Mate Choice

Question 1

Conflict Between Sexes

Answer 1

• ANISOGAMY (THE ROOT)
• PARTNER AMOUNT
• WHY BOTHER CHOOSING?

Question 2

CBS: Anisogamy (Humans)

Answer 2

• males ejaculate 5ml/350 million sperm daily:
  COPULATE: minutes
  RECOVERY: minutes
• females produce 1 egg “monthly”
  PREGNANCY: 9 months
  RECOVERY: months
• discrepancy in reproductive investments; high cost/investment for females compared to males = choice must be careful; low cost/investment in males = casual

Question 3

Mate Aggression

Answer 3

• “traumatic insemination”
• human concept of romance doesn’t exist; often mating is dangerous (ie. mallard males often rape females; beetles’ “penises” cause damage to female reproduction systems upon insemination)
• females often aggress too (ie. praying mantis eats male mate)

Question 4

CBS: Anisogamy (Animals)

Answer 4

• ie. lioness may copulate w/male every 15min (3000 times) BUT despite billions of sperm, she still only has 1 egg
• ie. female elephants are pregnant for almost 2 years; lactate 2-3 years; very high cost

Question 5

CBS-A: Scarcity of Females

Answer 5

• “scarcity” meaning few available/unbred females
• rarity increases value of unbred females to males
• this increases competition/aggression between males for the females’ attention
• so females have a larger choice pool in mate

Question 6

CBS-A: Quality VS Quantity

Answer 6

• QUANTITY = MALE; can afford to invest in low effort copulation w/many females and pass genes on as many times as he pleases
• QUALITY = FEMALE; can’t afford quick investments BUT can afford to be picky about which male she allows to copulate w/her

Question 7

CBS: Partner Amounts

Answer 7

MONOGAMY
POLYGYNY
POLYANDRY
POLYGYNANDRY

Question 8

CBS-PA: Monogamy

Answer 8

• 1 partner p/mate
• FAVOURED WHEN:
  1. Input from both parents needed to raise offspring (ie. dwarf hamster males keep female/litter warm)
  2. Male must guard mate to ensure fathering (ie. the more house sparrows feed their chicks, the more survive)
  3. Low chance of other females (ie. shrimp; females are scarce; males spend weeks w/mate)

Question 9

CBS-PA: Polygyny

Answer 9

• males >1 mate; females = 1 mate (ie. stags having a herd of does)
• share is sometimes disproportionate (ie. some bower birds have double the herds of others)
• PROMOTES:
  1. CONFLICT BETWEEN MALES
  2. CHOOSINESS OF FEMALES
• FAVOURED WHEN:
  1. One sex is operationally rare.
  2. Males can control resources/females.
  3. Females can exert free choice.

Question 10

CBS-PA-POLYGYNY: Conflict Between Males

Answer 10

• (ie. battles between stags/stag beetles/baboons)
• established dominance = control of female resources (ie. cichlid defending shell midden) = female (group) access (ie. lion prides)
• favours BIG, WELL-ARMED males

Question 11

CBS-PA-POLYGYNY: Choosiness of Females

Answer 11

• (ie. female birds-of-paradise; groups of males dance at once; difficult favour)
• favours elaborate beh/morphology (ie. ANDERSSON (1982); altered/longer tails of birds-of-paradise attracted more females; shorter/cut tails repelled them)

Question 12

CBS-PA: Polyandry

Answer 12

• female = >1 mate; male = 1 mate
• ecologically favoured = breeding short but big; little parental care; female can immediately reproduce after laying
• females often act stereotypically “male” (ie. spotted sandpipers): larger than males/first at breeding ground/fight for territories/attract several males/skewed reproductive success
• FAVOURED WHEN:
  1. Females can escape parental cost.
  2. Females require resources held by >1 males.
  3. Biased male sex ratio.

Question 13

CBS-PA: Polygynandry

Answer 13

• females >1 mate; male = >1 mate
• ie. macaques; females solicit copulations w/multiple males; males mate w/several females
• males gain females (vice versa); NOT exclusively (no guard).
• females gain huge resources/genetic benefits BUT may confuse males as fathers; increased paternity = decreased infanticide
• FAVOURED WHEN:
  1. Males can’t monopolise females AND…
  2. Females gain from multiple matings.

Question 14

CBS-PA: Female Choice

Answer 14

• ORIONS (1969); female pied flycatchers produced more eggs the better the quality of nest territory in MONOGAMY; still true but lower in POLYGYNY
• question of does a female prefer a low quality territory BUT monogamy and no female competition, or a high quality territory BUT polygyny and other females?

Question 15

CBS: Why Bother Choosing?

Answer 15

• choosiness isn’t cheap; female birds travel extensively around territories to sample males; requires memory of particular males/powerful investment once committed
• benefits include:
  DIRECT = female personally gains resources/survivability/high offspring chance (ie. territory/food/paternity/reduced harassment/sperm)
  INDIRECT = offspring benefits; survives longer/breeds more attractively

Question 16

CBS-WBC: Knowing Available Benefits

Answer 16

• simple for direct; she can sense/feel/see these benefits:
  PATERNITY = warblers signifying direct benefits via repertoire size (number of notes in song) = paternal care
  REDUCED HARASSMENT = male blue-headed wrasse open flap on head when area is safe for female to pass through
• specific for indirect; shown in males characteristics
  OFFSPRING SURVIVABILITY = the more eyes a male peacock has, the higher survivability/attractiveness his offspring have

Question 17

CBS-WBC: Female Aims

Answer 17

MAXIMISE BENEFITS
PREFER MALE SIGNALS THAT CAN’T BE “FAKE”
PREFER MALES W/EXAGGEERATED TRAITS
PAY ATTENTION TO SIGNALS OF POTENTIAL BENEFITS

Question 18

SUMMARY

Answer 18

• sexes invest differently in reproduction
• leads to conflict between/within sexes over mate choice/access (competition/choice)
  ANISOGAMY = quantity (males) VS quality (females)
  MATING SYSTEMS = monogamy (F1+M1); polygyny (M1+F); polyandry (F1+M); polygynandry (M+F); often determined via local environments