ECOLOGY LABS

OH DEER! BACKGROUND: Ecological systems undergo constant change. Fluctuations in wildlife populations are natural as these systems undergo change. Food, water and shelter are three essential components of habitats. As students participate in this simulation they will begin to understand how these limiting factors affect the importance of good habitats for deer. A variety of factors affect the ability of wildlife to successfully reproduce and to maintain their populations over time. Disease, predator-prey interactions, environmental pollution and the destruction of habitat are among these factors. Animals have fundamental needs—food, water, shelter and space. Any interruption in these essential components will affect the population’s ability to survive.

HOW TO PLAY Teacher will select 6 deer The remaining students will be resources a. Food (hands on stomach) b. Water (hands on mouth) Shelter (hands above their head) The students who are resources will decide which resource they want to be and position their hands accordingly The teacher will inform the deer of which resource to select When the teacher yells “Oh Deer”, the deer will turn and find that particular resource and the resource will then become a new deer. If the deer can not find the resource, it dies and becomes a resource itself.

OH DEER DATA Round (Year) Deer Population After Round Resources (food, water, shelter) Available after Round 1 2 3 4 5 6 7   8 9 10

PREDATION OR STARVATION Introduction: In 1970 the deer population of an island forest reserve about 518 square kilometers in size was about 2000 animals. Although the island had excellent vegetation for feeding, the food supply obviously had limits. Thus the forest management personnel feared that overgrazing might lead to mass starvation. Since the area was too remote for hunters, the wildlife service decided to bring in natural predators to control the deer population. It was hoped that natural predation would keep the deer population from becoming too large and also increase the deer quality (or health), as predators often eliminate the weaker members of the herd. In 1971, ten wolves were flown into the island.

Deer Population Change PREDATION/STARVATION DATA The results of this program are shown in the following table. The Population Change is the number of deer born minus the number of deer that died during that year. Fill out the last column for each year (the first has been calculated for you). Year Wolf Population Deer Population Deer Offspring Predation Starvation Deer Population Change 1971 10 2,000 800 400 100 +300 1972 12 2,300 920 480 240   1973 16 2,500 1,000 640 500 1974 22 2.360 944 880 180 1975 28 2,224 1016 1,120 26 1976 24 2,094 836 960 2 1977 21 1,968 788 840 1978 18 1,916 756 720 1979 19 1,952 780 760 1980 1,972 790

GRAPHING: Graph the deer and wolf populations on the graph below GRAPHING: Graph the deer and wolf populations on the graph below. Use one color to show deer populations and another color to show wolf populations.

ANALYSIS Describe what happened to the deer and wolf populations between 1971 and 1980. What do you think would have happened to the deer on the island had wolves NOT been introduced? Most biology textbooks describe that predators and prey exist in a balance. This "balance of nature" hypothesis has been criticized by some scientists because it suggests a relationship between predators and prey that is good and necessary. Opponents of this hypothesis propose the following questions: Why is death by predators more natural or "right" then death by starvation? How does one determine when an ecosystem is in "balance"? Do predators really kill only the old and sick prey? What evidence is there for this statement? What is your opinion of the balance of nature hypothesis? Would the deer on the island be better off, worse off, or about the same without the wolves? Defend your position.