Other modes of intrasexual competition- week 2, part 3. Flashcards
Are there other ways, apart from direct contest or combat, males from different species compete with each other for access to reproductive opportunities?
Yes.
In baboons, what do lower ranking males do?
Do they get to copulate with females when they are most fertile?
Spend more time with females- They get some copulations this way.
No- higher ranking males only do.
What is one alternative strategy for accessing females?
How is this done?
Evading dominant males.
Using tactics like resembling females or sneaking behaviours (sneak fertilizers).
Give an example of an animal which does alternative strategies.
Explain.
What then happens?
Do male marine iguanas do the same thing?
Horseshoe crabs.
When a female comes to shore to lay her eggs, a large male monopolises access to her and tries to inseminate her.
Satellite males come- they do not fight off the male but latch onto the side of the couple and sneak some fertilizations by delivering sperm to the eggs.
Yes- but is achieved by pre-copulatory ejaculation.
Can alternative behaviours arise in many different ways?
Where can some arise from?
Give an example of what a small male will do.
Yes.
Conditional strategy- this is where males have strategies to try to make the best out of a bad situation and use the tactic which works best for them based on their physical condition.
Small male- sneaker approach- large males do not need to do this as they can fight.
Give an example of an insect who has alternative tactics.
What do females want males to bring them before they mate with them?
What do big males do?
What do medium sized males do?
What do really small males do?
Panorpa scorpionfly.
Nuptail gift- Big dead insect.
Bring a big dead insect- they get to mate with the female.
Cannot keep hold of a large insect without it being stolen by other males- bring saliva- females accept this.
Offer nothing + try to force copulations.
What do you have here with Panorpa scorpionfly?
What is this an example of?
Conditional strategy.
Polyphenism- different behavioural phenotype- only behaving differently to make the best out of a bad situation, not due to genetics.
Are conditional strategies different tactics based on the same conditional strategy?
What are alternative strategies?
What is the difference with this strategy?
Yes.
Distinct strategies can be based on genetic differences (polymorphisms)- There are different types of males.
It is not conditional but hereditary- some males are born with the tendency to pursue one strategy whilst others are born with the tendency to pursue other strategies.
Alternative strategies in Paracerceis sculpta (marine isopod):
What do alpha males do?
What do the beta males do?
What do the gamma males do?
What is this an example of?
Alpha males- monopolise access to females by defending them from other males.
Beta males- mimic females- hope the alpha male does not realise.
Tiny gamma males- hide against females hoping not to be noticed.
Genetic polymorphism- genetically different to each other- inherited a tendency to behave in this way.
Continuation from alternative strategies in Paracerceis sculpta (marine isopod):
What do these three strategies have in common?
Explain why.
Similar level of reproductive success.
If there is too much of one type, alternative types tend to be more successful- it balances out- When there is a lot of them trying to be alpha males and fighting, it is advantageous being a gamma male.
Scramble competition:
What is scramble competition?
In many species, what do females do?
What does mating success for males depend on?
Who is scramble competition seen in?
What do males need to do to be successful?
Do they need to fight each other?
Competition to find females.
Stay in one location.
Ability to search and find females.
Explosive breeders- females will gather in location for a short period of time and lay lots of eggs- externally fertilising species.
Locate females + their eggs as fast as possible to be successful.
No.
Continuation with scramble competition:
What does scramble competition select for?
Give an example of three things it selects for + why.
Adaptations that help males find mates.
1) Highly developed sensory systems- helps males find females.
2) Mobility.
3) Increased spatial ability- ability to roam widely to find females.
Continuation with scramble competition:
What is life history strategy?
Explain.
Early reproduction.
Species which do not live long- selects for developing early- so they can find females before other males.
Who did a study on scramble competition?
Explain.
What was on tree trunks and leaves?
What did they find?
Nahrung and Allen.
Used sticky traps (put it in the forest) to see if males and female beetles where wondering around in the forest.
Roughly 50/50 balance of males and females.
Males were mostly trapped on the traps (94%)- because they were looking for females.
Continuation with scramble competition:
Give another example of an animal which does scramble competition.
What do squirrels have?
What does enhanced spatial ability allow them to be?
Squirrels.
Have good spatial ability- Use it to roam for females during breeding season.
Successful.
