Gorillas have very well developed social behavior. Their troop, or group, is a non-territorial harem that consists of 2 - 30 members. In general, the dominant male, or silver back, changes only with births or deaths however sometimes it may occur as a result of the addition of a solitary male. The home range, depending on habitat and size of the troop, is 7 - 9 square meters (8.4-10.8 sq. yd.) Their day range is 1 - 2 kilometers (.6-1.2 mi.) daily, and is not territorial. Diurnal, they are most active during the day, and wander casually, changing sleeping quarters daily and building new nests every night. When troops meet, they either disregard or greet each other, fighting is uncommon. The intimidating chest beating of a male gorilla is usually a bluff to scare off intruders, while the rest of his troop disappears into the forest. Staring is a sign of hostility to a gorilla. A direct gaze signals a challenge to the gorilla and may be stressful.