Psych 119 Week 3 Midterm

The Female Strategy: Making the Best Choice

• Choice based on behavior: Courtship behavior

• Extremely diverse, varies widely across species

• Examples:

§ Female spiders expect food from their potential suitors

§ Mating dances in birds; bird song→ how does it help you hunt 

§ Male bowerbirds: Decorate bowers with random knickknacks (e.g., shells, bottle caps,

buttons, shiny things, etc.)

§ Such behaviors confer no direct fitness advantage: “Show off

Main idea: Females in many species choose mates based on their behavior, appearance, songs, or displays. These behaviors are called courtship behaviors.

Examples of courtship behavior

. Male spiders offer food

• Some male spiders bring food to females during courtship.

• The gift may provide nutrition and reduce the chance of being eaten by the female.

• Females may prefer males that offer better gifts.

2. Bird songs and mating dances

• Males sing or perform dances to attract females.

• These displays may signal health, condition, or species identity.

• Does singing help with hunting? Usually, the main purpose of a mating song is attracting a mate, not hunting.

3. Male bowerbirds decorate bowers

• Males build structures called bowers and decorate them with objects such as shells, flowers, and shiny items.

• Females inspect these displays when choosing a mate.

• The decorations can help a male attract a female even though they do not directly provide food or help him survive.

• 
  

yes

What does “show off” mean?

Some courtship behaviors may not directly help an animal find food or escape predators. Instead, they help the animal attract mates and reproduce.

yes

Mysterious underwater “crop circles”

• First discovered off the coast of Japan in 1995

• Discovered the culprit in 2011: Male white-spotted pufferfish

(Torquigener albomaculosus)!

• Underwater “bowers”, takes 7 - 9 days

to build

• Males are only 10 - 12 cm in length (~4 - 5 inches), but their

circular “sculptures” are about 2 m (~79 inches) in circumferenc

• Build to attract females to lay their eggs 

• They need to have seashells to attract them 

• They need artistic perfection fro the female fish to enter the circle 

• They get together to mat 

• The eggs are layed in front of them

Easy way to remember: A tiny fish builds a huge, beautiful sand circle to attract a mate! 🐡💕

Courtship

means behaviors animals use to attract a mate and show they are a good partner for reproduction.

The Female Strategy: Proceptive Behavior

• Even though females tend to be the choosers, they

often initiate courtship

• E.g., Female cats caterwauling when they are “in

heat”; female rats wiggling ears

They females to initiate courtship when they are highest ovulation 

They 

Sexual Selection Produces Anatomical and Behavioral

Differences between Males and Females

• Interesting case of (almost) equal parental

“investment”, but with sexual dimorphism: Cuckoos

§ Majority of species of cuckoos are monogamous

§ Some species avoid the burden of offspring care

through brood parasitism – by pushing the duty

off to other unsuspecting bird parents

• Most cuckoo species are monogamous.

• Some cuckoo species practice brood parasitism, meaning they avoid the costs of raising their own young by having other birds raise them.

• The unsuspecting host birds may feed and care for the cuckoo chick as if it were their own.

• Brood parasitism:

• A bird lays its eggs in another bird’s nest, leaving the other bird to incubate the eggs and raise the chicks.

Size (females < males): To

facilitate the production of

smaller eggs to match that of the

size of host bird species

• Color (females slightly less

flashy than males): To avoid

detection by host birds

• Sexual dimorphism appears to

be a result of coevolution rather

than sexual selection

Yes

Physical and behavioral sex differences are minimized or

even reversed; the female may become the more brightly

colored sex, for example

§ Males may be choosier and females have to compete for

Mate

• Red phalaropes 

• Northern jacanas 

Yes

Seahorses, along with pipefishes and sea

dragons, are probably the most famous

examples when it comes to sexual role-

reversal in reproductive behavior

• Monogamous pair-bonding

•

Females deposit ova into a pouchlike

cavity in the body of the male, where it

gets fertilized by the male’s sperm

• Females begin producing new ova

• However, despite the reproductive role-

reversal, females do not compete for

males, and males do not play the

“choosy” role

§ Females still expend more energy in

making gametes

• In species where males invest more in care of offspring, even if not to

the same degree as females, competition and “choosiness” can be

observed in both sexes

• E.g., “Sexual swellings” in female baboon

• they have more to lose from choosing a poor mate, so they may become more selective, too

• Female baboons develop visible swellings around their genital area during certain parts of their reproductive cycle.

• These swellings signal information about reproductive condition and fertility to males.

• Males may compete for access to females, while females may also influence mating through their choices and behavior.

• 
  

Diverse Relationship Styles Have Evolved

• Sexual and social relationships are not the same

• In many species, reproduction does not involve

relationships (e.g., many invertebrates, fishes,

amphibians, reptiles)

• E.g., Cod, sea urchin, montane voles

Yes

Diverse Relationship Styles Have Evolved

• Relationship? What relationship?

• Iteroparity:

Multiple

reproductive cycles over

lifetime

§ E.g., Virtually all mammals,

all birds, most reptiles

Semelparity:

Single

reproductive episode, then

death

§ E.g., Salmon, male dusky

antechinuses (& most

females), ! , & male

praying mantises (but not

always)

When reproduction involves lasting relationships,

these can be monogamous or polygamous

§ Monogamy

is pair-bonding that may last for the

duration of the mating season (e.g., seagulls) or for

a lifetime (e.g., prairie voles, swans)

They have one mate 

Polygyny

refers to the “harem” arrangement of a

single male with multiple females; the opposite

arrangement is polyandry—a single female with a

harem of males

Promiscuity is the pursuit of sex outside of an established relationship

(extra-pair copulations or EPCs)

§ Males may be promiscuous to increase their number of offspring

with little additional effort (duh)

Yes

Female Promiscuity Leads to Adaptive Responses by Males

• Sperm competition: Displacement

§ But what if ejaculation into the female has already

happened?

§ Last resort: Sperm displacement

§ E.g., Damselflies have evolved penises for such

a purpose

Yes

One possible strategy is sperm displacement — a male removes or displaces sperm deposited by a previous male before transferring his own sperm.

Example: Damselflies

Specialized genitalia: Male damselflies have evolved specialized structures on their penises that can remove sperm deposited by previous males from the female's reproductive tract.

Advantage: By removing some of the rival's sperm, the male increases the relative proportion of his own sperm available for fertilization.

Yes

When Male and Female Reproductive Interests Collide

• Males may resort to force

§ Forced copulations

occur in many species

§ E.g., Scorpionfly

notal organs

§ Notal organs are

not used for

unforced sex, nor

do they serve any

other purpose

• Notal organs are only used for forced copulation 

Yes

Forced copulation when one animal forces mating on another animal that is resisting or does not consent.

• Why it happens: In some animal species, males may use physical force to gain mating opportunities.

• Sexual selection: This behavior can be studied as a reproductive strategy, although it can harm the other animal.

• Example: In some duck species, males may attempt forced copulation with females.

Yes

When Male and Female Reproductive Interests Collide

• Males may resort to force

§ Forced copulations: Blue-lined octopus (a.k.a.

Blue-ringed octopus)

§ Highly venomous: Tetrodotoxin (TTX)

§ Males inject females with TTX, immobilizing them

in order to mate (Chung et al., 2025)

§ Why? Self-preservation

• Without killing females, just immobilizing them 

• Females TTX, males minzing chances females eat them, they want to mate and self-persvation 

Yes

• The result is sexually antagonistic co-evolution

• — an eThe result is sexually antagonistic co-evolution — an evolutionary arms race between males and females, where adaptations that increase one sex’s reproductive success can reduce the reproductive fitness of the other sex.

• How does it happen?

• Male strategies: Males evolve ways to increase their reproductive success, such as coercive mating, preventing females from remating, or displacing rival sperm.

• Female interests: Females benefit from choosing mates that provide good genes, resources, or other reproductive advantages.

When Male and Female Reproductive Interests Collide

§ Females of some species have evolved anatomical

adaptations to aid in forced copulation

§ E.g., Rats (lordosis)

• Lordosis , male wants to meet iwth female, bu tshe doesnt, bc placement of female vainal opening hard to reach, the 

• She needs to arch, but she does not arch behavior, the male cannot use forced copulation 

\

When Male and Female Reproductive Interests Collide

§ Females of some species have evolved anatomical

adaptations to aid in forced copulation

§ E.g., Ducks (counter-male adaptation)

• Ducks have penises and spiked shapes 

• Females vagina have evolved to resist forced copulation 

• Female vagian clockwise and duck penis counterclise 

• Id the fmemale relaxes, then sex but does not penis does not 

Male

When  and Female Reproductive Interests Collide

§ Behavioral adaptations exist as well

§ E.g.: Pacific beetle cockroaches

(Stanley, Williams, & Preziosi, 2018)

§ Female clustering to deter male

Harassment

• Behavioral to resist forced coopulation 

• The beetles will gang up to block beetle male 

Yes

When Male and Female Reproductive Interests Collide

§ Combating sperm competition: Sperm ejection by females

§ E.g.: Red junglefowl & domestic chickens, Short-bodied cellar spiders,

Fruit flies (Drosophila melanogaster); Rhesus monkeys

§ Degree of ejection correlated with social ranking (where applicable

• Sperm had deposited 

• Females have evolved resit sperm ejection , they do not fidn accepables 

• Exmaple : female chickens , 

• Edxmaple social ranking monkeys, the lower rank of monkey, the female ejection and higher in rank of monkey less female ejecti

Yes

When Male and Female Reproductive Interests Collide

§ Post-copulatory mate choice

§ The Bruce effect: Females of certain species can

terminate pregnancies in the presence of a new

dominant male

§ Observed in polygynous species where infanticide is

common

§ Mice, voles, lions, gelada baboons

• Females are pregeant from another male, the new domina tmale will commit murder?

• Females terminate prgancy when new male comes along 

• The bruce effect notice in rats, where rather carry pregnacy to term, female scan abort babies to get pregnacy again new dominant male and not get killed with baby , surival reason 

• Female choice even in force copulations 

When Male and Female Reproductive Interests Collide

§ If all else fails: Play dead!

§ Dragonflies (Khelifa, 2017

• Surgery 

• Dragonflies , lays an egg and fly away, they doesnt want to mat with male, then crash and prening dead and flies away male, then she pretends shes dead and then flies away 

Yes

 all fails: Play dead! 

Tonic immobility - in female European common frogs (Dittrich and rodel, 2023)

• Explosive breathing 

• Female evolve playing dead, they play dead, so the males do not have sex with them. 

Yed

When Male and Female Reproductive Interests Collide

§ Another strategy: Join forces!

§ E.g., Baboons: Groups ruled by one alpha male, who

gets all the access to females

§ Problem for lower- ranking males: No opportunity to mate

§ Problem for females: No female choice (mate guarding)

• Alternate strategies

§ Lower-ranking males: Mr. Nice Guy

§ Females: Stolen copulations- she will go to 

• They are the nice guys, pay more attention to females, play wth babies, and take care of females, females then like the nice guy and view them attractive 

• The females might consent, but problem is alpha male 

• the female will walk next to rival group, then walks to back and forth, the\nm alpha male will pick a fight, then female goes in hides to bush and hadbaby with nice guy monkey and the alpha wont notice >

When Male and Female Reproductive Interests Collide

§ Another strategy: Join forces!

§ Another example of stolen copulations: Giant cuttlefish

§ Small males mimic females to “fool” the alpha

• The dominant male fish 

• The smaller fish has mmivs females, girl time with females; the dominant male does not know it's a guy, then the fish then mates with a female without the dominant one knowing 

Yes

Sometimes, Helping Relatives Is a Good Strategy

• In some circumstances altruistic behavior can be

adaptive, so the genes promoting it may be favored by

natural selection

• Altruistic behavior may be an evolutionary by-

product, or (in the case of humans) may be due to

cultural influences

• Parental care is an altruistic behavior with obvious

adaptive value

• Organism keeps producing 

• The offspring does not fit 

Yee

Sometimes, Helping Relatives Is a Good Strategy

• Hamilton proposed that natural selection causes individuals to

help their relatives reproduce to an extent determined by degree

of relatedness (kin selection) - the concept of inclusive fitness

• 1 offspring of your own (50%), vs. helping your brother or

sister produce 2 or more offspring (≥ 50%)

§ Kin selection explains behavior of social insects

§ E.g., Bees, ants

• Kin selection explains some, but not all, altruistic behavior

§ Females may adopt unrelated young

§ The effect of evolutionary mechanisms on human sexual

behavior and attitudes is difficult to separate from culture

• Cost and benefits 

• The more distant the relative 

• The more advantages it will be 

• Explaining beahvior of bees adn ants 

• The queen bee has smilartraits to adaptive bees then the beads they have the same 

• Infants 

Yes

Kin selection

Kin selection is when an animal helps its relatives reproduce or survive because they share some of the same genes.

Biologist W. D. Hamilton proposed this idea.

Yes

Did Sexual Morality Come from Evolution? The Case of Incest

• Incest is rare (at least in humans)

• “Immoral”, even “digusting”

• Is sexual morality a product of evolution?

• Inbreeding is harmful due to deleterious genes

• Natural selection acts against incestuous reproduction

• Suggests selective pressure for individuals who are NOT prone to

The Westermarck Effect: People raised in close proximity early on in life

become desensitized to sexual attraction (a.k.a. reverse sexual

imprinting)

Yes

Evidence: Siblings raised apart, and who were reunited post-sexual

maturity, are more likely to be attracted to each other than siblings

raised together

• More likely to be attracted to each other than siblings raised together 

• “Sexual morality” is probably the cultural interpretation of the

Westermarck Effect

• Bonobos are the most promoiius species tohave sex face to face 

• Evolved with adaptive reason other than prodicing ofsorings 

• 
  

Yes

Sex May Acquire Other Functions beyond Reproduction

• Nonreproductive sex is sex that occurs for purposes

other than reproduction, and it may take place

between a male and a female, or between two males,

or between two females

• For pleasure and/or for social cohesion

• E.g., bonobos, dolphins, Japanese macaques

Examples : bonobos use sex for convience for getting food 

• Pick fights with others to make up sex 

• When female leaves one gorup 

• Sex is not only reprodction 

Sex May Acquire Other Functions beyond Reproduction

• Bonobos use sex for conflict resolution and alliance formation

• Conflict in food allocation

• Females entering another social group are unwelcome at

first, but will engage in genito-genital rubbing to form

alliances with existing females

• Sex appears to be amicable - no forced copulation has been

Observe

Yes

Sex May Acquire Other Functions beyond Reproduction

• Bonobos: ”Make love, not war”

• Sex bonobos 

• Females have the power 

• Apes are highly social adn develop friendship nurse babies after 5 years 

• Avoid fights, by having sex, only last a few seconds, sex 

• Affectionand hierchy 

• 
  

Yes