Breaching

Humpback whales are renowned for their acrobatics. They can use their powerful tail to gain enough power and momentum to move up through the water and propel themselves into the air. This behaviour is called breaching ¹ .

Swimming

The dorsal fin of a humpback is like a surfboard fin; it helps keep the whale upright while swimming through the water ¹ . The dorsal fin is critical in helping whales swim huge distances. During the austral winter - from June to October each year - humpback whales make a 13,000km round trip from polar summer feeding grounds to tropical winter breeding grounds in Western Australia's Kimberley region.

The migration is a dangerous journey, driven by the need to procreate, give birth and care for their calves. Humpback whales feed in the Antarctic during the southern or austral summer and breed in the Kimberley during winter. Humpbacks almost never feed while away from the Antarctic continent, but in Australia on the east coast migration, humpback whales feed at Eden ² in southern New South Wales, which is a unique occurrence.

Breathing

When humpback whales breathe they exhale air from their lungs at a speed in excess of 480 kilometres per hour ¹ , almost the same speed as a cruising jet aircraft ² .

While exhaling and inhaling at the surface, the blowholes are held open wide but when they submerge whales consciously shut these blowholes, which now appear as two divergent lines. Humpback whales also keep their blowholes held tightly shut while sleeping. If they didn't they would drown.

Along with other marine mammals, humpback whales possess physiological characteristics that allow them to live in the marine environment. One of these is their voluntary respiratory system which maintains control over their blowholes as they surface and dive. This is known as conscious breathing ³ .

Other physiological characteristics for marine living include:

• Enormous lung capacity. Their lungs are proportionately larger than in humans.
• Whale or 'cetacean', muscle contains greater amounts of the oxygen-binding protein myoglobin, found in the muscles of all mammals. So cetacean muscle can store extra oxygen to compensate for lack of fresh oxygen while diving ⁴ .
• The ability to prioritise blood circulation to core body areas where oxygen is essential, such as the heart, brain and swimming muscles ⁴ .
• A higher tolerance to carbon dioxide allows the whale to hold its breath longer. Carbon dioxide levels trigger a breathing response that brings the whale to the surface so it can replenish its oxygen supply.

Conscious breathing and maintaining blowhole control can be seen in some behaviours observed in humpback whales. Often, whales in active, combative and competitive pods deliberately exhale loudly at the surface producing trumpeting sounds ⁵ .

Other whales create bubble trails by exhaling while swimming underwater. These trails can be aggressive behaviours directed at other bull males but are also used as protection by whales to hide from unwanted attention ⁶ . Bulls forming bubble trails beneath the belly of a female appear to express mating potential and desire ⁷ .

Feeding and Singing

Cetaceans such as whales, dolphins and porpoises, are classified into two orders: the Mysticete or Baleen whales and the Odontocete or toothed whales ¹ . Humpback whales are Baleen whales, meaning they use baleen to filter when feeding. The ventral pleats on the underside of its belly allow a humpback's mouth to expand enormously while filtering and feeding.

Humpback whales are filter feeders. Swimming through dense krill patches ³ , tonnes of water and krill are taken into the mouth and as the water is forced out again the small prey is filtered through the baleen plates hanging from the upper jaw into the lower mouth cavity. The huge tongue then comes forward and scoops the krill and small fish into a food 'bolus' for swallowing. The humpbacks' baleen filters are made of keratin, a fingernail-like material that is grey coloured and approximately 65 cm long. On average humpbacks have 330 baleen plates. Krill, or Euphausia superba, is the keystone species of the Southern Ocean Antarctic ecosystem and humpbacks - and many other species of whales, seals, penguins and seabirds - feed voraciously on these small crustaceans during the austral summer months ⁴ .

As humpback whales feed they open their lower jaw many times. The weight of large volumes of water contained within the mouth, and the repetition required for filtering up to 1.5 tonnes of krill each day, exerts huge pressure on the lower jaw, or mandible. To cope with these physical stresses, whale jaws are uniquely shaped and the bones possess varied 'flexural' rigidity, which means resistance to bending. The highest flexural rigidity is at the edges where the jaw attaches to the skull and the lowest flexural rigidity at the centre of the jaw ⁵ .

A unique feeding method employed by Northern Hemisphere humpback whales is bubble net feeding ⁹ . In pods of up to 20 they carefully work together in a coordinated fashion: ¹⁰ one whale dives down towards small schooling fish, such as herring, krill and capelin, and circles round the prey while exhaling. These exhalations from the "bubble-blower" whale become a bubble-net as they rise to the surface. Another individual makes vocalisations to scare and herd the prey into a tight ball within the bubble-net. The whales then position themselves beneath the bubble net and lunge towards the surface with their lower jaws open and extended. This co-operative feeding, showing complex social interactions ¹⁰ , is a truly wonderful sight to witness.

Only male humpbacks sing. They do so to attract females at the breeding grounds and advertise their availability and likely virility through the prowess of their songs. Composed of lilting and at times haunting sounds, a song comprises themes, phrases, sub-phrases and units ¹¹ , with most songs being up to 30 minutes long ¹² . Each population in the world has a unique song signature ¹² and the song changes annually.

Western Australian scientists collected songs in the early 1990's and shared these recordings with researchers on Australia's east coast. When they compared the east coast recordings they found that something unique had occurred. In 1996, two whales in the east coast data were singing the west coast song. The next year half the whales in the breeding season were singing the WA tunes, and by 1998 ¹³ almost all the animals recorded were singing WA's song. This was deemed a cultural revolution rather than a cultural evolution, because the changes occurred so quickly. The cause of the change was deemed a novelty: east coast whales seemed interested in experimenting with a new song, perhaps to increase their mating chances and opportunities?

Head Lunging

Male, or bull, humpback whales use their chin plate as a weapon against other competing males by landing right on top of them in a head lunge. Head lunging, or head slapping as this behaviour is also known, is extremely aggressive.

Scientists believe that the sensory tubercles on a humpback's head allow it to sense information about its environment, such as water temperature and quality. These tubercles are well innervated ¹ (meaning they have a good nerve supply) and well vascularised ¹ (they have a good blood supply). Scientists also believe the central single hair cell may play a role in courtship, be a navigation aid or assist in finding food ¹ .

Humpback whales are marine mammals. Three main features define (all) mammals.

These are:

• They possess hair.
• They breathe air.
• They provide milk and parental care for their young ² .

The humpback whale is a warm-blooded mammal. They breathe air, provide milk and care for their young and their hair is found in the single hair cell on its flat plate-like upper jaw in each of the bumpy sensory tubercles. These tubercles form patterns in their number and position and are unique to each individual ³ . Often there is a line of approximately five down the centre of the upper jaw - from the splashguard forward; then another line of three or four longitudinally and either side of the central line. Since the phalange bumps on the leading edge of the pectoral fins appear to assist with mobility when swimming, it would be interesting to investigate if these protuberances on the head assist with surfacing by breaking the water flow.

Pectoral Fin Slapping

Humpback whales slam their large pectoral fins on the water in a behaviour known as pectoral fin slapping ¹ . This highly visible and audible display can be a means of communicating and broadcasting their presence to other whales in the area.

Female humpbacks may pectoral fin slap to encourage males to interact with them but it can also be a sign of aggression towards unsolicited bulls ² . At the breeding grounds, males also use pectoral fin slapping to strike each other or slap the water as warning signals or displays of strength.

As with many behaviours, the context of the display helps with interpretation. For example, humans use their hands and arms to hug or fight and whales use their pectoral fins similarly. Females often lie on the surface and by waving and slapping their pectoral fins advertise their availability for mating. Whacking a 5 metre long, 1 metre wide pectoral fin on the surface of the water makes a huge noise and is a very effective advertisement! But by the same token, striking out with their pectoral fins can discourage unwanted attention.

Spyhopping

Humpback whales have very good eyesight but, when swimming, can only look down. However, they sometimes stand vertically out of the water to look at their surrounds. This behaviour is called Spyhopping ¹ . It is a beautiful behaviour to observe as the animal moves very slowly, with supreme control of its enormous body.

Humpbacks use different parts of their eye lens in different environments. For example, when underwater they use the centre of the lens and when looking in air they use the periphery ² . At the surface, curious whales appear to tilt their head to the side when looking - this is the whale using the periphery of its lens to observe.

The Tail

A humpback's tail is the powerhouse that propels it through the water. The tail and two lobes either side, called flukes, are positioned horizontally and move up and down ¹ . Sharks and other fish have vertical tails that propel them forwards with a side-to-side motion ² . A whale's tail is also its most powerful weapon and can be used effectively against predators, such as sharks and killer whales.

Photo-identification data requires three photos of each whale: the tail fluke, left dorsal fin and right dorsal fin. This process is not unlike the three mug shots police take to identify suspects. Long-term photographic identification is a tool used for comparison both within and between research seasons. This allows scientists to match individuals and produce population estimates ⁴ . Matching images and finding the same whale twice is called a 're-sight' and provides vital data about area usage. In this way we can identify critical habitats, such as resting areas or calving grounds ⁵ and recommend they be set aside as marine protected areas, like Camden Sound Marine Park.

The Dorsal Fin

A humpback whale's dorsal fin is positioned two thirds of the way along its back and provides a stabilising effect while swimming ¹ . This is particularly beneficial for its extensive migrations, helping to reduce the amount of energy required to travel these long distances.

Each humpback whale has a distinctive and uniquely shaped dorsal fin. When scientists work with a pod a name is given to each of its members, usually based on the shape of its dorsal fin, which is easily visible as the whale surfaces. Humpbacks are so-called because of the distinct fleshy ‘step’ located in front of its dorsal fin ² .

The humpback whale dorsal fin is a unique structure. There are no bones in the fin, it is fleshy but is stiffened by connective tissue ¹⁰ . Pregnant females appear to have extra flesh in the step in front of the dorsal and in a lump behind the blowholes.

Killer whales, or orca, are apex ocean predators that hunt in packs of 12-15 animals to target individual whales. These include blue whales, fin whales, gray whales, humpback whales and minke whales, as well as many species of dolphins, porpoises, seals and sealions ³ . Over the last few years off the coast of Western Australia, particularly in the Exmouth region ⁴ , attacks by killer whales on humpbacks have targeted very young calves ⁴ . Killer whales will also attach their large peg-like teeth to the trailing edge and tips of a whale’s tail flukes. By slowing it down and harassing it the orcas attempt to drown the whale.

In the past, on Australia's east coast, a unique relationship existed between the Davidson family, who were whalers, and killer whales, especially one they named 'Old Tom'. The orcas helped the Davidsons find the humpbacks and in return Old Tom and his pod received the first spoils - the humpback whale’s tongue ⁵ .

Barnacles are 'sessile' filter-feeders. This means they attach themselves to a surface with their head – it could be a rock or just as easily a passing whale - and then hang their legs in the current to feed. "Bristle-like" cirri are extended into the surrounding water flow ⁷ where they collect plankton, including both small plants (phytoplankton) and small animals (zooplankton). Barnacles are one of several ectoparasites that attach to the rough, knobby skin of humpback whales. In cold water humpbacks are infested with up to half a tonne of acorn and gooseneck barnacles, most of which tend to drop off as the whales move into warmer water ⁸ .

Whales can use barnacles as weapons. During fights, as the whales collide with each other, the razor–sharp barnacles attached to their skin inflict wounds on their opponents. It’s an unusual relationship, perhaps symbiotic, and each member profits. Whale lice, Cyamis boopis, are tiny crustaceans that replace barnacles once humpback whales reach warmer seas. They inhabit the corners of a whale's mouth and along its lips ⁸ . Sick and injured humpbacks can become entirely infested with these pink, star-like crab relatives.

The Blowhole

Humpback whales breathe through what is known scientifically as a 'diagnostic paired blowhole', positioned on the topside or dorsal surface of their bodies. With each breath air is expelled and almost instantaneously inhaled, creating a very efficient exchange of oxygen.

When whales exhale, their warm breath condenses as it hits the cooler surrounding air. This creates a tell tale ‘blow’ through their 2 nostrils, or nares, that can rise up to 3 metres into the air ¹ .

Whale researchers scan the horizon for these blows as they search for whales. Water often laps over the fleshy splashguard located in front of the two blowholes and is vapourised along with the condensation and mucus from within the lungs, making the blow even more visible.

The lung capacity of humpbacks is enormous; they can inhale almost 7,500 litres of air in a single breath. Their lungs are also very efficient, they exchange up to 90% of their lung capacity ² . Humans only exchange up to 13% ³ .

Humpback whales store oxygen in their muscles, enabling them to stay submerged for up to an hour and dive to depths of 240 metres ⁴ . However, humpback whale statistics pale in comparison with sperm whales. Sperm whales can dive to 3000 metres, staying underwater for over 2 hours ⁵ .

The Ventral Pleats

Humpback whales belong to the group of whales classified as rorquals ¹ . The word rorqual is Scandinavian and means 'furrow whale'. This is a direct reference to the large skin folds situated on its underside and extending from the mouth to the belly. Humpback whales have 12 - 30 of these throat grooves, or ventral pleats ² .

Although humpback whales are classified as rorqual whales due to the presence of the characteristic ventral pleats, they are more robust and rotund than the other more slender rorqual whales. The ventral pleats allow the mouth to expand during feeding so it can gulp vast mouthfuls of krill ⁴ . The humpback's enormous mouth, or buccal cavity, is up to two-thirds the length of its body ⁵ .

Humpback whale songs are the most complex in the animal kingdom ⁷ . The process by which a humpback produces sound and song is still unknown, but ongoing research has given scientists more understanding ⁸ . Humpbacks possess a larynx but don't have vocal chords. Some researchers have compared a human larynx with that of a humpback calf. The study determined that these two organs were not dissimilar and that a humpback's larynx was indeed capable of sound production. It's believed that sound may be produced when air flowing from the larynx passes the u-fold, which is aligned parallel to the airflow. Vibrations are caused within the air column inside the larynx, or the laryngeal sac. The vibrating air could then create pressure changes that are transferred through surrounding tissue into the water.

The Chin Plates

Humpback whales have knob-like protuberances on their heads, or rostrums. In fact, at one time their English name was the knucklehead whale ¹ .

These lumps are called sensory tubercles ³ . and are sensory nodes, each with a single central hair cell measuring about one and a half centimetres long. It's thought that the sensory tubercles could be involved in assessing water temperature and quality.

The Pectoral Fin

A humpback whale’s long, highly mobile pectoral fins are this species' main distinguishing feature. They are up to one third of the animal’s body length and in some are almost 5 metres long ¹ .

Humpback whales possess the longest pectoral fins of all the great whales and because of this have been classified in their own Genus, Megaptera.

Humpback pectoral fins have swellings on the leading edge called phalangic bumps. Although their function is not entirely understood, research indicates they give the fins special hydrodynamic properties, aiding movement through the water by providing better control and manoeuverability ² . Pectoral fins provide steerage and allow humpback whales to 'fly' underwater.

Humpback whales use their pectoral fins in many different ways, and the context within which displays are exhibited often gives clues to the purpose. For example, gentle caressing between a cow and calf indicates nurturing, while swinging wildly towards another whale is an aggressive behaviour.

Like tail flukes, pectoral fins can be used as a weapon against lurking predators ³ . Humpbacks also use their pectoral fins in fights between bull whales when competing for available females. Some whales, with extensively damaged tails, have been observed using their pectoral fins like oars - literally rowing themselves through the water.

The pectoral fin contains similar bones to those found in human arms ⁴ . In fact, the humerus, radius and ulna bones are present in cetaceans, just as they are in the forelimbs of most other mammals. Slight changes include the shortening and widening of these three bones, while the elbow lies flush with the body and the upper arm. Another difference is the humerus is attached to the scapula but is buried in the blubber ⁵ .

The Eye

Humpback whales inhabit a saltwater environment but also spend time on the surface. They also swim at a range of depths and migrate through tropical and polar climatic regions. To cope with all these different environments their eyes possess several unique features.

Humpback whales have brown coloured eyes about the size of a large orange ¹ . Soft folds of skin shield the eye, giving it an intriguing appearance. Different features equip humpbacks' eyes for their lives at sea, including the fatty eyelids and the ability to release a liquid that coats and protects the eye from salt water and other marine debris. Humpbacks have exceptionally good eyesight, both above and below the water. They possess a fibrous reflective lens called a 'tapetum lucidum' which assists with vision at night. This reflective structure is behind the retina and is remarkably similar to that present in cats' eyes, which glow green in the dark.

Researchers suggest that like humans, humpbacks have rods and cones in their eyes. Rods and cones are a specialised type of neurone (nerve cell) found in the retina, capable of phototransduction – converting light into electrical signals for the brain. The major difference between whales and humans is the proportion of rods to cones. Cones, in particular L-cones (long cones, sensitive to light of long wavelengths at the red end of the spectrum) only form 1% of the cetacean retina ² . Due to the low number of these cones in humpbacks' eyes, scientists believe that they cannot distinguish colour.

The Skeleton

Information about the whale skeleton has been divided up into the skull, pectoral fin, vertebrae, hip bone and tail.

Skull

Humpback whales are rorqual whales, possessing the characteristic throat pleats from the chin to the belly ¹ . Generally rorqual whales are streamlined, like other members of the Family Balaenoptera, including the blue whale,fin whale, bryde’s whale, omura’s whale, northern minke whale and Antarctic minke whale ¹ . Humpbacks differ from the other rorquals because their body is more rotund and robust, narrowing rapidly in front of the huge tail flukes ² . The skull differs noticeably too, with a very curved lower mandible ⁴ and the head being broad and rounded. The humpback's skull can be up to one-third of its total body length ³ .

Pectoral Fin

The pectoral fin of a humpback is not unlike the human arm ⁶ . The pectoral fin consists of several bones that are also found in humans, such as the humerus (the upper arm), radius and ulna (in the forearm), as well as the phalange bones which are similar to our finger bones. At the very tip of the pectoral fin is a collection of metacarpals (wrist bones) phalange bones (finger bones) and even a thumb-like bone ⁷ .

Vertebrae

Whales dolphins and porpoises have four different types of vertebrae: cervical vertebrae, thoracic vertebrae, lumbar vertebrae and caudal vertebrae.

There is a distinct variation between the Mysticete whales (baleen whales) and the Odontocete whales (toothed whales) in the number of thoracic, lumbar and caudal types of vertebrae.Generally, baleen whales possess more lumbar vertebrae and fewer caudal vertebrae and these are also smaller than in toothed whales. On average a humpback whale has7cervical vertebrae, 14 thoracic vertebrae, 10 lumbar vertebrae and 22 caudal vertebrae, giving it 53 vertebrae in all.

In contrast, dolphins, which are toothed whales, tend to have more caudal vertebrae, as well as more vertebrae overall, for speed and agility.

Hip Bone

It's believed that land-based mammals are the ancestors of marine mammals ¹⁰ , and indeed modern marine mammals retain some physical features. Cetaceans have vestigial pelvic bones – bones that appear to have become useless, but have been retained as the species evolved ¹² . Despite the apparent lack of need for a hipbone or pelvis in modern cetaceans, it appears two purposes might be served. First, during pregnancy, which in humpbacks lasts 11 to 12 months. It’s believed that during this period, while the foetus is developing in utero, (which means in the uterus or the womb) the unborn young is supported by the mother’s hips ¹⁸ .

Secondly, new research indicates that inon male dolphins the vestigial hip bones serve as an anchor for muscles manoeuvring the penis ¹⁹ .

Tail

A humpback has vertebrae extending from the chin to the tail but the vertebrae do not support the centre of the tail, nor are there any bones in the two lobes of the tail flukes ²⁰ . The tail in humpback whales consists of two broad flukes made of cartilage measuring up to 5.5 metres from tip to tip ²¹ .

A complex counter current blood system operates ²² in the tail flukes and this helps maintain a constant body temperature and even cools the whole body. 'Vasodilation' is where blood flow is increased to the peripheries ²³  of the whale’s body, such as close to the skin in the tail flukes. As it flows near the skin surface the blood cools, which in turn cools the body. To increase this cooling effect humpbacks sometimes hold their tail flukes high in the air. This behaviour is called tail sailing ²⁴ and the cooling is especially effective in a fresh breeze. Elephants use a similar cooling technique as they circulate blood through their large ears.