What is a Mammal?
A mammal is a class of animals that comprises the biggest species on earth, including humans. There are 5,400 mammal species, most of which live on land, excluding a few species such as dolphins, whales, and manatees. A mammal can be recognized by a series of unique characteristics, which include: • Mammary glands. A mammal can produce milk to feed its young, as opposed to other species, which feed their offspring with solid food. A mammal young is born alive, except for a few species, such as the monotremes family, which lay eggs. • Warm blood. A mammal has warm blood, which helps the animal maintain steady body temperature. A mammal also has a heart with four chambers, a unique characteristic that allows the lungs to receive oxygenated blood in proper amounts. Mammal bodies are all covered with some kind of hair or fur that helps with heat preservation. Even aquatic mammals have hair at some point during their life. • Neocortex. A mammal posses a brain section that does not occur in
The first mammals roamed the earth with the dinosaurs about 200 million years ago. Most scientists think they developed from reptiles snakes or crocodiles. Mammals are vertebrates (have a backbone). They are also warm-blooded (like birds). Mammals have three traits that make them different from any other animals: • their young are born, not hatched from an egg; • they have fur; and • they nurse their young. Like anything in nature, there are exceptions to the rules–some mammals lay eggs, for instance. But animals that have all or most of the mammal traits are put into the mammal group. Eagles, Blanding’s turtles, perch, and dragonflies lay eggs. Baby mammals grow inside the body of their mother, not inside an egg. Mammals are the only animals with fur or hair. Brown bears and beagles have a thick coat of fur that keeps them warm. Whales (yes–whales are mammals!) have just a few coarse hairs on their faces. Besides providing warmth, hair also gives protection. A prickly porcupine is a
This short enhanced podcast provides an overview of mammal characteristics. Excerpt from an interview with Dr. Ross MacPhee, curator and researcher at the American Museum of Natural History. This video is part of the Beyond Penguins and Polar Bears magazine issue: Mammals. http://beyondpenguins.nsdl.
