The Earth's magnetic field is aligned with the north and south poles, and has reversed many times during geologic history. Whales may use the magnetic field of the Earth for navigation purposes on their long migrations across the oceans. Mammal Mammals are warm-blooded animals with hair that nourish their young with milk. Primitive mammals evolved during the Triassic period.
Whales are mammals.
Mammary glands Female mammals have mammary glands that produce milk for their young. Whales feed their young with milk from their mammary glands. Marine mammals Marine mammals are mammals that live in the sea and breathe air. Whales, dolphins, seals, sea lions, and sea otters are marine mammals. Mass extinction Mass extinction is the process in which huge numbers of species die out suddenly.