HUMPBACK WHALE
Megaptera novaeangliae (Borowski 1781)

Order Cetacea : Family Balaenopteridae

DESCRIPTION. Humpback whales typically reach lengths of 15–16 m and weigh between 31 and 41 metric tons. Females are usually slightly larger than males, and the maximum recorded length is 18 m. They are greater in girth and present a bulkier, less streamlined appearance when compared with other balaenopterid whales. Coloration is black overall, with irregular white markings on the throat, sides, and abdomen. In some individuals the belly may be entirely white or there may be white patterns dorsally. The flippers are very long (up to 4.6 m) but are narrow. The flippers typically are white below but range from black to patterns of black and white dorsally, or even entirely white. The tail flukes are broad, serrated on the free edge, and black above with black and white coloration ventrally. Distinctive tail flukes may serve to identify individual humpback whales in many cases.

As with other balaenopterid whales, humpbacks have a dorsal fin that may be up to 31 cm in height and is falcate to rounded in profile. Although the humpback does have throat pleats, they are fewer and spaced wider apart than is typical for balaenopterids. Humpbacks, therefore, are not usually classed as rorquals. Other differences of the humpback whale include lack of a median head ridge, enormous flippers, and the presence of numerous knobby structures, or dermal tubercles, about the dorsal surface of the snout, chin, and mandible. The number and location of the head tubercles vary between individuals, and each tubercle contains a sensory hair.

Humpbacks typically submerge for 6–7 minutes at a time, with occasional dives of 15–30 minutes. The blow may be up to 3 m high and is not a slender plume but rather bushy. When diving, humpbacks arch the back steeply, thus the common name. The flukes rarely show in shallow dives, but when a deep dive is accomplished, the flukes may be lifted well above the water's surface Distribution. Humpback whales occur in all oceans of the world. In the western North Atlantic these whales are distributed from north of Iceland, Disko Bay, and west of Greenland, south to Venezuela and around the tropical islands of the West Indies. Population estimates indicate that the worldwide prewhaling population of humpbacks was approximately 100,000. More recent estimates have placed numbers at 9,500–10,000, with about 5,800 occurring in the western North Atlantic.

DISTRIBUTION.  Humpback whales occur in all oceans of the world.  In the western North Atlantic these whales are distributed from north of Iceland, Disko Bay, and west of Greenland, south to Venezuela and around the tropical islands of the West Indies.  Population estimates indicate that the worldwide prewhaling population of humpbacks was approximately 100,000.  More recent estimates have placed numbers at 9,500-10,000, with about 5,800 occurring in the western North Atlantic. 

In the Gulf of Mexico, humpback whales have been captured in the Florida Keys and northern Cuba. Sightings have occurred off the west coast of Florida and Alabama. The only known occurrence along the Texas coast is of a young, immature animal observed by David Weller (Marine Mammal Research Program, Texas A&M University–Galveston) and colleagues at the inshore side of Bolivar Jetty near Galveston on 19 February 1992. No population estimates are available for Gulf humpbacks.

Humpbacks are highly migratory. In the western North Atlantic these whales occupy high-latitude feeding grounds from Cape Cod to Iceland during spring, summer, and fall. In late autumn and winter, the whales move into Caribbean waters for mating and calving.

SUBSPECIES. Monotypic species.

HABITS. Humpbacks often congregate in groups of 20–30 to perhaps 100–200. These are among the most acrobatic and visible of whales; they breach completely out of water in spectacular displays of strength. Humpbacks commonly slap their tail flukes or flippers on the water's surface and occasionally lift their huge heads above water to peer about, a behavior known as "spyhopping." Tail slapping, breaching, and other such behaviors may serve as communication between the whales, possibly as warnings or a means of indicating location.

Humpbacks also produce a number of unusual sounds described variously as moans, groans, cries, squeals, chirps, and clicks. Sounds may be arranged into complex and predictable patterns known as songs. Humpback songs may be repeated for long periods of time and have been most often recorded on low-latitude breeding grounds. Although yet to be proven, songs are thought to be broadcast by sexually mature, lone males and may have some purpose in mating rituals.

Humpback whales eat krill, mackerel, sand lance, capelin, herring, pollock, smelt, cod, sardines, salmon, and anchovies. These whales are lunge feeders but use several different techniques to concentrate their food before lunging. An especially interesting technique is known as bubble netting, in which one or more humpbacks exhale while circling below a food source. The resulting bubble column effectively forms a net to concentrate food items; the whale then lunges through the concentrated food with open mouth.

Females give birth to a single calf in tropical or subtropical waters in winter. The gestation period is approximately 11 months. Newborn humpbacks are 4.6 m in length and weigh about 1.3 metric tons. The period of lactation lasts approximately 5 months. Sexual maturity is reached at 2–5 years, when the young whales measure about 12 m in length. Physical maturity occurs at 12–15 years of age. Females breed every other year.

POPULATION STATUS. Extralimital; rare; strandings and observations. Historically in the Gulf of Mexico, humpback whales occasionally were hunted near the Florida Keys, but they are uncommon in the Gulf proper. Only seven confirmed records have been reported. Sightings have been made off the west coast of Florida and near Alabama in the eastern Gulf and off the jetties in Galveston, Texas. Most cetologists do not believe there is a resident population of these whales in the Gulf; the few animals that have stranded or been observed are most likely strays that accidentally wandered into the Gulf from the West Indian wintering grounds during their migration.

CONSERVATION STATUS. The USFWS and the TPWD both list humpbacks as endangered, but the IUCN regards them as least concern and increasing. According to the IUCN, although no final assessment of the current global population relative to its 1940 level is available, recent rates of increase have produced numbers sufficiently above the threshold that would qualify the species for inclusion in a vulnerable category.

 

From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.