Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and porpoises. Dolphins and porpoises may be considered whales from a formal, cladistic perspective. Whales, dolphins and porpoises belong to the order Cetartiodactyla, which consists of even-toed ungulates.
Their closest non-cetacean living relatives are the hippopotamuses, from which they and other cetaceans diverged about 54 million years ago. The two parvorders of whales, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have had their last common ancestor around 34 million years ago.
The humpback whale is a species of baleen whale. It is a rorqual and is the only species in the genus Megaptera. Adults range in length from 14–17 m (46–56 ft) and weigh up to 40 metric tons (44 short tons). The humpback has a distinctive body shape, with long pectoral fins and tubercles on its head. It is known for breaching and other distinctive surface behaviors, making it popular with whale watchers. Males produce a complex song typically lasting 4 to 33 minutes.
The adult humpback whale is generally 14–15 m (46–49 ft), though longer lengths of 16–17 m (52–56 ft) have been recorded. Females are usually 1–1.5 m (3 ft 3 in – 4 ft 11 in) longer than males. The species can reach body masses of 40 metric tons (44 short tons). Calves are born at around 4.3 m (14 ft) long with a weight of 680 kg (1,500 lb).
Humpback whale groups, aside from mothers and calves, typically last for days or weeks at the most. They are normally sighted in small groups though large aggregations form during feeding and among males competing for females. Humpbacks may interact with other cetacean species, such as right whales, fin whales, and bottlenose dolphins. Humpbacks are highly active at the surface, performing aerial behaviors such as breaching and surface slapping with the tail (lobtailing) and flippers. These may be forms of play and communication and/or for removing parasites.