Mammals are best characterized by their warm blood, mammary glands and unique birth process. Birds are classified as avians, not mammals, notably, due to their egg birthing.

First, no one is sure why we, or any other animal, dream. During the past century, however, scientists have made significant progress in understanding the factors that influence sleep and dreaming ...

One solution is to shut down one half of their brain at a time. Called unihemispheric sleep, it's one way marine mammals, such as dolphins, can get some rest while in open water. "Unihemispheric ...

All mammals have hair, but sometimes they've evolved to appear naked. Cetaceans are the largest group of hairless mammals, made up of animals including whales, dolphins, and porpoises. This makes ...

Many mammals are true hibernators and remain dormant through the winter, but a lot of them stay active, at least to some degree. Sign in or Subscribe See Offers. Sign In: Login.

Sixty-six million years ago, our ancestors lived through the most violent event in the Earth's history. How did small, insignificant mammals survive a doomsday asteroid?

The first issue is that most other mammals do not menstruate in the sense of bleeding when the lining of the uterus is shed. Instead, the lining of the uterus is reabsorbed. If you define the ...

Some mammals may not experience vivid colorful dreams like humans do. Living in the water makes both sleeping and dreaming a challenge. First, no one is sure why we, or any other animal, dream.