Behavioral Ecologythe study of the adaptive significance of behaviorshow does a behavior influence survival and reproduction?Foraging - obtaining food has the benefit of taking inresources that are necessary for survival and can be used forreproduction but it has the cost of time, effort, and risk thatmust be invested to obtain themPrediction: if natural selection has shaped foraging behaviorthen organisms should take food items that have maximal foodvalue relative to the costs of obtaining themExample - Bluegill foraging for planktonic food -predictions:if prey are rare - take every food item as it is encounteredif prey are common - take only the prey that maximize energyintake relative to foraging time (large prey)The optimal foraging hypothesis is now called Optimal ForagingTheoryOther variables influence foraging behaviorpredation risk - if risk differs between habitats, feed where the reward relative to risk is greatestexample: Bluegills - when small - risk of being eaten by bass is high - especially in open waterFood is more available in open water than in vegetationPrediction - feed in vegetation when small - shift to open waterafter growing to a size where predation risk is low relative torewardfood value includes more than calories - forage on food items oflower calorie reward if they meet other nutrient requirementsfood may be more available somewhere else - there is an optimalswitching time for foragers that can move between food patchesReproductive Strategies - behaviors that increase the likelihoodof reproductive successMate choice -Females generally invest more in reproduction than malesMales often can produce offspring by multiple matesPrediction - females should be more discriminatory in matechoiceWhen males invest more than females they are more choosyOften male reproductive success is limited by the number ofmatings they can obtain - female reproductive success is limitedby their choice in a mateMales compete with each other for access to mates - traits thataid in competition are advantageousFemales choose males that are likely to produce the healthiestoffspring (most showy) or males that commit the most resources to the aid of the female - e.g. a nestSocial BehaviorsLiving in groups has benefits - greater protection from predatorsincreased ability to find foodand costs - increased disease, and parasitismSocial groups form because individuals benefit from suchassociations throughreciprocity - “tit for tat” exchanges - individuals make sacrifices now in exchange for reciprocity from others laterkin selection - traits for self-sacrificing (altruistic) behaviorcan increase in frequency if through altruism, relatives intotal benefit more than the individual loosessiblings on average share 1/2 of their genes - altruism canbe adaptive if it benefits a sibling by more than twicethe cost to the altruistSacrifices are not made “for the good of the species.”Eusociality - groups of related individuals with a division of laborfor overall reproductive benefitHoneybees and ants - workers have greater contribution to the nextgeneration through helping their mother (queen) raise their sisters(some of whom will be queens) than they would if they reproducedon their ownAll workers receive the samegenes from their father (whois haploid) and share 1/2their mother’s genesall are related 3/4 to eachother and to their futurequeen sistersthey would only be relatedby 1/2 to their own offspringHelping their mother produce sister queens is better than
View Full Document
Unlocking...