Lecture 7 Flashcards
1. Define functional response 2. Explain how Type I, II and III functional responses differ 3. Consider the implications of the functional responses from the ‘prey’ species’ perspective 4. Explain the concept of Ideal Free Distribution and how it relates to optimal foraging theory (21 cards)
What does a functional response describe?
The relationship between the rate of feeding of an individual predator and the density of the prey item
How is the graph in Type I functional response?
It’s linearly
What’s the theory behind type I functional response?
There is a limit, limited resources there are not always preys. As a prey density increases the feeding rate increases too
Type I. What does the slope of the line represent? What would a change in slope signify?
-Efficiency of the predator at capturing a prey
- Proportion of prey density consumed
Type I. If you know the slope of the relationship and density, how would you calculate feeding rate (i.e. number of prey captured per individual per time)?
The slope is the attack rate, it is the predator’s efficiency!
y = ax + b
Feeding rate = attack rate * prey density
What type of organisms would you expect to have a Type I functional response?
No handling time like filter feeders (zooplankton, blue whales)
Type II functional response graph
Its like a saturation graph
Type II. What is the graph saying about the feeding rate of the predator as a function of prey density?
The feeding rate will initially increase with prey density but will reach a maximal feeding rate
What might cause the curve to level off at high prey densities?
The predator cannot handle the prey any faster
What type of organisms would you expect to have a Type II functional response?
Most common – any organism that requires time to handle prey/food resource
Type III Functional response graph
Sigmoidal
Type III. What is the graph is saying about the feeding rate of the predator as a function of prey density?
- Low prey density:
- Medium prey density:
- High prey density
- The feeding rate increases slowly
- The feeding rate gets faster
- The feeding rate reaches a plateau
Type III. At what prey density is the predator feeding rate at a maximum?
At high prey density
Type III. What do you think causes this curve to level off at high prey densities?
Handling time
Type III. What do you think causes the feeding rate to be LOWER than the Type II functional response at low prey densities?
- Prey spatial refuge
- Predator learning/search image
- Prey switching
Type III. What type of organisms would you expect to have a Type III functional response?
Similar to Type II, but where one of
the above applies.
Now given these 3 functional response types, if you were a PREY which functional response would you hope your PREDATOR had?
Type III
Under what conditions are your chance of survival highest/lowest?
- Type I (lowest)
- Type II
- Type III
In the context of foraging and behavioural ecology, functional response refers to how:
a. populations adjust to changes in prey abundance
b. individuals respond to changes in the types of prey available
c. feeding rate of an individual responds to changes in prey abundance Your answer
d. the feeding rate of an individual responds to changes in energy demand
c. feeding rate of an individual responds to changes in prey abundance Your answer
Two types of functional response curves level off at high prey densities. Why is that?
a. Prey density can not get any greater
b. The predator gets full and stops eating
c. Handling time imposes a maximum consumption rate on the predator
d. The predator switches to another prey type
e. Only one type of functional response levels off at high prey densities
c. Handling time imposes a maximum consumption rate on the predator
