FOCUS ON THE HUMPBACK WHALE
Identity card :
Common name: humpback whale, shrew, jubarte
Tahitian name: Tohora, Parāoa
Scientific name : Megaptera novaeangliae
Class : mammals (vertebrate with hair and mammary glands)
Order: cetaceans (aquatic mammals with fins instead of legs and nostrils on top of the skull)
Suborder: mysticetes (cetaceans with baleen plates and two blowholes)
Family: Balaenopteridae
Where does their name come from?
Historically, the humpback whale got its name from the fishermen who regularly observed it, seeing only a “hump” in the distance. Before diving, the humpback whale arches its back sharply, revealing only a hump at the water's surface.
Their name also refers to the hump at the base of their dorsal fin.
GENERAL CHARACTERISTICS
Anatomy
Pectoral fins up to 4 m long
Caudal fin
Dorsal fin
Head covered with sensory tubercles (each containing a “hair”)
Throat with 12 to 36 gular grooves
Breathing is an act of mindfulness. It's not a reflex! The whale teaches its calf the rhythm of breathing.
Physiology
It can reach depths of 10 to 50 meters, with a record recorded at 616 meters in New Caledonia (Derville et al. , 2020).
On average, humpback whales remain apneic for 15 minutes, with a maximum record of 40 minutes.
Average size
Average weight
Average life expectancy
How to recognize it?
Its unique caudal fin enables identification. It's the equivalent of a fingerprint.
As it dives, its back becomes rounded, forming a hump.
Its 3-metre-high blast is shaped like a cauliflower.
Its pectoral fins are the most distinctive morphological feature.
World population
Humpback whales are found in all the world's oceans. The global whale population is now estimated at over 84,000 individuals. They are considered to be of “minor concern” (widespread and abundant) according to the International Union for Conservation of Nature (IUCN) Red List.
Polynesian Population
The Polynesian humpback whale population is currently estimated at between 934 and 1849 individuals, according to Poole and Baker. This is only an estimate, as the actual number of individuals is not yet known. It is considered “endangered” (very high risk of extinction in the wild) according to the IUCN Red List.
THE MIGRATION OF POLYNESIAN HUMPBACK WHALES
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Having arrived in the cold waters of the South Pole, some adults have lost up to 1/3 of their weight over the winter, living on their reserves alone. It's time to make new ones!
Some group together and form a net of bubbles towards the surface to encircle their prey, while others prefer to hunt alone, moving gradually with their mouths open and engulfing up to 6000L of water at a time.
It feeds mainly on copepods, small crustaceans, and krill, including the Euphausia superba
species that humpback whales love!
The mating, calving, nursing and resting periods take place in the tropical waters of Polynesia.
The humpback whale is commonly seen here from July to December.
These events are mostly observed in lagoons, bays and near barrier reefs, less than 2 km from the shore.
This allows them to shelter from potential predators, such as killer whales and sharks. Sometimes even from aggressive males.
Seasonal migration
~ 13 000 km (round-trip)
POLYNESIA
Breeding area
ANTARCTICA
Feeding zone
Did you know?
Humpback whale breast milk is over 4 times richer in calories than human breast milk, 8 times fattier, and 11 times higher in protein!
Thanks to breast-feeding, the whale calf will gain 45 kg per day for 6 to 11 months: in just 15 days, it has already doubled its weight!
According to some researchers, whales move by means of the Earth's magnetic field, the stars or prevailing ocean currents. But none of these theories have yet been verified. In any case, with a maximum speed of 8 to 20km/h, it will take them several weeks to reach their destination.
Whales push water away with their tongues, trapping their prey in baleen: they swallow up to 50 kg per mouthful! With nearly 1 tonne of food ingested per day, the whale quickly gains weight.
OBSERVING AND UNDERSTANDING SOCIAL BEHAVIOUR
IN HUMPBACK WHALES
The caudal strike
Repetitive vertical strokes of the caudal fin on the surface
Can indicate a presence considered undesirable: conspecific, boat, predator, etc.
In the presence of a whale calf, this is surely the moment of learning!
Caudal extension
Caudal fin and peduncle motionless or moving slightly out of the water
Potentially a refusal of a male's advances, a resting attitude or a possible role in regulating body temperature.
The pectoral extension
Pectoral fin out of the water, motionless or moving slightly.
Potential roles similar to caudal extension.
The pectoral strike
The animal rolls onto its side, raises one of its pectoral fins out of the water and strikes the surface several times.
This movement is described as an invitation. Females might use it to call a male or solicit competition in order to get rid of an unfortunate mate.
Forward projection
The head is held above the surface while the animal leaps forward, accelerating abruptly.
With its mouth sometimes filled with water, this may be an attempt to appear more imposing. This demonstration is usually made against a fellow species.
The spy position
The whale lifts its head vertically out of the water and rotates on itself.
This position enables them to observe the floating objects around them, and even locate and identify the nature of unusual noises (engine noise, turbine noise, etc.).
It is often observed close to shore.
Jumps
The whale propels itself two-thirds of the way above the surface.
Jumping allows the whale to rid itself of parasites on its skin.
It's also an extremely important means of communication
(courtship, alarm signal, deterrent).
HUMPBACK WHALE SINGING
The humpback whale's song is emitted only by the male at sexual maturity, from the age of 7. This song is used during courtship to attract females and/or repel other males.
The humpback whale is said to have the most complex song in the animal kingdom! The humpback whale's song is made up of notes, phrases (a succession of different notes) and themes (repetitions of phrases). The assembly of themes makes up the whale's song, which lasts on average between 5 and 20 minutes.
The particularity of this song is that it is transmitted horizontally, i.e. between individuals in close proximity, rather than from generation to generation. This is known as horizontal cultural transmission. In fact, several studies by C. Garland reveal that cetaceans are capable of modifying the sounds they emit as they travel. On an oceanic scale, from one country to another, the same songs were heard in : 2002 in Australia, 2003 in Tonga and 2004 in French Polynesia!
Around the island of Moorea, male singers tend to position themselves at the island's points, which are ideal for wide acoustic diffusion and thus reach more females for greater reproductive success.
THE ESSENTIAL ROLE OF HUMPBACK WHALES IN THE BALANCE OF ECOSYSTEMS
To test your knowledge and get even more content, you can visit the following site created by Léa Picon during her internship with the Oceania 2021 association.