The leading text in the field shows how researchers use scientific logic to study the underlying mechanisms and evolutionary bases of behavior, with emphasis on how evolutionary theory unifies the various sub-disciplines within animal behavior. It is a comparative and integrative overview of how and why animals as diverse as insects and humans behave the way that they do, linking behaviors to the brain, genes, and hormones, as well as to the surrounding ecological and social environments. The new edition, now in enhanced e-Book format, brings animal behavior and research to life like never before.