The largest creature ever known to have existed on earth is the present-day blue whale. The largest dinosaur attained a length of about 22 m and weighed about 36 tons. Today's blue whale, even larger than its ancestors, may reach a total length of 33 m and a weight of 145 tons.
This giant animal is placid and shy. On the ocean surface, its normal cruising speed is about 12 knots, but it is capable of attaining 20 knots in short bursts. The maximum reported depth reached by the species is 194 fathoms. It is capable of remaining submerged beneath the surface for 50 minutes, although 10 to 15 minutes is more typical. The life span of a blue whale is about 30 years.
The calves measure 7 m at birth and weigh about 2 tons. By the time they are a year old, the youngsters meaasure 18 m.
These enormous mammals eat tiny organisms, like plankton and krill, which they sieve through baleen. They live in pods (small groups). These gray-blue whales have 2 blowholes and a 2-14 inch (5-30 cm) thick layer of blubber.
REPRODUCTION
Blue whale breeding occurs mostly in the winter .The gestation period is about 11-12 months and the calf is born tail first.The newborn instinctively swims to the surface within 10 seconds for its first breath; it is helped by its mother, using her flippers. Within 30 minutes of its birth the baby whale can swim.Twins are extremely rare. The baby is nurtured with its mother's fat-laden milk (it is 40-50% fat) and is weaned in about 7-8 months. Calves drink 50-200 pounds (23-90 kg) of milk each day. The mother and calf may stay together for a year or longer, until the calf is about 45 feet long (13 m). Blue whales reach maturity at 10-15 years.
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