Rabbit Starvation
Since there are no predators on Grassland, the only ways a rabbit can die are of starvation or old age.
Rdie = Roldage + Rstarve
The number of rabbits that starve in a given month, Rstarve, depends on the current number of rabbits, Rstart, and the amount of grass per rabbit available. A rabbit needs 10m2 of grass per month to survive; rabbits that acquire less than this amount starve.
Rstarve = Rstart * fRS(x)
