A family member of the dolphin mother will help the mother dolphin have its baby dolphin. The largest dolphins are the bottlenose and the orca. Breathing Dolphins need oxygen to live. But dolphins are able to send oxygen-rich blood to the brain and heart. When dolphins dive, they store oxygen in their blood, muscles, and small blood vessels called retia.
Dolphins can also slow down their heart rate, so they use their oxygen supply slowly.
Even when a dolphin is swimming very slowly, it comes to the surface for only a very short time. It needs to know the exact time that its blow hole hits the surface, so that it doesn't breathe in water and drown. A dolphin has a lot of feeling around its blow hole. It can feel the differences between water and air. Dolphins can stay under water for 8 minutes and can dive to a depth of 500 feet.