Incredible But True Incredible But True Human World History Makers Cities Of The World Art And Music Sporting Headlines Plant Life Fish, Amphibians, Reptiles Birds and Mammals Creepy Crawlies Marine Life Restless Earth Earth's Secrets Changing Weather Seas And Oceans Comparisons Amazing Structures Machines And Man World Of Inventions Travelling Around Mysterious Universe	Heavyweight The blue whale is the largest animal on Earth. At birth it is already 6 to 8 metres long and weighs 2.99 tonnes. When mature it can be as long as 33.5 metres and weigh 190 tonnes.   Previous: Back Book: Incredible But True Section: Incredible But True Chapter: Birds and Mammals