DID YOU KNOW. FEBRUARY IS. HUMPBACK WHALE AWARENESS MONTH?. Please INCLUDE these majestic creatures in your thoughts this month. Taxonomy and Evolution.
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The Humpback is the sole member of the genus Megaptera, and is usually classified in its own subfamily Megapterinae within the family Balaenoptiidae, which contains eight other baleens whales. The literal translation of the binomial name is “the New England big-wing”, which reflects the large flippers and the location of the first described specimen.
More recent genetic studies indicate that the first filter-feeding whales, of which the Humpbacks are a descendant, arose in the late Eocene period 35-36 million years ago, and that species evolution then slowed for a long time before radiating again in the middle of the Miocene period, 12-15 million years ago. It is not known whether the Humpback species itself arose at this time.
However, the evidence does indicate that the fin and blue whales’ lineages separated more than 5 million years ago, and that these species split after the Humpback did. The Humpback Whale species is therefore between 5 and 12 million years old. Like other cetacean species, though, the Humpback fossil record becomes very patchy at times greater than 2.5 million years ago, and it is not currently possibly to narrow this age range further.
Probably the most famous humpback whale is “Humphrey,” who was rescued twice by The Marine Mammal Center and other concerned groups. The first rescue was in 1985, when he swam into San Francisco Bay and then up the San Joaquin River. Five years later, Humphrey returned and became stuck on a mudflat in San Francisco Bay near 3 COM Park. He was pulled off the mudflat with a large cargo net and the help of a Coast Guard boat. Both times he was successfully guided back to the Pacific Ocean using a “sound net” in which people in a flotilla of boats made unpleasant noises behind the whale by banging on steal pipes, a Japanese fishing technique known as “oikami.” At the same time, the attractive sounds of humpback whales preparing to feed were broadcast from a boat headed towards the open ocean. Since leaving the San Francisco Bay in 1990, Humphrey has been seen only once, at the Farallone Islands in 1991.
The Humpback Whale is found in all the major oceans, in a wide band running from about 60° S to 65° N latitude. It is a migratory species, spending its summers in cooler, high-latitude waters, but mating and calving in tropical and sub-tropical waters. Annual migrations of up to 25,000 km (16,000 miles) are typical, making it one of the best-traveled of any mammalian species. An exception to this rule is a population in the Arabian Sea, which remains in these tropical waters year-round. The species is not found in the eastern Mediterranean, the Baltic Sea or the Artic Ocean.
The Humpback Whale appears to be recovering much more strongly from the effects of whaling than the other large whales. The population has grown from a low point of 20,000 at the 1966 moratorium to about 35,000 today. By contrast, the blue whale population has remained static at 3,000 over the same period. There are estimated to be 11,600 Humpbacks in the North Atlantic, 7,000 in the North Pacific and at least 17,000 in the Southern Hemisphere.
Humpback Whales can easily be identified by their stocky bodies with obvious humps and black upper parts. The head and lower jaw are covered with knobs called tubercles, which are actually hair follicles and are characteristic of the species. The tail flukes, which are lifted high in the dive sequence, have wavy rear edges. The long black and white tail fin, which can be up to a third of body length, and pectoral fins have unique patterns, which enable individual whales to be recognized, in a similar way to the bill markings on Bewick’s Swans.
Humbacks have 270 to 400 darkly colored baleen plates on each side of the mouth. Ventral grooves run from the lower jaw to the umbilicus about halfway along the bottom of the whale. These grooves are less numerous (usually 16-20) and consequently more prominent than in other rorquals. The stubby dorsal fin is visible soon after the blow when the whale surfaces, but has disappeared by the time the flukes emerge. It has a distinctive 3 m (10 ft) busy blow.
The calf is about 4-4.5 m (13-15 ft) long when born and weighs approximately 700 kg (1500 lbs). Calves are nursed by their mothers for their first six months, then are sustained through a mixture of nursing and independent feeding for a further six months. Calves leave their mothers at the start of their second year, when they are typically 9 m (30 ft) long. Both sexes reach sexual maturity at the age of five. Full adult size is achieved a littler later. Grown size is commonly 15-16 m (49-52 ft) in males, 16-17 m (52-56 ft) in females, and a weight of 40,000 kg (or 44 tons); the largest ever recorded specimen was 19 m (62 ft) long and had pectoral fins measuring 6 m (20 ft) each. Humpback Whales can live for 40-50 years.