Spatio-temporal distribution and the polygyny threshold model

Question 1

Females fight to the death and males bicker for food. True or false?

Answer 1

False: females bicker for ‘more or less’ food, whilst males fight in an ‘all or nothing’ scenario.

Question 2

What limiting resource must males compete for?

Answer 2

Females.

Question 3

What limiting resource must females compete for?

Answer 3

Food.

Question 4

Thus what influences the distribution of females?

Answer 4

Food availability.

Question 5

What influences the distribution of males?

Answer 5

Where the females are.

Question 6

What does ‘spatio-temporal’ distribution mean with regards to males?

Answer 6

Spatio = where the females are
Temporal = when they are fertile

Question 7

Do all primates have menstrual bleeds?

Answer 7

No: only Old World and Apes do

Question 8

What is the periovulatory period?

Answer 8

When the egg is ‘ripe’, i.e. the period of time around ovulation.

Question 9

When do ano-genital swellings appear?

Answer 9

During the periovulatory period.

Question 10

Is the periovulatory period always indicated by ano-genita swellings?

Answer 10

No: in some species it is indicated by behavioural changes.

Question 11

What behaviour does a female Hanuman Langur execute to show she is in her periovulatory period?

Answer 11

She presents to the male, lifts her tail up and shakes her head.

Question 12

What is the APR model and what is it used to describe?

Answer 12

Describes the conditions required for copulation:
A = attractiveness (of female to male)
P = proceptivity (female solicits the male)
R = receptivity (female is receptive to male during copuation)

Question 13

What is the mid-cycle Estrus?

Answer 13

A period of time around ovulation where females solicit males.

Question 14

What are the 4 main stages of menstruation?

Answer 14

1. Follicular stage: egg develops
2. Ovulation: egg is released
3. Luteal phase: unfertilised egg degrades
4. Menstruation: womb lining is lost

Question 15

What environmental factor causes female to ovulate and why?

Answer 15

High food availability; signals optimum conditions for raising offspring

Question 16

What is this called when food availability causes females to ovulate?

Answer 16

Synchronisation, of females to their environment

Question 17

Based on this idea give a theory as to why periods stop in women with anorexia?

Answer 17

There is no food, thus it is an adaptive response by the body so as not to produce a baby during this time.

Question 18

Hanuman Langurs are sacred in India, thus they are provisioned by local communities. What does this mean for their menstruation?

Answer 18

They have become desynchronised from the environment as there is constant food availability.

Question 19

The synchronisation/de-synchronisation of menstruation to the environment affects grouping/mating systems. True or false?

Answer 19

True.

Question 20

In Hanuman Langurs that live in harems (polygyny), a female must ‘beg’ approx. 4 times before a male will copulate with her. Why are the males so reluctant?

Answer 20

Due to sexual harassment from other females; they will physically abuse both members of the couple during copulation.

Question 21

What is a a) conception and b) non-conception estrus?

Answer 21

a) menstrual cycle where the female will conceive

b) menstrual cycle when she will not

Question 22

During the mid cycle estrus, if more days are spent copulating it increases the likelihood of what?

Answer 22

Fertilisation

Question 23

In a harem, a single male is mating with multiple females. That means there is less chance they will conceive. Why?

Answer 23

Because his sperm is constantly depleted and he is tired.

Question 24

Thus what is the theory behind sexual harassment from other females?

Answer 24

The females doing the sexual harassment are not ovulating, thus they want the male to be fresh for when they are ready and not depleted from mating with another female.

Question 25

Why is the male then reluctant to mount?

Answer 25

Because he gets attacked every time he does (negative conditioning)

Question 26

What kind of competition is sexual harassment?

Answer 26

Female-female sperm competition

Question 27

If there are more females in a harem they have longer inter-birth intervals. Why?

Answer 27

The male is the limiting resource, he cannot mate with everyone all the time.

Question 28

In a polgynous system, are the menstrual cycles of the females synchronised or not? Why?

Answer 28

They are de-synchronised.

DESYNCHRONISATION = MONOPOLY

If they were synchronised and all fertile at the same time, the male would not be able to defend them from invading males, simply due to the distribution of his females in space (he cannot be everywhere at once). When desynchronised, the females that are not ovulating are not attractive to invading males so the dominant male does not need to protect them. He can monopolise the female that is ovulating.

Question 29

In what kind of mating system are menstrual cycles synchronised? Why?

Answer 29

Polygynandrous: there are multiple fertile females thus a dominant male cannot monopolise them all, meaning other males get a chance to mate.

SYNCHRONISED = NO MONOPOLY

Question 30

The social structure of groups varies based on synchronisation/de-synchronisation of females, and this can vary across a habitat range, e.g. the grouping systems of Hanuman Langurs varies across India. Why?

Answer 30

Because the environmental conditions vary across India, e.g. seasonality and climate. In seasonal regions the females are synchronised, in non-seasonal regions they are not.

Question 31

In a desynchronised group, the system is polygynous. What can be said about a) paternity certainty, b) infanticide risk and c) food competition between females and males?

Answer 31

a) It increases
b) It decreases
c) It decreases

Question 32

In a synchronised group, the system is polygynandrous. What can be said about a) paternity certainty, b) infanticide risk and c) food competition between females and males?

Answer 32

a) It decreases
b) It increases
c) It increases

Question 33

When females are desynchronised their distribution can be described as what?

Answer 33

Dispersed: they live solitarily/in a dispersed harem to avoid food competition with each other, e.g. orangs and gorillas

Question 34

When females are synchronised their distribution can be described as what?

Answer 34

Clumped: they live in a polygynandrous group based on where the food is

Question 35

Give 2 reasons that all primates do NOT live in polygynous groupings.

Answer 35

a) Mate defence: the male is unable to monpolise a group of females, e.g. in female menstrual synchronisation to the environment
b) Resource defence: a female is unwilling to settle with an already-mated male and compete for resources with his other females

Question 36

What is the polygyny-threshold model?

Answer 36

A model that predicts the likelihood of polygyny based on territory quality.

Question 37

Explain the polygyny threshold model.

Answer 37

African proverb: “It is better to be the second wife of a rich man than the only wife of a poor man”

If there are multiple males that occupy territories of different qualities, they will each possess different amounts of resources. If the males with the best territories already have one female, a new female will still choose to live in bigamy with one of these pairs rather than live in monogamy with a male whose territory is of low quality. Even though her reproductive success may be lowered by competing with another female, it would still be higher than if she was occupying a territory of low quality.

BETTER TO SHARE GOOD STUFF THAN SETTLE FOR MONOPOLY OF CRAPPY STUFF

Question 38

Therefore polygyny is likely to develop if territories display different qualities. Which strategy develops if all territories are of similar quality?

Answer 38

Monogamy; every female ends up with equal resources she doesn’t have to share with other females

Question 39

What factors contribute to the quality of a territory? List 4 things.

Answer 39

1. Food
2. Shelter
3. Micro-climate
4. Predation risk