Some interesting facts about dolphins are that they belong to the order Cetacea, are mammals that can live in either saltwater or freshwater environments, depending on the species, and have very good hearing and vision. Dolphins are intelligent creatures that also use echolocation to locate objects by the reflection of sound.
Dolphins are members of the same group as are whales. These animals are mammals that nourish their young with milk. An interesting feature in dolphins is that they are born with hair near the mouth area, but it falls off within 2 weeks after birth. Depending on the dolphin's species, it can have as little as eight or up to 250 teeth.
Because these animals are mammals, they need to breath air, especially while they sleep in the ocean. A dolphin's adaptation, which allows it to sleep under water without drowning, is that it uses half of its brain to sleep and the other half to stay alert. This ensures that it will rise up to the surface to get air.
There are more than 30 dolphin species that live in marine environments, and 4 that live in rivers. Dolphins tend to travel together in groups called pods. These animals can range in size from 23 to 3 feet. The largest dolphin species is the Orca, and the smallest is the Heaviside dolphin. The most common dolphin type is the bottlenose. Their diet includes small fish and squid. However, the larger dolphins, such as the Orca, can prey on penguins and seals.