Male reproductive strategies Flashcards
What is meant by an estrus female?
estrus means the time around the ovulation period. Estrus females can advertise timing of evolution through signs of sex swelling seen in the Hamadryas baboon, or they can have concealed ovulation where scent or sexual behaviour may clue males in as seen in black and white colobus.
why might a female use exaggerated sexual swellings?
This can be used as a graded signal to confuse paternity and bias paternity.
What does male monopolization potential depend on?
Depends on the distribution of estrus females.
If estrus is not synchronised, one male has a greater chance of monopolising access to fertile females.
If estrus is synchronised then one male has less chance of monopolising females and preventing other males from accessing female. E.g male influxes in guenons.
What is the definition of sexual coercion?
Use, by a male, of force or threat of force, that functions to increase the chances that a female will mate with him at a time when she is likely to be fertile, and to decrease the chances that she will mate with other males, at some cost to the female.
List the different types of sexual coercion
- Infanticide
- Harassment
- Intimidation
- Mate-guarding
- Forced copulation
What is the typical relationship seen between sexual coercion and sexual dimorphism?
In sexual dimorphism, relationships between sexes are more likely to involve some sexual coercion.
Where as, with sexual monomorphism, relationships between sexes are more egalitarian. Males do not have physical advantage over females
Describe male infanticide
When male-male competition may lead to males killing infants. This happens normally to eliminate another male’s offspring and to increase their own chances of mating.
What is the main hypothesis supporting male infanticide?
The sexual selection hypothesis by (Hrdy, 1974)
Male infanticide is selected to increase the performer’s reproductive success, relative to other males.
What 3 conditions are required for the sexual selection hypothesis of infanticide?
- Infanticidal male does NOT kill his own offspring.
- It should bring the female into estrus sooner than if the infant had survived.
- Infanticidal male should mate with the female whose infant he killed.
If the females who babies are being killed but then doesn’t mate with the infanticide male, then this is a behaviour that will slowly filter out
What is the “priority of Access” model?
The model predicts that a higher rank should lead to higher reproductive success.
What is observed in males fits this prediction as male mating success and paternity tend to correlate with rank in primates. An alpha male can probably monopolise females during their fertile period.
Thus, competition for rank among males often equal to competition for fertilisations.
What was the “priority of access” model based on?
Priority of access was first formed based on females - higher ranking females get priority to better quality food, this leads to higher reproductive success. They reach sexual maturity faster with smaller birth interval periods.
What is meant by the male dominance rank acquisition?
This is when the mother’s rank may influence her son’s rank in patrilocal species or in matrilocal species where sons of high-ranking females choose to stay.
Give an example species where the male dominance rank acquisition is observed
Vervets have a very strong matrileanal society. Both female and male gain the rank of their mother. When the son reaches sexual maturity they will use paralell dispersal and integrate into a new group.
But if you are a male vervet with a high ranking there are lots of privileges so they don’t really want to leave. Higher ranking vervets tend to stay longer than the other bachelors but will eventually be pushed out by older males and new males coming in. Once they are pushed out there is a very high mortality rate. Because they’re alone and have to fight into a new group without coalition.
They also don’t have the social ability to get a long in normal vervet society without the privileges. So the higher ranking is almost a disadvantage. (poor little rich boys)
How can male rank be influenced in a patrilocal society and the effects of this?
Male rank may be influenced by benefits of remaining with male kin as they can form coalition partners for between group competition plus there are extra-group males to contend with.
In a society when males disperse there are a lot of aggressive bachelor males in the forest. But in a patrileaneal society there isn’t the problem of rogue males trying to integrate into other groups.
Coallition between related males is that they can work together to monopolize fertile females.
This is seen in chimpanzees, bonobos, muriquis and spider monkeys.
Why are male hierarchies not as stable as female hierarchies?
Unlike female hierachies, male hierachies are unstable and can move around the dominance rank so there is a lot of instability if the social structure of the group.
There is a high turnover of dominance males, so there is a limited amount of time to increase their reproductive success which leads to intense waves of competition.
