Megaptera novaeangliae

Megaptera novaeangliae

The humpback whale (Megaptera novaeangliae Borowski, 1781) is a cetacean belonging to the Balaenopteridae family.

Systematics –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Phylum Chordata,
Mammalia class,
Order Artiodactyla,
Infraorder Cetacea,
Family Balaenopteridae,
Genus Megaptera,
Species M. novaeangliae.
The terms are synonyms:
– Balaena allamack Gray, 1846;
– Balaena atlanticus Hurdis, 1897;
– Balaena boops Fabricius, 1780;
– Balaena gibbosa Erxleben, 1777
– Balaena gibbosa Gray, 1843;
– Balaena lalandii Fischer, 1829;
– Balaena longimana Rudolphi, 1832;
– Balaena longipinna (Gray, 1846);
– Balaena nodosa Bonnaterre, 1789;
– Balaena novaeangliae Borowski, 1781;
– Balaena sulcata subsp. antarctica Schlegel, 1841;
– Balaenoptera astrolabae Pucheran, 1853;
– Balaenoptera astrolabe Pucheran, 1843;
– Balaenoptera australis Lesson, 1828;
– Balaenoptera capensis A.Smith, 1834;
– Balaenoptera leucopteron Lesson, 1842;
– Balaenoptera syncondylus A.Mueller, 1863;
– Kyphobalaena keporkak Van Beneden, 1868;
– Megaptera americana Gray, 1846;
– Megaptera antarctica Gray, 1846;
– Megaptera australis Iredale & Troughton, 1934;
– Megaptera bellicosa Cope, 1871;
– Megaptera boops Van Beneden & Gervais, 1880;
– Megaptera brasiliensis True, 1904;
– Megaptera braziliensis Cope, 1867;
– Megaptera burmeisteri Burmeister, 1866;
– Megaptera burmeisteri Gray, 1866;
– Megaptera gigas Cope, 1865;
– Megaptera indica Gervais, 1883;
– Megaptera kusira Gray, 1850;
– Megaptera kusira Trouessart, 1904;
– Megaptera kuzira Gray, 1850;
– Megaptera lalandii (Fischer, 1829);
– Megaptera longimana (Rudolphi, 1832);
– Megaptera longimana subsp. morei Gray, 1866;
– Megaptera longipinna Gray, 1846;
– Megaptera nodosa (Bonnaterre, 1789);
– Megaptera nodosa subsp. bellicosa Elliot, 1904;
– Megaptera nodosa subsp. lalandii Tomilin, 1946;
– Megaptera nodosa subsp. Nodosa;
– Megaptera nodosa subsp. novaezealandiae Ivashin, 1958;
– Megaptera nodosa subsp. novaezelandiae (Gray, 1864);
– Megaptera nodosa subsp. osphyia (Cope, 1865);
– Megaptera novaeangliae (Brisson, 1762);
– Megaptera novaeangliae subsp. australis (Lesson, 1828);
– Megaptera novaeangliae subsp. kuzira (Gray, 1850);
– Megaptera novaeangliae subsp. novaeangliae (Borowski, 1781);
– Megaptera novaeangliea;
– Megaptera novaezealandiae (Gray, 1864);
– Megaptera novaezelandiae Gray, 1864;
– Megaptera osphya Cope, 1865;
– Megaptera osphya Mead & Brownell, 2005;
– Megaptera poescop Gray, 1846;
– Megaptera poeskop Gray, 1846;
– Megaptera versabilis Cope, 1869;
– Poescopia lalandii Gray, 1866;
– Rorqualus antarcticus F.Cuvier, 1836;
– Rorqualus australis Hamilton, 1837.

Geographic Distribution and Habitat –
The Megaptera novaeangliae is a cetacean widespread in the oceans and seas of the whole world. These mammals generally make annual migrations of up to 16,000 kilometres, feeding in polar waters and moving towards tropical or subtropical waters to mate and give birth.
This species normally moves at an average speed of 3-14 km/h, but in particular circumstances, such as during migrations, it can reach 27 km/h. These are long distances with a record displacement of 9800 km.
Despite the migrations, the populations of the Northern and Southern hemispheres are separate, as the times and places of reproduction never coincide. The populations of the two hemispheres also differ morphologically: for example, the extent and ventral patterns of the connective tissue forming the caudal fin and the lateral pigmentation change; moreover, the specimens of the southern hemisphere tend to have a more marked white pigmentation, especially visible in the lateral area of the body.
Recently, it has been proposed that specimens from the three major ocean basins (North Pacific, North Atlantic and Southern Hemisphere) represent 3 different subspecies.
The marine habitat of the Megaptera novaeangliae therefore includes a vast oceanic area, from the polar regions to the tropical zones. These whales are known for their spectacular leaps and songs, and are a major attraction for tourists interested in whale watching.
Importantly, while M. novaeangliae has a large marine habitat, it is a threatened species due to past commercial whaling and human activities that can cause noise pollution, collisions with vessels, and habitat degradation. Therefore, the conservation of these whales and their habitat is critical to their long-term survival.

Description –
The adults of this whale measure from 14 to 17 meters in length and can weigh up to 40 tons. They can be recognized by their characteristic shape, with long pectoral fins and a lumpy head.
The females are usually 1-1.5 meters longer than the males and at birth the young measure 4.3 meters in length and weigh 680 kilograms.
The body is massive, with a slender rostrum and proportionally long pectoral fins, each of which is one-third the length of the body. The dorsal fin is short and varies from a barely visible outline to a long, curved structure depending on the individual. The caudal fin has a fringed posterior margin.
It has grooves, varying in number from 14 to 35, from the tip of the jaw to the navel.
The mouth is lined with 270-400 baleen per side.
As mentioned, they have protuberances or tubercles on the head and on the anterior margin of the pectoral fins. The tubercles on the head are 5-10 centimeters wide at the base and protrude up to 6.5 centimeters. Mostly hollow in the center, often containing a small hair protruding 1-3cm from the skin, 0.1mm thick. The tubercles already develop in the uterus and may have a sensory function, as they are full of nerves.
They have the dorsal, or upper, side generally black, whilst the ventral, or lower side, has a mottled black and white livery.
Southern hemisphere specimens tend to have a greater amount of white pigmentation. The pectoral fins also vary from being completely white to being white only on the underside.
The different color scheme and scars on the tail allow different individuals to be distinguished.
The end of the female genital cleft is marked with a round lobe, which allows the two sexes to be visually distinguished.
Her jumps and other distinctive surface behaviors have made her popular.
The males produce a complex set of sounds which can last from 10 to 20 minutes and which is repeated for several hours: due to its duration and repetitiveness, it is defined as whale song. This song is part of the so-called social sounds, as it is used by whales to communicate with conspecifics; in particular, the songs are fundamental in the reproductive and sexual selection processes. The females, on the other hand, do not produce real songs but shorter sounds suitable for communication. Therefore, whether it is a song or a simpler sound, vocalizations have very specific purposes.
The sounds produced by whales are very complex and are structured according to population: humpback whales that occupy the same geographical regions tend to sing in a similar way, with slight variations, as if they were speaking regional dialects. Adding to the complexity of such communication, each humpback’s song also varies with tempo, in terms of pitch and rhythm.
Humpback whales may also make other types of sounds called feeding calls; these are prolonged sounds (from 5 to 10 seconds) produced by solitary specimens and with an almost constant frequency. The function of this type of sounds is not yet fully understood. According to some researchers, since humpback whales feed in groups, they could serve as a signal to conspecifics. Other researchers also argue that these sounds are recognized by fish: experiments conducted on herring show that fish exposed to the sound tend to flee even if there are no humpback whales.

Biology –
Megaptera novaeangliae is a species with a cycle similar to that of other whales.
Breeding usually occurs during the winter or spring months when whales are in warm waters near the equator to mate. During this period, males compete with each other for the opportunity to mate with females.
Courtship can include a variety of behaviors, such as leaping out of the water, tail flicking, and complex singing by males to attract the attention of females.
Once a pair has formed, mating takes place underwater. The male inserts his reproductive organ, called the penis, into the female’s genital opening, called the cloaca. Fertilization occurs internally and the female retains the sperm for a certain period before starting the process of developing the embryo.
Gestation usually lasts between 10 and 12 months. During this time, the female carries on the development of the embryo inside her body. After gestation, the female gives birth to a single pup, which is born in water. Common whale pups are known for their large birth weight, which can reach 2 tons and lengths of about 4-5 meters.
After birth, the mother takes care of the cub, feeding it her fat-rich milk to promote growth and nourishment. The pups stay with their mother for a variable period of time, which can last from 6 months to a year, during which they learn to swim, hunt and adapt to the marine environment.
Reproduction therefore follows a complex life cycle, which requires time and care on the part of the females to ensure the survival of the pups and the continuity of the species.

Ecological Role –
Megaptera novaeangliae is a species that lives mainly in the oceans. Its history is rooted in the past, going back millions of years ago.
The first traces of this species date back to the Middle Miocene, about 14 million years ago. Fossil remains of this species have been found in various parts of the world, including North America, Europe, South America and Australia. This indicates that the anchor whale has had a wide geographic distribution over the millennia.
During the Late Pleistocene, about 100,000 years ago, the population of Megaptera novaeangliae experienced a steep decline due to climate change and the influence of human activity. However, the species has survived to the present day, albeit with a more limited distribution than in the past.
M. novaeangliae is one of the best studied and best known whale species. During the 1970s and 1980s, it was a major victim of whaling. Fortunately, a global ban on commercial whaling was introduced in 1985, and the population of anchor whales has gradually increased since then.
Its evolutionary history and adaptation to environmental challenges over millennia make it a fascinating subject for scientific study and conservation.
Humpback whales can interact with other cetacean species, such as right whales, fin whales and bottlenose dolphins. They are extremely surface active and exhibit a whole range of aerial behaviors, such as hopping and flapping the surface with their tails and pectoral fins. Such activities could constitute a particular form of play and communication and/or a way to remove parasites.
Humpback whales rest on the surface with their bodies horizontal.
They never seem to dive below 150m and only rarely go beyond 120m. Dives typically last no longer than five minutes during the summer, but typically last 15 to 20 minutes during the winter. When diving, humpback whales typically lift their tails high, exposing their undersides.
Generally, they live in small groups, with fewer than 10 individuals. When there is a humpback whale with offspring in the group, another humpback whale in the group (usually a male) assumes the function of guard: when a conspecific unrelated to the group approaches, the guard moves him away (for example by emitting bubbles or of the body). However, this behavior must not suggest that the male and the female form a stable couple. Just like most mammals, humpback whales are polygamous; in fact, the male competes for the conquest of the various mature females.
As far as life expectancy is concerned, according to some, these cetaceans can live up to 50 years, while other studies claim that they can even reach 80 years.
As far as food is concerned, although krill (a term that indicates various species of invertebrate marine organisms belonging to the order Euphausiacea) is their favorite food, humpback whales also feed on other animals, such as small fish, remaining in any case carnivorous . The procurement techniques are different and often vary according to the season.
In the Southern Hemisphere, the most commonly consumed krill species is Antarctic krill, replaced further north by boreal krill and various species of the genera Euphausia and Thysanoessa. Among the fish hunted are herring, capelin, ammoditi and mackerel from the Atlantic.
Like other fin whales, humpback whales are “swallowers” that lunge forward at their prey, in contrast to right and bowhead whales, which filter prey by swimming with their jaws open.
The humpback whale increases its mouth capacity by expanding the grooves on its throat. The water is expelled through the baleen.
In the Southern Hemisphere, humpback whales have been seen feeding in large, compact nuclei that can comprise up to 200 individuals.
Humpback whales capture their prey by creating what is known as a “bubble net”. A group of specimens swims in a narrowing circle while blowing air from blowholes, trapping the prey above in a cylinder of bubbles. When they perform this technique they can dive up to 20 meters. The bubble network can come in two main forms: upward spirals and double loops. In the first case, the humpbacks continuously blow air from the blowhole as they circle towards the surface, creating a spiral of bubbles. The double ring consists of a long, deep ring of bubbles that group prey, followed by a flick of the tail on the surface and then a smaller ring that heralds the final catch. Combinations of the two techniques have also been recorded.
After the humpbacks create their “nets,” they swim inside them with their mouths wide open, ready to swallow.
Humpback whales are themselves subject to predation by other species.
Visible scars indicate that killer whales prey on young humpback whales. A 2014 study in Western Australia reported that, when available in large numbers, young humpback whales can be attacked and sometimes killed by orcas. Also, mothers and other adults (perhaps their relatives) accompany the young to discourage predators. Scholars believe that orcas turned to other prey after humpbacks were pushed to the brink of extinction in the whaling era and are now reverting to their former habits. There is even evidence that humpback whales attack or harass orcas that are preying on newborn or juvenile humpback whales, as well as members of other species, including pinnipeds. Humpback whales’ protection from other species may be unintentional, a ‘fallout’ of behavior intended to protect members of its own species. Humpback whales’ powerful pectoral fins, often infested with large barnacles, are formidable weapons against killer whales. When they feel threatened, these whales turn their pectoral fins and tails towards the orcas, trying to keep them away.
Two attacks by the great white shark have also been documented (although, as a rule, this predatory fish does not attack large cetaceans such as whales, although it will feed on the carcasses in case it encounters them in the open sea). In 2020, marine biologists Dines and Gennari et al. documented the case of a group of great white sharks which, working as a school, managed to attack and kill an adult humpback whale. The second case of a humpback whale being killed by a great white shark has been documented off the coast of South Africa. The shark in question was a female nicknamed “Helen.” Working alone, she attacked an emaciated 10-metre humpback whale entangled in a net, biting its tail to paralyze it and cause it to bleed before eventually drowning it by biting off its head and dragging it under the water.
From an ecological point of view, humpback whales have suffered a significant reduction in populations in recent years, with a decrease of up to 95%, before the introduction of the moratorium on commercial hunting in 1985.
More than 60,000 humpback whales were killed between 1910 and 1916 in the Southern Hemisphere, with further peak exploitation in the 1930s and 1950s. In the North Pacific, catches of more than 3,000 specimens were recorded from 1962 to 1963.
The International Whaling Commission (IWC) moratorium on whaling, in effect since 1985, has played a vital role in the recovery of humpback whales. The humpback whale is also currently listed in Annex IV of the Habitats Directive, which identifies species in need of strict protection in the European region.
The humpback whale is still an endangered species, as threats arise not only from deliberate hunting, but also from chemical pollution, noise and collisions with boats. Although the size makes these animals look like indestructible giants, humpback whales live thanks to a delicate environmental and social balance. Their communication, as well as their movements, in fact, are mediated by sounds.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Facilidad Global de Información sobre Biodiversidad.
– Gordon Corbet, Denys Ovenden, 2012. Guide to mammals of Europe. Franco Muzzio Publisher.
– John Woodward, Kim Dennis-Bryan, 2018. The Great Encyclopedia of Animals. Gribaudo Publisher.

Photo source:
– http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/picture?id=192