The biggest dolphin is the orca or killer whale. Others species such as pilot whales and false killer whales are also dolphins as well as the seven species of porpoise.

Which is the smallest dolphin? In terms of length, the New Zealand dolphin and the vaquita (a species of porpoise) are probably the smallest at about 1.4 metres. However, in terms of weight the finless porpoise probably wins as the lightest cetaceans, reaching a maximum weight of 55kg.  Approximately 3,000 finless porpoises would weigh the same as one blue whale.

How long do dolphins live? In the wild dolphins can live for a long time. Orcas may live for 70 years or more. Bottlenose dolphins can live for at least forty years. Dolphins that are kept in captivity die much earlier than those living in the wild.

They use many sounds including clicks, whistles and squeaks to communicate.