Nest build fresh nests daily out of leaves and other vegetation in which they sleep at night. They sometimes also build nests during the day for resting in. The smaller species of gorilla build their nests in trees, while the larger are confined to the ground. Nests of the western gorilla, the largest species, measure about in diameter. Some species of frog build nests ranging from simple to modest complexity. Many stream-dwelling frogs lay their eggs in a gelatinous mass which they attach to underwater vegetation. The jelly structure prevents the eggs from washing away. Fish engage in nest building activities
Mammal females mate with (polyandry), or multiple males have exclusive relations with multiple females (polygynandry). It is much more common for polygynous mating to happen, which, excluding [[lek mating|leks]], are estimated to occur in up to 90% of mammals. Lek mating occurs when males congregate around females and try to attract them with various [[courtship display]]s and vocalizations, as in harbor seals. All [[higher mammal]]s (excluding monotremes) share two major adaptations for care of the young: live birth and lactation. These imply a group-wide choice of a degree of [[parental care]]. They may build nests and dig burrows to raise their