AEC 360   Ecology

Lecture 3: Predator-prey interactions and behavior

I.  There are many types of defenses prey have to protect against predators


II.  Predator and prey behaviors affect their population dynamic
        Example: Dr. Gilliam's work on behavioral responses of prey fish (Rivulus) to predatory Fish (Hoplias)

        A. Landscape of fear: predators can affect prey without actually killing them

        B.  Reduced growth under threat of predation

        C.  Reduced fecundity under threat of predation

        D.  Local population dynamics influenced more strongly by local emigration than by death rate

        E.  Assessing behavioral tradeoffs between feeding and predator avoidance  (Fig. 4.21)
                -Prey swim farther and faster when predator is present

        F. When are prey willing to risk being eaten

III.  Choices by individual animals involve behavioral tradeoffs, that affect fitness

        A.  Space: safest places not necessarily the places with highest energetic return
        B.  Time: Safest times for foraging not necessarily times with the highest energetic return
        C.  Time, again: Time spent foraging detracts from time spent hiding or mating

IV.  Ecologists study foraging decisions, given these tradeoffs

        A.  Optimal foraging theory
        B.  Benefits: growth, reproduction, survival
        C.  Costs: energy expenditure, mortality

V.  Aspects of optimal foraging 
        A.  Rate of prey captures decreases with search time (Fig. 4.18)

        B.  Animals should adjust their foraging to maximize feeding rate rate of food acquisition (Fig. 4.19)

        C.  Shorter travel times should lead to shorter foraging times in otherwise similar habitats

         D.  Figure 4.20 shows how theory can predict real behaviors in birds

VI.  Behaviors of predators and prey affect population dynamics

       A.  Predators affect prey behavior:  tadpole responses to predators (Fig. 14.15)

VI.  Predators affect prey behavior
        A.  Example: Coyotes and bird diversity

            1. Absence of medium-sized increases bird diversity and abundance
            2. Coyote presence reduces abundances of medium-sized predators
            3. Coyote presence reduces cat abundance