Sea animals have always been a source of curiosity for humans, particularly because of their beauty and intelligence. While most of them are wild and deadly, some of them are inherently unique in their own ways. Whales, sharks, and dolphins are subjects of intense research among marine biologists. Dolphins stand out from whales and sharks owing to their peculiar, friendly behavior with humans. Origin These marine mammals are mostly believed to have been evolved from land mammals some 50 or 60 million years ago. Among aquatic mammals, dolphins are the most advanced and adapted to aquatic life. One surprising and interesting fact is that dolphins are the closest relatives of the hippopotamus, camel, and cow family. The debate about the origin of dolphins and whales is an unending one. Some believe that dolphins have evolved from land-based hoofed mammals (ungulates) like hippos, while some believe that they have evolved from mammals millions of years ago. Types There are about 32 types of dolphins and all are unique in their color and body constitution. Looking at them together will really fascinate anyone. While these 32 types thrive in salt water, there are some types of dolphins who live in the freshwater. Some of these are the Ganges river dolphin, Yangtze river dolphin, Amazon river dolphin, and the Irrawaddy dolphin. The Bottlenose dolphin, the Killer Whale, the Common dolphin, the Black dolphin, and the Dusky dolphin are some types of marine dolphins. Eating Habits An adult dolphin eats nearly 20 to 22 kilos of fish every day. The eating habits of dolphins are dependent on the area where they thrive and the season of the year. Seasons in which fish like mullet, mackerel, herring, and cod are found abundantly are the best feeding times. Depending on the fat content of the fish, the dolphins decide how much they are going to eat. They have a good sense of understanding about their hunger. Life Expectancy The bottlenose dolphin is the most studied species, and according to research, the life expectancy of a bottlenose is about 40 to 50 years. Generally, on an average, dolphins live for about 17-25 years. However, as mentioned earlier, they can live up to 50 years without veterinary care. The reason for their agility is their natural way of evolution that has given them a healthy body. Dolphin and Human Relationship Dolphins are very much interested in humans just like we're interested in dolphins. Many sailors and people traveling in boats are known to spot dolphins popping their heads out and looking at them. Not surprisingly, many cultures of the world worship and respect dolphins as the symbol of agility, health, and joy. The socialization and intelligence skills of dolphins have intrigued man, as they have been used in zoos and exhibitions to show off their amazing diving skills and intelligence. They communicate with each other by special frequency sounds, similar to sonar equipment. More Facts Some dolphins are endangered species, but they evoke a sense of curiosity among people. The following are some more interesting facts about dolphins.

• The echolocation abilities of dolphins are better than any human made sonar system. The US Navy uses these animals as their helpers in locating lost divers.
• Dolphins can recognize themselves in a mirror.
• They are known to do a sonar scan for objects in the water, and they can know about the distance, shape, and size of the body approaching.
• Dolphins have healing powers and they're known to cure ailments in humans.
• Dolphins generally sleep with one eye open.
• They are known to have fun in the sea; they love to irritate turtles and other animals in the sea by rolling over their back and running away.
• A group of dolphins living together is called a pod.
• Orca, commonly known as the killer whale, is the largest known type of dolphin.
• Like we are identified by our thumbprints, dolphins identify each other by their whistles.
• These creatures can go to a depth of about 260 m below the sea level.
• The scientific name of the dolphin family is delphinidae.
• These creatures give birth to their young ones by rotating fast in the water. The young ones come out with their tails first to ensure that they're not drowned.
• Dolphin, in Greek, means fish with a womb.
• The weight of a dolphin's brain is nearly 1700-1800 grams while that of humans is about 1200 grams.

These were some fun facts about dolphins, who are definitely interesting and intriguing animals. Unfortunately, some dolphins have become endangered and it is our responsibility to protect them from disappearing completely. It's a call for humanity.