Have you ever wondered why falling cats always seem to land on their feet? Or why cats are compelled to hunt birds and rodents no matter how well the pets are fed? Like cat owners, many scientists are intrigued by the cat's behavior and physical features. Ecologists say that the sheer number of cats kept as pets—about 67 million in the United States alone—means that the animals have a significant influence on the ecology of urban areas. And studies of the domestic cat's physical makeup and behavior not only add to our knowledge of all members of the cat family, but also provide practical benefits for millions of pet owners.

Much of the current scientific interest in cats stems from their changing relationship with human beings. For years, most cats in the United States lived in wild or semiwild states in cities, on farms, or in the countryside. They reproduced and flourished because people brought them food or because stored food attracted rodents, which the cats preyed upon. Today, although there are still many feral (wild) cats, millions of others have achieved the status of family members and live in a human-dominated environment. And, after long being neglected as subjects for scientific inquiry, the cat has caught the interest of biologists.