Predation and harvest homework

You can also find this homework at: http://rpubs.com/mistymcphee/600101

due: 6 May, 11:59pm

• You do not have to use R for this homework. If you use do R, put all of your answers in chunks. If your answer is text and not code, precede each line of text with #.
  
• If you do use R, please put your .rmd file in your Google folder.
• No matter how you do this - show me the equation you are using, define your variables, and show ALL of your work!

As always:

• Copy each question into your document and make sure your answers are clearly outlined and labeled. If you use R, double space between paragraphs so that lines don’t run into each other.
• Include a 0 before the decimal point in a number less than 1.
• I will deduct points for typos - especially incorrect use of “data”.
• You can discuss with classmates, but you must do the work on your own.
• Please proofread before turning it in!

Question 1

When speaking of predation, what is a numerical vs functional response?

Question 2

Below are two types of functional responses: (a) change in kestrel predation as a function of Microtus (vole) density (from Korpimaki and Norrdahl 1991, Ecology), and (b) change in hen harrier predation as a function of grouse chick density (from Redpath and Thirgood 1999, J Animal Ecology). Tell me which type of functional response each graph represents.

Question 3

You are a biologist with the Wisconsin DNR and have been asked to look at the effects of hunting on the lesser sandhill crane population. Before you can assess the impacts of harvesting, you need to know what the the natural predation rates are.

You know that crane density is 12 birds per 26 km². On average, a single coyote kills 3 colts (young cranes) in spring and summer. (Assume that this is the only time coyotes kill cranes - there are no kills in fall or winter.)

If the coyote density is 0.75 coyotes per 10 km², what is:

1. the total kill from coyotes (state your answer in kills per km²)?

2. the annual predation rate?

3. What will happen to the crane population’s growth rate if harvesting is additive?

4. If it is compensatory?

5. You need to estimate a harvest quota. What is the difference between a fixed-quota and a fixed-effort harvest model?

6. If you go with a fixed-quota harvest model and you know that the carrying capacity in Wisconsin is 45,000 birds and the growth rate is 0.32, what would be the maximum sustainable yield of cranes?

Question 4

You are working with a released population of endangered Wyoming toads. You have them in a pond enclosure that excludes predators and their survival rate is in this enclosure is 0.78. After you remove the enclosure, you will monitor mortality due to avian predators.

1. What is the maximum predation rate the toads can withstand in order for the predation to be compensatory?

2. If predation is completely compensatory, what is the total annual survival rate?

3. If predation is additive and the probability of surviving predation is 0.12, what is the annual survival of the toads?