Transcript Chapter 16
Chapter 15 Predation 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 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 Relationship between predator and prey • Increase in prey increase in predators • Decrease in prey predator decrease 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 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 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 VI. Prey defenses Bumbl;e Bee • Chemical defenses— • Poisonous skin • Odors • Toxins Robber Fly • Camouflage—differ between female/male Monarch – Mimicry • Batesian mimicry • Mullerian mimicry Viceroy Coevolution between Predator and Prey • •Exerting selective pressure on prey •To maintain the population, successful avoidance •Moving in place to stay where they are Predator Defenses • Physical defenses—armor coats / hard shells / modified hairs • Behavioral defenses—alarms not species specific • Distraction—misdirecting attention • Group living • Reproduction timing VII. Predation 1. Ambush—lying in wait • • Frogs, alligators, lizards, insects Low success / little energy 2. Stalking—deliberate / quick attack • • Alligator mississipiensis Herons, small cats Search requires time / pursuit minimal 3. Pursuit—known location of prey • • Large cats, hawks, wolves Pursuit time great / minimal search Blue Heron, Ergetta caerulea Crypitic coloration blends into environment Northern Cardinal, Cardinalis cardinalis Red-tailed Hawk, Buteo jamaicensis 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 competitorsdecreases chances of extinction or can doom population 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 X. Foraging strategy • • 1. 2. 3. 4. Optimal foraging strategy – provides maximum energy gain Robins— Concentrate on most productive Remain until profitability falls Leave patch when reaches average level Ignore low productivity patches American Robin, Turdus migratorius 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 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 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