This study is based on the observation and imitation of nature. It is expected, by studying live walking animals, to find interesting parameters that could be used in various fields of robotics, especially the four-legged locomotion. Another goal is to find parameters that don't vary from one type of animal to another. This could be used to build a virtual walking model of a disappeared animal just from its known geometry for example. The steps described here are the different experiments on live animals, the conception of a computer model, and some results obtained with dynamic simulations. Different animals have been studied in the past like the hedgehog, the tenrec and the shrew, and a first model has been achieved. A new model, which is based on the tortoise of Hermann, consists in a 15 links, 22 degrees of freedom system, animated with proportional-derivative control, which references are actual recordings of live animals