Perhaps one of the most renowned marine mammals, dolphins have certainly splashed their way into the hearts and curiosity of people worldwide. Scientists currently recognize over 49 different species of dolphin and porpoise across the world's oceans and rivers, from the cosmopolitan bottlenose dolphin to the endangered Amazon River dolphin. All of the various species share the same characteristic dolphin anatomy, as well as dolphin structure and function.
What Are the Body Parts of a Dolphin?
Dolphins all share a similar streamlined, torpedo-like body shape, which is also known as a fusiform shape. They also share the same general anatomy, which you can examine more closely in the following regions:
- The head: On a dolphin's head, you can find their blowhole, eyes, mouth, melon and two small ear holes. The blowhole is the hole through which a dolphin breathes. They can open their blowhole and seal it closed to prevent water from entering their lungs. Unlike humans and many other mammals, dolphins cannot breathe through their mouths. Speaking of mouths, the dolphin's mouth is also known as a rostrum. Also, unlike many other mammals, dolphins do not have external ears. Instead, they have a small ear hole on each side of their head behind their eyes that they use to hear. Finally, they use their large forehead, known as a melon, during the process of echolocation (more on echolocation later).
- The tail: Dolphin tail structure and function is one of the easiest ways to differentiate them from sharks and various other fish species. Unlike fish, which swim by moving their tail from side to side, dolphins use an up-and-down motion to propel themselves through the water. Their tail fin, also known as a fluke, connects to the rest of their body via the muscular peduncle region. The powerful muscles in the peduncle allow the dolphin to drive their fluke up and down to swim through the water, and even strike fish to stun them.
- Other fins: In addition to their tail fluke, dolphins have three other fins - two pectoral fins on the underside of their body and one dorsal fin on their back. Unlike the dorsal fin of a shark, which is typically triangular in shape, dolphins have a curved dorsal fin. Like the dorsal fin, the pectoral fins also have a curved shape. Located on the underside, or ventral side, of the dolphin's body, the pectoral fins help the dolphin steer while swimming.
Is a Dolphin a Mammal or a Fish?
Dolphins are mammals - marine mammals - but mammals all the same! Though they live their entire lives in the ocean, dolphins share all of the same mammalian characteristics that we do. They are warm-blooded, give live birth and nurse their young with milk, and they even have hair!
Though adult dolphins do not have any hair on their body, calves are born with fine hair that falls off shortly after birth. This hair, known as lanugo, grows on the young dolphin's rostrum.
Echolocation: How It Works
Another important characteristic that all dolphin species share is echolocation. Echolocation is the process that dolphins, whales, bats and some other animal species use to help them navigate. National Geographic describes it perfectly as "nature's built-in sonar."
Dolphins echolocate by emitting a series of clicks, honing and directing them using the fat in their melon, and then listening to the sound as it bounces back to them to create a mental image of their surroundings. They do not use echolocation all the time, however. They do have eyes, and they can certainly use them! Dolphins typically use echolocation in unknown surroundings or murky waters to complement their eyesight.
About the Author
Marina Somma is a freelance writer and animal trainer. She holds a B.A. in Psychology and a B.S. in Marine and Environmental Biology & Policy from Monmouth University. Marina has worked with a number of publications involving animal science, behavior and training, including animals.net, SmallDogsAcademy and more.