Dolphin and shark both are aquatic animals that belong to the vast group of vertebrates as both have a backbone. People often confuse these two aquatic animals as they look alike from outside. Let us study these animals more closely to better understand how they differ from each other!
Dolphin:
Dolphins are mammals that belong to the order Cetaceans. They are very intelligent animals and are very playful and friendly with humans. They are mostly found in warm and tropical marine habitats, whereas some species are also found in large rivers and known as river dolphins. There are more than 40 species of dolphin in the world. The largest species is orca which is also known as a killer whale.
Dolphins are generally gray in colour. However, their colour may vary, depending on the subspecies. Dolphins are carnivorous mammals as they mostly feed on squids and fishes. They are highly adapted to the aquatic environment. They have streamlined body with a horizontal tail, a dorsal fin and a pair of flippers. Their snout is long with interlocking teeth.
Dolphins are warm-blooded mammals and their young ones are totally dependent on their mothers during the early stages of their life. Dolphins are social creatures and often form groups called herds, there can be as many as one million dolphins in a group. Furthermore, they use high-frequency sound waves to communicate with each other and to locate obstacles and prey.
Shark:
Sharks are fishes that belong to the class, Chondrichthyes. They are characterized by their cartilaginous skeleton, multiple rows of teeth and five to seven gills located at each side of its head. There are more than 460 species of shark found all over the world. The size of the shark varies greatly, e.g. the smallest shark is spiny dogfish shark and the largest shark is the whale shark.
Sharks are not only adapted to the aquatic environment but also for a predatory lifestyle. They have streamlines body with fins, a vertical tail, strong jaws with sharp teeth and sharp vision. Their vertical fin moves side-to-side as they swim and they have gills for the respiration or to extract oxygen from water. Sharks are cold-blooded animals which means they are not able to regulate their body temperature on their own. They are carnivorous as they generally feed on seals, penguins and fishes etc.
Based on above facts, some of the key differences between dolphin and shark are as follows:
| Dolphin | Shark |
| Dolphin is an aquatic mammal. | Shark is a fish. |
| Their skeleton is made up of bones. | Their skeleton is made of a flexible material called cartilage. |
| Dolphins have lungs so they have to resurface often to inhale fresh oxygen through their blowholes. | Sharks have gills to extract oxygen from water while breathing underwater. |
| They have only one dorsal fin. | They can have as many as four fins. |
| Their fin is curved to create an arc. | Their fins are broad, not curved and stand straight up from their back. |
| They have flat, horizontal tails that move up-down while they swim in the water. | They have tall vertical tails that move side-to-side while they swim in the water. |
| They are born with hair. | They are born without hair. |
| They nurse their babies. | They do not nurse their babies. |
| They are warm-blooded animals. | They are cold-blooded animals. |
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