Blue Whale – Balaenoptera musculus
The Blue Whale, also known as sulfur-bellied whale or giant whale, belongs to the family of the Rorqual and is therefore part of the infraorder of the whales. Balaenoptera musculus was first described by Linnaeus in 1758. It is the largest and heaviest known animal that has ever lived on earth.
Description, Anatomy & Characteristics
With up to 33.6m of length and over 200t of weight, the blue whale is the biggest and heaviest animal on earth. Females are 6% bigger than males on average on that occasion. Just its heart can weigh up to one ton. The aorta is 20cm in diameter. With 2 to 6 heartbeats per minute, the heart ejects between 2000 and 5500 liters of blood. Its total blood volume is up to 7500 liters.
Balaenoptera musculus has a dark blue-grey colouration with a lighter belly. In addition, his whole body is covered with light spots. Animals that have spent a long time in polar regions may have a yellowish couloration of the abdomen. This is due to harmless algae growth of the species Cocconeis ceticola. Therefore, it has also its further colloquial name sulfur-belly-whale.
In comparison with other whales, its fin is very small with 45cm. In addition, it lies very far back at the back.
Habitat, Distribution & Occurrence
The blue whale is widespread world-wide in all oceans, whereby it seems to avoid small seas, with narrow access. While it spends the winters in temperate and subtropical zones, it travels to the polar regions in summer.
Although its migration routes and feeding grounds are constant, little is known about reproductive areas.
As a sea dweller, it is rarely seen near the coasts. Accordingly, Balaenoptera musculus is rarely seen diving on the Canary Islands.
Feeding & Biology
Since it belongs to the parvorder of the baleen whales, its food consists mainly of plankton, krill and Copepods. However, it comes also before that it hunts small fish-swarms. On the food-search, it dives down in depths of approximately 100m. On that occasion, it consumes approx. 3,5t of food per day. Alone its main stomach section nearly contains 1t. In the winter months, it eats nothing and survives only thanks to its fat reserves.
The blue whale is to be seen usually a solitary or in mother-calf constellation. Larger accumulations are rare and can be led back to food-occurrences for example. There does not seem to be a social bond on that occasion.
Reproduction & Development
Balaenoptera musculus becomes sexually mature with an age of 5 to 6 years. Males have then a length of 22m, whereas females are already 24m long.
Before birth, females migrate to subtropical zones. After a pregnancy of 11 months, a calf, with approx. 7m of length and 2,5t of weight, is born. The nursing time is about 6 to 7 months. A weaning takes place during the migration into the food-grounds.
A female blue whale is pregnant on average every 2 years.