Not to be confused with the Mahi-Mahi, a gamefish commonly called Dolphin, true Dolphins are warm-blooded, air-breathing marine mammals closely related to whales and porpoises. Dolphins are carnivores that eat mostly fish and squid. About forty species of Dolphin live in the shallow continental shelf waters of oceans worldwide. The Atlantic Bottlenose Dolphin is the most common species around Key West. Adult Dolphins vary in size from about 4 feet in length and 90 pounds in weight to 30 feet and 10 tons in the case of the Orca, or Killer Whale, the largest member of the Dolphin family. Dolphins live in family groups called pods, and female Dolphins bear live young called calves. Dolphins are among the most intelligent animals on the planet. They seem to enjoy interacting with humans at times, and guided Key West Dolphin Tours out to the shallow Backcountry waters to visit the Key West Dolphins are very popular with visitors.