Passage: Adult males are called silverbacks because a saddle of gray or silver-colored hair develops on their backs with age. The hair on their backs is shorter than on most other body parts, and their arm hair is especially long.The tallest silverback recorded was a 1.95 m (6 ft 5 in) with an arm span of 2.7 m (8 ft 10 in), a chest of 1.98 m (6 ft 6 in), and a weight of 219 kg (483 lb), shot in Alimbongo, northern Kivu in May 1938. There is an unconfirmed record of another individual, shot in 1932, that was 2.06 m (6 ft 9 in) and weighed 218.6 kg (482 lb). The heaviest silverback recorded was a 1.83 m (6 ft 0 in) shot in Ambam, Cameroon, which weighed 267 kg (589 lb).The mountain gorilla is primarily terrestrial and quadrupedal. However, it will climb into fruiting trees if the branches can carry its weight, and it is capable of running bipedally up to 6 m (20 ft). Like all great apes other than humans, its arms are longer than its legs. It moves by knuckle-walking (like the common chimpanzee, but unlike the bonobo and both orangutan species), supporting its weight on the backs of its curved fingers rather than its palms.The mountain gorilla is diurnal, most active between 6:00 a.m. and 6:00 p.m. Many of these hours are spent eating, as large quantities of food are needed to sustain its massive bulk. It forages in early morning, rests during the late morning and around midday, and in the afternoon it forages again before resting at night. Each gorilla builds a nest from surrounding vegetation to sleep in, constructing a new one every evening. Only infants sleep in the same nest as their mothers. They leave their sleeping sites when the sun rises at around 6 am, except when it is cold and overcast; then they often stay longer in their nests.

Question: What does it do at night?
resting at night