Predator/Prey Lab

Introduction



The objective of this experiment is to discover the connection between a predator and it's primary prey in a mock habitat. We will attempt to understand better how the populations of each affect one-another directly.

Hypothesis

I believe that as the rabbit population grows, the lynx population will as well. I believe that if the lynx population grows too large, it will have the potential to wipe out the rabbits completely. My reasoning for this is that with a growing rabbit population, the lynx will have a much more expansive food source. This will lead to a much larger lynx population, which could be highly detrimental to the rabbits' growth.

Procedure

I used 300 1" rabbit cut-outs to represent the rabbit population and 1 3" lynx cut-out to account for the lynx population. The habitat takes place in a 12" square that I marked with tape.

For generation 1, I began by population the habitat with three rabbits (spaced out evenly within the 12 inch square) and one lynx. The lynx has one opportunity to "capture" (land on top of after tossing into habitat) three or more rabbits in order to survive, as well as, create 1 lynx offspring leading into the next generation.


At this early stage it's nearly impossible for the lynx to survive, thus, another lynx will replace it for the next generation. Also, the rabbit population will double by the amount of survived rabbits for the next generation. Thus, generation 2 will include 6 rabbits evenly spaced and 1 lynx. The lynx will still struggle, but now have a better opportunity of surviving a moving into the next generation with 1 offspring.

As generation 2 on the right shows, the lynx caught only 2 rabbit, meaning that it will not survive. Generation 3, then, will include 1 lynx, and 8 rabbit (number of rabbit survived doubled).

For every 3 rabbits that a lynx "catches" it will survive and create 1 offspring (if it catches 6 it will survive and create 2 offspring). Each lynx will account for 1 toss into the habitat. This process will continue for about 18 to 20 generations and will be documented on a spreadsheet to show a rise in both populations and how they affect each other.

Results

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	2	4	1	0
3	1	8	1	7	1	0
4	1	14	3	11	0	1
5	2	22	4	18	2	0
6	1	36	5	31	0	1
7	2	62	10	52	0	2
8	5	104	35	69	0	5
9	15	138	89	49	2	13
10	36	98	98	0	23	13
11	39	3	3	0	39	0
12	1	3	0	3	1	0
13	1	6	2	4	1	0
14	1	8	2	6	1	0
15	1	12	3	9	0	1
16	2	18	5	13	1	1
17	2	26	7	19	0	2
18	4	38	16	22	0	4
19	9	44	31	13	2	7
20	14	26	23	3	10	14

The spreadsheet above looks slightly confusing, but the number to the bottom right of the above title displays the accurate information. As you can see, as the population of rabbits increases, so does the lynx population. This eventually accounts for too many lynx which greatly decreases the rabbit population and, thus, greatly decreases the lynx population. The cycle then repeats.

Once I got to generation 9 (pictured above), I had the largest amount of rabbits, as well as, the largest amount of lynx. The picture on the left is the beginning of generation 9, while the right shows the end of generation 9. As you can see, a large rabbit population coupled with a large lynx population is highly detrimental to the rabbit population.

In the following generations, there simply weren't enough rabbits for lynx, which became highly detrimental to the lynx population. This caused for a crash in the food cycle and eventually brought us back to the beginning of the cycle.

Questions:

What sort of variables could subject a natural population to pressure or disturbance?

There is potential for various separate variables that could take place which would directly affect the natural population. Some of these may include: Introduction of a foreign species which may prey on rabbits and limit the food source for the lynx, introduction of a foreign species which may prey on lynx and cause for overpopulation of rabbits, destruction of habitat (e.g. expanding agriculture, drainage, etc.) which may cause the species to adapt differently or move elsewhere, pollution of water or elsewhere which may infect and decrease population of either species, disease which may decrease either species, natural disaster which could wipe out both species.

What might be the outcome if the lynx was exterminated?

If the lynx were exterminated, the rabbit population would grow immensely. This could potentially lead to overgrazing and become detrimental to the rabbit population due to lack of food source per the high rabbit population. This would also greatly affect the organism at the trophic level below the rabbit.

What patterns did you observe? Describe any evident lag times.

The most clear observation, as shown in the spreadsheet, is that it takes about 4 or 5 generations for the rabbit population to grow large enough to sustain the lynx population. At this time it only takes about 3 or 4 generations for the lynx population to grow too large to sustain itself. The most evident lag times are between 1 and 4 or 5 generations. The cycle repeats after about 10 generations.

Conclusion


This experiment accurately shows how separate organisms in the food chain directly affect one another. A high population of prey accounts for a high population of predators, yet, too high of a predator population will kill of the prey population and eventually cause for killing off its own population. It is a great representation of a food chain cycle and how top trophic levels rely on lower levels to survive, while lower levels need the higher level in order to not over-populate.