Sea Mammals
Blue whales:
The
blue whale is the biggest animal that ever lived. They grow upto 30m (98ft) as long as three buses end to end and much larger than elephant or giraffe.
Blue whales are also world's heaviest animals. They weigh upto 190 tonnes-as much as 2000 heavy men or 52 buses.
Blue whales feed on some of the world's smallest creatures- Krill, a kind of small shrimp. They have no teeth. Instead they take a huge gulp of water and sieve the food through their baleen plates, swallowing upto 1000 kg (2205ibs) of food at each meal.
A new born blue whale calf is about 7 m (23ft) long and weighs upto 3 tonnes. By the time itis a year old it weighs about26 tonnes, which means it puts on about 2.5 kg (5.5ibs) every hour!
Blue whales spend the summer feeding in the icy waters of the Antartic or Arctic. Then thet swim about 15000 km (nearly 10,000miles) to the tropical waters near the equator to breed. But there is very little food for them in the tropics. They have to live off the fat they put on in summer.
Dolphin language:
Dolphins are a kindof whale. They use a range of high-pitched clicks, groans and whistles to communicate with each other. Dolphins are short-sighted and they also use these sounds to help them find their way. Like bats they can tell from the returning echoes how close they are to the submerged mountains, rocks and other things.
A dolphin nick-named Pelorus Jack, used to swim with ships through part of Cook Strait in New Zealand. He would meet a ship at one end of the Strait and escort it part of the way. Pelorus Jack did this for 24 years before some one shot at him in 1912.
Seals and walruses:
Seals and walruses spend part of their lives on land. The fins they use for swim become legs for walking.
Walruses use their long tusks to dig out shellfish from the seabed. They also use them to haul themselves outof the water onto the ice.
Humpback whales:
As humpback whales migrate to warmer water, they sing. The song gradually changes as they move along, but as they set off on the return journey back to the poles they take up the song where they left off.
Humpback whales scratch themselves against under-sea rocks to scrape off the barnacles that cling to the skin.
Dolphins:
Dolphins are a very intelligient creature. For some reason they seemto like humans and willoften play with swimmers in the sea.
Sperm whales:
Sperm whales dive deep to catch giant squid, octopuses and other prey.They dive upto a km below the surface and can stay under water for 1.5 hours.
Killer whales:
Killer whales hunt in pack. They attack penguins, seals, fish and even other whales. They eat them with their sharp teeth. Killer whales donot attack human beings. Killer whales can swimupto 55kph (34mph).