setup button to setup the rabbits (red) and
grass (green). Click the go button to start the simulation.
The number slider controls the initial number of rabbits.
The hatch-threshold slider sets the energy level at which
the rabbits reproduce. The grass-growth-rate slider controls
the rate at which the grass grows. (Note: You can not change
the grass-growth-rate in the middle of a simulation; the
change will not take effect until the next setup.)
total-rabbits monitor to see how the rabbit
population changes over time. At first, there is not enough
grass for the rabbits, and many rabbits die. But that allows
the grass to grow more freely, providing an abundance of food
for the remaining rabbits. The rabbits gain energy and
reproduce. The abundance of rabbits leads to a shortage of
grass, and the cycle begins again.The rabbit population goes through a damped oscillation, eventually stabilizing in a narrow range. The total amount of grass also oscillates, out of phase with the rabbit population.
These dual oscillations are characteristic of predator-prey systems. Such systems are usually described by a set of differential equations known as the Lotka-Volterra equations. StarLogo provides a new way of studying predatory-prey systems and other ecosystems.
In the current version, each rabbit has the same
hatch-threshold. What would happen if each rabbit had a
different hatch-threshold? What if the hatch-threshold of each new rabbit was slightly different from the
hatch-threshold of its parent? How would the values
for hatch-thresshold evolve over time?
IF (RANDOM 1000) = 0 [SETPC GREEN]
But that command would be much slower, since all 10,000 patches would need to execute the command.
