15/04/2015 06:02 BST | Updated 14/06/2015 06:59 BST

15 Interesting Facts About Dolphins

Our best friends of the sea, the dolphins have always been a great fascination to humans. They are friendly, happy and social animals and have been positively noted for their playful nature, intelligence and occasional help to humans, whether it is fishing or rescuing their lives! Here's 15 facts about dolphins that you might not know.

1. There have been 43 recognised species of dolphins! 38 are marine dolphins and the other 5 are river dolphins.

2. It has been researched that dolphins are're-entrants' and actually lived on land before adapting to the water. When studying their fins, scientists have found that they are actually formed like legs and toes. So maybe our closest sea friends were wolf-like land animals once.

3. Images of dolphins have been found carved into the desert city of Petra, Jordan. Petra was established as early as 312 BC, so given that estimation dolphins have been around for quite a long time.

4. Dolphins are the only animals give birth with the baby coming out tail first; the calf would drown if it was the other way.

5. Just a tablespoon of water in a dolphin's lung could drown it, while a human would drown after two tablespoons.

6. The blowhole of a dolphin is actually an adapted nose which has moved to the top of its head.

7. Dolphins can see with sound, they use their tell-tale clicks which travel long distances and bounce off of objects. This allows them to know how far away the object is and the shape, density, movement and texture of it.

8. Dolphin sonar is the best within nature and superior to bats sonar and man-made sonar.

9. While sleeping, a dolphin must stay at the surface so its blowhole is not covered with water and it only switches off one side of its brain to keep breathing and staying alert.

10. The Cove is an academy award winning documentary about the treatment of dolphins in Japan. It discusses cruelty towards dolphins and the strong risks of mercury poisoning from eating dolphin.

11. Dolphins were thought to be a lot smaller hundreds of years ago, it is also thought that echolocation is an evolutionary process and that dolphins haven't always had this ability.

12. Dolphins do not use their 100 teeth for eating, rather for catching the fish which they then just swallow whole. They actually don't have jaw muscles for chewing!

13. If you killed a dolphin during the time of Ancient Greece it was considered sacrilegious and was punishable by death. They Greeks called them 'hieros ichthys' which means sacred fish.

14. It has been recognised by scientists that dolphins give themselves names. They develop their own individual whistles and even after the tone of the whistle is changed the dolphins still recognised theirs and other dolphins' names.

15. Dolphins must tell themselves when to breathe; it's not an automatic response like it is for humans.

Dolphins are amazing animals, and they keep surprising us with their very intelligent behaviours. This Dolphin Day try to find out more about these fascinating animals and truly discover the extraordinary lives of dolphins!

By Fay Partridge

Check out 'Into the Wild' for more articles like this.

Fay Partridge is an Online Journalism Intern for Frontier, a non-profit conservation NGO that helps people plan their gap year with over 300 opportunities to volunteer abroad and take part in adventure travel across the globe.