Description
A humpback whale can easily be identified by its stocky body with an obvious hump and black dorsal coloring. The head and lower jaw are covered with knobs called tubercles, which are hair follicles, and are characteristic of the species. The fluked tail, which it lifts above the surface in some dive sequences, has wavy trailing edges. The four global populations, all under study, are: North Pacific, Atlantic, and Southern Ocean humpbacks, which have distinct populations which complete a migratory round-trip each year, and the Indian Ocean population, which does not migrate, prevented by that ocean's northern coastline.
The long black and white tail fin, which can be up to a third of body length, and the pectoral fins have unique patterns, which make individual whales identifiable. Several hypotheses attempt to explain the humpback's pectoral fins, which are proportionally the longest fins of any cetacean. The two most enduring mention the higher maneuverability afforded by long fins, and the usefulness of the increased surface area for temperature control when migrating between warm and cold climates.
Humpbacks have 270 to 400 darkly coloured baleen plates on each side of their mouths. The plates measure from a mere 18 inches (46 cm) in the front to approximately 3 feet (0.91 m) long in the back, behind the hinge. Ventral grooves run from the lower jaw to the umbilicus about halfway along the underside of the whale. These grooves are less numerous (usually 14–22) than in other rorquals but are fairly wide.
The stubby dorsal fin is visible soon after the blow when the whale surfaces, but disappears by the time the flukes emerge. Humpbacks have a 3 metres (9.8 ft), heart-shaped to bushy blow, or exhalation of water through the blowholes. Because humpback whales breathe voluntarily, the whales possibly shut off only half of their brains when sleeping. Early whalers also noted blows from humpback adults to be 10–20 feet (3.0–6.1 m) high.
Newborn calves are roughly the length of their mother's head. At birth, calves measure 20 feet (6.1 m) at 2 short tons (1.8 t) The mother, by comparison, is about 50 feet (15 m). They nurse for approximately six months, then mix nursing and independent feeding for possibly six months more. Humpback milk is 50% fat and pink in color.
Females reach sexual maturity at the age of five, achieving full adult size a little later. Males reach sexual maturity at approximately seven years of age. Humpback whale lifespans range from 45–100 years. Fully grown, the males average 13–14 m (43–46 ft). Females are slightly larger at 15–16 m (49–52 ft); the largest recorded specimen was 19 metres (62 ft) long and had pectoral fins measuring 6 metres (20 ft) each. Body mass typically is in the range of 25–30 metric tons (28–33 short tons), with large specimens weighing over 40 metric tons (44 short tons). The female has a hemispherical lobe about 15 centimetres (5.9 in) in diameter in its genital region. This visually distinguishes males and females. The male's penis usually remains hidden in the genital slit.
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