Humpback Whale |
Rorqual à bosseMegaptera novaeangliae
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Length |
11 to 13 m, up to 16 m |
Weight |
25 to 30 t, up to 35 t |
sociability |
Solitary, often in pairs of groups |
Longevity |
30 to 50 years |
Dive time |
8 to 15 min, up to 30 min |
Observations |
Regular in summer in the Gulf, few regular visitors in the Estuary |
Worldwide distribution |
From the Arctic to the Antarctic |
Worldwide population |
Estimated at 35 000 |
Not at Risk |
Description
- large, stout body, black back
- big, flat head, lower jaw sports a number of round protuberances
- very long, white pectoral fin: one third of the body length
- large and widely spaced ventral pleats extend to navel
- When it surfaces: Its balloon-shaped blow, which is nearly as wide as it is tall, can attain a height of three metres. Its stocky back appears in a slow movement, followed by a variably shaped dorsal fin that often has a bulge at its base.
Acrobat, singer and traveller
Despite its round and stocky profile, this rorqual whale leaps and swims with elegance. It brings its tail out of the water with each dive. Easy to identify, researchers know a great deal about this species, particularly its migratory habits. Equipped with a rich vocal repertoire that is fundamentally linked to diverse social activities, it remains a fascinating study subject with many secrets yet to be discovered.
Population, range and habitat:
In the St. Lawrence: Humpback whales visit the coastal waters of the Gulf and Estuary in summer. They move around quite a lot and can be identified in several regions of the Gulf‹the Mingan Archipelago, Anticosti Island, the Gaspé Peninsula‹and Estuary over the course of a season. Observations by MICS researchers have revealed a rise in humpback whale visits to the St. Lawrence since the late 1990s, while visits to the Estuary have shown a tendency to be more numerous and of longer duration since 1999.
Migration: Over 7500 humpback whales leave their winter mating grounds in the Caribbean Sea every spring. They travel 5500 km to feeding areas in the North Atlantic Ocean and St. Lawrence River. They return south following the same route in the fall. These whales spend the winter in large gatherings, rarely feeding and living off their fat reserves.
Worldwide: The humpback whales that visit the St. Lawrence are members of the North Atlantic population that, according to the most recent studies, exploits six summer feeding grounds: the Gulf of Maine, Newfoundland and Labrador, the Gulf of St. Lawrence, Western Greenland, Southern Iceland and the Barents Sea. This population is estimated at between 11 800 and 14 300 individuals. Humpback whales are present in all of the world¹s oceans.
Behaviour:
Feeding: The humpback whale is a gulp feeder. It eats planktonic crustaceans (krill) and small, schooling fish such as herring, capelin and sand lance. It feeds alone or cooperates with others of its kind to hunt prey. Groups of these rorqual whales sometimes create bubble nets or clouds to scare or entrap their prey by exhaling beneath the surface. Bubble techniques are not used everywhere and vary from ocean to ocean. Such feeding strategies are taught by the mother, although learning can also take place between adults within the same population. When humpback whales occasionally feed at the surface, gaping mouths display baleen plates and the enormous throat pouches deployed by expanding throat pleats.
At the surface: Its movements are rather slow. Its pectoral fins are used for steering and maintaining balance. A wide range of aerial behaviours include breaches where an animal will leap above the surface to fall back noisily either on its back, belly or side; humpback whales can breach up to 30 times in a row. They are also known to slap their pectoral fins (flipper slapping) or tails (tail slapping) against the surface. Finally, humpback whales sometimes spyhop by slowly bringing their heads out of the water vertically. Certain individuals can be quite curious about boats. Humpback whales arch their backs as they dive, raising their tails slowly into the air to a vertical position. Thus, the ventral face of the tail becomes visible and every individual whale can be identified using the colouration pattern‹with a dominant white or black background‹, marks, scars, the overall shape of the tail and the jagged edge of each fluke.
While diving: Dives last on average five to 10 minutes, up to 30 minutes. These whales rarely dive deeper than 120 m.
Social behaviour: Predominantly solitary, humpback whales can also be observed in pairs or in small, rather unstable, groups. The humpback whale is the most socially active of the rorqual whales. The formation of small groups in summer is often associated to areas of high food abundance. Groups are also observed during migration in the fall. During winter, humpback whales form small, compact groups and sometimes larger gatherings during the mating period. In the summer of 2006, Pi-rat and Gaspar, two juveniles less than two years old, spent six weeks in the Estuary, often in tandem. When they returned in 2007, their association was less stable; Pi-rat spent 10 weeks in the area, Gaspar only spent eight.
Vocal behaviour: Competing males adopt aggressive behaviour and also sing long, melodious and complex songs to attract females and to establish dominance during the mating season. The songs are quite varied and are population specific. Results from a 2007 telemetry monitoring project carried out on western North Atlantic humpback whales demonstrate that individual animals emit sound pulse sequences over a large frequency band in association with night feeding behaviour. While humpback whales vocalize mainly to communicate, they may also use sound to ³read² their surroundings, orient themselves and identify large targets. These powerful, low frequency sounds can travel over great distances.