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This 4 page Class Notes was uploaded by Hiba Kouser on Wednesday March 30, 2016. The Class Notes belongs to BIOL 4700 at Clemson University taught by Michael J Childress in Fall 2016. Since its upload, it has received 35 views. For similar materials see Behavioral Ecology in Biology at Clemson University.
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Date Created: 03/30/16
I. Optimal Foraging A. Prey Selection Model (What size prey items should be selected to maximize the net rate of energy intake?) 1. Holling’s Disc Equation a. R = rate of energy intake b. Eg = Energy gained by R = (E – E )/ (T + T ) g h s h consumption c. E h energy lost to handling d. T s time spent searching e. T h time spent handling 2. Assumption: prey items of different sizes will have different profitabilities (energy gained/ energy expended) 3. Prediction: optimal foragers should select prey that maximize their net energy intake 4. Predictin: optimal foragers should be choosy about the size of prey they select B. Diet Selection Model (Which prey type should be included in an optimal diet to maximize the net rate of energy intake) 1. a. Model predicts being a specialist when (E h /E1 1– 2 > 12 λ1 b. Searching and handling are mutually exclusive activities c. Encounter with prey is sequential and random d. E, h, λ remain constant e. Forager has complete information 2. Potential Constraints a. Excessive handling time/energy b. Nutritional needs other than energy c. Balancing the risk of predation C. Patch Selection Model 1. Marginal Value Theorem: a rate maximizing forager will choose the residence time or each patch type so that the marginal rate of gain at the time of leaving equals the long term average rate of energy intake in the habitat 2. a. Searching for patches and feeding within one are mutually exclusive b. Encounters with patches are sequential and random c. The gain function remains constant d. Forager again has complete information 3. What determines the optimal time spent in a patch? a. Understand the shape of the curve, and the distance between you and your next patch b. Giveupdensity (GUD) when travel time between patches is short, the GUD is larger D. Risk Sensitive Model 1. Patches equal in mean rewards differ in their variance 2. A satiated forager should be risk adverse and choose the less variable patch 3. A hungry forager should be risk prone and choose the more variable patch E. Predation Foraging Trade Off 1. Forager should forage optimally so long as it does not result in higher risk of predation 2. When predators are present, alternative foraging strategies that minimize predation risks are favored 3. Ex. Sticklebacks a. Sticklebacks choose high prey density when predator is absent but low prey density with predator is present because it is easier for them to watch for predators II. Antipredatory Behaviors A. Evolutionary Arms Race 1. RedQueen hypothesis: organisms must constantly adapt to survive while pitted against everevolving opposing organisms in an ever changing environment 2. Evolutionary Arms Race: predators and prey coevolve due to their strong evolutionary influence on one another 3. Prey should: a. Avoid encounters b. Avoid detection c. Avoid capture Predators Prey Visual activity Cryptically Search image Polymorphism Search patterns Spacing patterns Learning ability Mimicry Speed Evasive maneuvers Offensive weapons Defensive weapons Detoxins Toxins B. Predation Risk Model 1. P (death) = 1 – e^(α *d *T) a. α = rate of encounters b. d = probability of death per encounter with predator c. T = time spent vulnerable to encounters with a predator 2. d = [ p(1a)(1i1)(1e1) + q (12i ) (12e )] (3e ) a. p = probability prey detects predator first b. q = probability predator detects prey first c. a = probability prey avoids predator d. i = probability predator ignores prey e. e = probability prey escapes predator 3. Avoiding Encounters a. Reducing α or T parameters b. Timing of Activity i. Circadial patterns ii. Circatidal patterns c. Sheltering behavior i. Crevices or burrows ii. Commensal spaces 4. Avoiding Detection a. Coloration i. Disruptive ii. Cryptic iii. Polymorphism b. Distribution and spacing c. Cryptic behavior i. Remaining motionless ii. Swaying rhythmically 5. Discouraging Attacks a. Coloration i. Aposomatic coloration (bright coloration to demonstrate toxicity) ii. Batesian mimicry (similar coloring to toxic animals) b. Advertising Unprofitability i. Stotting – deer jump in air which advertises their fitness ii. Inspection visits c. Group behaviors can discourage predators by i. Increasing your apparent size ii. Disguising your true identity d. Individual behaviors can discourage predators by i. Illustrating superior escape abilities 6. Escaping Attacks a. Startle coloration i. Bright flash patches ( eyespots)2 z s b. Evasive maneuvers c. Group Behaviors i. Vigilence ii. Confusing effect iii. Mobbing 7. Avoiding Consumption a. Defensive Structures (spines and stings) b. Defensive Behaviors (autonomatization and bites) c. Chemical Weapons ( sprays and toxins) C. Risk Effects 1. Predator risk effects arise when: a. Predator alters the behavior of prey b. Negatively influences the fitness of prey c. Antipredator responses can reduce either survival or reproduction d. Risk effects can exceed direct predation effects 2. Whether prey should minimize direct predation or risk effects depend on their relationship? a. Ex. Spiny lobsters adaptations i. Gregariousness begins: When crypsis ends When seeking crevices shelters Before group defense is effective ii. Gregariousness is Favored by reducing attacks Not favored by escaping attacks May be decreasing in lobsters today
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