Ecology

Worksheet 6 – Predation (100 pts)

This worksheet is designed to help you:

i)       Understand the consumptive and non-consumptive effects of predation on prey.

ii)     Investigate how trade-offs affect prey in the context of optimal foraging theory (OFT).

Reminder: Follow the correct formatting for all worksheets and assignments (12 pt font, double-spaced, do not include original questions or instructions). Incorrect formatting will result in a 5% penalty on this assignment. Plagiarism is unacceptable and will result in an automatic 0 on this assignment.

Answer/address all of the following questions. In all cases, we require that your work be typed and that you insert any tables, figures, and statistical outputs from R. Refer to Lecture 2 (Statistics 1) for help with statistics and R.

1. In your own words, describe optimal foraging theory (OFT). Then, explain one example of an optimal foraging theory study from primary peer-reviewed literature only. In complete sentences, BRIEFLY summarize the methods and results of the study (minimum 2 sentences). Include in-text citations and add your citations to the references in Q#5 (10 pts)

2. Explain one example about predator-induced non-consumptive effects on prey (e.g., on prey behavior, life history, morphology, etc.) from primary peer-reviewed literature only. You may NOT use an article that your TA explained in class. (Find something new and exciting to you!) In complete sentences, BRIEFLY summarize the methods and results of the study (minimum 2 sentences). Include in-text citations and add your citations to the references in Q#5 (10 pts)

3. The following question will be on consumptive effects of predators on the prey.

a. Write out the null and alternative statistical hypotheses. BE SPECIFIC. Include all relevant information that describes the experiment biologically (e.g., extenuating circumstances). (5 pts)

b. Create a scatterplot for the number of prey killed . Include appropriate axes titles (with units). Below your figure, write a specific figure caption. (5 pts)

c. Perform an appropriate statistical test on the data. (Hint: both your independent and dependent variables are numerical.) Provide the complete outputs and highlight the appropriate P-value based on your hypotheses. (10 pts)

d. First, evaluate your P-value by comparing it to alpha. Then, reject or fail to reject the null hypothesis. (2 pts)

e. Write out the conclusion based on your original statistical hypotheses, i.e., write out the null or the alternative again. (2 pts)

f. How well can the number of prey killed be predicted by the number of predators present? (Hint: look at the R2 value). (2 pts)

g. Use the equation for this linear model to explain the relationship between these two variables IN WORDS. (Hint: refer back to Statistics PowerPoint in Lecture 2.) (2 pts)

h. Interpret why you observed this result in biological/ecological terms. Discuss principles from the lecture (Hint: factors that affect predation frequency and intensity) and how they would shape your results. Do NOT just put “because the prey get eaten.” (10 pts)

4. The following question will be on non-consumptive effects of predators on prey (reproduction).

a. Write out the null and alternative statistical hypotheses. BE SPECIFIC. Include all relevant information that describes the experiment biologically (e.g., extenuating circumstances). (5 pts)

b. Create a scatterplot for the number of prey that reproduced . Include appropriate axes titles (with units). Below your figure, write a specific figure caption. (5 pts)

c. Perform an appropriate statistical test on the data. (Hint: both your independent and dependent variables are numerical.) Provide the complete outputs and highlight the appropriate P-value based on your hypotheses. (10 pts)

d. First, evaluate your P-value by comparing it to alpha. Then, reject or fail to reject the null hypothesis. (2 pts)

e. Write out the conclusion based on your original statistical hypotheses, i.e., write out the null or the alternative again. (2 pts)

f. How well can the number of prey reproduced be predicted by the number of predators present? (Hint: look at the R2 value). (2 pts)

g. Use the equation for this linear model to explain the relationship between these two variables IN WORDS. (Hint: refer back to Statistics PowerPoint in Lecture 2.) (2 pts)

h. Interpret why you observed this result in biological/ecological terms. Discuss principles from the lecture (Hint: prey trade-offs while foraging and avoiding predators) and how they would shape your results. (10 pts)

5. Write out your “Literature Cited” section here. Follow the guidelines for Ecology Lab presented in previous worksheets and the full lab report. (2 pts)

6. Your TA will use this space to assign you a grade and provide feedback on grammar and spelling. (2 pts)

· 0 pts: Frequent grammar/spelling errors. Writing style is rough and hard-to-read.

· 2 pts: Very few grammar/spelling errors. The writing style is mature and readable.