Chapter 14 - Predation and Herbivory Flashcards
(34 cards)
What are the two populations of predators?
Mesopredators and top predators.
What are mesopredators? Provide examples.
Relatively small carnivores that consume herbivores. Feral cats, coyotes, weasels.
What are top predators? Provide examples.
Predators that typically consume both herbivores and mesopredators. wolves, mountain lions, sharks.
Why is it not usually beneficial to remove a top predator?
Enables mesopredators to increase in abundance, nothing controlling that population makes them eliminate herbivores they prey upon.
How do herbivores affect species abundance?
If herbivore populations are not controlled, they can eat plants to extinction from their community. OR if herbivores are removed, plants may grow exponentially.
What enables predators and prey to coexist?
Suitable refuges for the prey.
What are the two types of time delays that cause predator-prey populations to cycle?
- Predators dispersing more slowly between food patches and prey
- Time needed for predators to reproduce
What is the Lotka-Volterra model?
A model of predator-prey interactions that incorporates oscillations in the abundances of predator and prey populations and shows predator numbers lagging behind those of their prey.
What does the Lotka-Volterra model tell us about the population growth of prey?
Growth rate of prey population depends on the rate of individuals being added to the prey population minus the number of individuals being killed by predators.
Define the variables in the Lotka-Volterra model of prey population growth:
dN/dt = rN - cNP
rN = exponential growth of population
cNP = loss of individuals to predation
What does the Lotka-Volterra model assume about predation rate?
It is determined by the probability of a random encounter between predators and prey (NP) and the probability of such an encounter leading to a prey’s capture.
What does the Lotka-Volterra model tell us about the population growth of predators?
Depends on the birth rate of predators and the death rate of predators.
Define the variables in the Lotka-Volterra model of predator population growth:
dP/dt = acNP - mP
cNP = number of prey consumed
a = efficiency of converting prey into predator offspring
m = mortality rate
P = number of predators
What does this indicate: rN = cNP
Prey population becomes stable when the addition of prey is balanced out by the consumption of prey.
What does this equation imply: P = r/c?
Prey population will be stable when number of predators equals the ratio of the prey’s growth rate and the predator’s capture efficiency.
What does this equation indicate? rN > cNP
Prey population will increase when addition of prey exceeds the consumption of prey.
What does this equation imply? acNP = mP
Predator population becomes stable when the addition of predators is balanced by the mortality of predators.
What is an equilibrium isocline?
The population size of one species that causes the population of another species to be stable.
What do numbers above the equilibrium isocline mean?
There are relatively few predators and the prey population increases.
What do numbers below the equilibrium isocline of prey mean?
Predators remove prey faster than prey can reproduce; prey population decreases.
What do numbers on the right of the predator equilibrium isocline mean?
Increased abundance of prey; predator population increases.
What do numbers on the left of the predator equilibrium isocline mean?
Not enough available prey; predator population decreases.
What is joint population trajectory?
The simultaneous trajectory of predator and prey populations.
What is the joint equilibrium point?
The point at which the equilibrium isoclines for predator and prey populations cross.
