Symmetry

• Symmetry of body form: similarity of left and right sides.

• Related to developmental stability• Which is related to ability to adapt to change.

here

Summary: good gene hypothesis

• Females should choose males with “good genes”

• How do they do it?• Survival tests and health evaluations• Obviously equating health with genetic well

being. • Likely not something “conscious” related to

evolutionary selection of those who do select the “right thing”.

Runaway Sexual selection

• This one is tricky• Example: two genes exist, one for a trait in

males and another for mating preference in females.

• Key is that over time these two genes become associated with each other: if male trait gene is in male offspring, mating preference will be in their sisters

And it gets more complicated!

• If a proportion of females have gene for brightly colored males and rest don’t

• If male coloration is genetic, then females that prefer bright colors will mate with the bright ones

• Now have offspring with both traits• Assume: coloration is switched on in males,

preference in females

Lastly

• So, have females with preference trait also have latent color trait.

• If, as they prefer, mate with colorful male, will produce young male who are even more colorful AND females that prefer color MORE than their mothers did!

• Etc. etc. in a positive feedback or runaway selection.

Example

• Book gives one about stalk-eyed flies where after many generations of females only having access to short stalk-eyed males

• Given the choice they preferred short stalk-eyed males.

• Another example might be height in humans.• Some females prefer tall men: offspring (male

and female) have tall gene AND preference for tall males

Examples

• So daughters, who prefer tall men also have tall genes to pass on and pair up with tall genes from mate.

• The key to all of this is that preference for a trait is in itself a genetic trait that can be passed on!

Sensory exploitation

• Sensory bias; preexisting bias• Females initially prefer traits that elicit greatest

stimulation of sensory systems• Example: red berries good and nutritious• Females equate red with good and nutritious• IF red color shows up in males, females will show

preference for it.• Proposes the origin of female preference for a

trait

Example

• Primates with trichromatic vision: can see reds and oranges

• Initially to help find red-orange fruits• Females also have preference for red-orange

skin/hair coloration in males• IF Sensory bias: “preference” for red-orange

developed as a foraging aid had to come first.

What did they find?

• Evidence that trichromatic vision evolved BEFORE red coloration in males.

• The key here is ability to sense a trait comes from a sensory capability that developed BEFORE and for some other reason, than that trait, which predisposes the female to prefer that trait.

• Cart and horse thing.

Learning and Mate Choice

• So far talking about female choice as having a strong genetic base.

• Need to examine role of learning in this• How much of a role it plays?• What kind of learning?

Sexual imprinting

• Review: imprinting is learning a behavior after brief exposure to it during a critical period

• Two lines of research:• 1) cross-fostering: do young raised with

adaptive parents, show different preferences?• 2) Novel traits: Introduce a novel trait and see

if young use this in their mate preference

Example

• Novel traits: Mannikin bird – put red feather on parents’ heads.

• Do young with red feather parents, then prefer opposite sex with red feathers?

• Answer seems to be YES!

• Various other examples supporting idea that there is a certain amount of imprinting going on

Traditional conditioning and mate choice

• Can individuals be “trained” or conditioned to modify their mate choice?

• Quail: brown and blond• Male brown raised brown, imprinted on

brown.• Given opportunity to mate with blond but

only opportunity to “see” brown female.• Result: after time, when had choice, preferred

blond female.

What does this mean?

• Mate choice may be imprinted BUT can be overridden by conditioning.

• IF positive reinforcement for change, will possibly change

• IF also negative reinforcement against imprinted, will most likely change.

Cultural Transmission and mate choice

• Mate-choice copying: Female’s mate-choice preference affected by preferences of other females in population – mate choice peer pressure!!

• Defined operationally: If Y - X > 0, then mate copying!!??

• X - chance of male mating IF he has not recently• Y – chance of male mating IF he has recently

done so

Mate-choice copying

• So… If a male becomes preferred by other females because he has mated with previous ones, that is mate-choice copying.

• Example: female black grouse

• Dominate male can account for 80% of breeding.

Black grouse

• Is this because of mate-choice copying?

• Observed that older females mated earlier and younger ones, “followed suite” mating with the same males.

• Is it because they copied older ones?

Black grouse

• Tested by putting in dummy female birds randomly in males’ territories.

• Males with more dummy females, regardless of location on lek, attracted more real females!

• So evidence for mate-choice copying

Song learning and mate choice

• Many birds use songs• Males learn songs• Females who also hear songs develop preference• Evidence of learning when switch juveniles to

other subpopulation with DIFFERENT songs• Males learn new songs AND females seem to

prefer them.• Might be combination of imprinting/copying

Cultural transmission

• Summary• Females “learn” mate choice by copying other

females: often older ones.• Advantage? “trust” older birds’ judgment.• In birds, males learn song that females

develop preferences for.

Mate choice summary

• Genetic basis: four models; Direct benefits, good genes, runaway selection, sensory exploitation.

• Ways to explain how mate-choice can be maintained or originate

• Learning: Imprinting, cultural transmission• Ways mating preferences are passed on beyond

genes, though may still have genetic basis!

Mate-choice summary

• Usually involves female and how she may develop mating preferences

• Important point: In all of this we tend to talk like individuals “purposely” do this.

• E.g. survival testing• Behavior passes selection filter and may not be

purposely done but just what is done by those that survive. No good, bad, divas, vamps, charlatans, etc. Terms we use!

Lets look at the males!

• Said that we now realize females are doing the choosing and thus shaping male anatomy/behavior.

• So now have basis for the male behaviors, still need to look at what they are.

• Males, like females not “purposely” doing behaviors, what is shaped by selection, sexual selection.

here

So what do males have to do?

• Mainly involves some type of male-male competition.

• As mentioned, this is the glamorous part of sexual behavior: males butting heads, dancing, etc.

• Now know it is often a health test but…• Need to look at a little closer

Male-male competition before copulation

• Often the “testing” of males’ genetic quality done before females choose mate.

• These are the dramatic ones!• However often very stereotypic in pattern• What males need to do BUT don’t want to get

killed doing it!• Goes from initial mutual assessment to final

combat if needed.

Example

• Red deer: Each step is designed to test the relative strength of the other.

• Less evenly matched, quicker inferior one leaves• More evenly matched, more likely to end in fight.

Lots of talk, little action!

• The “glamour” of it all is mostly the elaborate testing that goes on before actual physical combat.

• Most times, very little combat, just between closely matched males.

• Designed to maximize access to females while minimizing injuries from serious fights.

• Elaborate displays often for other males!

When it comes to a fight!

• Often anatomical adaptations• Thick manes on lions!!• Spongy bones on bighorn sheep

Male-male competition by interference

• Interference while attempting to copulate• Heavier larger males often interrupt

copulation attempts by lighter smaller males• Sometimes solicited by females: If not the

male she wants, attracts attention of larger more dominate male (Elephant seals).

Cuckoldry and male-male competition

• Males mating with other male’s female/s• Lots of examples in wild• Age old practice• Attempts by “subordinate” males to out

compete dominate males via “trickery”

Cuckoldry• Book example: Blue gills• Three different male morphs: parental,

sneaker and satellite.• Parental male attracts females• Sneaker males sneak in and release

sperm as male and female are doing the same

• Satellite: look like females!

Female-female competition

• Commonly accepted that females choose• Males compete, a test for choice by females• If we have a system where many females mate

with the “winning” males, no real competition among females.

• BUT…. In many cases, there will only be one female mating with the winner/s

• Territorial birds, wolf packs (one alpha male and female), lots of examples

So how decided which female gets the winner?

• Very little studied aspect of mate choice.• In humans, it is the stuff of sitcoms and high

school drama/pop songs!• In nature???• When female birds come north, males already

have territories: Assume there is some type of contest among females as to who goes where.

• Some might be age, older ones• Some, re-mate with same from previous year

Female-female competition

• In wolves, there is aggression between alpha female and subordinate ones: interference competition if male attempts to mate with other females

• Basically, males initially compete to be chosen but once you win, you become a limited resource and should be competed for!

• Need lots of study in this.

Overall summary

• First step in reproduction: mate choice• Females have most to loose so most times do

the choosing• Basically various tests designed to determine

genetic status of potential mates.• LOTS of variation, even within species!• Designed to get over those awkward initial

steps!

Mating systems (chap 7)

• Ok, you have now decided on with whom your going to reproduce.

• Saw lots of variation, lets try and make some sense out of it all.

• Are there basic categories of mating systems?• Well, yes and no….• Why do some species use certain systems and

others different ones?

Mating systems

• So will look at two major things:• 1) Types of mating systems

• 2) Evolution of different systems

Types of mating systems

• Four basic types: figure sums them up regarding participants, in general!

First Monogamous mating systems

• One male-one female only! True love!• At least for a mating season• Sometimes for life but rarely.

• Commonly change partners next season• Termed: Serial Monogamy

Long term: Fitness consequences?

• For female: If you have a good one, you stay with him. Sounds like a country-western song!

• For male? Might lead to more offspring: old field mice experiment.

Fitness consequences?

• For both, reduces energy and time needed to find a mate.

• Can reproduce sooner.• If territorial, experienced pair can gain/hold

on to territory.• Various reasons why staying together over

time advantageous.

Serial Monogamy?

• What are advantages?• Short-lived species: serial not by choice, mate

dies• Monogamous during raising of young is

advantage• Switching partners, either sex, increases

variability of your offspring.

Just how Monogamous are they??

• Monogamy sounds good but how well is it practiced?

• Long term monogamy? Old field mice?• 10% were not genetically related to male

Serial monogamy?

• Even in one season serial monogamy, are they truly monogamous??

Monogamy

• Of socially monogamous bird species studied, only 14% found to be genetically monogamous!

• Extra-pair copulations 11% up to 50% in some species!

• What is going on!!? Soap operas!!• Two types of “cheating”!• Cuckoldry: where other male mates with

“your” partner. E.g. purple martins.

Monogamy??

• Promiscuity: Females side: If she mates with more than one, promiscuous.

• Two player game!• Reasons? Male: more genetic offspring,

female: more genetically diverse offspring.• Example: Female blue tits with “cheat” with

only “quality males” i.e. high ranking males or males from farther away (the foreign factor!), leads to outbreeding!

Monogamy summary

• For female, can see more advantages• For male may lead to higher overall

reproductive output.• However, may not be as blissful as it seems!• What one would expect regarding natural

variation in a trait or behavior.• Depending on selection force will depend on

how Monogamous a species will be.

Polygamous mating systems

• For many species, this selection force leads to other non-monogamous mating behaviors.

• A common one is Polygamous mating systems

• Defined: either males or females have more than one mate during a given breeding season.

Two forms

• Polygyny: male mates with more than one• Polyandry: female mates with more than one

male

• Can be simultaneous: leks, elk• Can be sequential: Jacanas

Polygyny

• One male: many females• Passive: Males do not defend females• Leks or arena mating, an example• Saw earlier, males compete for favored locations• Females then come, bypassing “inferior” locations

and mate with male in favored one• One male can inseminate up to 80-90% of females.

Polygyny

• Active: Male actively defends actively defend access to females

• Female defense polygyny• Example: Epsilon wasp where males mature

earlier, locate cells where females will emerge and defend them.

• When females emerge, they mate with the territorial male.

In between

• Lots of variation between arena mating and female defense polygyny.

• Many ungulates such as elk: male defends or tries to, a harem. Kind of female defense but more fluid relative to female participation, she chooses to stay with male.

• Other ungulates: pronghorn, have lek like behavior but can be more mobile.

Advantages?

• Females: do not need to compete for “better male/s”.

• Assured of access to “best” genes

• Males: Obvious advantage to winner• Losers? Often related to winner so don’t lose

so much genetically!

here

Polyandry

• Female with many males:• Jacanas, tropical shore bird• Sex reversal: males incubate eggs/defends young• Female lays eggs sequentially in several male nests-how do males know eggs are theirs?? 93% of the time

Polyandry

• Rare in vertebrates but seems very common in social insects: ants, bees, termites

• One queen mates with many males (some worker males, some especially raised, lots of variation)

• Result: colony made up of one female lineage but many male ones.

Advantages to female?

• Sperm replenishment: New supply, no need to store sperm

• Material benefits: - Nutrients: nuptial gifts, chemicals in seminal fluids

female can use, male parental care. • Genetic benefits: Increases genetic variance of

offspring• Convenience: avoids costs of avoiding copulation

attempts

Promiscuous mating systems

• So far one male; many females or one female: many males

• If have both within population, referred to as Promiscuous mating systems.

• Two types: • 1)truly promiscuous: many males mating with

many females usually with no pair bonds forming.

Polygynandry

• Second type of promiscuous system• Here several males form pair bonds with

several females. Dunnock: small passerine bird is example.

• # of mates variable

Summary

• Again, quite a range of mating systems have been discovered.

• Basically all possible combinations and even some in between.

• But why so many?• Why such variability?

Why variability?

• Each represents an approach to capturing new energy for the population AND passing on genes

• Each system represents a functional way both of these are achieved, under the environmental conditions that exist.

• As with selection for body traits, there are selection pressures that favor one over the other, including within the same species!

• What can be some of those selection pressures?

Ecological drivers

• Remember: goals are 1) add young to the population and 2) “improve” genetic quality of offspring.

• Both of these can be considered related to resource levels and distribution.

Resource distribution

• Again, female driven• No general need to find mates BUT definite

need for resources.• Based on this proposed that female

distribution/mating patterns tied to resource distribution.

• Males follow female distribution

Resource distribution

• Dispersed resources: females must cover larger area and makes it difficult for male to mate/defend more than one female

• Clumped resources: Many females can use same resource in small area, defendable by one male, leads to polygynous systems

• Resources range from disperse to clumped in a continuum so proposed that at some point becomes more advantageous for females to participate in a polygynous system.

• Called the Polygyny threshold model (PTM)• Basically, when female can be more

productive in a multiple mate system than in a monogamous one, should see a switch to Polygyny.

• Still a theory but would explain the range of mating systems across species.

• May also help understand multiple systems in single species.

• Difference in resource distribution across a species range, could then lead to differences in mating systems.

Last words

• Mating systems important: How individuals interact for reproduction.

• Can be considered the most important intra species or social behaviors.

• However, note that type of behavior we see impacted by environment:

• So even for most “pure” behavior, behavioral ecology emerges

• But before we move on to behaviors of individuals with environment, including other species.

• Cover several other intra-specific or social behaviors not directly related to reproduction

• Cooperation, play, aggression, etc.

• These none directly sexual social behaviors can be found in all species, solitary to truly social.

• Just vary in types and amounts.• Viewed as behaviors of interactions between

and among individuals.• Involve communication, learning, innate.

First question

• First questions to ask are how and why such social behaviors develop?

• For example: warning calls: why put yourself at risk for the group?

• Perplexed many ethologists for long time. • Began looking at relatedness of individuals.• Know parent and offspring related but…

Kinship

• Briefly mentioned examples of related individuals: leks, bee hives

• Others: wolf packs, lion prides, flocks of geese, etc.

• One emerging observation is that there are a lot of groups of animals where members are related.

• Also that this relatedness affects the degree of social behaviors we see.

Kinship theory

• Began to look at this relationship and how it could affect the evolution of social behavior

• Led to new area: Kinship theory• Basic idea behind kinship theory is:• Social behaviors of species evolves …where

individual will value its neighbor’s fitness against its own according to the coefficients of relationship….

• So your degree of social behavior will depend on how related the other participants or recipients are to you.

• Thus the concept of kinship• Defined: probability that individuals share

genes they have inherited from common ancestors.

• “identical by decent” : genes from common ancestors.

• Can calculate relatedness: stuff of genealogy.

• Do you have common genes with the Queen?

Why is this important?

• Can view evolution working on individual: If you survive, your genes passed on.

• Kinship: your genes not the only copies out there!

• If you help someone with “your” genes survive, this behavior would be selected for

• Most likely this would be someone related to you: kin

• So you can be “more fit” by helping relatives• Idea of inclusive fitness

• So that is the evolutionary driver behind these social behaviors.

• What are some of the basic predictions?

Start with the family

• Since members of family closest related….• Emlen in late 90’s proposed 15 predictions!• Pg. 270 of your text.• Some important ones:• 1) Family groups will become unstable when

reproductive opportunities arise. - You will stay with the family until you have a

chance to reproduce

Families

• 2) Family stability will be the greatest in groups that control high quality resources

• Concept of dynasties: Not just humans!! - Survival advantage to pass on inheritance to offspring

Helping around the house

• 3) Help rearing offspring will be highest between closest genetic relatives.

• You will take care of your brother and maybe your cousin but more than that, you will need to get PAID!!

One more

• 4) Replacement mates will invest less in existing offspring than in biological parents.

- Cinderella, Snow white, the list goes on!

- Lions, tigers, oh my: infanticide!

Central theme

• Central to all these is that the closer your related the more cooperative social behaviors you will have.

• We can use kinship theory to directly explain behaviors we see.

• Parental care: is obvious, but not universal!• Will look at this one in more detail

Cooperation behavior

• This covers a lot of behaviors and will cover separately.

• One interesting one that kinship theory predicts is when conflicts would arise!

• Example: sibling rivalry

Sibling rivalry

• Basically, when resources plentiful, advantage to share with your sib.

• When scarce, that advantage is reduced.• Remember you are your closest relative!!

Parental care

• Next logical step: Producing them is the easy part, raising them is more difficult!

• Just as important as mate choice/mating systems.

• Does no good to pick a good one if you let your young die! Or does it??

• What is the best way to be a parent? Is there a best way???

here

Parental care

• Wide variety: would seem to contradict kinship theory:

• Would predict ALWAYS see extended parental care

• Your offspring best shot at future!• Need to look at variation and see how we can

reconcile this with kinship theory.

Ranges of parental care

• Four states:• 1) no parental care• 2) maternal care• 3) paternal care• 4) biparental care

What are the considerations?

• Why one form in one and different one in another?

• Benefits: Obviously, this is your link to the future….

• Costs: But… how much are you willing to pay for this?

• As cold as it may sound, may just be an economic cost/benefit analysis!

Benefits?

• Benefits double sided.• Benefits to your offspring IF you put a lot of care

into them• Benefits to you IF you put in little AND they

survive! (increased reproductive opportunities)• So there are benefits for and against parental

care!• The underlying benefit is to your fitness

What are the costs?

• Same idea, costs in caring and not!• Cost in production: how much did you put into

them?• Cost of not taking care of them: they will die!• Cost of taking care of them: you die, you lose

other reproductive opportunities, • Again, cost is to your fitness

Easiest to see

• Animals where both sexes release large quantities of gametes into the water.

• No cost in production• Playing the odds, which evidentially works!• Low cost regarding survival of SOME young• Benefits to you: successful without cost of

caring for them• So, no or little parental care!

The rest little more complex

• First case: males vs females• Why do females usually exhibit more parental

care than males??• First possibility:• Female investment: invest much more energy

than males so “have more to lose” if offspring fail…. Thus provide more care.

• Sounds good!

But…

• In many species, females make large investments into eggs only to leave them in total care of males!

• So not automatic, need to assess fitness gains or loses after young produced.

Another “rule”?

• Lets look at it from the male’s view.• Cost benefit ratio of male to give care will

normally be higher than that for females.• Assume: amount of energy invested in care

reduces male and female future reproductive output equally.

• In this case, cost to male and female would be equal…. Unless, not all offspring are his!

• Does not “pay” for male to lose future reproductive opportunities caring for young not his own.

• Also IF care by one is sufficient, then evolution pressure (better cost benefit ratio) for male to NOT care for young and inseminate as many females as he can (Polygyny)

• So not just that the female has invested so much but that it is advantageous for the male NOT to!!

Good fathers!• But there are instances where males do provide

care!• Male only: Seems contrary to above. However

common in fish.• Why? In cases studied, it seems the cost to the

male is less than to the female.• Example: Stickleback fish – males can guard up to

10 clutches of eggs/females only produce 7 without guarding, one if she guarded.

Result?

• IF female cares for young also loses weight, which is related to fecundity!

• More advantageous for female NOT to care for young than it is disadvantageous for males to care for them!

• Interplay with other anatomical/physiological traits that co-evolve with reproduction.

Maternal and paternal care

• Many species exhibit care by both parents.• Monogamous breeders (usually)• Still, male could do better if he was not

monogamous nor gave care, why should he?• Development of young: altricial vs precocial

Needs both!

• Again, constraint from other selection factors.• If young altricial, may need care of both to

survive. • Strong selection pressure for males who stay!• Why see these two forms: altricial vs

precocial?

In birds

• Nesting environment: • More dangerous ground favors precocial.• Selection pressure for successful use of a given niche dictates parenting patterns.

Trophic position

• Prey: ungulates precocial: need to be “ground ready”!

• Also, can develop longer, no need to move real fast to catch grass!

• Predators: Disadvantage to have young inside for 9 months! Get them out quick, your mobile but then have to care for them!

• Again, interplay with environmental factors.

• Basic idea is the relative cost benefit ratio of parenting for males and females.

• Usually, this ratio is larger (less favorable) for males, so paternal care is rare.

• Cases where is larger for females and in these cases roles switch.

• Cases where it is approximately equal, dual parenting.

Given parental care….

• Ok someone is taking care of the kids!• What are some of the parental care behaviors

that are important?• Young identification would be nice!• If your kids are the only ones around, no

problem!• Many species breed and raise their young in

groups. Happy Feet! Seals, ocean birds, bison

• “Wonder of nature” mother is able to come and find her young out of a gang of kids.

• How does she (or he) do it?• One major one is vocal communication:

voice/song recognition• Odors also play a role• Related to whether there is a need for

recognition.

Does it always work?

• Apparently not!• Major parenting deviation: Brood parasitism!• Female of another species lays eggs in other

bird’s nest!• Goes counter to offspring recognition!

Parasite and host

• Advantage to parasite: get someone else to successfully raise kids!

• African cuckoos lay up to 25 eggs per season, one per host nest!

• Need to get around recognition:• Similar species, similar eggs• Solitary species with little recognition ability.• Arms race between parasite and host!

And the young?• A side point: young parasites adapted to

enhancing survival over host chicks!

Parental favoritism

• Another consideration is behavior of parents to individual young.

• Saw differences in sibling rivalry but is it all just the kids?

• Parents actively show bias toward young• Older/larger ones, not just size or aggression• Parents seem to be evaluating reproductive

value of offspring

Reproductive value of offspring

• How young beg for food indicator of health, especially in times of low resources

• How they look! Mouth gap color, brighter – gets more attention

• Alternate hypothesis: brighter color = healthier!• Current active research into if parents can

judge reproductive value and give food to those with higher value!

Parental abandonment

• Will a mother defend its young to the death?

• Commonly held belief/myth.• What would kinship theory predict?• You are your closest relative so to put yourself

in danger to save some one only half related to you….

• Go ahead kill them, I can make more….

here

Inbreeding behavior

• Can’t leave kinship and parental care without talking about “inbreeding” or incest: mating between close relatives, including mother-son, father-daughter, brother-sister.

• In one instance we see selective advantages of helping related individuals

• But genetically, view this type of gene concentration, Inbreeding, as bad!

Is it done?• Almost all species practice some level of

inbreeding.• Male cougars will mate with their daughters

• Humans, even with their ridged taboos against it, do it. Some cultures more acceptable.

• Royal families!• Read the histories and a lot of them married

daughters, sisters, even mothers

Why do it?

• Out of necessity: small isolated populations, no other choice.

• Genetic advantages??

Advantages?

• Kinship theory deals with helping closely related to enhance passage of your genes.

• Logically would extend to reproducing with closely related individuals!

• Why take the change with a genetic stranger when only have 50% chance of passing on “good” genes and will be heterozygous!!

• If your offspring have your “good” gene, 50% chance next offspring will be homozygous!

New Genes

• Only way for new genetic material is via mutation.

• Difficult to imagine how a single mutation, no matter how good it is, will increase in a population without inbreeding!

• So good side of inbreeding behavior is that it can concentrate new genetic material

• Also increase more rapidly “good” existing genes.

Down side?

• Can also pass and concentrate “bad” genes!• This is where human taboos have developed• To try and prevent the concentration of such

genes• Many of our genetic diseases today are

concentrated in ethnic groups.• Inbreeding depression: can lead to variety of

fitness reductions: sperm deformities, reduced reproductive output,

Then why do it?

• Under “natural” natural selection, will be strong selection pressure on small inbreeding groups.

• Form of group selection: IF your small group does have deleterious genes, will not do well as a group – increased selection against them

• IF your small group does NOT have deleterious genes but also good genes, GREAT!!

Summary on parental care• Various factors involved:• 1) can young live without care?• 2) If needed, will depend on relative

cost/benefit for males vs females.• 3) The amount of investment by female not

only determining factor• 4) How it may affect future reproductive

opportunities.

Summary

• Related again to environment that can override and dictate if and what form of parental care is necessary.

• In that framework, relative cost/benefit ratios play out.

Cooperation (Chap 9)

• Talked about kinship theory and how it could favor cooperation among related individuals.

• However we also see cooperation occurring among unrelated or genetically more distant individuals.

• Can’t evoke kinship selection as reason so how can we evolutionarily justify this type of behavior?

Over view

• Actually imbedded in an overall view of cooperation, which includes kin selection

• In this scheme there are four pathways to cooperative behavior.

Reciprocity

• Why would unrelated individuals help each other?? What is evolutionary advantage?

• Reciprocal altruism: • 1) Individual A pays a cost to help B• 2) Cost “paid up” in future IF B helps A

• Such a system might be favored by natural selection

How does it work?

• Depends on chances that you will get a payoff• Reduces it to a probability problem• Can be envisioned in the light of game theory• Most games: whether you win or not depends

on the reciprocal action of the other players• R. L. Trivers suggested it could be understood

via a math game: Prisoner’s dilemma

Prisoner’s dilemma

• 2 prisoners, both guilty

• Separate rooms• Either cooperate

with each other, don’t “squeal” on other

• Or squeal.

• Each outcome has different penalties/ rewards

• R, S, P, T.• What do you do?• IF:T > R > P > S• You have a dilemma!

Prisoner’s dilemma

• Obvious the most tempting is to tell: T –home free!

• BUT only if your buddy chooses not to tell! (R)

• If you both choose to tell (P), your toast!

• THAT is the dilemma!

What is the right thing to do?

• In a single incidence, it is a dilemma• But lets extend this a little: you have gone

through the first time.• Now your faced with it again WITH the same

partner!!• Now what do you do???• Depends on what your partner did last time!

The if, then rule

• If your partner cooperated last time, then you will cooperate this time, you trust him!

• If he squealed on you, then you squeal on him this time and only get 3 years rather than 5!

• Called Tit for Tat or reciprocity-based response

Characteristics of reciprocity

• Nice: you are never the first to “cheat”• Retaliatory: IF he cheats on you, next time you

will!• Forgiving: Current action based on last of other.

What does this have to do with animals?

• Attempt to explain when no-related individuals would help (cooperate) each other.

• And when they wouldn’t!• Example: predator inspection in guppies:• Usually two guppies advance from group to

inspect danger level from predator

Possibilities

• 1) go together (cooperation)• 2) one goes, other lags (cheats)• 3) visa versa• 4) both lag back• Classic Prisoner’s dilemma• You gain most IF you lag back: you live AND

you assess danger (If buddy gets eaten, high danger!!!)

• Both gain, but not as much if both go (cooperate).

• So, tendency to cheat, tendency to cooperate• What do you do?• Depends on what your co-inspector did

before!• IF he cheated AND you survived, it is best to

cheat on him next time, IF your stuck with him• IF he cooperated, this is the one you want to

go with in the future, thus cooperation!!

How about non-lethal situations?

• Reciprocity• Example: vampire bats• Need to have a blood meal. If they don’t get

one, often will beg from one that has.• IF it gives it to you, more likely to also give it

to that one if table is turned.• If you give first, likely will ask same one in

future, should reciprocate!

Summary: Reciprocity

• Game theory can provide insights and testable predictions regarding non-related cooperation.

• Basic premise is that your actions based on past experience with potential cooperator.

• Somewhat selfish, you do it because you know the other one will “pay you back”!

• But it seems to work…as a model!

Byproduct mutualism

• Second possible way cooperation behavior can develop

Defined

• Cooperation is a byproduct of the fact that an individual would incur an immediate HIGH cost or penalty IF it did not act cooperatively!!

• Talk about incentives!!• The immediate benefit from cooperating

would outweigh that of cheating.

• Your damned if you don’t but saved if you do!

How does it differ from reciprocity?

• 1) the cost of cheating is so high, never really a consideration.

• 2) don’t need to think about past performance of partner, in this case it will ALWAYS be in best interest of both!

Example?

• Chirrup calls in sparrows: no or little food, fewer calls to bring conspecifics

• More food, more calls!

Explanation

• Explained as byproduct mutualism:• When there is a lot of food, and the bird

wants to stay long to eat it, best to have others around for predator detection.

• Price of staying longer by self, greater than price of sharing food, so cooperate!!

Wolves

• Live in related pack, kinship• BUT part of it is byproduct mutualism in that

can’t hunt large animals alone!• Indicates the blurry lines that can exist among

the different causes of cooperation!

Summary

• Cooperation can evolve IF benefits of not cooperating are extremely low and benefit of cooperating are high, will be selection for cooperation even if unrelated.

Group selection

• Controversial concept• Distinguishes between within and between

group selection

• Argument is that between group selection favors cooperation because groups that cooperate survive better than those that don’t.

• Proposed as possible reason for such things as alarm calls.

• Not advantageous to individual but is to group.

• A group that has more “selfless” callers, does better.

• Group selection in itself is controversial and as a promoter of cooperation behavior, may be stretching it!

• Does provide different way of looking at this type of behavior.

here

Interspecific mutualism

• Last type of cooperation behavior to cover• We are all familiar with mutualism• Two species providing service to the other for

benefit of each.• LOTS of examples• General idea is BECAUSE they both benefit,

results in the behavior.

Summary of Cooperation

• Four proposed ways it could develop• 1) If your GENES benefit (Kin selection)• 2) If YOU benefit: depends on the chances

that the other will will help in future.• 3) If you don’t help, your toast!• 4) If you help and it helps group, selected for• All have their basis in the selfish gene concept.

Play (Chap 15)

• Now turn our attention to specific behaviors we see either in the individual or in the group.

• First of these is play• Want to look at types of play• And function of play

What is play?

• Can we define it??

• We know it when we see it but difficult to define!

• Bekoff and Byers (1981): motor activity performed that appears purposeless, contains motor patterns from other contexts, usually in a modified form and altered temporal sequence.

What is Play?

• Important points: • 1) should not be for a specific reason• 2) contains other behaviors• 3) Which are modified in some manner.

• Definition centers on form rather than function.

Sounds good but…

• Is an animal in a cage, pacing back and forth with seemingly no purpose play?

• How do we know it is purposeless?

• Is it purposeless?• 1) we may not be able to tell!• 2) may have purpose or potential benefit later

Others?

• Many have tried.• So why don’t we?• Practice• Future social status• Teaching• Building alliances• Building social bonds• Defining future sexual bonds

• Learning social/survival skills• Passing the time• Stress reliever

• Maybe a possible one is: behaviors that don’t seem to have direct connection to some immediate end, e.g. eating, building a nest, etc., the animal appears to “take pleasure in” doing it, and possibly learns from it.

Where does this leave us?

• Back where we started! • May not be able to define it exactly but MOST

times when we see it, we know it!

Types of play

• May not be able to define it but we can categorize it!

• Three different types of play recognized• 1) Object play• 2) locomotor play• 3) social play

Object play

• Centers on use of inanimate objects, sticks, rocks, feathers, Barbie, GI Joe, etc.

• Found in a wide array of taxa• Well studied in captive animals• Wide variation, try to distinguish it from Object

exploration: trying to figure out what an object is

• Object play: trying to see what they can do with it.

Object Play

• In some, novelty seems more important than an object’s characteristics: shininess or conspicuousness.

• In some, will use over again….toys??

Locomotor play

• As name indicates, involves some type of movement.

• Most common is leaping• Can also be running turning, somersaults,

shaking, etc. LOTS of variation

Social play• Again, as name indicates, playing with

someone else.• Can consist of what we would classify as play:

stalking, crouching, chasing• Majority consists of “play fighting” (sexual

play)

Function of play?

• Basic categories, pretty straight forward.• But… is it “purposeless”?• Saw in our discussion of defining it, most

believe there is/are reason/s behind play.• What would be the function or benefits of

play?

Benefits

• Can look at each category to see how each type may have a “purpose”

• Then we can look at an overall theory on function.

Functions of object play

• 1) In ravens: enables them to better identify new food sources.

• 2) Helps in prey recognition: parent brings dead prey that young play with (playing with your food is a good thing!)

• 3) can build paw-eye coordination• 4) extension of #3, practice hunting

techniques IF “object” is live prey.

Locomotor play

• Two major hypotheses:• 1) Exercise and training of specific motor skills

needed later. - can see this in both predator and prey where

running, turning, jumping, etc. is important.

Exercise and training

• List of benefits:• Increased oxygen uptake• Decreased heart rate• Increased total blood volume• Bone development• Modification of muscle fiber• Modification of cerebellar synapse

distribution

Exercise and training

• Byers and Walker (1995) listed 19 possible benefits.

• Only found two that were likely permanent and advantage to adult

• BUT all the rest likely easier to maintain as an adult IF you do so as a juvenile.

Locomotor play

• 2) Provides opportunity to learn area

• Way of learning what each area provides and their juxtaposition.

• Valuable again to both predator and prey

Social play

• Three possible functions proposed• 1) same sex play may build alliances that

would be useful in later life - A form of socialization and bonding

Social play

• 2) May improve physical skills for fighting, hunting, mating.

• - Often seen more in males than in females

• 3) May improve cognitive skills - Use play to assess their own abilities - Often young of same age play, equal partner - Learn how to fight, without harm, practice

One question: how do you know he is just playing?

• If this is practice for later, real fighting, how do the participants know this is not the real thing?

• 1) Order and frequency of play activity not the same as the real thing: exaggerated and misplaced

Not the real thing

• 2) Play markers or signals: stereotypic activities designed to signal intent. Behaviors of dogs: pawing, bowing, etc.

• 3) Role reversal or self-handicapping - Here what would normally be a dominate

individual will take a subordinate role, let the other one “win”.

- Letting your little brother “beat” you or he may not play with you!

here

General theory

• Some separate/some overlap.• How about a general theory?• Main function of all play is to develop physical

and psychological skills to handle unexpected events were you lose control.

- Increases versatility of movements used to recover loss of balance

- enhance ability of animals to cope with unexpected stressful situations

Summary

• Three types of play, based on whether you play with objects, yourself, or others.

• Each has some unique functions and common ones

• Overall function is to prepare individual, not just for adulthood, but for the uncertainties of adulthood

• Increases your reaction capabilities and coping skills.

Aggressive behavior (Chap 14)

• Not all fun and games!• As mentioned, play gets you ready for adult

life, one filled with a lot of aggression