WFSC 403 6th Edition Lecture 16 Outline of Last Lecture I Basic Concepts II Theory a Math b Phase Planes III Lab studies IV Field Studies V Evolution of predator prey systems Outline of Current Lecture I Lab Studies a Essay page 197 II Field Studies a Essay page 197 III The Big Question a The Answer IV The Approach a Predator responses to changes in prey density V Evolution of predator prey systems Current Lecture Where do computer studies like we are doing fit How do lab computer field studies work together o Could make a theory or hypothesis why something occurs in the computer lab and simplify it and investigate in lab and then could do more efficiently out in the field The way in which the field examples differ in a way that we expect generally tells us o Theorize under really restrictive assumptions work in computer lab under really restrictive assumptions go out in the field and see where what is violated o Computer labs just remember it is really restrictive assumptions See what may work efficiently rejects things o Complementary control lab in natural world more natural setting where can t restrict as much Practical considerations make some field experiments difficult to do dangerous expensive Spatial heterogeneity These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Big question In the field do we see predator prey cycles Big question Do predators prey control prey predators o Woodland caribou o Indirect competition shared enemy o Wolves black bears lynx preying on caribou and wolves and bears preying on moose o Are the predators controlling the prey The classic experiment if you can do it would be to remove predator in one spot and leave them in the other to see what happens Doomed surplus of muskrats o Lemmings hurling selves off cliffs o Predation is compensatory to other forms of mortality Compensatory mortality some agent of mortality is going to kill prey but that prey is going to die shortly anyways o Going to shoot a deer but little do you know that in 5 seconds he is going to die anyways from a heart attack compensatory mortality Mortality was going to happen Additive mortality If don t kill would have lived live to reproduce o What looks strange o The Alee effect for small populations o This is kind of strange because usually the theory is that the smaller the density the higher the R0 is Mortality increase Natality decrease Emigration Immigration Density dependent feedback the straight declining line o As population density is lower R0 is higher o Number hare killed per lynx per day o Dotted line is energy requirement for lynx how many are required to have energy o Can only kill so many hares per day o Per capita mortality rate is getting smaller Hare has escaped mortality more reproduction then predator can kill o When get to high hare numbers lynx is not controlling The Big Question o Page 201 o What makes some predators effective in controlling their prey The total response increases as prey density increases the predators may limit the density of the prey By contrast if the total response remains constant or falls as prey density increases the predator cannot limit prey numbers Functional response Number of prey consumed per predator per day over some time o Response of individual predator and how fast they can consume kill prey o Type 1 linearly increase predation rate per predator o Type 2 convex curve o Type 3 Sigmoid Why kinds of predators exhibit each of theses curves o The handling time