9781422279151

animals. However, they are still categorized as marine mam- mals because they depend on the sea to survive. All mammals, whether they live on land or in the sea, share some characteristics. They give birth to live babies who drink milk from their mothers when they are very young. They breathe using lungs, and have some kind of hair or fur. They are warm-blooded, meaning that their body tem- perature stays the same even when the air or water around them gets very hot or cold. That’s one reason marine mam- mals can get so big—they need a lot of fat to stay warm in the water. Seals have thick coats of fat to help them survive the cold water.