in the life-history strategies of many strepsirrhine species and some New World monkey species. Alternative strategies of infant care which involve carrying the infants rather than leaving them have evolved several times but have reproductive costs and generally slower rates of population increase than species which build nests. Use of nests for leaving young is thought to have evolved from nocturnal primates with solitary habits which possibly led to the evolution of nesting and parking behaviour in strepsirrhines such as galagoes. Galagoes give birth to a single young which is left in a nest as an infant and carried to a parking place in the vegetation orally by the mothers. In addition, the use of nests or tree holes as shelters for young infants differs functionally from the use of resting places by adult animals (which may be accompanied by infants). See also Ecosystem engineer Niche construction Structures built by animals Tool use by animals References External links National Geographic image of Aye-aye on nest with caption "An aye-aye wakes in its arboreal sleeping nest to begin foraging." Ethology Shelters built or used by animals Primate behavior