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• Male bird mimicing song of other birds and
  activities in the forest to get females attention

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Reproduction

• Gamates that are good at fertilizingsperm
• Gamates that provide an advantage after
  fertilizationegg

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Why bother with sex?

• COSTS
• Recessive alleles may combine to produce a
  homozygotic trait
• Meiosisonly half your genes are passed on
• Females waste efforts on making males
• Mating under conflicting best interests with
  females usually getting the worst of it

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Benefits Variable offspring

• Long term benefitprevents extinction of the
  species (controversial, sounds like group
  selection
• Short term benefithigh fitness for some
  individuals
• Some species reproduce sexually or a sexually
  depending on ecological conditions (aphids,
  parasites)
• Variable offspring dont compete as much as
  identical ones (lottery tickets)
• Repair DNA and sex is a byproduct

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Parental Investment Theory (Robert Trivers)

• Female Large gametelow reproductive ratelow
  levels of sexchoosybetter malehigher female
  fitness
• Male Small gametehigh reproductive
  potentialhigh levels of sexcompetition for
  femalesmore femaleshigher male fitness

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Tests of PI theory

• Sex role reversed species pipefish and sea
  horses
• Males get pregnant

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More PI Sex Role Reversal

• Mormon cricket male contributes a spermatophore
  that may be 25 of his body mass. Called a
  nuptial gift
• Females compete for males

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Sexual Selection

• Females choose male mates based On
  characteristics of the females choice
• Coloration, ornaments and other showy features
• Features are usually a disadvantage to survival,
  but enhance reproductive fitness

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The Case of Bowerbirds

• Builds a structure displaying craftsmanship and
  artistic abilities
• Female visits and inspects while male dances his
  best makes vocalizations
• Females go away, come back after a week and make
  another inspection
• Finally settles on a suitable male and goes into
  the bower and show her receptivity

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Speciation in Bowerbirds

• Separate populations of the same species
• Preferences for the shape of the bower change
  among females
• Breeding between the two populations is inhibited
• Behavior based isolation may result in
  physiological/genetical isolation

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Male and Female Partners

• Males that build good bowers and dance well have
  an advantage
• Females only need one or two males
• Results in higher variance in number of mates for
  males

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Females Mate with One or Two males for the most
part
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Some males have many mates other have few or none
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Are Females Choosing Wisely?

• Nice bowers are correlated with healthy male and
  large body size
• Other markers of male quality are also used

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Heres What She Wants
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Other Ornaments

• Quetzal bird of the cloud forest
• Sage grouse from Texas
• Not the horn of the beetle

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Male Tactics for Obtaining Matings

• Persistent searching
• Dominance Hierarchy Southern Elephant
  Sealssexual dimorphisms. Alternative strategies
  for non-dominant seals
• Chimps, gorillas, and other primates form
  alliances

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Alternative Mating Strategies

• Shine et al. Transvestite garter snakes, Anim.
  Beh. 2000, 349-359.
• Male mimic female upon emergence from the winter
  den by producing female lipids

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Transvestite Male Garter Snakes

• She-males attract he-males to mating balls
• Intensity of response
• 0 no interest
• 1 elevated tongue flick
• 2 press chin
• 3 align body

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Results

• She-male and real female are about equally able
  to produce responses
• Experiment on rubbing he-males to females and
  testing sexual response of other males.
• Only she-males elicit the response so its more
  than just the lipids

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Why does this phenomenon occur?

• Confuse other males (it only lasts for 24 to 48
  hours)
• Doesnt waste his time when hes not sexually
  ready
• Reduced competition when he is ready
• Males are aggressive toward each other, but not
  females

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Conditional strategies

• Thornhills study of scorpionflies (Panorpa)
• guard a dead insect for large fly,
• produce saliva for medium fly,
• grab and force copulation for small fly
  
• Remove two large males and medium start insect
  guarding, small produce saliva

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When Can Males Be Choosey?

• Shine et al., Garter snake male mate choice,
  Anim. Beh. 2001, 1133-1141.
• Males have a limited number of sperm when they
  emerge so they must be picky (sperm do not renew)
• Asortative mating by size
• Snout-to-vent length less than 45 cm.small,
  45-55cm.medium, greater than 55cmlarge

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Asortative Mating

• Placed in an arena with 3 females, S, M or L and
  6 males, 2 of each size.
• Males court larger females, except small males.
• Limited sperm means males must maximize its use

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Sperm Competition

• Obtaining mating may not be enough to insure
  fitness.
• Dunnock male sees hisfemale near another male, he
  pecks her cloaca to cause sperm ejection

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More Sperm Competition

• Sharks administer a power douche before
  depositing sperm
• Testes size varies in proportion to body weight
  and degree of sperm competition
• Cryptic female choice Sperm storage and
  selective use

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Sperm Competition in Lemurs

• Radespiel et al., Sperm competition in grey mouse
  lemurs (Microcebus murinus) Anim. Beh. 2002,
  259-268.
• Small, nocturnal primate
• Dominance hierarchies for both males and females
• Females dominant over males.

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Mating Night

• Females allow copulation only on oestrous night
  of conception.
• Otherwise not receptive
• Dominant male gets 11 copulations, subordinate
  gets 1.

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Sperm Selection by Female

• DNA analysis shows Dominant fathers 54.5,
  submissive fathers 45.5
• Younger males (likely subordinate) fathered 70
• Reason Avoid older because it may be her father.

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Mate Guarding

• Preventing sperm competition
• Fluids in seminal fluid
• Physical aggression toward competitor
• Warning song
• Prolonged copulation

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Social experience and Mate Choice

• Dugatkin (1998), Beh. Ecol. 323-327.
• Guppies (Poecilia reticulata) females choose to
  mate with males who have most orange coloration
  (sexually selected).
• Use males who differ in coloration by 40.

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Social Experience Effect

• Female watches drab male court female for 5
  minutes, 10 minutes, two 5minute periods, of
  alone for 10 minutes (control group)
• Culture over rides genes in the 10 and two 5
  minute exposure conditions with female preferring
  the drab stud male over the brighter colored
  male.

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Female Choice Without Material Benefits

• Healthy mate theory
• Males that show signs of good health will not
  infect the female
• Male bower bird is an example Non-parasite
  carrying male builds a better bower

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Female choice without material benefits

• Good genes hypothesis Anders Moller (1990)
  Evolution, 771-784.
• Barn swallows coloration and tail feather length
  determines mate choice
• Parasite load is related to coloration and tail
  length

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Why Tail Length?

• Parasites reduce fitness
• Resistance to mites is heritable, mite load
  correlations (cross fostering)
• Own offspring, own nest .57
• Own offspring, others nest .48
• Other offspring, own nest -.14
• Tail length reflects past parasitism

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Experiment

• Shorten or lengthen tail length (or unchanged
  control)
• Long tail gets mate in 3 days, shortened in 13
  days, control in 7 days.
• Supports good genes hypothesis.

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Female Choice Without Material Benefits

• Runaway Selection Theory
• Females choose sexually attractive male so they
  will have sexy sons
• They also insure their female offspring will have
  a preference like theirs

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Testing the Theories

• Peacocks in a captive, but free-ranging group
• Shorter tails higher mortality due to foxes
• More area of eye spots on tail, offspring have
  higher probability of surviving

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Chase-Away Selection Theory

• A male mutation that takes advantage of a female
  pre-existing sensory bias
• Some females resist the ornament, so males
  develop a more exaggerated one
• An arms race ensues for a useless trait

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Competition and Conflict

• Sperm competition in fruit flies Males seminal
  fluid kills other males sperm
• It also harms the female, shortening her life
• Male doesnt care because he wont mate with her
  again

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Breeding Experiment

• Make fruit flies monogamous
• Males that dont produce harmful sperm will be
  more successful because they only have one mate
• After 30 generations mate a female from the
  specially bred line with a normal male
• She has lost her defense against the toxin

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Multiple Matings with Polygynous Males
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Conflict Summary

• Males and females have the same goal Maximize
  reproductive output (fitness)
• Whats best for a male is not always whats best
  for a female and vice-versa
• Much of mating is analogous to an arms race