Most visitors to Rwanda come to track the endangered mountain gorillas in the far northwest of the country, on the slopes of the Virunga Mountains within the Parc des Volcans. Despite their fierce reputation, gorillas are peaceable primates, the largest and most ferocious looking of the ape family, and the chance to view them from up close is a thrilling as well as awe-inspiring experience. Tracking them usually entails a one to four-hour trek through the forest, and on steep mountain slopes, but groups are only permitted to stay with the gorillas for one hour once they have been located, to prevent behavioural disturbances and the possible transmission of diseases from humans to gorillas. Gorillas share 95% of their genes with humans and people with even a common cold are not allowed to join a group, as this could be fatal to the animal. Experienced guides, trackers and anti-poachers lead all treks, with permits allowing for a maximum of eight visitors per group.