[判断]  CETACEANS: FACT FILEThere are over 80 species of whales, dolphins and porpoises, known collectively as '"cetaceans", throughout the world. They come in all shapes and sizes. Here are some facts and figures, about these incredible animals. 1. LargestThe blue whale is the heaviest and longest animal on Earth. The average adult length is 25m for males and 26. 2m for females, with body weights of 90-120 tonnes.2. Smallest Hector's dolphin is the world's shortest cetacean. They may be only 1. 2m long when fully grown.3. Largest AppetiteA blue whale eats up to 4 tonnes of krill daily. This is equivalent to eating a fully grown African elephant every day. 4. Deepest Dive The sperm whale is believed to dive deeper than any other cetacean. They have been known to dive as deep as 2000m.5. Longest LivedOne bowhead whale is reported to have been 130 years old when it died.6. Heaviest BrainThe sperm whale has the world's heaviest brain which can weigh up to 9. 2kg. This compares with the average 1. 4kg for the brain of an adult human.7. Most EndangeredThe baiji dolphin, or Chinese river dolphin, is the rarest dolphin in the world and is reported to be endangered. It lives in the Yangtze River in China. Conservation measures are being taken by the Chinese to save it.