ECOL Predation 2

Question 1

What are the changes expected in predators, because of prey numbers?

Answer 1

-too few prey, predator decreases
-abundant prey, predator increases

Question 2

What are the changes expected in prey, because of predator numbers?

Answer 2

-too many predators, prey decreases (leftward arrow)
-too few predators, prey increases (rightward arrow)

Question 3

Mathematical equations are used to help understand exactly how the size of predator and prey populations will change over time by taking into account…

Answer 3

-population size to start with
-birth rates of predators & prey
-predator efficiency at catching prey
-mortality rate of predators
-how efficient predators are at using the energy from consuming prey to grow new offspring

Question 4

What Lotka-Volterra Model formula is used to predict changes in prey population size?

Answer 4

dN/dt = rN - cNP

Question 5

In the changes of prey population formula, dN/dt = rN - cNP, what does each thing stand for?

Answer 5

dN/dt = instantaneous rate of increase in prey (# of prey added per unit time)
r = intrinsic growth rate of prey per capita (max birth and min. death rates possible per individual)
N = number of prey
c = fraction of prey population caught by each predator (capture efficiency)
P = number of predators

Question 6

Suppose that rabbits are the only prey of foxes, and that the predator-prey interaction between these species follow Lotka-Volterra dynamics. The mortality rate of foxes in the absence of rabbits is 0.1 per week, and the intrinsic growth rate of rabbits is 0.2 per week. The efficiency at which each predator can capture prey is 0.002.

If there are 30 foxes and 400 rabbits in a given habitat, the instantaneous rate of change in the rabbit population will be a net ____ of ____.

(loss/gain, #)

Answer 6

gain, 56

Question 7

What Lotka-Volterra Model formula is used to predict changes in predator population size?

Answer 7

dP/dt = acNP - mP

Question 8

In the changes of predator population formula, dP/dt = acNP - mP, what does each thing stand for?

Answer 8

dP/dt = instantaneous rate of increase in predators (number added per unit time)
a = efficiency of converting 1 prey to 1 predator offspring
N = number of prey
c = fraction of prey population caught by each predator (capture efficiency)
P = number of predators
m = mortality rate of predators, per capita

Question 9

Suppose that rabbits are the only prey of foxes, and that the predator-prey
interaction between these species follow Lotka-Volterra dynamics. The
mortality rate of foxes in the absence of rabbits is 0.1 per week, and the
intrinsic growth rate of rabbits is 0.2 per week. The efficiency at which each
predator can capture prey is 0.002, and the efficiency of converting the energy
from each capture to a new predator offspring is 0.04.
If there are 30 foxes and 400 rabbits in a given habitat, the instantaneous rate
of change in the fox population will be a net ________ of _____.

(loss/gain, #)

Answer 9

loss, -2.04