Volume 2 Whales, dolphins and porpoises are air-breathing animals that live in water. They are mammals, giving birth to live young.
Whales live in water for their whole lives.
Except in very exceptional circumstances, they do not come onto land. There are around 80 known species of whale, or cetacean as scientists call them. They range in size from the gigantic 100 foot blue whale down to some species of river dolphin that rarely exceed 4 feet in length. Some whales like the killer whale are not much larger than some dolphin species. Blue whales can weigh up to 150 tons, while a small porpoise may weigh as little as 50 pounds.