Flashcards in Spatio-temporal distribution and the polygyny threshold model Deck (39):
Females fight to the death and males bicker for food. True or false?
False: females bicker for 'more or less' food, whilst males fight in an 'all or nothing' scenario.
What limiting resource must males compete for?
What limiting resource must females compete for?
Thus what influences the distribution of females?
What influences the distribution of males?
Where the females are.
What does 'spatio-temporal' distribution mean with regards to males?
Spatio = where the females are
Temporal = when they are fertile
Do all primates have menstrual bleeds?
No: only Old World and Apes do
What is the periovulatory period?
When the egg is 'ripe', i.e. the period of time around ovulation.
When do ano-genital swellings appear?
During the periovulatory period.
Is the periovulatory period always indicated by ano-genita swellings?
No: in some species it is indicated by behavioural changes.
What behaviour does a female Hanuman Langur execute to show she is in her periovulatory period?
She presents to the male, lifts her tail up and shakes her head.
What is the APR model and what is it used to describe?
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)
What is the mid-cycle Estrus?
A period of time around ovulation where females solicit males.
What are the 4 main stages of menstruation?
1. Follicular stage: egg develops
2. Ovulation: egg is released
3. Luteal phase: unfertilised egg degrades
4. Menstruation: womb lining is lost
What environmental factor causes female to ovulate and why?
High food availability; signals optimum conditions for raising offspring
What is this called when food availability causes females to ovulate?
Synchronisation, of females to their environment
Based on this idea give a theory as to why periods stop in women with anorexia?
There is no food, thus it is an adaptive response by the body so as not to produce a baby during this time.
Hanuman Langurs are sacred in India, thus they are provisioned by local communities. What does this mean for their menstruation?
They have become desynchronised from the environment as there is constant food availability.
The synchronisation/de-synchronisation of menstruation to the environment affects grouping/mating systems. True or false?
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?
Due to sexual harassment from other females; they will physically abuse both members of the couple during copulation.
What is a a) conception and b) non-conception estrus?
a) menstrual cycle where the female will conceive
b) menstrual cycle when she will not
During the mid cycle estrus, if more days are spent copulating it increases the likelihood of what?
In a harem, a single male is mating with multiple females. That means there is less chance they will conceive. Why?
Because his sperm is constantly depleted and he is tired.
Thus what is the theory behind sexual harassment from other females?
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.
Why is the male then reluctant to mount?
Because he gets attacked every time he does (negative conditioning)
What kind of competition is sexual harassment?
Female-female sperm competition
If there are more females in a harem they have longer inter-birth intervals. Why?
The male is the limiting resource, he cannot mate with everyone all the time.
In a polgynous system, are the menstrual cycles of the females synchronised or not? Why?
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.
In what kind of mating system are menstrual cycles synchronised? Why?
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
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?
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.
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?
a) It increases
b) It decreases
c) It decreases
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?
a) It decreases
b) It increases
c) It increases
When females are desynchronised their distribution can be described as what?
Dispersed: they live solitarily/in a dispersed harem to avoid food competition with each other, e.g. orangs and gorillas
When females are synchronised their distribution can be described as what?
Clumped: they live in a polygynandrous group based on where the food is
Give 2 reasons that all primates do NOT live in polygynous groupings.
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
What is the polygyny-threshold model?
A model that predicts the likelihood of polygyny based on territory quality.
Explain the polygyny threshold model.
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
Therefore polygyny is likely to develop if territories display different qualities. Which strategy develops if all territories are of similar quality?
Monogamy; every female ends up with equal resources she doesn't have to share with other females