paternity

intraselection

male-male competition

inter selection

female choice

animals more keen to raise offspring than siblings

how do we know who older siblings are, males more sure of offspring, females know who they birth

male effort spent ensuring his paternity

ensuring kids he looks after and the kids females produce are his

meeting more females increases paternity

mating more often

adder males and travel distance

increase encounter rate of females, exploitation competition

exploitation competition

organisms compete indirectly through the consumption of a limited resource

direct fighting between males- interference

selection for bigger size, weapons, sexual dimorphism

sexual dimorphism

Differences in physical characteristics between males and females of the same species.

sexual dimorphism exists because male fighting

indicator of competition in a species

dominance hierarchies set up by fighting

males get matings dependent on their position most of the time

elephant seals

dominant male gets most matings, fights, females call out if male mates with her to attract larger or better mates

baboons

all males mate, timings matter, females only allow high ranking males to mate when they are fertile

ritualised fights in red deer

stags roar for many hours, lower roar indicator of strength, then pace side by side to intimidate, then fight as last resort

female red deer

watch fights and stand offs to asses males, may induce fighting

blue gill sunfish

3 mating strategies

large- defend nests and attract females to it

medium- mimic females to get sneaky mates

small- rush in and fertilise eggs

female mimicking

rove beetles emit odour of females when entering rivals territory, resident male tries courting when male mates with female

forced matings

rape by less attractive males, females resist which is dangerous for everyone

gang rape seen in dolphins

males cooperate to force matings

violence raises the cost of rejecting the male

at a certain point females best fitness is to accept matings

violence is rare

persistence is sufficient

why do females submit to persistent males

poor of males health- good genes

costs of resistance can be greater than cost of sub optimal offspring

gender role reversal

some males do parental care

pipe fish

males select females with large bodies and long folds- lay larger and hold more eggs,

pipe fish males must mate with the most fertile female as he spends the rest of the season caring for eggs

females may fight, may get sneaky matings

infanticide

ensures paternity by killing previous males young, present in lions, primates and some spiders

new males kill young to

get females into receptive state quicker

bruce effect

females mice reabsorb unborn young when exposed to male pheromones, horses abort foetuses when new male

multiple matings reduce infanticide

bonobos, chimps, wild dogs

no male is sure he is father, leads to reduced killings and small amounts of parental care

females may form coalitions with lower ranking males

give them more matings, males contribute to child care in exchange

embryonic diapause

the embryo (blastocyst) does not immediately implant in the uterus, but is maintained in a state of dormancy, found in rodents, bears, mustelids and marsupials

badger and embryonic diapause

female mates at one time of year but does not cub until winter so cubs are born and suckled in sett and emerge in spring when conditions are good

superfetation

carrying multiple pregnancies at different stages of development

animals capable of superfetation

american mink, brown hare, casiragua, N. Africa gundi, badger and common tenrec

superfetation can work in combination with embryonic diapause

means females can mate with multiple males and reduce infanticide, ensuring variation in genetics

mate guarding

a behavior in which one partner prevents the other partner from participating in extra-pair copulations

mate guarding is expensive on time

prevents male from mating with other females

cost of mate guarding decreases when

chances of finding another female decreases, may as well guard female

benefit of mate guarding increases when

chance the female will remate increases, need to guard her to drive off other males

white fronted bee eater

males only mate guard when females are fertile, 0 guarding a few days either side of fertility

only guard when males harass female, aim guarding to cover greatest chance of rival fertilisations

as season progresses

unmated females get fewer

great reed warbler

sings less and less through season as chance of attracting female reduces, better to guard current female

Heliconious butterflies

males hang on pupa and mate female as she emerges, covers her in anti aphrodisiac to prevent males mating her

Anti-aphrodisiacs

- Added to the female after mating that turn other males off, lowering the chances of males coming to court the female

red sided garter snakes

females coming out of hibernation release pheromone to attract males, males add pheromone to make her unattractive after mating

making plugs - common in invertebrates like butterflies

sticky secretion put into females or covering their genitals which hardens

males spiders

pedipalps to insert sperm, 2nd one breaks off and blocks female genitals

acanthocephalans

put plug in females and males

sperm competition

a form of sexual selection that arises after mating, when males compete for fertilization of a female's eggs

birkhead and Moller 1992

suggested colonial animals should mate more often than solitary to increase chance of egg fertilisation

barn swallow

solitary, mates 1/3 as often

red rumped swallow

social breeder, mates 3x often

large ejaculatory loads swamp out rivals sperm

promiscuous species have larger testes than monogamous

humans change sperm amount depending on chance of engaging in sperm competition

if girlfriend has been away, boyfriend will produce stronger ejaculate as theres more chance shes had sex with other men

males clean out rivals sperm

dunnock males and chicken

dunnock males

peck female cloaca until she ejects sperm packet of previous male

chickens

females mate most persistent cockerel, eject sperm when hes not looking if hes not the best mate

female dragon flies have spermatheca to store sperm of many males

very complex, can select better sperm later

cryptic female choice

A form of sexual selection that arises after mating, when females store and separate sperm from different males and thus bias which sperm they use to fertilize their eggs.

male dragonflies have complex intermittent organs

clean out spermatheca, then fill all sections with their own sperm

male- female dragonflies arm race

females for more complex spermatheca, males for better cleaning

limited eventually by time it takes to made

Bedbugs and Traumatic Insemination

puncture females abdomen with penis, sperm transported in haemolymph

female bed bugs and traumatic insemination

risk of infection, increases immune response and takes energy to heal

female bed bugs and spermalege

collect sperm and reduce infection and immune response

xycloris maculipennis- flower bug

traumatically inseminates rival males so his sperm gets passed on through rival males effort

male water striders

cannot penetrate female genital shield so bounces on water to attract fish unless female lets him mate