Models interactions between prey who eat grass, and predators who eat prey.
While I have been able to obtain stable oscillations, the numbers involved a a little extreme - as the number of prey will range from ~45,000 to 30, and similary predators from 1 or 2 to 16,000. Such extremes are accounted for by the model, and it is likely that these numbers are related to the size of the environment (300x300 = 90,000 pixels) - and thus the relative density of the prey and predators, and could therefore be reduced if the environment was made smaller (this wouldn't actually decrease the disk of population extinction through random chance - as the lows would still be low, the highs just wouldn't be as high)
These interactions produce oscillations (is stable parameters are chosen, they should resemble typeof:lotka-volterra ) - The ringing of the prey graph is caused by competition & availability of grass.