Are dolphins mammals?
Dolphins are mammals, not fish. Although they live in the sea and look a bit like sharks, which are fish, there are many differences between dolphins and fish which mean that they are technically classed as mammals. The differences are not always easy to tell just from looking at a dolphin, but they are all there. Dolphins are warm-blooded vertebrates which breathe air and give birth to live young. These are the three main distinguishing characteristics which mean that they are definitely mammals and not fish. Fish have gills which allow them to breathe underwater. The gills process sea water to extract the oxygen which is trapped inside and this allows them to spend their whole lives under the surface. Dolphins do not have gills, instead, they need to breather air just like any other mammal. This is why dolphins have blowholes on top of their backs. Every so often, dolphins will need to return to the surface in order to take a breath. They do not breathe continuously like humans do, but they have no way of converting the oxygen in the water around them into oxygen which they can use in their bodies. Another key difference is that all fish lay eggs. Dolphins do not lay eggs. The exact gestation period of a dolphin will vary depending on each species, but the baby dolphin will grow in the mother’s uterus and the female dolphin will then give birth to live young. This is one of the main characteristics of all placental mammals and one of the main reasons why dolphins are classed as mammals and not fish. The mothers will also produce milk to feed their young.
Dolphins are warm-blooded. They regulate their own body temperature rather than allowing external forces to do it for them. Fish are cold-blooded and do not have the ability to control their own body temperature.
Although it is difficult to tell from a distance, dolphins do actually have hair on their bodies. They do not have slippery scales like fish but instead have skin and hair just like any other type of mammal. There is usually a small amount of hair located around the blowhole and some dolphins also have hair on their backs and heads.Dolphin Facts | Dolphin Information | Dolphin Species | Dolphins FAQ