predation pt 2 (lotka/volterra criticism->marginal value theorem)

why has the lotka/volterra model been criticized? what does it fail to represent?

1) cover + refuges for the prey

2) difficulty of locating prey as it becomes scarcer

3) choice among multiple prey species

4) co-evolution

as N_prey increases, what should happen to the predator population’s growth rate?

it should respond positively

→ a numerical response can occur through reproduction by predators (b)

→ aggregative response

aggregative response

results in the movement of predators into an area of high prey density

the ability of a predator population to regulate prey population is related to the response of predators to _______

aggregate

→ predator populations grow slowly in comparison to those of their prey

irruption

increase in size of population in a rapid period of time

optimal foraging theory

considers the tradeoffs between conflicting demands (defense, avoiding predators, trying to care for young)

what is the optimal foraging theory based on?

the hypothesis that natural selection should favor “efficient” foragers—those who maximize their energy or nutrient uptake per unit of effort

how is cost of foraging decisions measured?

in terms of the time + energy expended in the act of foraging

how are benefits of foraging measured?

in terms of fitness

the _________ of prey is the net energy gained per unit of time

profitability

what does the optimal foraging theory predict?

the preferred prey (P₁ or P₂) will be the one with the greater profitability

→ which prey do i eat that costs the least amount of time but yields the most amount of return?

in what situation would a predator choose the less profitable prey, P₂ over P₁, the more profitable prey?

the predator should eat P₂ IF the net energy gained per unit of time is HIGHER in P₂ than in P₁

marginal value theorem

predicts that the time an individual should stay in a resource patch before leaving and seeking another

the length of a stay in a patch is related to what traits?

• food patch richness (prey density)

• the time required to get there (travel time)

• the time required to extract the resource

the rate of return at any point in time =

cumulative value of G/combined t and T

G

cumulative energy gain from foraging activities in the patch

t

the initial time cost associated with traveling to the patch

T

foraging time

the optimal foraging theory predicts that the predator should ______ the patch when the rate of energy gain is at its maximum value

abandon

according to the marginal value theorem, what should a predator do in a rich food patch compared to a poorer one?

the predator should remain in the rich food patch longer than they remain in a poorer one

according to the marginal value theorem, what should a predator do in patches of the same quality?

the amount of time spent there should increase with the amount of time it took to get there

→ T in a patch should increase with an increasing value of t