Predator Prey Interaction

Our world is full of different and very fragile ecosystems. Inside each one of these ecosystems a delicate game of predator and prey is played. When the ecosystems tilts in favor of one or the other it may risk destruction. The predator-prey lab that follows is a simulation of that game as it pertains to the lynx and the rabbit.

                The lynx is a natural predator of the rabbit. The higher the population of rabbits grows, the higher the population of lynx will grow. This will continue until which point there rabbit population can no longer replace what has been consumed by the lynx population. When the rabbit population begins to decline, so the lynx population will also decline.

                I Began with a taped of 12” by 12” square and about 300 paper rabbit cut outs (however, soon into my experiment I surpassed the 300 mark and had to make more copies). For the purposes of this simulation, the rabbit population doubled at the end of each generation (for example if there were six rabbits at the end of generation two, then generation three will began with 12 rabbits). In order for the lynx to survive it needed to catch three rabbits. If it did not catch at least three rabbits then it starved (and another lynx moved into the area). If the lynx caught three rabbits it survived to the next generation. For every three rabbits the lynx caught, it will populated another lynx.

                The first generation of my simulation began with three rabbits and one lynx. Given that I was tossing the lynx into what seemed like a large empty space, the lynx was unsuccessful in catching any rabbits. The rabbit population doubled and the lynx population stayed at one (simulating that another lynx moved into the area to replace the dead one).  Generations two through five resulted in much the same way. The rabbit population doubled and they lynx continued to die off. The area was too large for one lynx to catch enough rabbits to survive.

(I colored my lynx blue to make it stand out a little. This is the end of the first generation. The lynx had little chance of catching any rabbits)

                By the sixth generation I realized that I was trying to aim for rabbits so I started closing my eyes when I tossed the lynx into the square. This enabled me to guarantee that where my lynx landed was completely random. At the end of the sixth generation the one lynx caught enough rabbits to survive and to populate and additional lynx.  The seventh generation began with over 150 rabbits and two lynx. The odds seemed to be improving.

                By the ninth generation there were 27 lynx and over 400 rabbits. The square was covered with rabbits and every toss landed no less than 20 rabbits. The tenth generation began with 88 lynx and 366 rabbits. This is when the shift began. With so many lynx feeding in the square the rabbit population began to drastically decline. The eleventh generation brought 189 lynx and not enough rabbits to keep them all alive.

(There were so many rabbits, the lynx landed over 20 on each toss)

                By the fifteenth generation there were only two lynx left and the rabbit population began to recover. As the rabbit population increased the lynx population grew again as well. By the nineteenth generation there were 67 lynx and once again not enough rabbits to supply them.

(The end of the fifteenth generation brought a little balance back)

               

This is the data that I collected based on the results of this simulation.  

Predator-prey Simulation Data
Generation of Rabbits	Number of Lynx	Number of Rabbits	Rabbits Eaten (Total)	Rabbits Remaining	Lynx Starved	Lynx Surviving
1	1	3	0	3	1	0
2	1	6	0	6	1	0
3	1	12	1	11	1	0
4	1	22	1	21	1	0
5	1	42	2	40	1	0
6	1	80	4	76	0	1
7	2	152	10	142	0	2
8	5	284	81	203	0	5
9	27	406	223	183	0	27
10	88	366	305	61	0	88
11	189	122	97	25	125	32
12	64	50	29	21	53	9
13	18	42	13	19	14	4
14	8	38	4	34	7	1
15	2	68	12	56	0	2
16	6	112	27	85	0	6
17	15	170	47	123	0	15
18	30	246	112	134	0	30
19	67	268	133	135	22	44
20

               

This the line chart that shows the relationship between the rabbit population and the lynx population. 

As in any simulation, certain variables were not considered and some assumptions were made. I assumed that the climate was optimal for lynx to hunt. My square did not take into account the food supply to rabbits, or any other natural predators that the rabbit may have in this ecosystem (such as the hawk or other large animals).  I also did not take into account the survival rate of the offspring. I assumed that every lynx offspring born survived to hunting/feeding age. I also did not take into account other food sources for the lynx (i.e. other small rodents). In the text Principles of Environmental Science the authors state that, “External factors are habitat quality, food availability, and interactions with other organisms.” (Cunningham, 65)

                The lynx and the rabbit, in this simulation, are dependent on each other. Without the rabbit, the lynx would not survive, and without the lynx the rabbit population would continue to grow until they too ran out of food sources and began to die. Both species are critical to keeping the balance of their ecosystems intact.

 
After completing my simulation, I looked for a real life equivalent and found the below line chart comparing the population of hares to lynx in Canada. After reading the article and viewing the chart, I concluded that, even though I was throwing a piece of cardboard into a square of paper, the simulation was surprisingly accurate. (http://pzweb.harvard.edu/ucp/curriculum/ecosystems/s6_res_lynxhare.pdf