Ch. 5 Flashcards
What is one of the basic aspects of predator-prey interactions?
the predator’s feeding rate.
What are some factors contribute to the predator’s feeding rate?
Prey population density
How long it takes to capture the prey
What is the equation for Predator Feeding rate?
Feeding rate = aN
a = a constant for the predator’s per capita attack rate
N = population density of the prey
the relationship between prey density and predator feeding rate is termed as
the predator’s functional response.
What are the three types of functional responses
Type I functional response: presumes that a predator’s feeding
rate (measured in units of number of prey consumed per individual predator per unit time) increases linearly with prey
density
Type II functional response: introduces the idea of handling
time.
Type III functional response: reflects a sigmoidal relationship where
a predator’s feeding rate accelerates over an initial increase in prey
density, but decelerates at higher prey densities.
Describe Type 1 functional response
Type I functional response: presumes that a predator’s feeding
rate (measured in units of number of prey consumed per
individual predator per unit time) increases linearly with prey
density.
Likely unrealistic for most predators as it assumes the
predator can consume some percentage of the prey
population per unit time despite the prey’s density.
see graph
Describe Type 2 functional response
Type II functional response: introduces the idea of handling
time. Using this equation:
Feeding Rate = aN/1+ahN
Where h is the handling time.
Note that at very low prey densities, the ahN term in the denominator is small and feeding
rate is approximately the type I functional response.
see graph
describe type 3
Type III functional response: reflects a sigmoidal relationship where
a predator’s feeding rate accelerates over an initial increase in prey
density, but decelerates at higher prey densities.
Feeding Rate = cN2/d2 + N2
Where c = h-1 is the maximum feeding rate and d = (ah)-1 is
half-saturation constant (the prey density at which the feeding
rate is half the maximum)
So, with a type III functional response the prey’s per capita death
rate peaks at an intermediate prey density.
see graphs
What are the types of foragers
Specialists
generalists
Define a specialist forager
Specialists: predators that feed on a single type of prey and commonly exhibit a type II functional
response.
ex. polar bears which primarily eats seals
define generalist foragers
Generalists: predators that use many different prey types and commonly exhibit a type III
functional response.
now ecologists think whether populations fit a type II or type III response might be based on
foraging mode.
do predators switch between type 2 and type 3
Some predators switch between type II and type III, particularly if they are a specialist, but that particular
prey source is not available.
ex. killerwale
Does the population density of predators might also play a role?
yes
Competition for food resources can be intense if the predator population is dense.
What is the ratio-dependent predation?
use N/P, where P is equal to the number of predators, in place of N.
This would mean then that the population density variable would be the proportion of the number of
prey divided by the number of predators.
