A rooster (also calle a cock or chanticleer) is a male chicken (Gallus gallus), the female being called a hen. Immature male chickens of less than a year's age are called cockerels. The oldest term is "cock", from Old English coc. But because "cock" is more frequently used as a slang term referring to the penis, this term is generally avoided for the sake of both propriety and clarity, although it remains accurate. It is replaced by synonyms: "cockerel" (which properly refers to a young male chicken) in the United Kingdom, and "rooster" (a relative neologism) in North America and Australia. "Roosting" is the action of perching aloft to sleep at night, and is actually done by both sexes. The rooster is non-monogamous, but cannot guard several nests of eggs at once. He guards the general area where his hens are nesting, and will attack other roosters who enter his territory. During the daytime, he often sits on a high perch, usually 4–5 feet off the ground, to serve as a lookout for his flock. He will sound a distinctive alarm call if predators are nearby.