Blue whale - Ecology & Habitat

Young that grow at a rate of 90 kg per day

The blue whale is found mostly in cold and temperate waters, and it prefers deeper ocean waters to coastal waters. Like many other baleen whales, it feeds in cool waters at high latitudes, and generally migrates to warmer temperate and tropical waters to breed and give birth, although in some areas it appears that the species may be resident year-round.

Social Structure
Blue whales mostly travel alone or in groups of 2-3. Larger groups of up to 60 whales have been reported and are probably associated with feeding grounds. However, the blue whale has the most powerful and deepest voice in the animal kingdom, and its low-frequency sounds can travel in deep water over hundreds, or even thousands, of miles. Under these circumstances, animals which may appear to us to be traveling alone may actually be in constant contact with one another.

Life Cycle
At birth, a blue whale calf is the largest baby on earth: approximately 8 m long and weighing about 4 tons. They grow at a rate of 90 kg and one inch per day and wean after 7-8 months, once they have reached about 15 m in length, to follow the normal migration pattern alone. They reach sexual maturity at 5-10 years.

This growth rate is astonishing, and is probably the fastest in the animal kingdom. From conception to weaning, it represents an increase in tissue of several billion-fold in little more than a year and a half.

Like other baleen whales, the blue whale has no teeth so it is difficult to tell its age (teeth can be used to estimate age in other mammals). However, scientists believe they live until they are at least 50.

Breeding
Usually one calf is born, every 2 - 3 years. Recent evidence suggests however that the inter-breeding interval is shorter than before whaling occurred, possibly to increase the growth rate of the populations. Gestation is 10 - 11 months. Virtually nothing is known about the mating system.

Diet
During the summer feeding period, a blue whale eats about 40 million krill each day, amounting to about 3,600 kg (7,900 pounds). It expands its throat plates and takes in water with krill, then pushes out the water through the baleen plates, and swallows the krill that has stayed inside the mouth.