Ecology – Lecture 18
Lotka-Volterra Model of Predation
Discovered that L-V could show all of these factors
( ** Increased predators = higher predation)
- Prey affect predators, predators affect prery - & because they aren’t synchronized (lag),
this creates cycles.
Graph on the left is a mutually stable equillibrium Assumptions
- Model is pretty good at accomadating these assumptions Go round & round & get closer to where the 2 lines cross – middle; harder to get out
of the middle (stable equillibrium) (red arrow pointing up shouldn’t be there). Graph 2: Prey have refuges, so they don’t get eaten at low densities.
Graph 1: arrows pointing to centre; very stable equillibrium – predator isocline is
verys steep & to the left = very efficient.
Graph 2: more spirals/cycles to get to the middle. Still stable because it ultimately
ends up in the middle, but will take longer.
- Huffaker (1958): 40 oranges – 20 food, 20 covered in paper. The prey increased & then
when extinct, the predators did the same: the prey ate themselves out of a home.
Retry: 252 oranges & numerous petroleum jelly barriers (provide refuge) = cycling
populations. Density dependence & prey refuge; predator also eats other things
- If you have a metapopulation of predators & a metapopulation of prey; the populations
- We stabilize the predator-prey interactions (neutral