Humpback Whale (Megaptera novaeangliae) Natural History

Anatomy
Humpback whales grow up to 50 feet (15 metres). The females are generally a little  larger than the males. At around a ton a foot they average around 40 tons or 80,000 pounds (36 metric tons). The tail flukes are huge and can be as much as 15 feet  (5metres) across from fluke tip to tip. The Latin name Megaptera novaeangliae translates to “Big winged, New Englander” in reference to their massive pectoral fins and the New England whaling days. The pectoral fins may weigh as much as 2 tons and are 15 feet (5 metres) long.

Colouration
The northern hemisphere population is distinct from the southern hemisphere population and the isolation of these gene pools is most noticeable by the colouration of the two separate groups. The northern population have generally more black colouration on their bodies where as the southern population have much more white colouration with a number of individual whales even being totally white.

Distribution & Migration of Humpback Whales
Humpbacks are found worldwide in both north and south hemispheres.
It is estimated the world population is around 15,000 whales. This represents less than 10% of the pre-whaling numbers. They are classified as an “endangered Species”. The northern Pacific population is estimated to be approximately 6,000 animals of which 4,000 visit the Hawaiian breeding grounds.

The two survival imperatives to which the humpback whales respond are eating and mating. The Hawaiian population live between their breeding grounds around the Hawaiian Island archipelago and the food rich waters of Alaska. The Hawaiian waters are virtually baron when it comes to a food source for the whales, although some opportunistic feeding has been observed. Areas like the Inside Passage of South East Alaska are extremely abundant in a bio-mass which can support the whales. However as the calves are born without a insulating fat layer the mothers must migrate to warmer water in winter to have their calves. Hence this amazing migration of 3,000 miles (4,800 kilometres) has evolved.

Mating & Calving
Humpback whale babies are 12 to 15 feet (4-5 meters) in length at birth weighing around 3,000 pounds (1.4 metric tons). The general thought is that these whales mate and give birth amongst the Hawaiian Islands. Neo-natal (new born) calves are frequently observed here. The gestation period is around 11 to 12 months with mums giving birth on a 2-3 year cycle but some may mate every season.

Researchers think the calves nurse for a year. The yearling are 26-30 feet (8-9 meters) in length. Mother’s milk is often compared to yogurt with an extremely high fat content which helps the calf grow rapidly and build up their protective layer of blubber. The calves will need this protective insulation when they migrate north to Alaskan waters with their mothers.

It appears that a third male whale is commonly seen accompanying the mother and calf in the breeding grounds. This animal is know as the primary escort and is most likely waiting for the female to come into estrous.  Mating has also not been directly observed, however it is generally thought mating occurs around the Hawaiian Islands.

Feeding
Humpback whales feed in Alaskan waters on a number of different prey species. They can be observed consuming huge amounts of krill and herring. They have developed a number of clever strategies to catch their prey. The krill are a shrimp like crustacean which teams in massive swarms. It is relatively slow moving and the whales use tools such as blowing bubble nets to surround the krill and force them into a tight ball before being totally engulfed by the whale’s open mouth.

The herring are some what more agile and cunning. The whales employ a group feeding technique to catch these schools of fish. Known as co-operative feeding or co-ordinated feeding, they work together like a gigantic football team to catch the herring. All the whales in these feeding groups have specific rolls. Some blow huge bubble nets, some make terrifying high pitched sounds to scare the fish into a tight ball. Others wave their white pectoral fins, flashing the herring. As the feeding event happens all of the whales come rocketing up through the school of herring and engulf them in one big action. The food filled water floods into their gapping mouths as they strain the water through plates
known as baleen which hang from the tops of the upper jaw. The food is then swallowed and the whales consume tons of food this way every day.

Identification of Whales
Research scientists have discovered that each  individual humpback whale has a unique pattern on the underside of their tail fluke, known as a “Fluke ID”. They are somewhat similar to finger prints on people, or even our noses. Each one is different and identifies each and every whale. The white is created from area on the skin which lack the black pigmentation. The fluke range from all white to all black with every conceivable variation in between. Scientists use these “Fluke prints” to reveal many of the mysteries of their migration and social interactions.

Whale Song and Communication
Humpback whales are perhaps most well known for the haunting sounds that they create. Sailors from yesteryear spoke of sirens calling to them from the depths of the sea. We now know these songs are produced by the whales. Humpback whales produce a range of sounds for social interaction and for manipulation of prey like a tool. Males in the winter breeding grounds are often observed hanging motionless in the water column, at an angle with their pectoral fins gently swaying back and forth as they emit powerful, evocative sounds. They shunt air around the air spaces in their bodies to produce moans, meows, clicks, squeaks and rumbles as they sing complex compositions which may be twenty minutes in length and are often repeated over and over for many hours in one song session.

A song in composed of a complex structure of notes in the form of tones and frequencies which change as the season progresses. In an extraordinary collaboration, all of the males in the one ocean basin, sing the same song, note for note during the same year. The song likely has a function which is related in some way to reproductive behaviour as it occurs most often in the breeding grounds.
 
Humpbacks also utilise infrasonic sound to communicate with each other. This is sounds well below our limit of hearing. The infrasonic sound wave carry long distances underwater and it is theorised that the infrasonic social sounds can be heard many miles away. Humpbacks also make a range of noises that’s can be heard by the human ear and often this chatter can be heard as animals interact.

Humpbacks also create high pitched feeding sounds, a “wild ghost” like noise which they use to scare herring into tight balls which can easily be consumed as the whales feed.

Social Whales
Humpback whales are extremely social mammals. The social behaviors vary dependent on where the animals are at the time. There is an extraordinary variety of different behaviors seen in the breeding grounds. Mothers are clearly demonstrative in their affection to their babies. They can be seen touching and caressing in a maternal interaction showing great sensitivity to each other. Calves can be observed suckling from the mammary slits on the lower ventral surface back near the tail.

The female is often the center of attention and the focus of much of this behavior. The females commonly have a male escort near by. He will defend his position as the primary escort as a primary challenger may confront him to displace him. If there are more than one challenger highly energetic and animated action usually follows as each male maneuvers to try and get in a position to challenge the Primary escort. Whales are regularly injured as competition gets aggressive.

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