Animal behaviour is, obviously, the way in which animals - nonhuman-lead their life, such as, feeding, migration to different parts in different seasons, sexual life, gregariousness etc. Different factors need to be studied to have right knowledge about animal behaviour. One of them is the concept of "Natural Selection" propounded by Darwin. He observes that species compete with each other for survival. Apart from animals, there also occurs a peaceful contest among birds. For example, the severest rivalry between the males of many species to attract their female counterpart is one of the patterns of animal behaviour. It also includes a genetic component similar to the morphological and psychological traits. The present multi-volume encyclopaedia is a painstaking research work on animals behaviour. It would certainly prove to be an asset for psychologists and those who seed thorough knowledge on the subject.