Answer: Other characteristics of dolphins that make them mammals rather than fish are that they give birth to live young rather than laying eggs and they feed their young with milk. Also, like all mammals, dolphins even have a tiny amount of hair, right around the blowhole. Whales and porpoises are also mammal
Step-by-step explanation: How do we know dolphins are mammals?
Even though they live in the ocean all of the time, dolphins are mammals, not fish. Like every mammal, dolphins are warm blooded. Unlike fish, who breathe through gills, dolphins breathe air using lungs. Dolphins must make frequent trips to the surface of the water to catch a breath.