Singer Predator-Prey Simulation

    This is my presentation of the Predator-Prey simulation for Biology 105. The purpose of this simulation is to show the relationship between the population of rabbits (prey) and lynx (predators) over 20 generations.

    My hypothesis for this simulation experiment is that as the rabbit population grows, the lynx population will also grow. I would expect that a balance would eventually be reached that supports a steady number of lynx and rabbits without any uncontrolled outside factors such as drought or disease.  

    I begin the simulation by gathering and creating the needed materials. Using a piece of yellow poster board, I marked off an area that was 12"x12". I then printed out and cut 300 1" square rabbits, and 1 3" square lynx.

Rabbit Generation 1

First Generation Lynx

    The experiment beings with 3 rabbits populating the simulation. The first generation lynx was able to capture a single rabbit. The parameters of the simulation indicate that for a lynx to survive to the next generation, it had to capture at least 3 rabbits. This meant our initial lynx did not survive. The remaining rabbits from each generation will then double in number. This means that for the second generation of the simulation, there will be 4 rabbits for the lynx to try and capture.

    Using these parameters it took until the 5th generation for a lynx to survive. The lynx survived by capturing 3 rabbits. This also means that the lynx was able to produce offspring, as the simulation states that for every 3 rabbits captured, a lynx will produce one new lynx.

First Lynx Survivor

Reduced rabbit population of Gen 8.

    The population of rabbits and lynx then continued to grow over the next few generations. However in Generation 8, something interesting occurs. While 9 lynx successfully live and produce offspring, there are only 7 surviving rabbits. In Generation 9, 17 lynx have to try and survive off of only 14 rabbits. None of the 17 are able to get enough rabbits to survive, and in Generation 10 the cycle starts over with only 1 lynx and 3 rabbits.

Large rabbit population of Gen 7.

    In generations 11-20 we see the same cycle being followed, although this time we have new peaks with 140 rabbits (Generation 19) and lynx at 43 (Generation 20). As with the previous cycle however, the reduced rabbit population from the previous generation cannot support the increased lynx generation, and 34 of the 43 lynx starve in Generation 20.

    The Predator-Prey simulation appears to disprove my hypothesis that a stable balance would be reached between the rabbit and lynx populations. Instead, both populations would increase and then quickly decrease. For the rabbits this could be seen as the population grew too large and their food (vegetation) would become scare, and for the lynx too much competition along with fluctuations in the rabbit population would lead to sharp decreases in their populations.

    This was without the simulation taking into account other variables that could also have heavy influences on the population of both species. Disease is one example that would affect both populations, regardless of which one actually was carrying the disease. Drought would be another example that would affect both populations. Not factoring other animal species into the simulation would also affect outcomes, as there would be more competition for the resources provided in the simulation zone. The roaming pattern of lynx could also affect the outcome, as environmental issues could cause more neighboring lynx or rabbits to move into the simulation zone. Of course there's also the effect that Man would have on the simulation, with pollution, hunting, and destruction of the environment all factors that would change the outcome of any simulations.

    One outcome to consider would be if the lynx were exterminated, perhaps by overhunting. In this case the rabbit population would continue to grow, but would most likely also suffer a sharp decrease. The large population would not be something the producers of the zone would be able to support, and the vegetation would be severely reduced. This would lead to a sharp decline in the rabbit population after an initial spike. It might take several generations for the vegetation to recover enough to support the rabbit population again.

    The pattern that seemed to occur in the simulation was that as the rabbit population increased, the lynx generation would also increase. This would reach a peak level however, and then both populations would quickly drop down. There would be about a one generation lag between when the rabbit population would drop and the lynx population would drop. So at a time when you might think the lynx population was healthy and strong, would usually indicate there was about to be a severe drop in the population due to not enough food being available. It would then take the lynx several generations to start to increase in number again.

A true apex predator displays how rabbit hunting is done.

    What we learned from this experiment is that while we can attempt to chart out projections for different animal species, it's much more difficult to project due to so many random factors being present in real world conditions. It does give us a good example though of how delicate the balance in nature is, and we should always pause before taking action that will impact the environment.