Animal Behavior Statistics Assignments (Four very short)

ZO 420/620 Assignment 7 (30 pnts)

Answer the questions below. Use a separate sheet for your answers. Show your

work.

Variables λi= encounter rate

hi= handling time

ei= energy

Ts= Search time

T = total time

E = Total Energy

E/T = Ts λi ei / (Ts+Ts λi hi) = λi ei / (1+ λi hi) (1)

For one item E/T = λ1 e1 / (1+ λ1 h1) (2)

For two items E/T = (λ1 e1 + λ2 e2 )/ (1+ λ1 h1 + λ2 h2) (3)

If λ1 e1 / (1+ λ1 h1) > (λ1 e1 + λ2 e2 )/ (1+ λ1 h1 + λ2 h2) Then only take prey 1

Else prey 2

or λ1 > e2 / (e1h2 - e2h1) If true then take prey 1

Estimating λ

λ = 1/(100 √(1/di)/s ) (4)

di = density of prey i

s = predator search speed

1) Suppose a bird has the potential to encounter two seed types. Moonflower seed is encountered every 8 minutes, takes 3 minutes to handle and is 100 calories Evening Glory seed is encountered every 6 minutes, takes 4 minutes to handle and is 150 calories a) Which seed is more valuable? b) Should the bird specialize on one of the two seeds?

If so which one? 2) Suppose prey 1 takes 8 minutes to handle, and is 60 calories. Prey 2 takes 10 minutes to handle, is encountered every 12 minutes and is 30 calories. What would be the minimum encounter rate for prey 1 in order for the predator to include prey 2 in its diet? 3) Suppose a Ladybird Beetle can encounter 2 aphids. The spider moves at 10 cm/sec Green Aphid: takes 3 minutes to handle and is 9 calories Yellow Aphid: takes 5 minutes to handle and is 15 calories The green aphids are found at 8 aphids/ cm2 and the yellow aphids 3/cm2

Should the Beetle specialize on one of the two aphids? If so which one?

4) Suppose a Bass has the potential to encounter three prey items. Crayfish: encountered every 6 minutes, takes 7 minutes to handle and are 25

calories. Frogs: encountered every 10 minutes, takes 3 minutes to handle and are

24 calories. Minnows: encountered every 3 minutes, takes 3 minutes to handle and are 28

calories. Given these three prey items, what would be the optimal diet for the predator? 5) You encounter a cave system which contains a pool of water. The pool only contains blind fish and their two prey items, cave shrimp and cave midge larvae. You are curious if the fish are following the optimal diet model. You measure the caloric value of the prey items, the handling times, the density of the prey, and the speed of the fish. You also observe what the fish eat. The data set can be found in an excel file on-line. Based on these results are the fish following the optimal foraging model? Be sure to justify your answer.

6) The graph below represents the rate of resource intake from Patch A (Solid black line) and Patch B (Dotted Grey line). There are only 2 patches. The forager moves back and forth between bthe patches. When the forager is gone the patch resets. a) If the travel time between patch A and Patch B is 30 minutes. How long will the forager stay in Patch A before moving on? How long will it stay in Patch B? b) Will the forager stay longer in Patch A or Patch B? Why? c) If the forager stays in patch B for 15 minutes before leaving for patch A, How long will it stay in Patch A before moving back to Patch B?