Life of Early Man, vol. 31, ed. S.L. Washburn, pp. 91-105, 1961). The great apes, because of their close phylogenetic relatedness to humans, also became models of human evolution. Jane Goodall had been observing wild chimpanzees in Gombe Stream, Tanzania, since the early 1960s, and she was making discoveries that narrowed the traditional gaps between humans and apes. It was Goodall's mentor, paleoanthropologist Louis Leakey, who, in his search for someone to conduct similar work on gorillas, helped launch Dian Fossey's project.

The ecological setting
Karisoke Research Center lies in the Rwandan portion of the Virunga Volcanoes (Figure 1), a chain of mountains stretching 77 km across the bottom of the Albertine Rift. The eight volcanic peaks (two still active) and their intervening saddle areas comprise one continuous ecosystem of largely moist montane forest. Today, the region encompasses the borders of three different countries: 211 km lie within the Parc National des Virungas, in the Democratic Republic of Congo (formerly known as Zaire); 125 km belong to Rwanda's Parc National des Volcans, and 44.5 km to Uganda's Mgahinga Gorilla Park (Figure 1). The Virungas are the "classic home" of mountain gorillas, Gorilla gorilla beringei, being the place where they were discovered by a German officer, Oscar von Beringe, in 1902.

But why were mountain gorillas the choice for a long-term study and why have they dominated the gorilla scene ever since? They are hardly representative of the genus. Gorilla gorilla beringei is the rarest of the subspecies, and is widely thought to occur in only two populations of about 300 individuals each. The Virunga gorillas live at the ecological extreme of the gorilla's distribution. Their habitat ranges up to 4507 m, far higher than any other gorilla habitat, and its montane vegetation is notably lacking in fruit. Furthermore, it is the only gorilla site where gorillas do not overlap with their closest relatives, chimpanzees.

The nature of their habitat, however, is precisely what makes mountain gorillas more observable than other populations. This is as true today as it was back in 1967. Their highly folivorous, fruit-poor diet results in shorter daily ranges and presumably in smaller home ranges than those of gorillas in lowland tropical forest (D.M. Doran & A. McNeilage, Gorilla ecology and behavior in Evolutionary Anthropology, vol. 6, pp. 120-31, 1998). When the gorillas feed and travel in the dense undergrowth of montane forest, they leave behind a well-marked trail of trampled vegetation that enables humans to follow them relatively easily. In addition, the rugged terrain sometimes permits excellent visibility (for both humans and gorillas) while maintaining a fair distance with the observer that may help reduce the initial fear response of the gorillas. Finally, the Virunga gorillas have not been traditionally hunted for food by humans, as have other gorilla populations. These last two points have probably contributed to making the mountain gorillas more amenable to habituation than their lowland counterparts.

This combination of logistical factors no doubt contributed to the "gorilla-friendly" attitude of westerners towards the Virungas from the 1920s onwards, when expeditions began to focus on observing the animals rather than "collecting" them. In fact, gorillas were a main reason for the creation in 1926 of Albert National Park, Africa's first national park. Thus, when Dian Fossey arrived in Rwanda in 1967, the gorillas were, at least on paper, legally protected, but known to be threatened; and history had shown that observing them was feasible.