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Alternative Male Strategies Male Mating Behavior: Discrete Behavioral Phenotypes Anatomical Dimorphism Mating Opportunities Producers/Scroungers; Social Parasites Frequency Dependent Equilibrium (ESS)?
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Alternative Male Strategies Green Treefrog (Hyla cinerea) Two Male Mating Strategies: Callers Satellites
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Green Treefrog Strategies Amphibians Males at Pond, Calls Attract Females, Females Arrive & Mate, Oviposition Calling Necessary Energetic Cost (?), Predators(?) Costs of Aggression
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Green Treefrog Strategies Callers Larger Defend Calling Site (Cost) Call to Attract Females Females May Prefer Callers as Mates Over Satellites
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Green Treefrog Strategies Satellites Smaller (Minimally) Silent Position Near Active Caller Try to Intercept Females Attracted to Vocalizations of Caller(s)
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Green Treefrogs Perrill et al. 1982. Anim Behav 30: 43. Release Female Green Treefrogs Satellites Same Reproductive Success as Callers Satellites Intercept Females, and Mate When Females Briefly Outnumber Callers
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Male Strategy Equilibrium? p Frequency of Callers (1 – p) Frequency of Satellites Consider Fitness of Each Strategy at p = 0, and p = 1
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Male Strategy Equilibrium? p = 0; All Satellites Satellites: No/Low Fitness; Females Not/Less Attracted in Absence of Male Vocalizations Rare Caller Attracts “All” Females; Caller Has Higher Fitness (Invades)
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Male Strategy Equilibrium? p = 1; All Callers Females Attracted Rare Satellite Mates Without Incurring Costs of Calling Rare Satellite Higher Fitness (Invades)
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Male Strategy Equilibrium?
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p < p^Callers More Fit, Increase p p > p^Satellites More Fit, Decrease p p = p^Equal Fitness, Equilibrium Evolutionarily Stable
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Alternative Male Life Histories Discrete Male Lifetime Strategies Bluegill Sunfish (Lepomis macrochirus) Males Differ: Age First Reproduction, Growth Rate Size, Coloration, Parental Care, Length of Life
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Alternative Male Life Histories Gross, M.R. & Charnov, E.L. 1980. Proc. Natl. Acad. Science USA 77:6937. Bluegill Sunfish: Ontario Freshwater Lakes: Nesting Colonies Males Obtain Small Territory, Substrate Nest, Parental Care
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Bluegill Sunfish Life Histories Colony Males & Nests: Attract Females School of Gravid Females Arrives Enter Nest Single, Release Eggs Territorial Male Usually Fertilizes Eggs; Cares for (“Fanning”) Eggs & Larvae
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Bluegill Sunfish Life Histories As Females Spawn Small Male May Intrude, Release Sperm Medium-sized Male, with Coloration of Female May Approach Nest & Release Sperm “Parasites” on Territorial Male’s Effort
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Bluegill Sunfish Life Histories Three Male Behaviors: Parental (7 yrs old & older) Sneaker (2 – 4 yrs old) Satellite/Female Mimic (4 – 6 yrs old) Simply Age-Dependent Behavior?
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Bluegill Sunfish Life Histories
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Sunfish Growth Sensitive to Energetics Testis Growth, Sperm Production Reduces Increase in Body Size Fix Age, Males Capable of Reproduction Show Reduced Linear Growth
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Bluegill Sunfish Life Histories Analysis of Sperm Production/Male Growth Two Alternative Reproductive Life Histories First 2 Yrs: No Difference Diverge as 2-Year Olds
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Bluegill Sunfish Life Histories
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Sneakers Age to Satellites Parental Past Age 7? Sneakers Injured, Susceptible to Infection Sneakers & Satellites Greater Age- Specific Mortality than Future Parentals Same Lifetime Reproductive Success?
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Females: Courtship Costs Should Female Tolerate Courting Male? Benefits of Mating Reduced for Already-Mated Female Costs Loss of Foraging Opportunities Transmission Pathogens/Parasites Attraction of Predators
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Females: Courtship Costs Female’s Decision Reproductive Status (Mated vs Virgin) Nutritional Status (Sated vs Food Deprived)
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Courtship: Orb-Web Spider Herberstein et al. 2002. Behavioral Ecology and Sociobology 51:440. Orb-web Spider Agriope keyserlingi Female Tolerance of Male on Web: Mating to Pre-copulatory Cannibalism
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Courtship: Orb-Web Spider Virgin: Requires Eggs Fertilized Maximal Benefit of Mating Females May Mate With > 1 Male Improve Offspring Viability (Variability) Reduced Benefit of Mating Same Costs
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Courtship: Orb-Web Spider Males: Tug Silk Threads of Web Signal to Female May Signal Potential Prey, Predators Steal Prey Female Has Captured
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Courtship: Orb-Web Spider Costs to Female: Loss of Foraging Efficiency Prey Avoid Web, Males Damage Web Loss of Stolen Prey Exposure to Predators (Mantids) Increased Chance of Infection Males Can Injure Female
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Courtship: Orb-Web Spider Field: Male on Web Prey Capture Rate reduced from 0.243 to 0.05 items/hr Approach by Mantid Predators: 5 Times as Frequent at Courting Pairs
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Courtship: Orb-Web Spider Lab: Frequency Female Attack & Cannibalism Greater Among Mated than Among Virgin (Fertilization Benefits) Mated Females: Only Sated Remated Frequency Female Attack & Cannibalism Greater Among Food-Deprived than Sated Females
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Courtship: Orb-Web Spider Males: Preferred to Court Virgins Safer, More Eggs to Fertilize Deserted Larger Females
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