It’s no secret that at the Wild Dolphin Project, we find dolphins endlessly fascinating. After all, we have been studying them for 40 years!

What makes the so interesting? Well, they have unique anatomy designed for a life beneath the waves, from their sleek bodies to sensory superpowers.

Read on to find out more about their amazing anatomy. 

Sleek and Streamlined

Dolphins zoom through the water around 8 to 10 miles per hour, but can reach up to 20 miles per hour when they are cruising fast.  Orcas — the largest dolphin species — can reach speeds up to 35 miles per hour!

Their sleek, torpedo-shaped bodies glide through the water. This is called a fusiform shape, and it helps reduce resistance from the water.

Flippers and Fins

Dolphins have several different types of fins and flippers that help them navigate and maneuver in the water Located on either side of their body, pectoral fins act like steering wheels helping them turn and change direction. Their dorsal fin, which sits on their back, helps them maintain stability while swimming. Lastly, their powerful tail flukes propel them through the water.

Dolphins, like all cetaceans, have evolved from land-dwelling mammals, and their flipper bones are modified versions of the limbs their ancestors once used for walking. A dolphin’s flipper contains a simplified version of the bones found in a human arm. These include the humerus (similar to our upper arm bone), radius and ulna (similar to our forearm bones), and various smaller bones that correspond to wrist and finger bones in humans.

Blowholes and Breathing

Unlike fish, dolphins don’t have gills to breathe underwater. Instead, they have lungs and blowholes, which sit atop their heads. Because they are mammals, they need to come up to the surface to breathe air. When a dolphin surfaces, it opens its blowhole and exhales first, then takes a breath before diving back down.

Sensory Superpowers

Hearing/Echolocation: One of dolphins’ most impressive senses is echolocation. They produce high-frequency clicks — or sounds— which bounce off an object in their environment and return to them as echoes. By listening to these echoes, dolphins can see their environment. It’s especially useful in murky water or at night. Dolphin echolocation clicks typically range in frequency from about 40 to 150 kHz. The human hearing range, for comparison, is approximately 20 Hz to 20,000 Hz (20 kHz). When we observe the dolphins feeding at night on squid and flying fish, the water is buzzing with the sounds of their echolocation.

Denise Herzing, Ph.D., research director and founder of the WDP, has spent many years understanding more about dolphin echolocation and other sounds they produce, like whistles. They create these sounds using special air sacs near their blowholes.

Sight: Surprisingly to many people, dolphins can see well both above and below water due to their double slit pupil. They have special muscles in the eye that are able to change the shape of the lens to adjust between seeing an object below water versus seeing an object in the air. Without this adaptation a dolphin would be nearsighted above the water.

Their eyes are located on the sides of their heads, which allows them to see almost 360 degrees around them without moving their heads. They can also see well in dim light. Also, their eyes can move independently of each other, allowing them to look in two different directions at one time.

Touch: Dolphins have sensitive skin, especially around their mouths and on their fins. They use touch to communicate with each other and to explore their environment.

Taste: Dolphins don’t have a very strong sense of taste compared to humans, but they can still taste different things.

Smell: Dolphins don’t rely much on their sense of smell. Their blowhole, the hole on top of their head that they breathe through, is separate from their nose, so they don’t use it to smell things like we do.

Electroreception: While not as extensively studied in dolphins as in some other aquatic animals like sharks and certain fish, there is evidence to suggest that bottlenose dolphins, like the Amazon river dolphin, do have some level of electroreceptive capability, as well as Sotalia guianensis (Guiana dolphin) and Tursiops truncatus (bottlenose dolphin). (Read the study here)

Electroreception allows animals to detect electric fields generated by living organisms or changes in electrical currents within their environment. In the case of dolphins, electroreception may play a role in detecting prey, navigating through murky waters, or sensing the bioelectric fields produced by other animals.

Blubber

Blubber is a thick layer of fat under the skin that many marine animals, including dolphins, have. For dolphins, blubber acts like a special jacket that keeps them warm and helps them float in the water. It also helps them float in the water, providing buoyancy.

Diving and Breath Holding

Though dolphins are mammals and breathe air, they spend their lives underwater, which means they must be able to hold their breath. To do this, they have several adaptations, such as collapsable lungs that allow them to withstand increasing pressure as they dive deeper.

They also have relatively large lungs compared to their body size. They can take in a lot of oxygen with each breath, and they work very efficiently to quickly absorb oxygen from the air they breathe. This maximizes the oxygen available for their bodies.

Dolphins have a protein called myoglobin in their muscles, which stores oxygen. This allows them to have an extra oxygen supply available while they’re underwater, helping them endure longer dives.

And one more thing: Dolphins have the ability to lower their heart rate dramatically when they dive. This reduces the amount of oxygen their bodies need, further extending the time they can stay underwater without needing to come up for air.