More closely related to humans than fish, these air breathing,
warm blooded marine mammals give live birth and nurse their
young on milk. More than 70 species range from the 30m blue
whale (the world's largest creature) to the 1.2m Vaquita from the Gulf
of California.
Cetaceans possess a range of adaptations for aquatic life, including streamlined,
smooth bodies with few hairs, no external ears, flipper-like
forelimbs for manoeuvring, and a layer of insulating blubber. They are propelled
by an up and down tail motion, not side to side like a fish.
Humpback Whale.
The Humpback whale Megaptera novaeangliae is aptly named from the Greek 'megas' meaning
great and 'pteron', a wing, because of its huge wing like flippers. It is the fifth largest of the great whales.
Adult females 15m, slightly longer than males. A mature humpback can weigh 40 tonnes.
Humpbacks are generally blackish with white under and at
the sides. The flippers or pectoral fins often carry large barnacles, Golf ball protuberances
on the head are called tubercles. A long coarse hair which grows from the centre of each tubercle is believed to act as a sensor.
Each year humpback whales migrate from Antartic to the sub-tropical coastal waters of western and eastern Australia and South Pacific Islands
where they give birth and mate during winter and spring.
At least 2000 humpbacks migrate approximately 6000km to Australia's eastern
coast. Groups (or 'pods') of whales start to arrive in Southern Great Barrier Reef waters in mid-June and in the following weeks move further along the Reef.
Around September, the whales migrate south back to Antartic waters, many stopping for a period of time in Hervey Bay. Most Humpbacks have left
Queensland by late October.
Breeding
Antartic waters provide whales with their richest food source, but the cold water is too harsh
for newborn calves which have no protective blubber layer. So Humpbacks mate and give
birth in warmer waters.
Gestation takes 11-12 months. At birth, calves are about 5m long and weigh more than one tonne. A cow feeds her calf milk with an unusual high fat content (35 percent compared with 2 percent
for human milk). Hundreds of litres are drunk daily.
Calves are nursed until they are one year old and about 8m long. Humpback whales mature in
less than 10 years. Pods of mothers and calves are often escorted by
an adult male.
Feeding
One of the world's largest whales, the Humpback's bulk is supported by a diet of krill (shrimp
like crustaceans up to 5cm long), plankton and small fish. Humpbacks sieve food from huge volumes
of water using specialised fringed mouth-plates. These mouth-plates or
baleen are made of keratin (like our fingernails). Bristle edges form a mesh to filter food from the water.
These bristles give the baleen whales their scientific name Mysticetes,
Greek for 'Moustached whale'.
Humpbacks feed in the Antartic where food ios plentiful in preparation for their lengthy
northern migration. Anecdotal evidence suggests opportunistic feeding of
small bait fishmay occur along the migration path. Blubber reserves provide the bulk of
their sustenance during migration.
Humpback Whales
