Behavioral Ecology

Adaptive value

Adaptive value

Extent to which an adaptation improves the evolutionary fitness of an individual

Tinbergen’s questions

• Mechanism

  • What factors trigger a given behavior in an individual

• Ontogeny

  • How this this behavior develop over the lifespan of an  individual

• Adaptive value

  • Why is this behavior adaptive for the individual

• Phylogeny

  • How has this behavior evolved and why does it differ between species

Central-place foraging

Repeatedly venture out from a central place or nest to forage and then return to consume for cache their food

Pika

• Questions they need to answer

  • How far should i travel

  • How much food should i collect per trip

  • What kind of food should i collect

• Most effective strategy is collecting from patches at an intermediate distance

• Currency

  • Energy spent running back and forth to the patches

• Alpine flowers take some time to recover so as a foraging season continues, pika have to travel further and the further patches are more dense

  • The energy collected from a given patch increases as the patch’s distance increases. This levels off at far distances

  • Danger linearly increases with distance

• Under the influence of fear, pika should forage closers to the cache

  • Adding rock piles allows for pika to forage further

Optimal foraging theory

• Evolution has favored behaviors that maximize an individual's rate of food harvest 

• Measuring fitness is difficult

  • Researchers evaluate behaviors according to how they affect some other variable that is related to fitness

  • currency

    • Account for benefits and costs

Predation risk affects foraging decisions

• Ecology of fear

• The risk of being killed is a significant cost of foraging

• Foragers would reduce their foraging effort as their perception of predation risk increases

  • Foragers should be affected both by direct changes in perceived predation risk caused by an increase in predator abundance and indirect changers in perceived predation risk caused by changes that make the environment seem riskier

Giving-up density

• A measure of the perceived cost of foraging. The amount of food remaining in a specific location after one or several foragers have eaten and then given up

• Urbans birds are less affected by predation risk

Optimality theory

Evolution has favored behaviors that are optional. Cost-benefit, currency

Profitability

• The rate at which a predator gains energy from a given prey item

• Energy content divided by handling time

• Understanding profitability is one key to understanding optimal diet choices

• Search time impacts how likely a pika is to eat the less optimal food item

Optimal diet model

• A forager should either take only the most profitable prey item or should take both profitable and less profitable items as they are encountered

• A forager should either be a specialist or a generalist

Why might an animal got forage exactly as predicted

• Animals do not have perfect knowledge about their choices

• Decisions may be complicated by other factors like predation risk and prey defense

• Energy may not be the only currency animals use to make choices

• Foragers may mistake one prey item for another

Marginal value theorem

• Determines when an organism facing diminishing returns on investment should abandon a patch, mate, or other resource

• An optimal strategy is one where the resource is absconded when the organism average gain rate is maximized 

  • If travel time increase, the forager should spend more time at the patch

  • Foragers should collect more food from distant patches

Game theory

• Study of strategic decision making in contests

• Playes act in their own self interest to secure the best possible outcome given the rules of each game and they the payoff for any strategy depends on other players’ strategies

• Evolution favors players whose choices maximize their fitness

Hawk-dove game

• Two players compete for control of a resource. 

• Hawks

  • Aggressive and will escalate every contest to a fight, risking injury if their opponent also plays hawk

  • Hawks always beat doves, but only win half of their battles with hawks

  • Cost of losing is an injury

• Doves

  • Never fight and are never injured. Will attempt to win contests through displays

  • Doves always lose to hawks, but win against other doves half of the time

  • Cost of losing is the expenditure of the display

Evolutionarily stable strategy

When it is adopted by all the members of a population, cannot be successfully invaded by an individual with a different strategy

Pure

Is not composed of other strategies a player should adopt. Set of behaviors an individual always performs in a given type of contest

Mixed

• A mix of other strategies each of which is played with some strategy

• Each individual always plays a particular strategy and at eq there is a certain frequency of each type of individual

• Each individual in the population plays both strategies each with certain frequency

It is always better to be the rare strategy of the two

Both types coexist because both strategies do better when they are relatively rare

Frequency-based selection

The fitness of a phenotype is a function of its relative abundance within the population as a whole

Payoff matrix

Summarized all possible payoffs for a particular game

• Benefit of victory affects the expected payoffs for all three of the contests that the challenger could actually win

• Cost of injury affects only the expected payoff involving fights which is that for hawk vs hawk

• Cost of display affects only the expected payoff involving displays, which is that for dove vs dove

• Fighting should be the most common when contestants benefit greatly from winning the fight but risk little of they lose

Hunters vs. pirates

• Hunters hunt for their food

• Pirates are kleptoparasites 

Hawk-dove-bourgeois

• Individuals rarely enter contests as equals

• Vacant territories are rare

  • Territory owner vs intruder

  • Territory owners value the territory more and are more likely to escalate fights due to this

• Owner plays hawk while invader plays dove

Maraud or guard

• Marauder seeks to destroy

  • Are not deafening their own bower 

• Guarders stay home and protect their bowers

  • Are not impacting any competition

• A pure guarding population would provide the best payoff for males

  • Prisoners dilemma, when when two contestants would collectively do best by cooperating, they often don’t 

Monogamy is likely when both parents can increase their fitness more by providing care than by seeking additional mating opportunities

Polygyny

One male mats with multiple females

Polyandry

• One female mates with more than one male, but each male mates with only one female during a single breeding season.

• Fertility insurance

Polygynandry

Both males and females take multiple partners during a given breeding season

Anisogamy

• Difference in size and every production of gametes

• Sexes experience different selective pressures

• Females will be choosy when it comes to selecting mates

Sexual selection

• Form of evolution by natural selection that acts on traits affecting mating success

• Competition for access to mates

• Mate choice

Intrasexual selection

When one sex directly competes with members of the same sex for mating opportunities

Intersexual selection

One sec choses among members of the opposite sex

Widowbird experiment

• H1 female widowbirds prefer ornamented males

• H2 female widowbirds chose males based on territory quality

• Cut tails, reattached, lengthened, untouched

• H1 was supported

Females gain indirect benefits from choosing showy males

• Good genes

  • Increase the fitness of offspring by ensuring heterozygosity or conferring advantages like disease resistance. Ornaments are a signal that they have better genes

• Runaway sexual selection

  • Female preference creates a feedback loop that selects for more and more extreme male ornaments. Females that prefer extreme traits will create songs with extreme traits and daughter that prefer extreme ornaments

Female choice is more responsible for exaggerated ornaments like long showy tails while male-male competition is likely responsible for exaggerated weapons like thick horns

Sneaky males

• Small, unfit

• Will sneak in while a more fit male is reproducing 

• Large migratory mals do best when comparatively rare

• Small sneaky males do best when comparatively rare

Parents should only invest resources in their current offspring if they can't do better by investing those resources in their own survival or future offspring

Cuckolders

Mimic females to trick parental males into thinking that they are getting a 2 for one when in reality :/

Neff test whether males reduced the amount of parental care they provided in response to a decrease in paternity certainty

• A parental male cannot determine if any eggs in his next were fertilized by another male simply by inspecting the eggs. Visual cues. Was another dude there?

• Once hatched, chemicals released by newly hatched fry indicate if they ARE the father

Altruism

Potentially costly act that benefits the recipient without providing the actor with any benefits in return

Mutual benefit

Benefits both the actor and the recipient

Selfishness

Benefit the actor while negatively impacting the recipient

Spite

Neither individual gains a fitness benefit. Both individuals are harmed

Cooperation is more likely to evolve when individuals repeatedly play the same partner and remember that partner’s former behavior

Reciprocity

• When individuals repeatedly have the opportunity to help one another, cooperation may evolve in individuals who receive help in turn help those who donated the assistance

• Favored when the benefit for the recipient is greater than the cost of the actor, there are frequent opportunities for repayment, and individuals can recognize each other and remember past behavior

Waring call hypothesis

• Benefits caller 

  • Calling benefits the caller by helping it avoid getting caught

    • Calling increases predation risk

    • Calling decreases predation risk

• Reciprocity 

  • Calling benefits the caller because the warning is reciprocated at a later time by squirrels who are warned by the caller

    • Females are more likely to call

    • Males and females are equally likely to call

• Alerts relatives

  • Increases the survival of relatives

    • Callers do not discriminate against non-callers

    • Callers do not discriminate against non-callers

Direct fitness

Benefits that improve the reproductive success of the actor

Indirect fitness

Benefits that improve the reproductive output of related individuals carrying som eo the same alleles as the actor

Inclusive fitness

Combination of the two above

Cooperation will be favored when

• The actor and recipient are closely related

• The benefits to the recipient are relatively large

• The costs of the behavior are relatively small

Kin selections

Subordinate males can maximize their inclusive fitness by forgoing breeding in order to help closely related dominant males achieve greater reproductive success

Patient males

If breeding territories are limited, a subordinate male may maximize its fitness by helping a dominant male until an opening appears

Eusocial

• Strict division of reproductive labor

• Cooperative care of the young

• Overlapping generations

• Kin selection may help explain the evolution and maintenance of eusociality 

Hamilton's rule

Behaviors are favored when ember inclusive fitness is positive