Deer and Wolf Population Graph

Student Handout: Oh Deer, Here Come the Wolves Imagine you are a wildlife manager working to restore the population of an endangered species of deer. Currently, the herd is small and your task is to find the best habitat and situation for the population to grow and develop into a healthy herd. Which of the following scenarios do you think would provide the best situation for your herd of deer? Scenario 1: The herd is currently living in a 100 square mile range in the Bitterroot Mountains of Montana which has been continually inhabited by this species for centuries. Human settlers eradicated wolves (one of the deer’s principle predators) over 100 years ago although other habitat changes caused by human development have continued to keep the deer’s populations low. Now, the habitat is improving and the deer population is growing slowly but steadily. However, some wildlife managers are planning to reintroduce wolves to your region. They plan to bring in several families of wolves into the area. The deer population is just beginning to rebound and you are concerned about the effects of the wolf introduction on the continued growth of the herd. Scenario 2: You have the opportunity to move the deer herd and reintroduce it to a new, more favorable habitat. The new area is a deserted island in the arctic region. There is a lot of food (no animal has filled the deer’s niche for many many years) and there are no natural predators. The island has 41 square miles of good habitat for the population. Prediction: Which of these scenarios would produce the fastest growth of the deep population? Which would potentially provide the healthiest long-term situation for the deer? Graphing: Graph the following data showing the changes in deer population over time for each of the two regions described above. You will make 2 line graphs. Data Set A: Year 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 Deer Population 2000 2100 2060 2010 1980 2000 1840 1710 1590 1440 1400 1290 1300 1260 1310 1360 1290 1330 Data Set B: Year 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 Deer Population 25 78 180 100 500 800 2000 700 8 25 Step 2: Describe and hypothesize. 1. What do you see happening to the two deer populations over time? 2. What similarities do you see in the two graphs? What differences? 3. Why do you think the population changes that you see have occurred? 4. At some point, wolves were reintroduced, write a hypothesis explaining when you think this happened (which graph and what year) and why you think it happened at that point. Before moving to the analysis portion of this activity, obtain the information that shows when and where the wolves were reintroduced from your teacher. Step 3: Analyze Answer the following questions: 1. Look at graph B. If there were no predators, why couldn’t the deer population continue to increase indefinitely? 2. Limiting resources are factors that limit the growth of a population. What are some limiting resources that might control the population of deer? 3. Carrying capacity is the maximum number of individuals an environment can support for an extended period of time. Explain what happened in each of the graphs in terms of carrying capacity. 4. What shape do you think the local ecosystem of graph B was in when the deer population crashed? 5. Did the wolves have the effect that you expected? 6. Do you think the carrying capacity of a region can change? 7. Did the wolves have an effect on the region’s carrying capacity? 8. Is reintroducing a native predator species harmful to the local ecosystem? 9. According to wildlife biologist Daniel Pletscher, after wolves were reintroduced, they may have depleted the deer population from between 3% and 12% each year. Why do you think this rate may have varied?