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Animal Behavior (Game Theory (Animal behaviorists use it to . . .…

- - - - specialists vs. generalists
        
        Animals with long "h" and relatively short "s" should tend to be specialists
        
        in productive environments
        
        Animals with long "s" and relatively short "h: should tend to be generalists
        
        in unproductive environments
      - Limitations
        
        Foraging is often risky buisness
        
        Tactics that yield a high rate of energy may also be dangerous
        
        High rate of gain doesn't matter if you're dead
    - - How long should foragers search in one "patch" before moving on to a new patch
        
        Gain curve: energy intake over time; increases rapidly at first and then levels out
        
        Travel time: time required to get to a patch before energy can start climbing the gain curve
        
        Case Study: Great Tits (Parus major)
        
        proved accuracy of the gain curve
    - - Caloric content (energy gain from eating them!)
      - Abundance (affects time spent searching for them)
      - ease of capture/consumption (affects time spent handling them)
  - - - Costs of foraging
        
        h = time spent handling a prey item (capture & consumption)
        
        s = time spent searching for a prey item
      - Benefits of Foraging
        
        E = energy gain (e.g., calories)
      - "Optimal" foraging means maximizing benefit/cost ratio = maximizing rate (R) of energy gain (calories/time)
        
        R (average) = E / (h + S)
        
        Comparing the old diet to the new diet
        
        P > R, E(new)/ h (new) > E (avg.)/ (h (avg) + S (avg.))
        
        Follow the "Principle of Lost Opportunity"
        
        Eat worse things only if better things are hard to find
        
        Can "lose opportunities" to search for best item while handling worse items
        
        Always eat the best type...
        
        Cannot "lose the opportunities" by taking the best thing
- - - - Case Study: A swordtailfish
        
        Males have long tails and females like them
        
        For a system like this to evolve we need 2 traits
        
        Female preference for swords
        
        Males with swords
        
        Which came first?
        
        Preference for swords evolved before the sword
        
        exploits a "pre-existing sensory bias"
  - - - Optimal distance includes
        
        One that maximizes benefits of reduced attraction of predators to the nest
        
        One that minimizes costs of energy or reduces parental care
        
        Maximized distance between costs and benefits at an intermediate distance
        
        Found by E (new)/ h (new) > E (average)/ (h (avg) + S (avg))
      - Optimality Theory requires
        
        A fitness surrogate or currency (e.g. rate of food gain, # mates acquired, # offspring produced)
        
        Variation among behavioral phenotypes for selection to act on (e.g. differences in what time of day that males court females)
        
        Constraints: data, hypotheses or model assumptions that connect currency & phenotype to each other (e.g., the curves relating behaviors to fitness costs and benefits)
  - - - One big problem is that evidence of most behaviors does not fossilize
        
        Therefore one uses the phylogenetic comparative method
        
        which uses information on the historical relationship of phylogenies to test evolutionary hypotheses
        
        Compare behaviors of extant species in a phylogenetic context
    - - Function: how a behavior benefits survival & reproduction ("fitness value" or "adaptive value")
        
        Darwinian Premise: behaviors evolve in ways that optimally balance benefits and costs
        
        Behaviors also have costs
        
        ex. while looking for food, animals expend energy
        
        "opportunity cost"
        
        Case Study: Black-headed gulls
- - - - Frequency Dependence
        
        Fitness consequences of behavior are often frequency depedent
        
        Benefits & costs of adopting a particular behavioral "strategy" depend on the frequency of other strategies in the population
        
        Relative frequency determines which strategy has the advantage
      - Frequency Dependent Predation
        
        Involves the concept of a "search image"
        
        When an individual in the group does not fit within this search image they have an advantage over the others
        
        This advantage is lost as more individuals without the specific image become more common
        
        Relative frequency determines which phenotype has the advantage
  - - - evolutionary fitness!
    - - Determines behavioral strategies that evolve based on benefits and costs
      - How to keep score
        
        Each column is separate optimization problem
        
        A "pure strategy" ESS is the box which contains the highest number in a column
        
        There may be 2 ESSs
        
        There may be 0 ESSs
        
        The population will then evolve to a stable mixture of strategies, called a "mixed ESS"
        
        Consider diagonal principle as it is when most individuals are conducting the same behavior
      - Ex. "Prisoner's Dilemma Game"
        
        Shows that ESS may not always make logical sense, go off of the average benefit when the ENTIRE population is making the same decision and a choice that may not be invaded by another population
  - - - Reproduction
      - Communication
      - Conflict/ Fighting
      - Cooperatoin
      - Predator/Prey
- - - - Most conflicts are resolved with displays, not fights:
        
        The "optimal" contest strategy is likely to . . .
        
        Depend on the strategy of other "players"
        
        Be frequency dependent
  - - - 2 strategies are available
        
        Dove: Display to other doves; retreat if challenged by hawk
        
        Hawk: always fights no matter what
        
        3 possible outcomes
        
        Dove v. Dove
        
        50:50 chance of winning; neither is injured but both pay display costs
        
        Hawk: Dove
        
        Hawk wins with no costs; Dove retreats with no costs
        
        Hawk v. Hawk
        
        50:50 chance of winning; loser incurs injury costs
    - - Cost of a display
        
        D = -10
      - Cost of being Wounded
        
        W = - 100
      - Value of the resource
        
        V = + 50
      - This is a "mixed ESS"
    - - Convention
        
        Use some sort of conventional rule (aka arbitrary asymmetry) to settle contest
        
        "ownership" of some contested resource is one possible convention
        
        Human exs.
        
        Flipping a coin . . .
        
        "I was here first . . ." arguments
        
        "Possession is 9/10ths of the law . . ."
        
        A new strategy
        
        Bourgeois: Mixed attack/retreat behavior is the most stable for a population
        
        This strategy resists invasion by either hawks (always attacking) or doves (always retreating)
        
        An all-hawk or all-dove population can be successfully invaded by bourgeois individuals because their expected payoff is higher than either pure strategy
      - Assessment: Predict the likely winner in advance by assessing your rival's Resource Holding Potential (RHP)
        
        To avoid costly, escalated contests, you should . . .
        
        advertise your strength, fighting ability, motivation
        
        assess your opponent's strength, fighting ability, motivation
        
        Often accomplished using communication signals
- - - - This form of selection depends, no on the struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex, generally the males, for the possession of the other sex
      - why is there a struggle in the first place??
        
        Sperm are cheap! Eggs are limited!
        
        New Concept: Anisogamy
        
        Typical
        
        Male: Gametes small, abundant and cheap
        
        Female: Gametes big, few and costly
        
        Can have profound influences on sex differences in behavior
        
        Females often the "limiting sex"
        
        "operational" sex ratio
        
        M:F >> 1
        
        Potential reproductive rate
        
        M >>>> F
      - 2 Types of sexual selection:
        
        Intra-sexual selection
        
        Members of one sex (usually the males) compete among themselves for access to members of the other sex
        
        Types of Intra-sexual selection
        
        Endurance rivalry
        
        Differences in reproductive success determined by differences in the amount of time spent courting or searching for mates
        
        1 more item...
        
        Direct Fighting (over females or the resources they need)
        
        Males compete for direct access to resources females need for reproduction
        
        1 more item...
        
        Sperm competition
        
        Competition among males to determine whose sperm fertilize the female's eggs
        
        2 more items...
        
        Mate - guarding
        
        Males guard the females they mate with to prevent them from subsequently mating with other males
        
        1 more item...
        
        Alternative mating tactics
        
        May be behavioral polymorphism
        
        2 more items...
        
        May be genetic polymorphism
        
        2 more items...
        
        Use by small, weak, wimpy males that cannot compete against the tactics of dominant males
        
        "male-male" competition
        
        Inter-sexual selection
        
        Members of one sex (usually the females) prefer to mate with members of the other sex that have particular traits
        
        "female choice"
        
        Male traits evolve because females prefer them
        
        Sexually selected traits are costly to the males that possess them!
        
        Decrease foraging time
        
        Increase energy expenditure
        
        Increase predation risk
        
        "Cryptic" Female Choice
        
        can even go beyond obvious mate choosing . . .
        
        males deposit sperm in packets called spermatophores
        
        females mate with several males
        
        females preferentially move sperm from larger spermatophores into the spermatheca
        
        What do females get from being choosy?
        
        "Direct Benefits"
        
        male parental care
        
        territory resources (food, shelter, oviposition site)
        
        nutrition (nuptial gifts or courtship feeding)
        
        protection / decreased harassment
        
        more or better sperm / increased fertilization
        
        "Indirect Benefits"
        
        "good genes" in offspring
        
        sexy sons attractive to females
        
        higher genetic compatibility
        
        Sometimes males contribute sperm but not much else (eg, some frogs, many insects)
  - - - Trait is costly and indicates some heritable aspect of a male's genetic or physiological quality
        
        Idea that females pick good mates
      - aka the "good genes" hypothesis
        
        Case Study: gray tree frogs
        
        function of long v. short calls
        
        calling is very energetically costly
        
        only high - quality males with "good genes" can produce the longer calls females prefer
    - - Trait and preference co-evolve in a positive feedback loop that "runs away"
        
        Over time, trait and preference become genetically linked!
        
        Females come to prefer males with the trait who produces sons with the trait and daughters that prefer the trait (i.e. positive feedback!)
        
        The preference is selecting for itself! It can RUN - AWAY
        
        Eventually, the trait may become costly:
        
        Natural selection can oppose (and stop) the process if trait becomes too costly
        
        oxytocin being released during delivery which causes baby's head to push on cervix
      - Initially, the trait can be completely arbitrary:
        
        It doesn't have to have anything to do with male quality
        
        Females just have to like it (e.g sensory bias!)
      - Genetic correlation is key:
        
        The predicted genetic correlation between trait and preference drives the "runaway" process
    - - trait exploits a "pre-existing sensory bias" of females
        
        Case Study: A "hidden preference" in birds . . .
        
        Red coloration in birds & parasite load
        
        red pigments must be acquired in diet
        
        sick males not good foragers
        
        "fluctuating asymmetry"
        
        only males in good condition develop symmetry
        
        developing bilateral symmetry is hard
        
        Preference may evolve before the trait
        
        may explain origin of many traits males exhibit
      - trait is costly and indicates some heritable aspect of a male's genetic or physiological quality
    - - Trait evolves through a co-evolutionary "arms-race" between male attractiveness and female resistance
        
        similar to predator-prey relationship
      - Not covered in class
- - - - 3 Hypotheses
        
        Mate Guarding
        
        males remain with female . . .
        
        to prevent her from subsequently mating with other males
        
        because "receptive" females are rare, widely scattered, or hard to find
        
        Mate Assistance
        
        males remain with females to help care for offspring especially when parental care increases offspring survival
        
        Female Enforcement
        
        monogamy is enforced by female partner
      - 2 different types:
        
        Social Monogamy
        
        male and female share territory/resources and engage in behavior indicative of a social pair bond
        
        does not imply anything about sexual fidelity or reproductive pattern
        
        Genetic Monogamy
        
        a female-male pair reproduce exclusively with each other
        
        Only small portion of "socially monogamous" species also exhibit strictly "genetic monogamy
        
        a.k.a "sexual monogamy"
    - - Polygyny : one male mates with multiple females; females (generally) mate (exclusively) with one male
        
        Predicted to be common mating system due to anisogamy
        
        How can males maximize reproductive success?
        
        How can females maximize reproductive success?
        
        Comes in 4 varieties
        
        Resource defense polygyny
        
        Males compete for access to resources that females need for reproduction
        
        Female defense polygyny
        
        Males compete for access to groups of females (e.g. harems)
        
        Number of males searching for a female >>> number of sexually "receptive" female
        
        Scramble competition polygyny
        
        Males actively search for receptive females but do NOT defend females or resources
        
        Common when . . .
        
        females and/or resources are widely scattered
        
        reproductive period is short & synchronous
        
        Lek polgyny
        
        males aggregate in "leks" where they display to attract females
        
        they do NOT
        
        provide parental care
        
        defend females or resources
        
        actively search for mates
      - Polyandry : one female mates with multiple males; males may mate with only one female
        
        More common than predicted by anisogamy
        
        2 Types of polyandry
        
        Male-driven polyandry: females submit to matings with multiple males because it is less costly than resisting
        
        female-driven polyandry: females solicit matings with multiple males because it provides adaptive advantages
        
        Why do females choose to mate with multiple "best" males?
        
        Direct Benefits
        
        Infanticide reduction hypothesis - mating with multiple males creates greater confusion about paternity
        
        Better protection hypothesis - mating with multiple males means females receive more protection / decreased harassment
        
        More resources hypothesis - mating with multiple males means more nutrition (e.g. nuptial gifts) or parental care
        
        Fertility insurance hypothesis - mating with multiple males reduces risk of unfertilized eggs
        
        Indirect (Genetic) Benefits
        
        Good genes hypothesis - females solicit EPCs from higher quality males than their social partner
        
        EPCs are common & successful
        
        EPFs (extra-pair-fertilizations) can account for a male's reproductive success
        
        Genetic compatibility hypothesis - mating with multiple males increases likelihood of more genetically compatible sperm
      - Promiscuity (Polygynandry): males and females mate with multiple partners a mixture of polygyny and polyandry
- - - - But some Parents DO care
        
        Parental care evolves when benefits of care (in terms of lifetime reproductive success) outweigh costs of providing it
    - - Maternal Only
        
        Large benefits for females
        
        Already invested a lot
        
        internal development
        
        long gestation periods
        
        large gametes
        
        Single parenting is feasible
        
        Single parenting is feasible: Female mammals can feed babies, boy mammals cannot
        
        Large costs for males
        
        Lost mating opportunities during prolonged gestation and nursing
        
        With internal fertilization
        
        Lower paternity certainty
        
        have the first chance to desert
      - Bi-Parental Care
        
        Birds: quite common
        
        Other taxa: exists, but uncommon
        
        Why in these groups?
        
        both parents CAN provide care
        
        e.g. male birds can feed dependent offspring (unlike mammals)
        
        Care by both parents is essential for offspring survival
        
        e.g. often found in species inhabiting harsh environments
        
        e.g. among endotherms with relatively high metabolic demands (birds and mammals)
        
        When opportunities for both sexes to breed again are very costly or relatively few
      - Paternal Only
        
        Rare in birds and mammals
        
        occurs in some fish and frogs
        
        Why does this occur
        
        there is external fertilization
        
        females often have the first opportunity to desert!
        
        Males can often continue to attract other females while caring for offspring
        
        There is indeterminate growth . . .
        
        means they generally keep growing their entire lives
        
        this effects male/female fecundity differently
        
        fecundity is affected by gametes produced which is affected by body size
        
        3 more items...
        
        makes parental care relatively more costly for females
      - Dependent on . . .
        
        Who invests more in gametes?
        
        Who has first chance to desert? . . . may depend on mode of fertilization
        
        Internal
        
        mammals, birds, reptiles, etc.
        
        External
        
        Most amphibians, fish, arthropods, etc.
        
        Who has greater certainty of parentage
        
        Who can provide better
        
        Who has better chance of reproducing again soonest
  - - - Increased survival of individual offspring
    - - Female
        
        INcreased predation risk
        
        Reduced foraging behavior
        
        Reduced future fecundity
        
        Physiological costs (e.g., gestation, lactation)
      - Male
        
        Increased predation risk
        
        Reduced foraging behavior
        
        Reduced future fecundity
        
        Lost opportunities to mates (e.g., with other females)
        
        Uncertain paternity (e.g., inadvertently caring for offspring of other males)
  - - - Use a "rule of thumb" : if there is a begging chick in my nest feed it"
      - "Brood parasites" can exploit parents adopting this rule
      - Brownheaded cowbirds & cuckoos (the parasites) lay eggs in the nests of other birds (the hosts)
    - - "mafia behavior" on the part of parasites
      - Discrimination between "own egg" and "parasite's egg" is not always easy