Perhaps the most familiar of the great whales, the humpback whale is found in all the world’s oceans. There are three distinct populations: the North Atlantic, North Pacific, and southern oceans. Each group does not interbreed, however, there is a similarity to the migration route, from tropical water winter breeding grounds to temperate, polar water summer feeding grounds. The migration of this species is the longest of any mammal with some whales making a round trip journey of ten thousand miles.
The head and lower jaw of the humpback whale have a variable number of rounded protuberances, called tubercles, each containing at least one hair follicle. The flippers are one-third the length of the body with large knobs on the leading edge. The chunky body is black above and black, white, or mottled below. Two-thirds back is an irregular shaped, low, lumpy dorsal fin, often located on a hump. When going into a dive it will usually throw its flukes upward exposing a distinctive pattern, unique to each humpback. Ventral pleats, twenty-five to fifty, or throat grooves on the underside extend from the tip of the lower jaw to the umbilicus and are fewer and wider than in other rorquals.
With a gestation period of eleven months and born in the tropical waters, humpback calves are between ten to twelve feet long and weigh up to two thousand pounds. Nursing on the mother’s rich milk, the calf gains up to sixty pounds per day while learning to find food and how to feed on fish through observation from the mother. Humpback calves experience a growth spurt during the first year and are weaned to solid food later that year. The juvenile has a second growth period at three to four years of age. Sexual maturity is reached at six to ten years. Adults measure of forty to fifty feet and weigh approximately thirty tons. Females are slightly larger than males and typically bear one calf every two to four years. Life expectancy is approximately fifty years. On the feeding grounds, humpbacks hunt cooperatively, however a more stable association is between mother and calf. Small groups will travel the migration route. On the breeding grounds, males sing long complex songs, with each of the humpback’s three distinct populations being uniquely different.
Humpbacks feed on krill and a variety of small schooling fish, herring, capelin, and sand lance. Humpback whales have developed a unique method of gathering concentrated masses of prey, spectacular, bubble cloud feeding. Each whale eats up to one and a half tons per day, six to nine months while on the feeding grounds. At the breeding grounds, they rarely feed and depend upon their fat reserves.
The humpback whale was an easy target for early whalers. Best estimates are there are now thirty thousand in the North Atlantic, North Pacific, and the southern oceans. These populations are protected and now considered an endangered species. Today the threats to humpbacks come from entanglement in fishing gear, ship traffic collisions, and pollution the coastal waters.