The giant of the seas
Blue whales live in oceans all around the world. Some live in their own neighbourhood and don't travel very far. Others travel for thousands of kilometres every year. Nobody knows why some stay at home and why others travel.
The blue whale is the biggest creature on Earth. Adults are usually 30 metres long and weigh about 150,000 kg. Some can grow to 33 metres and weigh 200,000 kg.
The biggest land animal is the African bush elephant. The largest ever found was 10.6 metres tall and weighed 12,272 kg.
Although big blue whales are easy to spot in the water, it's quite difficult to study these big mammals.
Blue whales usually swim at about 10 km/h. But when they want to, they can swim at speeds of 50 km/h. They also dive 100 metres below the surface to eat and can stay down for 10 or even 20 minutes. It's not easy to keep up with them.
Luckily, there are ways to tell blue whales apart. Their backs have different patterns of blue and grey. Many blue whales also have patches of yellow algae called 'diatoms' on their tummies. These different patterns act like fingerprints - each is unique.
