Dolphins are marine mammals and share many characteristics with land mammals, such as breathing air, giving birth, being-warm blooded, and producing milk.
They also share other physical characteristics with land mammals that affect how they move, which we’ll explain shortly.
Dolphins belong to the cetacean family, composed of around 80 – 90 different species of marine mammals.
As a whole, the cetacean species comprises all whale, dolphin, and porpoise species.
It is broken down into two suborders known as toothed and baleen, depending on their physical characteristics.
All dolphin and porpoise species are part of the toothed whale suborder because they possess teeth instead of baleen.
The baleen whale suborder, however, is made up exclusively of large whales that possess baleen plates with bristles.
The physical characteristics that make cetaceans, such as dolphins, move differently from other fish and other aquatic species are how their bones are designed, which can be observed by watching how they move through the water.
The earliest ancestors of dolphins did walk, hunted, and survived on land, which explains why the dolphin’s vertebrae resemble that of an animal designed for walking and running rather than swimming.
It also explains other characteristics, such as their need to obtain air and being warm-blooded animals.
Dolphins move by arching their backs and moving their flukes vertically up and down to generate momentum in the water and propel themselves forward.
At top speeds, some dolphins have been recorded traveling as fast as 30 miles per hour.
This is very different from fish or sharks (sharks belong to the fish family), which move from left to right to propel themselves forward.
All dolphins possess flippers that help these marine mammals turn, rise, and lower themselves in the water.
Many species also possess a dorsal fin which helps stabilize the dolphin as it swims through the water.
To make swimming as streamlined as possible and to minimize water resistance, most dolphins have a tapered streamlined body that’s thick near the center and tapers down towards the ends.
A few dolphin species (such as the killer whale) possess thicker, more robust bodies.
To observe their surroundings, dolphins have an un-fused neck which allows some species to turn their head a full 90 degrees.
To help dolphins navigate the ocean in dark waters, these marine animals are also equipped with echolocation, which allows them to identify objects in their environment, search for food and look for predators by producing high-pitched sounds and listening to the echo that returns.
The returning sounds can inform the dolphin about the location, size, density, direction, and movement of the objects around them, allowing them to figure out whether the thing is prey, a predator, or a fixed object.
In terms of behavior, some dolphins are very acrobatic and fast, as they have been observed leaping and flipping out of the water.
In contrast, other species are known to keep a low profile and rarely make disturbances in the water, preferring to remain hidden and unseen from potential predators and observers.
There are also a few other characteristics that separate dolphins from fish and other aquatic animals.
As stated earlier, because dolphins are marine mammals, they are warm-blooded, produce milk, bear offspring, and breathe air.
On the other hand, fish are cold-blooded, lay eggs, and extract oxygen from the water through their gills.