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Chapter 15 Predation. I. Terminology Predation = one organism is food for another Carnivory = feeding on animal tissue Parasitoidism = killing of host.

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Presentation on theme: "Chapter 15 Predation. I. Terminology Predation = one organism is food for another Carnivory = feeding on animal tissue Parasitoidism = killing of host."— Presentation transcript:

1 Chapter 15 Predation

2 I. Terminology Predation = one organism is food for another Carnivory = feeding on animal tissue Parasitoidism = killing of host by larvae Parasitism = feeds on host w/out killing Herbivory = feeding on plants w/out killing Cannibalism = predator and prey same species

3 II. Lotka-Volterra Mathematic equations predicting effects of predation on population growth Population growth for prey –Maximum rate of increase –Removal by predation Predator population equation –Efficiency of converting kills –Death rate of predators/absence of prey

4 Relationship between predator and prey Increase in prey  increase in predators Decrease in prey  predator decrease

5 III. Predator response 1.Functional response—prey population increases  predator eats more –3 types of functional responses 2.Numerical response— prey population increases  predator population increases

6 IV. Predator choices May choose alternative prey Turn to more abundant prey type = prey switching –Predator spends less time with less abundant prey –Species may increase as a result Predator may switch back to original prey— preferences

7 V. Numerical response 1.Direct response – predators increase as prey increases 2.No response – predator population remains same 3.Inverse response – predator population cannot keep up with prey density

8 VI. Prey defenses Chemical defenses— Poisonous skin Odors Toxins Camouflage—differ between female/male –Mimicry Batesian mimicry Mullerian mimicry Robber Fly Bumbl;e Bee Viceroy Monarch

9 Coevolution between Predator and Prey Exerting selective pressure on prey To maintain the population, successful avoidance Moving in place to stay where they are

10 Physical defenses—armor coats / hard shells / modified hairs Behavioral defenses—alarms not species specific Distraction—misdirecting attention Group living Reproduction timing Predator Defenses

11 VII. Predation 1.Ambush—lying in wait Frogs, alligators, lizards, insects Low success / little energy 2.Stalking—deliberate / quick attack Herons, small cats Search requires time / pursuit minimal 3.Pursuit—known location of prey Large cats, hawks, wolves Pursuit time great / minimal search Crypitic coloration blends into environment Blue Heron, Ergetta caerulea Red-tailed Hawk, Buteo jamaicensis Northern Cardinal, Cardinalis cardinalis Alligator mississipiensis

12 VIII. Cannibalism Form of intraspecific predation –Found in stressed populations Conditions: 1.Crowded / dense populations 2.Stress – low ranked attacked by dominant ones 3.Presence of vulnerable individuals May decrease numbers of intraspecific competitors  decreases chances of extinction or can doom population

13 IX. 3 way interaction B eats A C and D eat B D eats C Intraguild predation = one species eating another sharing same prey (potential competitor) Resource manager manipulation

14 X. Foraging strategy Optimal foraging strategy – provides maximum energy gain Robins— 1.Concentrate on most productive 2.Remain until profitability falls 3.Leave patch when reaches average level 4.Ignore low productivity patches American Robin, Turdus migratorius

15 XI. Herbivore grazing Biomass consumed = 6-10% of total Effects may be detrimental / may stimulate new growth Results indirect or direct Plants differ in quality of food –Tough, woody, hard to digest –Plant defenses—chemical defenses

16 XII. Plant defenses 1.Quantitative inhibitors—long-lived woody plants More expensive to plant Reduce digestibility 2.Qualitative inhibitors—toxins Interfere with metabolism Low cost to plant 3.Structural defenses—interfere with herbivory Least costly defense

17 XIII. Predator-prey relationships Not separate entities One level influences interactions at other levels Vegetation, snowshoe hare and lynx –Food shortage for hares causes malnutrition –Increased predation causes decline of hares –Food shortage for lynx


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