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Humpback whale: the story on HearLore | HearLore
Humpback whale
The humpback whale is the only species in the genus Megaptera, a name derived from the Ancient Greek words for giant and wing, referring to its massive front flippers. This creature, first identified by Mathurin Jacques Brisson in 1756, was later renamed by Georg Heinrich Borowski in 1781 as Balaena novaeangliae, meaning New Englander, likely due to frequent sightings off the coast of New England. Adults typically range from 12 to 16 meters in length and can weigh up to 40 tons, with females generally being longer than males. The species is easily recognized by its distinctive body shape, featuring long pectoral fins that can reach one-third of its body length and a unique set of bumps called tubercles on its head and the front edge of its flippers. These tubercles are thick at the base and protrude up to 10 centimeters, often containing a fragile hair that erupts from the skin. The tubercles are rich in nerves and may serve a sensory function, allowing the whale to withstand high water pressure during dives. The dorsal side of the animal is generally black, while the ventral side displays various levels of black and white coloration, with some individuals like the famous albino Migaloo being entirely white. The tail fluke has a jagged trailing edge, and the varying color patterns and scars on the flukes distinguish individual animals.
Songs That Span The Ocean
Male humpback whales produce complex songs during the winter breeding season that can last from 4 to 33 minutes, with some recorded vocalizing for as long as seven hours in Hawaii. These songs range in frequency between 100 Hz and 4 kHz, with harmonics reaching up to 24 kHz or more, and can travel at least 800 kilometers. The structure of the song is intricate, divided into subunits, units, subphrases, phrases, and themes, following a pattern similar to Zipf's law, which is also observed in human languages. The function of these songs has been debated, with theories suggesting they may serve to attract females, establish dominance, or even locate other whales through echolocation. Songs are similar among males in a specific area, and males may alter their songs over time, with others in contact copying these changes. In the northern hemisphere, songs change more gradually, while southern hemisphere songs go through cyclical revolutions. A 2023 study found that as humpback whale numbers have recovered from whaling, singing has become less common. The vocal folds of the humpback are more horizontally positioned than those of land mammals, allowing them to produce underwater calls that are amplified by a laryngeal sac. The species can hear at frequencies between 15 Hz and 3 kHz when stimulated at the tympanic membrane, and between 200 Hz and 9 kHz if stimulated at the thinner region of the tympanic bone adjacent to the tympanic membrane.
Common questions
Who first identified the humpback whale species in 1756?
Mathurin Jacques Brisson first identified the humpback whale species in 1756. The species was later renamed by Georg Heinrich Borowski in 1781 as Balaena novaeangliae.
How long can humpback whale songs last and how far do they travel?
Humpback whale songs can last from 4 to 33 minutes, with some recorded vocalizing for as long as seven hours in Hawaii. These songs can travel at least 800 kilometers.
What is the bubble-net feeding technique used by humpback whales?
Bubble-net feeding is a unique hunting technique where a group of whales swims in a shrinking circle while blowing air from their blowholes to create a cylinder of bubbles. This method captures prey above and allows whales to consume more food per mouthful while using less energy.
How long does gestation last for humpback whales and when do they give birth?
Gestation in the humpback whale species lasts 11.5 months, and females reproduce every two years. Mothers typically give birth in mid-winter, usually to a single calf.
Which predators attack humpback whales and when were great white shark attacks documented?
Orcas are the main natural predators of humpback whales, and great white sharks are another confirmed predator. In 2020, Marine biologists Dines and Gennari et al. published a documented incident of a pair of great white sharks attacking and killing a weakened 10-meter humpback whale.
When did NOAA declare an unusual mortality event for humpback whales in 2017?
NOAA declared an unusual mortality event in April 2017 due to an increase in stranded whales. Virginia Beach Aquarium stranding response coordinator Alexander Costidis concluded that vessel interactions and entanglements were the two causes of these events.
Humpback whales are generalist feeders that consume krill, copepods, other plankton, and small schooling fish, with the most common krill species eaten in the southern hemisphere being the Antarctic krill. They are gulp feeders, swallowing prey in bulk, and use a unique hunting technique known as bubble-net feeding, which is considered a form of tool use. In this method, a group of whales swims in a shrinking circle while blowing air from their blowholes, creating a cylinder of bubbles to capture prey above. The whales may dive up to 20 meters while performing this technique, and bubble-netting comes in two main forms: upward spirals and double loops. Upward spirals involve the whales blowing air from their blowholes continuously as they circle towards the surface, creating a spiral of bubbles. Double loops consist of a deep, long loop of bubbles that herds the prey, followed by slapping the surface and then a smaller loop of bubbles that precedes the final capture. This technique allows whales to consume more food per mouthful while using less energy, and is particularly useful for low-density prey patches. In the southern hemisphere, humpbacks have been recorded foraging in large, compact gatherings numbering up to 200 individuals, with a study undertaken in May 2009 finding a super-aggregation of krill in Wilhelmina Bay, on the west side of the Antarctic Peninsula, with a density of 5.1 whales per square kilometer. At Stellwagen Bank off the coast of Massachusetts, humpback whales have been recorded foraging at the seafloor for sand lances by brushing their jaws against the bottom.
The Mating Game And The Escort System
Mating takes place during the winter months, when females reach estrus and males reach peak testosterone and sperm levels. Humpback whales are polygynandrous, meaning both sexes have multiple partners. Males frequently trail both lone females and cow-calf pairs, with these males known as escorts. The male that is closest to the female is known as the principal escort, and fights off the other suitors, known as challengers. Other males, called secondary escorts, trail farther behind and are not directly involved in the conflict. Agonistic behavior between males consists of tail slashing, ramming, and head-butting. Males have also been observed engaging in copulation with each other. Females may experience pleasure from bubble stimulation, a novel concept among cetaceans. Video taken near Hawaii documents three male humpbacks producing bubbles directly under a female's genitalia twelve separate times. Instead of fleeing, the female seems to accept these bubbles, exhibiting behaviors such as rolling toward, arching, or slightly lifting and/or moving her tail above the bubble releases. Gestation in the species lasts 11.5 months, and females reproduce every two years. Fetuses start out with teeth and develop their baleen during the last months of their gestation. Humpback whale births have rarely been observed by humans, with one birth witnessed off Madagascar occurring within four minutes. Mothers typically give birth in mid-winter, usually to a single calf, and move to shallower water near the coast to reduce the chance of being harassed by escort males.
The Predators And The Prey
Orcas are the main natural predators of humpback whales, with visible scars indicating that they prey upon juvenile humpbacks and even adults. A 2014 study in Western Australia observed that when available in large numbers, young humpbacks can be attacked and sometimes killed by orcas. Mothers and possibly related adults escort calves to deter such predation. The suggestion is that when humpbacks suffered near-extinction during the whaling era, orcas turned to other prey but are now resuming their former practice. There is also evidence that humpback whales will defend against or mob orcas who are attacking either humpback calves or juveniles as well as members of other species, including seals. The powerful flippers of humpback whales, often infested with large, sharp Cornula barnacles, are formidable weapons against orcas. When threatened, they will thrash their flippers and tails, keeping the orcas at bay. The great white shark is another confirmed predator of the humpback whale. In 2020, Marine biologists Dines and Gennari et al. published a documented incident of a pair of great white sharks attacking and killing a weakened 10-meter humpback whale. A second incident of a great white shark killing a humpback whale was documented off the coast of South Africa. Working alone, the shark attacked a 10-meter, emaciated and entangled humpback whale by attacking the whale's tail to cripple and bleed the whale before she managed to drown the whale by biting onto its head and pulling it underwater. In 2006, an ailing humpback fell prey to a group of tiger sharks near Hawaii.
The Whaling And The Recovery
Humpbacks still face man-made threats, including entanglement by fishing gear, vessel collisions, human-caused noise and traffic disturbance, coastal habitat destruction, and climate change. Like other cetaceans, humpbacks can be injured by excessive noise. In the 19th century, two humpback whales were found dead near repeated oceanic sub-bottom blasting sites, with traumatic injuries and fractures in their ears. While oil ingestion is a risk for whales, a 2019 study found that oil did not foul baleen and instead was easily rinsed by flowing water. NOAA recorded 88 stranded humpback whales between January 2016 and February 2019 along the Atlantic coast of the US, which is more than double the number of whales stranded between 2013 and 2016. Because of the increase in stranded whales, NOAA declared an unusual mortality event in April 2017. Virginia Beach Aquarium's stranding response coordinator, Alexander Costidis, concluded that the two causes of these unusual mortality events were vessel interactions and entanglements. Around the Strait of Magellan, humpbacks have been the whale species that is most commonly reported to be involved in ship-whale collisions since at least 2013. To decrease the number of collisions, speed limits have been proposed in the area around the Francisco Coloane Marine and Coastal Protected Area. Whale watching, which brings in a revenue of $20 million per year for Hawaii's economy, can raise awareness of humpback whale conservation, but whale watching boats can have negative impacts on humpback whales, including causing stress and disturbing behaviors like feeding, mating and socializing. This is particularly deleterious for mothers with calves. Regulations on whale vessels have included restrictions on how close the vessels can get to the whales.