Nest-building in primates refers to the behaviour of building nests by extant strepsirrhines (lemurs and lorisoids) and hominid apes (humans, chimpanzees, gorillas and orangutans). Strepsirrhines build nests for both sleeping and raising families. Hominid apes build nests for sleeping at night, and in some species, for sleeping during the day. Nest-building by hominid apes is learned by infants watching the mother and others in the group, and is considered tool use rather than animal architecture. Old World monkeys and New World monkeys do not nest. It has been speculated that a major evolutionary advance in the cognitive abilities of hominoids may first have occurred due to the development of nest-building behaviour and that the transition from nest-building to ground-sleeping led to "modifications in the quality and quantity of hominid sleep, which in turn may have enhanced waking survival skills through priming, promoted creativity and innovation, and aided the consolidation of procedural memories". In strepsirrhines Strepsirrhines may be nocturnal, diurnal, or crepuscular. Some may either occupy holes in trees or build nests. Unlike the hominid apes, strepsirrhines build nests by instinct and use them for breeding purposes. Strepsirrhines' mothers either carry their young on their bodies, conceal their young in foliage while they venture out to feed, returning periodically to feed and groom them, or leave them in a nest built for that purpose. In lemurs Among lemurs, females of smaller species, such as the mouse lemur and giant mouse lemur, build leaf nests before birth for the protection of their young. Leaf nests in golden-brown mouse lemurs may provide thermoregulation benefits. Male mouse lemurs have been found sharing nests with up to seven females at a time during the mating season. In the Ruffed lemur (Varecia variegata), nests are made from locally collected material and may also be lined with hair plucked from their own body. In larger lemur species such as the Verreaux's sifaka, ring-tailed lemur and common brown lemur, the young cling to the mother and nests are not built. Aye-ayes, being nocturnal, build oval-shaped nests from nearby branches and lianas for day time use. These may be built in a tangle of lianas or in a fork of a tree, at a height of above the ground. These nests may be re-used by other aye-ayes once the original occupant moves on. A single occupant uses a nest for a few days, refreshing it regularly with fresh vegetation.