Dolphins live in the water, so they must be fish, right?Contrary to popular belief, dolphins are not regarded as fish. They’re mammals.Yes, mammals with lungs just like us, humans. But why is that? By classification, a dolphin is not a fish but a mammal. That’s because it fulfills many of the criteria of a mammal, but it doesn’t meet certain requirements for it to be called a fish. For example, dolphins don’t lay eggs but give birth, they are warm-blooded and not cold-blooded. There are many more differences which you will learn in this article.If you like this article, check out dolphin facts and is a black snake with yellow stripes poisonous here on Kidadl.Why are dolphins mammals and not fish?Dolphins are mammals and not fish because they evolved from land mammals, while fish evolved from aquatic animals. Dolphins were land mammals with their feet underneath the water. That’s the reason their tail moves up and down while they swim, whereas a fish’s tail moves sideways.As dolphins went completely underneath the surface of the ocean, they retained the characteristics of a mammal. For example, dolphins give birth to live young. The pregnancies in certain species like the bottlenose dolphin last for about 12 months. Dolphins are also born with belly buttons and umbilical cords, just like humans. Female dolphins also nurse their young ones and feed them milk for 2-3 years. They have mammary glands that secrete milk for babies. For all these reasons, dolphins are mammals and not fish, who lay eggs.Then, there are other differences too. Dolphins are born with hair. The calves’ rostrum is hairy and falls out soon after birth. However, you can spot hair follicles in that area through to adulthood. Dolphins are warm-blooded and do not need hair on their body to keep themselves warm. They have plenty of blubbers for this purpose. On the other hand, fish are cold-blooded. Their body adjusts to the water temperature of their habitat.Are dolphins related to fish?A dolphin is not related to fish despite sharing the marine ecosystem. Fish have evolved underwater throughout recorded history, while dolphins were mammals with only their feet underwater. So dolphins aren’t part of the fish family.Dolphins are not even related to dolphinfish, also known as mahi-mahi. As opposed to dolphins, mahi-mahi is an actual bony fish that is cold-blooded, lives underwater, and has gills. It is a strong fish with a dorsal fin, found primarily near the shores of the Gulf of Mexico, the Caribbean, and Hawaii in the Pacific and Atlantic Oceans. Dolphins aren’t related to them.What features do dolphins and fish have in common?Despite the differences, there are noticeable similarities between a dolphin and a fish. The first similarity is they both live underwater. They’re marine animals and have adapted to similar conditions. This is reflected in their streamlined body. Both dolphins and the fish family have a streamlined body that allows them to move freely and quickly through dense water. You can also conclude that they have smoother outlines to help them swim.This is thought of to be because of convergent evolution when different species of animals evolve in the same environment where their external appearance gets similar and thus are thought to be converging. Dolphins, fishes, and sharks in the ocean also have similar body parts like fins and tails that benefit them under the water. All of them feed primarily on other fish as prey, which is another similarity. Dolphins prey on shrimps, squids, and a range of smaller fish like herring and mackerel for food as their usual diet.Another similarity you may consider is both dolphins and fish are edible. You can consume a dolphin’s meat wherever available. Although many people think it’s illegal, there are no laws in the US that criminalize capturing and eating a dolphin.Do dolphins and fish breathe in the same way?Both dolphins and fish live underwater, so it’s easy to postulate that they must be breathing the same way. But upon inspection, you’ll notice that their breathing mechanism is vastly different.Dolphins are marine mammals, and mammals have lungs and breathe through their nose. In the case of a dolphin, they inhale and exhale through their blowhole. Like fish, a dolphin cannot intake oxygen directly from the water. From time to time, they will come up to the surface of the ocean and expose the blowhole that’s located at the top of their heads. After exposing it for several minutes, they head back underwater. A dolphin is capable of inhaling 8 gal (30.3 l) of air per second and it could exhale at the rate of 34 gal (128.7 l) of air per second. Underwater, it can hold its breath for 8-10 minutes before being required to breathe again. All dolphins, including bottlenose dolphins, follow this breathing mechanism. So, dolphins are very much similar to whales when it comes to breathing underwater.The breathing mechanism in fish might be more familiar to you. They extract oxygen directly from the water using their gills. These are feathery filaments filled with blood vessels. The filaments extract the oxygen and transfer it directly to their blood. They also expel carbon dioxide into the water just like we exhale CO2 after inhaling O2.Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for ‘Is a dolphin a fish? No, they are marine mammal! And here’s why?’ then why not take a look at ‘What causes snow? fascinating weather facts for curious kids!’ or ‘Jungle vs rainforest: curious forest difference facts for kids’.
Dolphins live in the water, so they must be fish, right?
