Roman siege engines BC, and surrounded by Roman fortifications. As was standard siege technique at the time, "ballistae" were placed up in the towers with other soldiers armed with either bows or slings. The onager was a post-classical Roman siege engine, which derived its name from the kicking action of the machine, similar to that of an onager (wild ass). It is a type of catapult that uses torsional pressure, generally from twisted rope, to store energy for the shot. The onager consisted of a frame placed on the ground to whose front end a vertical frame of solid timber was rigidly fixed;
Animal studies and to understand animals as beings-in-themselves, separate from our knowledge of them. Because the field is still developing, scholars and others have some freedom to define their own criteria about what issues may structure the field. As an interdisciplinary subject, animal studies exists at the intersection of a number of different fields of study. Different fields began to turn to animals as an important topic at different times and for various reasons, and these separate disciplinary histories shape how scholars approach animal studies. In part, animal studies developed out of the animal liberation movement and was grounded in ethical questions