Monogamy (1 male, 1 female)

Polygamy:

Polygyny(1 male, >1 female or >1 male, >>1 female)

Polyandry: (no need to discriminate b/t on exam, just know that unlike in book, we define in terms of number of males contributing to parental care; polygyny far more common than polyandry)

• Need for male parental care** (albatross, other birds)
• Spatial and temporal distribution of females both influenced by:
  • Distribution of resources
  • Predation Pressure (dik-dik)
• Female-female competition (tigers/leopards)

• Resource defense polygyny
• Leks
• Female defense polygyny

• Male(s) defends an area to which females are attracted

• Males and females in many of these species maintain long-term social bonds. 
• Some are comprised of multi-male groups in which males are genetically related and cooperate at high rates
• Ex. Male black-winged damselfies wait for females to come to them, defending territories that contain the kind of aquatic vegetation in which females prefer to lay their eggs
• Where females eave natal herd, often thought to be resource defense polygyny

• Loose aggregations of males to which females are attracted

• Males provide nothing but genetic material, only occur in species where males contribute NO direct parental care
• Attracted to beautiful bowry or feathers, mate, and may never see them again
• Wildebeast may be leks, or may be resource defense polygyny; he stands and waits
• Most species of frogs-->males croak together a night to attract females
• Why do males aggregate and attract predators and risk rejection/no mating?
• Sometimes leks comprised of males who are close reatives

• Male(s) defends a group of females that are already social for other ecological reasons
• Female 'puts up' with another female because of male's resources
• Females form the stable core of the group, independent of any attributes the group's males might have.
• Males migrate, females remain in the groups in which they were born.

ex. Bighorn rams go where potential mates are and then fight with other males to monopolize females there

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• Redwing blackbird
• w/o fitness cost, no dilemma about territory
• this model doesn't build in male parental care
• female comes along and likes territory Y but there is fitness cost
• Female fitness varies as a function of territory quality
• Female Y2 says, "I could be first female on x or second female on y," so she essentially allows polygyny if fitness will be greater as second female on territory y than as first female on territory x

Cooperative defense against predatoin

Cooperative defense of resources against other groups of females

Close bonds among female kin

Strong between-group competition

(Often) within-group competition resulting in female dominance hierarchy 

• Lion, Hyena, Elephants; Vervet monkeys, baboons, many other monkey species
• Hyena females are dominant and are larger than males
  • Form dominance hierarchy
  • High rates of cooperation (hunting)
  • Androgenation (becomes more male-like)
• Vervet monkeys-->female bonds, defense against predation

• Female group size or range may be too big for a male to defend alone
• Males may benefit by cooperating (e.g. chimps, lions)
• Multi-male groups can arise through either resource-defense or female-defense polygyny

Female lays a clutch, male incubates; female lays another clutch, she incubates.

Female may not be ‘faithful’ to first male

 Monogamous pair accepts a ‘helper’; sometimes unrelated male helps rear offspring

‘Cooperative’ polyandrous breeding

 Cooperative groups with reproductive suppression of

       subordinates 

       Only the dominant female in the group breeds;

       occasionally >1 male breeds

Occasional polyandrous breeding

Polyandry is inherently unstable. It often reverts back to monogamy, cooperative breeding with only 2 breeding adults

Some birds that have precocial young (can move around immediately after birth)

Some mammalian species that take on adult helpers: e.g. tamarins, wild dogs, meerkats