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POPULATION MODELINGThis section of the project involved developing a population model, using a program called VORTEX, to show how well different management strategies will work. VORTEX requires some previous knowledge of biological parameters of the population that is being studied, like mortality and reproductive rates. It can then incorporate random (stochastic) or unpredictable events and predict what will happen to the population over time by averaging multiple runs of the model. We developed a model that assumed that the population is at the highest level that can be supported by the environment, called the carrying capacity. Because we wanted to demonstrate how different strategies will affect the population and not exactly what will happen to the Stevens Point deer population, we arbitrarily set the carrying capacity at 1,000 deer. We ran four management scenarios; harvesting 40% of the total population, harvesting 40% of females only, harvesting 30 to 200 individuals from the population, half male and half female, and harvesting 30 to 200 females. Harvesting many deer each year will reduce the population faster than harvesting only a few individuals each year. These figures also show that removing only females decreases the population faster than taking equal numbers of males and females.
Figure 1. A harvest of 40% of females only from the population reduces the population more quickly than a harvest of 40% of the total population (male and female).
Figure 2. A harvest of more individuals, both male and female, reduces the population more quickly than a harvest of fewer individuals.
Figure 3. A harvest of more female individuals reduces the population more quickly than harvesting fewer individuals. A harvest of only female individuals also reduces the population more quickly than a harvest of both sexes. |
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For more information contact
Dr. Tim F. Ginnett, (715) 346 - 4191
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