LE 11: Predation and Herbivory Flashcards
How do predators affect the community?
Predators can reduce the abundance of prey (top-down regulation)
Example: herbivores
- cactus moth in Australia can act on invasive species of cactus as a biological control
Moderate predation can maintain biodiversity directly or indirectly through modulating competition
What is a numeric response in relation to predation?
Number of prey consumed per predator vs the density of prey
Type I: prey are easy to find and handle, so predators are satiated
- even as prey increases, the predators ≠ eat anymore
Type II: Prey require quite a lot of handling time, so predators ≠ have time to eat more
- eating prey most of the time
- as density increases, predators are eating more numerically but functionally = less percentage of population is decreased
Type III: Prey are hard to find when rare/at low densities, so predators only eat them when they are abundant
What is a functional response, in relation to predation?
the proportion of prey consumed per predator vs density of prey population
- based on the numeric response
What is the optimal foraging theory in relation to functional response? Give examples:
When predators will eat a diet that is most profitable in their community, which can be determined by the profitability equation.
Cooper’s hawks eat MEDIUM sized birds, small mammals, and organisms that have a low handling time.
Seagulls employ techniques to optimize foraging on sea urchins (kleptoparasitism):
- urchin is larger = peck at it because it is high profit and they ≠ want to lose it to other seagulls
- urchin is smaller = drop it because it is low profit and they ≠ mind losing it
What are consumptive effects?
when predators drive down prey numbers by eating them
What are non-consumptive effects and the methods used?
any effect on a prey population due to the presence of the predator, but not due to consumption and through a behavioral/trait change.
Methods:
- Reducing fecundity by driving them away from mating locations/ killing more females than males
- Foraging behaviors are altered by driving organisms from where they forage, reducing energy intake and increasing expenditure
- Antipredator defenses such as toxins etc.
How does top-down regulation affect mesopredators and the trophic levels?
mesopredators: predators that are eaten by top predators and prey on smaller animals
If top predators eat more mesopredators, then there will be more smaller animals + vice versa
What are the trends of predator prey cycles?
The growth and decline of prey population affects the growth and decline of predator population + vice versa.
- an increase in prey, leads to an increase in predators
- an increase in prey, leads to a decrease in predators
What is the Huffaker experiment and its findings?
Mites were counted and cycling was trying to be reproduced.
originally, there would be spikes in prey and predators that would then lead to extinction
Cycling only occurred when there is a heterogenous environment.
What are some examples of the different anti-predator defenses?
behavioral defenses:
- predatory alarm calls
- rabbits stay still because it becomes harder to be seen
chemical defenses:
- spray chemicals at predators
- plants have alkaloids that can cause illness (tobacco, nicotine, and caffeine)
structural defenses:
- shells/spines decrease predation by increasing handling times
- aposematic coloration: warns predators that they are dangerous
- mimicry
What are the different types of mimicry?
Mullerian mimicry: a group of species have similar coloration patterns to show that they are harmful
Batesian mimicry: one species copies another species who is actually harmful
- dishonest mimicry
