This book is a new critical edition of Aelian's seventeen books on De natura animalium, a work of a Roman author writing in Greek, which leads us to the world of late Greco-Roman culture and thought. This is an important work for scholars interested in zoology, animals' habits and behaviour, Stoic Philosophy, Medieval bestiaries backgrounds, and Greek language of Late Antiquity. In Aelian's own words, he aims to collect all material about animals´ habits and behaviour. Aelians' deep stoicism emerges from the text in a peculiar didactic and moralistic tone.