Lecture 12: Mating systems Flashcards
Categories of mating system:
- monogamy
- Polygamy
- -polygyny
- -polyandry
- -polygynandry
- Promiscuity
most birds mating system:
socially monogamous, also engage in extra pair copulation. so not sexually monogamous apart from in some rare cases.
most mammals have
socially polygynous mating system
monogamy is
one male and one female form a pair bond for part or all breeding season or in some species even there entire lifetime and they then work together to rear offspring.
polygyny is
- males have multiple females (most mammals)
- probably arises from evolutionary constraint in which FERTILISATION and DEVELOPMENT of offspring is internal and female LACTATE to feed young giving males first opportunity to leave and mate again & offspring do not require biparental care
explanations for monogamy:
- Biparental care is important for reproductive success. Two parents may be needed to care for offspring because of
- Food delivery needs
- Protection from predators
- e.g. obligate monogamy in seabirds - Males are constrained from having multiple mates, because females are spaced throughout the environment and males can only defend one female’s range.
e. g. facultative monogamy in songbirds
does social monogamy = genetic monogamy
NO
3 types of polygyny
- Female-defence Polygyny
- Resource-defence polygyny
- Lek polygyny
Female-Defence polygyny
- Females are ‘clumped’ in their distribution and males control access to a harem.
- Ability of males to monopolise females depends on
- -Female home range
- -Female group size
Resource-Defence polygyny:
Males control access to a resource that is desirable for females.
Lek polygyny:
Males congregate at certain sites to display to females. Male reproductive success is highly skewed. Male only mate, no parental care
polyandry:
1 female, multiple males
polyandry explanation
small numbers of birds, some marmosets and some populations of humans.
- Females cannot successfully incubate > 4 eggs in a clutch.
- They only improve their reproductive success by laying more clutches.
- Superabundant resources females can lay many more than 4 eggs.
- They lay multiple clutches and different males incubate each and then care for the broods.
Polygynandry is a mating system in which
both males and females have multiple mating partners during a breeding season
polygynandry in dunnocks:
- In dunnocks, the mating system is variable.
- Males do best in polygyny because they sire more offspring.
- Females do best in polyandry because their offspring receive more care.
- Often, polygynandry results from social conflict over the optimal mating system
promiscuity occurs when
males and females in a population mate randomly and with multiple partners. In general, the theory of mating systems suggests that promiscuity should be rare or absent in animals, as it is usually to the advantage of one or both of the genders to choose their mates.
human mating system (849 different societies)
- monogamy 16%
- polyandry 1%
- polygyny 83%
Why would a female pair with a male who has already paired?
- If he provides access to good enough resources that it outweighs the cost of having to share them with another female.
- Monique Borgerhoff-Mulder’s polygyny threshold model.
How common is extra-pair paternity in socially monogamous people?
- Figure commonly quoted for western (WEIRD) societies is 10%.
- Recent research suggests this was an overestimate – actually more like 1-2%. Contraception likely to mean EPCs rarely result in offspring.
- But research from traditional societies suggests historical levels of EPP were also around 1-2%, despite lack of contraception.
Animals show a diverse range of mating systems which are favoured by
different ecological and life-history pressures.
Polygyny is favoured when
males can effectively monopolise females, have the first opportunity to desert after mating, and females can care for offspring alone.
Monogamy is favoured when
males cannot monopolise females and/or offspring need more than one carer. In extreme conditions this can favour polyandry e.g. people in rural Tibet.
Polygynandry can result from
conflict over the optimum mating system for males (usually polygyny) and females (often polyandry).
Promiscuity is
(random mating) is more of a null hypothesis than a natural mating system.
