Humpback whales are the best-known members of the family Balaenopteridae. Like other rorquals, humpbacks have a dorsal fin, and they have ventral throat grooves running from the tip of the lower jaw to the belly, but humpbacks differ in many ways from the other species in the family Balaenopteridae, and because of these differences, humpbacks are classified in a separate genus from the other rorquals. The body of a humpback is more robust and not as sleek as the bodies of fin, sei, blue, and minke whales. The top of the head and the lower jaw of a humpback are covered by rounded bumps, each containing at least one stiff hair, and the pectoral flippers are very long, spanning one-third of the body length. The tail stalk is thin, and the tail has a series of ridges on the trailing edge. Humpbacks are slower swimmers than other rorquals, but they are more acrobatic than their cousins. They often raise their tails high in the air before diving and engage in breaching, tail slapping, flipper slapping and other physical activities. It is this acrobatic behavior, their curiosity, and their beautiful, haunting songs that make them so popular with humans.
Adult humpbacks average 49 ft. (15 m) in length and weigh approximately 35 tons. They are predominantly black on the dorsal side and have varying degrees of white on the throat, belly, flippers, and flukes. The shape and color pattern on a humpback’s dorsal fin
and flukes are unique to the individual, much like a human’s finger prints. Once biologists realized this, they were able to catalog and follow individual whales during their migrations and throughout their lives, greatly increasing our understanding of humpbacks’ social, mating, calving, and feeding behaviors, as well as giving researchers a better estimate of population sizes.
The baleen of a humpback is black in color, and like most other baleen whales, humpbacks feed in high latitudes and breed and give birth in low latitudes, near Mexico, Hawaii, and in the western Pacific near Japan. We mostly see humpbacks in the summer near Kodiak Island, but a few individuals spend the winter here as well. Since humpbacks don’t reach sexual maturity until they are 5 to 7 years old, it is possible that some whales we see in the winter are not yet sexually mature, so they do not migrate to breeding and birthing areas. Humpbacks feed on krill, other zooplankton, and small schooling fish. As with other baleen whales, humpbacks feed almost exclusively during the summer months and live off their fat reserves in the winter. It has been estimated that a humpback eats up to 1.5 tons of food per day when it is feeding. Humpbacks sometimes employ a method known as bubble net feeding, where they release air bubbles while swimming in circles beneath their prey and then lunge open-mouthed to the surface through the center of the concentrated prey.
Humpbacks are known for their acrobatic displays, including breaching, spy-hopping, lob-tailing, tail-slapping, and flipper slapping, and some of these displays can last for hours, especially during mating. In a few weeks, I will discuss these behavioral displays in more detail
Humpbacks are also famous for their long, complex songs. These songs are sung by male humpbacks in the winter, and it is believed that their primary function is to attract females, although it has also been suggested that the songs may be used between two males in order to establish dominance. All whales in a particular population sing essentially the same song, and as the song changes slowly over time, the males somehow coordinate these changes. A typical song lasts 10 to 20 minutes, but it may be repeated continuously for hours. During mating, males compete very aggressively for females, and these competitions that sometimes last several hours may involve tail slashing, ramming, and head butting. Although humpback whales are quite social during the mating season, they are usually found alone or in small groups on their summer feeding grounds.
Next week, I will post about gray whales, one of the most-researched and best-understood species of whales. As always, I welcome your comments, and would love to hear about some of your whale encounters.
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