The Dolphin is a mammal even though it lives its whole live in the water. There are alot of dolphin species in the world today, but most of them live in Australia. The Amazonian River dolphin is the smallest of the dolphin species at five feet long. It weighs only 100 pounds. The largest is the Orca. Male Orcas grow to 18 feet in length, and are 19,000 pounds. Alot of the dolphin species have a long life. Some dolphins once have lived for more than 100 years. Dolphins eat squid, fish, and crab. No body knows the exact population of the Bottlenose dolphin, for example. They just know that they are endangerd. Their populations are dwindling because of boating and fishing accidents.