Who!, Who!, Who Did I Eat? Part III
Purpose: To explore what owls eat and how it affects different populations.
Procedure:
1. After the class data has been collected from Who, Who, Who Did I Eat, Part II, record the results in data
table 1.
2. Use the Biomass Conversion Table (conversion factor) to calculate total biomass for each type of animal
eaten.
Prey
Mouse
Bird
Vole
Rat
Mole
Shrew
Biomass Conversion Table
Mass
Conversion Factor
20g
1
40g
2
40g
2
240g
12
55g
2.75
5g
.25
Data: Copy this entire section into your lab book
Total number of animals in the class ____________________
Total number of pellets __________________
Approximate number of animals per pellet ________________
Number of Animals—Class Data Northern
Prey
Number found
Percentage of Total
Mouse
50
50/total * 100 =
Bird
2
Vole
57
Rat
25
Mole
0
Shrew
4
(calculate)
100
Total
Number of Animals—Class Data Southern
Prey
Number found
Percentage of Total
Mouse
38
38
Bird
3
3
Vole
2
2
Rat
40
40
Mole
1
1
Shrew
16
16
100
100
Total
Biomass—Class Data
Prey
Total biomass
Mouse x 1
50*1=
Bird x 2
2*2=
Vole x 2
57*2=
Rat x 12
25*12=
Mole x 2.75
0
Shrew x .25
4*.25=
(calculate)
Total
Percentage of Total
50/total * 100 =
0
100
Analysis/Conclusion Questions: Show your work and write in complete thoughts
1. If a barn owl produces one pellet each day estimate the number of animals the owl would eat per year.
2. Using your answer from #1, approximately how many of each type of animal would this consist of?
(Northern population only)
3. Compare Northern and Southern data. What differences and what similarities do you see?
4. What do the differences in number two suggest about the Northern and Southern climates, animals, and
plants?
5. Calculate the average biomass represented by one pellet.
6. How much biomass does the average owl eat in one year?
a) How many mice does this represent?
b) How many rats?
c) How many voles?
d) How many shrews?
7. Explain whether you think this data accurately represents the proportions of animals in the wild, why or why
not?
Use the following chart to answer questions 8-12
Percentage of Animals as Owl Food in Various States
Prey
State percentage
Colorado Oklahoma Texas Massachusetts Nebraska
Mice
32%
35%
40%
5%
51%
Birds
4%
1%
3%
1%
1%
Voles
53%
1%
2%
64%
40%
Rats
1%
54%
32%
1%
1%
Moles
1%
1%
1%
11%
1%
Shrews
1%
4%
15%
18%
4%
Note: other animals like gophers and rabbits make up the additional percentages.
8. Using your number of animals eaten per year from question 1, give the number of mice, shrew, voles, and
rats a barn owl from Colorado would eat in a year. (Northern only)
9. If a virus killed all of the rats in the U.S., which states’ barn owl population would be affected the most?
10. Give an explanation for the differences in rat and vole populations between Texas and Oklahoma, and
Colorado and Nebraska.
11. How does the class data compare to the data in the chart above?
12. Adult owls must hunt for their young. If a young owl eats one pellet a day until it leaves the nest, how many
extra pellets does its mother need to catch in a year if she lays seven eggs each time she nests? What
connection might this have to the death rate of young owls?
Conclusion: Use your rubric!