Humpback Whale

The adult humpback whale is generally 14–15 m (46–49 ft) long, though individuals up to 16–17 m (52–56 ft) long 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). The longest recorded lengths were 17.4 m (57 ft) for a male and 18.6 m (61 ft) for a female. However, records for humpback whales measuring 17–18 m (56–59 ft) are considered unlikely. Calves are born at around 4.3 m (14 ft) long with a mass of 680 kg (1,500 lb). The species has a bulky body with a thin rostrum and proportionally long flippers, each around one-third of its body length. It has a short dorsal fin that varies from nearly nonexistent to somewhat long and curved. Like other rorquals, the humpback has grooves between the tip of the lower jaw and the navel.

Humpback whales are found in marine waters worldwide, except for some areas at the equator and High Arctic and some enclosed seas. The farthest north they have been recorded is at 81°N around northern Franz Josef Land. They are usually coastal and tend to congregate in waters within continental shelves. Their winter breeding grounds are located around the equator; their summer feeding areas are found in colder waters, including near the polar ice caps. Humpbacks go on vast migrations between their feeding and breeding areas, often crossing the open ocean. The species has been recorded traveling up to 8,000 km (5,000 mi) in one direction.

Humpback whales feed from spring to fall. They are generalist feeders; their main food items are krill, copepods, other plankton, and small schooling fish. The most common krill species eaten in the southern hemisphere is the Antarctic krill. Farther north, the northern krill and various species of Euphausia and Thysanoessa are consumed. Fish prey include herring, capelin, sand lances, and Atlantic mackerel. Like other rorquals, humpbacks are "gulp feeders", swallowing prey in bulk, while right whales and bowhead whales are skimmers, and the whale increases its mouth gape by expanding the grooves. Water is pushed out through the baleen.

Humpback whale groups, aside from mothers and calves, typically stay together 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, surface slapping with the tail fluke (lobtailing) and flippers, and peduncle throws, which involve the tail crashing sideways on the surface. These may be forms of play and communication, and may help to remove parasites. The species is a slower swimmer than other rorquals, cruising at 7.9–15.1 km/h (4.9–9.4 mph). When threatened, a humpback may speed up to 27 km/h (17 mph).

Mating takes place during the winter months, which is when females reach estrus and males reach peak testosterone and sperm levels. Humpback whales are polygynandrous (both sexes have multiple partners). Males frequently trail both lone females and cow–calf pairs. These males are known as "escorts"; the male that is closest to the female is known as the "principal escort", and fights off the other suitors, known as "challengers". Other males, called "secondary escorts", trail farther behind and are not directly involved in the conflict. Agonistic behavior between males consists of tail slashing, ramming, and head-butting. Males have also been observed engaging in copulation with each other.

Humpback whales often have barnacles living on their skin, the most common being the acorn barnacle species Coronula diadema and Coronula reginae, which in turn are sites for attachment for goose barnacle species like Conchoderma auritum and Conchoderma virgatum. They are most abundant at the lower jaw tip, along the middle ventral groove, near the genital slit, and between the bumps on the flippers. C. reginae digs deep into the skin, while attachments by C. diadema are more superficial. The size of the latter species provides more sites for attachment by other barnacles. Barnacles are considered to be epibionts rather than parasites, as they do not feed on the whales, though they can affect their swimming by increasing drag.