Species: Megaptera novaeangliae

Humpback whales belong to the family of baleen whales known as rorquals. These whales have long pleats (or grooves) that run from the tip of their rostrum to their navel on the underside of their body and a flat upper jaw.  Rorquals are generally streamlined and slender, though the humpback is stocky and rounded with very long pectoral fins. The long pectoral fins distinguish humpbacks from other baleen whales and is the reason for the Genus name Megaptera (meaning big-winged).  

Bundjalung name: Unknown

Status (IUCN): Least concern

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Characteristics

 

Length/size: Adult: 11-17m; Newborn: 4-5m

Weight: Adult: 25-40 tonnes; Newborn: 1-2 tonnes

Females tend to be 1-1.5m larger than males but it is difficult to determine females from males in the wild as both have internal sex organs. Sighting the genital slits on the under-belly is required to confirm sex. The male’s genital slit is located mid-way between the anus and the navel. The female’s genital slit is located in front of the anus and is separated by feature known as a hemispherical lobe. The presence or absence of this lobe is used for sex determination.

 

Colour: Humpback whales are black or dark grey on the upper dorsal side and they generally have large amounts of white on the ventral underside of their body, pectoral fins and tail flukes. Southern Hemisphere humpbacks tend to have more white on the underside of their body which extends further up the sides of their body. The unique black and white markings on the underside of the tail flukes are life fingerprints with no two being the same. Occasionally completely black individuals are seen in eastern Australian waters, and an all-white (probably albino) individual has been a regular visitor here in the past.

 

Shape: Humpback pectoral fins can be up to a third of the body length (approx. 3-5m) and have a series of bumps called tubercles on the leading edge. The dorsal fin is located approximately two thirds of the way back from the tip of the rostrum and is low and broad based, often sitting on a raised hump of tissue more obvious when they arch their back to dive. The tail flukes have a serrated trailing edge, these serrations along with markings on the underside of the tail fluke can be used to identify individuals. The rostrum is covered in golf ball sized lumps known a tubercles. Each tubercle has a stiff sensory hair or vibrissa around 1.2 to 2.6 cm long which has a rich blood supply and is connected to a nerve suggesting a function as a sensory organ – perhaps to detect current and temperature changes in the water to aid in navigation.

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Behaviour & Ecology

 

Diet: Southern hemisphere humpbacks feed almost exclusively on krill (small shrimp-like crustaceans), which occurs in vast quantities in Antarctic waters, but they also consume small schooling fish including sardines, herring, mackerel and anchovies. Humpback whales feed by taking take large gulps of water and prey. As they fill their mouth the throat grooves expand and the mouth balloons outward. When they bring their jaw together the throat grooves contract and the whale uses its tongue to force water through the baleen fringes and out the sides of the mouth. The fringes act as a sieve to collect prey which is then swallowed. Humpbacks usually feed in the top 100m of the water column mainly in polar feeding areas where there are large swarms of plankton. They have been observed feeding during migration however this is thought to be more opportunistic rather than a nutritional requirement.

 

Feeding Behaviour:  Lunge Feeding – where a whale comes up from a depth at an angle to the surface and takes a large gulp of water and prey. They have also been observed lying on their side swimming in circles with the mouth partially open so water flows through the baleen as it swims. Flick feeding – where the whale herds its prey and then flicks its tail to splash down in front of the school of prey and startling the prey so it remains still as the whale engulfs it Bubble netting – this is where a whale dives down, then swims up in a spiral releasing bubbles of air from its blowholes. The bubbles float up in a column forming a ‘bubble net’, keeping prey inside the column. The whale lunges up through the center of the column with its mouth open. People have seen several humpback whales lunge-feeding up through a “bubble net”, one at a time.

 

Ecology: Humpback whales occur in all oceans of the world and are separated into Southern and Northern hemisphere populations. The international whaling commission separated the southern hemisphere populations into 6 groups, 2 of which migrate along the east and west coast of Australia. The migratory route around Australia is close to the land usually at a depth of less than 200m and generally within 20km of the coastline.

 

Reproduction & Life History: Humpbacks whales are generally observed singularly or in small groups but larger groups of 10-15 are often observed in feeding and breeding areas. Life expectancy is recorded as at least 48 years but is likely to be significantly longer (up to 80 years) as shown in other balaenopterids. They are fully grown at around 12 to 15 years and sexually mature at 4 to 8 years (average 5 yrs), at a size of 11-12m. After 11-12 months gestation females give birth to live young. Individual females give birth every 2-3 years. Only 1 calf which is born at a time, fluke first. Calves are well developed and immediately able to swim. Calves stay close to their mother for the first few days to weeks and are suckled under the water close to the surface. Calves are weaned at around 11 months. Other adults known as escorts help protect calves from predators.

 

Behaviour: The humpback whales found off the east coast of Australia are part of the Southern Hemisphere population that generally feeds in Antarctica from December to April and migrates to the Great Barrier Reef to mate and give birth from June to October. They have a cruising speed of 8km/h but can reach 32km/hr in short bursts. In adults, dives usually last 10-15 minutes (sometimes up to 45 minutes) followed by 3-4 blows at the surface at 15-30 second intervals. Before a deep dive, they usually raise their flukes at the surface, known as a ‘fluke up’ dive. They are thought to dive to around 120 m. Their blow pattern is small and bushy and up to 4m high. Humpbacks are the most acrobatic of the great whales. Breaching, tail-lobbing, pectoral fin slapping and spy hopping are common behaviours. They often do full body breaches where their whole body is out of the water. Humpback whales can be highly active at the surface with breaching, pec slapping and tail slapping, particularly at the breeding grounds.

 

Communication: The male humpback whale is famous for its extraordinarily long and complex songs which travel very far throughout the oceans. These submarine songs, composed by several elements, can last for hours. They are specific to different populations and can be heard hundreds of kilometres away. Scientists think that the humpbacks do this to communicate with other whales and to potentially attract a mate. Humpback whales also produce a variety of different sounds for communication including low frequency grunts, moans and groans.

 

Threats: Humpback whales were subject to intensive commercial hunting until their protection in 1965 following the collapse of populations across the southern oceans. In Australia, they have been protected since 1965 and have continued to increase in abundance each year. They are one of the few species that have returned from the brink of extinction, yet their future remains uncertain due to a cocktail of threats from human activities. Human threats include: Entanglement in fishing gear and shark nets, boat/ship strikes, whaling, pollution, climate change, ocean noise, unsustainable tourism and overfishing. Killer whales and sharks can also prey on calves and sick/injured whales.

 

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