“Characteristics of Mammals” Discovery Education Video Transcript
There are two main things that make mammals different from other vertebrates. The body of a mammal is covered with fur, or hair. A gorilla is a mammal covered with hair. An adult elephant is a mammal with very little hair. But you can see the hair easily on this baby elephant. A second way mammals are different from other vertebrates is that all mammal mothers produce milk for their young. Mammals give their young much care and attention. The mother's milk is important to helping the young grow strong and healthy. In fact, the name "mammal" comes from "mammary glands," the part of the female's body that produces milk. Almost all mammals give birth to babies instead of laying eggs like fish, amphibians, reptiles, and birds. The baby develops inside the mother's body and then is born alive. The young aren't hatched from eggs outside the mother's body like so many other animals. The time needed for the young to grow inside the mother varies from one kind of mammal to another. The whale requires 450 days. The giraffe needs about 442 days. A small mammal like a hamster needs only 16 days to develop inside the mother. A human usually needs nine months before being born. Once born, the parents of mammals look after and feed the young. Some mammals are born completely helpless, hairless, and blind. Some mammals, such as horses or deer, are able to walk, and even run, within minutes of their birth. The duckbilled platypus hatches from an egg, but its mother gives it milk, so it's a mammal. Some mammals, like kangaroos and koalas, carry their young in a pouch. When born, the babies are very tiny and weak, so they need the protection of the mother's pouch to grow. Mammals with pouches are called "marsupials." Mammals have four limbs usually four legs but for some mammals, like primates, there are two legs and two arms. Seals are mammals, and their limbs are called flippers. Look how graceful they are in the water. They can use their flippers to walk, or to power them through the water with speed and agility. A whale starts out with four limbs, but as it grows, the two back ones disappear. Many people think the whale is a fish, but it's a mammal. There are great differences in the sizes of mammals. The blue whale is the largest animal of all time, reaching lengths of 100 feet, and weighing in at 200,000 pounds. A shrew is one of the smallest mammals, with a length of a few inches and a weight equal to three paper clips. Giraffes are the tallest animals, with the largest recorded giraffe reaching a height of 19 feet. Different types of mammals eat different kinds of food. Shrews and bats eat insects. Rabbits and mice have teeth designed for gnawing. Large mammals, like zebra, giraffe, and elephants, eat grass and leaves. Their teeth are blunt for chewing. Animals that eat plants are called "herbivores." Some mammals, such as tigers, are meat eaters. Their teeth are sharp for cutting and biting into their prey. Meat eaters are called "carnivores." Monkeys and humans eat both plants and animals. They are called "omnivores." Mammals are warm-blooded, which means they keep their body at a constant temperature. They can do this from the food they eat. Hair or fur helps to keep the heat in. If a mammal gets too warm or hot, then it will sweat, or pant, to cool down. Mammals that live in the water have thick layers of fat, called blubber, instead of fur or hair. This blubber keeps them warm in the ocean. Mammals have a lot of different kinds of feet. A horse has only one big toe, called a hoof, at the end of each leg. This one has an iron horse shoe to protect the hoof. Flat hooves keep the horse from sinking into the soft ground, and help it to run fast. Goats, and a lot of other animals, have divided hooves. The goats can climb easily on rocky mountain areas. Mammals of the dog family have soft paws with nails. Members of the cat family have claws that help them catch prey or climb trees to get away from enemies.