Identification

• Dolphins are in the order cetacea and members of the delphinidae and platanistoidea families. There are 36 different species of dolphins.
  
  

Types

• While most dolphins live in salt water oceans, river dolphins live primarily in fresh water rivers. Another group of dolphins, sometimes called blackfish, are often referred to as "whales" by most people and include orcas and pilot whales.
  
  

Size

• Dolphins range in size but the largest dolphin is the killer whale, or orca, which grows up to 30 feet in length. The smallest dolphin is only 3 1/2 feet and is called the Heaviside's dolphin. Its weight ranges respectively from 4 1/2 tons to only 88 pounds.
  
  

Geography

• Dolphins are found in every ocean in the world and many large rivers as well. Some dolphin species are found only in very localized and specific geographical locations, while other species can be found in many oceans.
  
  

Considerations

• Six species of dolphins are currently endangered because of pollution, dwindling food supplies or habitat destruction. Other species are considered threatened, but the dolphins in the most danger right now need special attention. These endangered species are the baiji, vaquita, Hector's, susu, Amazon river dolphins and harbor porpoises. Scientists hope that with dolphin conservation efforts these unique dolphins can be kept from extinction.