Name ____________________________________
Date ________________
The Predator-Prey Relationship
(Informational Text and Graphing Activity)
Key Terms:
Term
Part of
Speech
Definition
Picture / Example
predator
prey
presence
limit
scarce
competition
reduced
odds
sufficient
pelt(s)
1
Introduction:
The predator-prey relationship is one of the most effective ways of controlling the size
of a population. In this relationship, a predator species captures, kills and consumes
the individuals of the prey species. The prey organism is the food for the predator.
Predation can affect the number and types of species living in an area.
The presence of predators usually increases the number of different species that can
live in a specific area. Since predators limit the size of prey populations, food and other
valuable resources are less likely to become scarce. Competition between species is
reduced as a result. The predator-prey relationship is important for the health of
populations. Usually, the prey that are caught by the predators are the young, old, sick
or injured members of the prey population. This increases the odds that there will be
sufficient resources for the healthier members of the population.
During the 1800’s and into the early 1900’s, trappers collected and sold the pelts of
both the Canadian lynx and the Snowshoe hares. The lynx, a member of the cat family,
stalks, attacks and eats the snowshoe hare as a primary source of food.
Canadian lynx
Snowshoe Rabbit
2
The table below contains the data of the number of pelts bought by the Hudson Bay Company between
1845 and 1935. Make a graph of the data. Your graph will contain two lines. There will be one line for
lynx and a second line for rabbits. Use separate colors for each line.
Year
1845
1850
1855
1860
1865
1870
1875
1880
1885
1890
Number of
Lynx*
39,000
10,000
38,000
17,000
51,000
71,000
38,000
29,000
40,000
30,000
Number of
Rabbits*
21,000
71,000
69,000
22,000
129,000
9,000
56,000
70,000
47,000
21,000
Year
1895
1900
1905
1910
1915
1920
1925
1930
1935
Number of
Lynx*
39,000
9,000
40,000
26,000
60,000
12,000
78,000
8,000
83,000
Number of
Rabbits*
60,000
9,000
29,000
10,000
42,000
9,000
39,000
40,000
19,000
* These figures have been rounded to the nearest thousand.
3
1. Describe the relationship between the number of lynx and the number of rabbits between the
years of 1845 and 1900. Explain your answer.
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2. As the rabbit population increases, the lynx population increases. Why does this happen?
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3. What happens when the lynx population increases?
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4. What year is the rabbit population the highest? ___________________________________________________________
5. Why do you think there was a huge (dramatic) increase in rabbit population during that year?
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6. What happened to the rabbit population in the year after the highest rabbit population year (Look
at question #5)? Why did this happen?
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7. If the entire (all of the) lynx population disappears, what is could happen to the rabbit population?
Explain your answer.
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4
8. Predict what might happen to the predator population if:
a) there is a lot of food for the prey species. _________________________________________________________
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b) a disease kills the prey population. ___________________________________________________________________
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c) a new predator species that feeds on same prey moves into the habitat. _
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9. List 2 traits that help predators survive. (They should be traits that make them good at catching
their prey.)
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13. List 2 traits that help the prey survive. (They should be traits that help them not get caught by the
predator.)
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5