Population ecology is the study of these and other questions about what factors affect population and how and why a population changes over time. Population ecology has its deepest historic roots, and its richest development, in the study of population growth, regulation, and dynamics, or demography.
While running, the neck of a giraffe moves backward and forward to keep the animal balanced. Giraffes have a top speed of about 56 kilometres per hour (35 miles per hour), however, because its legs are so long a galloping giraffe does not appear to be going very fast.
The first is the faster belly run which I've already mentioned, in which the legs move very rapidly in a typically reptilian pattern to propel the crocodile forward. During this belly run, the crocodile starts to move its body in a sinusoidal manner along the horizontal plane, almost as if it were swimming.