Modern farm environments are profoundly different from the natural habitats of the ancestors of today's farm animals, and through genetic selection, the appearance and behavior of the animals themselves have also changed. However, the legacy of the ancestors is still obvious, and some apparently bizarre actions are only possible to understand in the light of the evolutionary history of the species. On the other hand, some of the behavior we can observe in animals in a modern farm or in a laboratory are not part of the normal, species-specific behavior at all. They may even indicate that the animal is under stress and that its welfare is poor. Distinguishing between these possibilities is one important goal for applied ethology. This revised and updated edition includes extended coverage of dog behavior and human-animal interactions as well as novel and intriguing research findings. The issue of animal cognition, central to understanding welfare, has also received a more thorough examination. It is suitable for the students of animal and veterinary science, zoology and psychology.