Lecture 12: Mating systems

Question 1

Categories of mating system:

Answer 1

• monogamy
• Polygamy
• -polygyny
• -polyandry
• -polygynandry
• Promiscuity

Question 2

most birds mating system:

Answer 2

socially monogamous, also engage in extra pair copulation. so not sexually monogamous apart from in some rare cases.

Question 3

most mammals have

Answer 3

socially polygynous mating system

Question 4

monogamy is

Answer 4

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.

Question 5

polygyny is

Answer 5

• 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

Question 6

explanations for monogamy:

Answer 6

1. 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
2. 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

Question 7

does social monogamy = genetic monogamy

Answer 7

NO

Question 8

3 types of polygyny

Answer 8

• Female-defence Polygyny
• Resource-defence polygyny
• Lek polygyny

Question 9

Female-Defence polygyny

Answer 9

• 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

Question 10

Resource-Defence polygyny:

Answer 10

Males control access to a resource that is desirable for females.

Question 11

Lek polygyny:

Answer 11

Males congregate at certain sites to display to females. Male reproductive success is highly skewed. Male only mate, no parental care

Question 12

polyandry:

Answer 12

1 female, multiple males

Question 13

polyandry explanation

Answer 13

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.

Question 14

Polygynandry is a mating system in which

Answer 14

both males and females have multiple mating partners during a breeding season

Question 15

polygynandry in dunnocks:

Answer 15

• 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

Question 16

promiscuity occurs when

Answer 16

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.

Question 17

human mating system (849 different societies)

Answer 17

• monogamy 16%
• polyandry 1%
• polygyny 83%

Question 18

Why would a female pair with a male who has already paired?

Answer 18

• 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.

Question 19

How common is extra-pair paternity in socially monogamous people?

Answer 19

• 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.

Question 20

Animals show a diverse range of mating systems which are favoured by

Answer 20

different ecological and life-history pressures.

Question 21

Polygyny is favoured when

Answer 21

males can effectively monopolise females, have the first opportunity to desert after mating, and females can care for offspring alone.

Question 22

Monogamy is favoured when

Answer 22

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.

Question 23

Polygynandry can result from

Answer 23

conflict over the optimum mating system for males (usually polygyny) and females (often polyandry).

Question 24

Promiscuity is

Answer 24

(random mating) is more of a null hypothesis than a natural mating system.