The humpback whale is a giant yet graceful marine mammal that can reach a length of more than 40 feet. It occurs throughout the world's oceans, spending its summers at the poles and winters at lower latitudes. Both males and females sing, but the song of the male is long and complex, containing variations in rhythm and melody and sometimes lasting 30 minutes or more. It is used to attract females, to warn other males, and possibly to locate individual whales. The primary threat to the humpback whale comes from commercial whaling.