Mammals have several unique characteristics that differentiate them
from other animals. Most mammals have hair, or fur, covering their body.
They are also capable of regulating their body temperature. The mammals
metabolism controls heat production, and the sweat glands help cool the
body. These allow the mammal to maintain a constant body temperature, regardless
of the environmental temperature. One other difference is that mammals
give birth to fully formed babies, and the female mammals produce milk
to feed their young.
Most mammals walk on 4 legs, with only the humans walking upright on
2 legs. Aquatic mammals have flippers, or fins, for swimming rather than
legs. Common mammals include: primates, such humans and monkeys;
marsupials; rodents; whales; dolphins; and, seals.