Block 9 - Social behaviour Flashcards
What is the study of social behaviour?
The study of the co-operation between individuals
- parental behaviour in families
- helping behaviour in extended families
- cooperation in flocks/ herds/ social groups
Two or more (can be thousands)
In what way is group living adaptive?
Living in groups can increase the reproductive fitness of individuals in that group (e.g. natural selection)
What is Wynne-Edwards’ theory?
That individuals restrain their reproduction in order to avoid overcrowding and resource depletion
Theorised that starlings flocking was a cencus to determine levels of reproduction and that it was a population level adaption
How was Wynne-Edwards’ theory disproved by G.C Williams?
Why is it not an ESS?
- ‘Mutant’ bird does not show restraint, thus produces more offspring than the average for the population.
- Mutant type would therefore increase in frequency (if genetic), thus the same would happen in the next generation causing the ‘mutant’ (selfish) type to prevail
W-E’s ‘restraint’ behaviour is not an Evolutionary Stable Strategy (ESS) because it can be invaded by selfishness.
What are the benefits of group living?
- Greater protection from predators
- Enhances obtaining, locating or maintaining resources
- Creates mating opportunities
- Reduces the probability of infanticide (in mammals)
. the killing of non-weaned offspring by dominant males.
. living in groups confuses paternity
How does living in groups protect against predators?
Dilution effect:
- probability of being predated goes down (WD Hamilton’s slefish herd hypothesis
Increased vigilance:
- ‘many eyes’ hypothesis
- animals in larger groups are typically able to detect predators at a greater distance
How does living in groups enhance obtaining locating or maintaining resources?
Group hunting:
- there is a cost in hunting (energy expenditure)
^ this could be lower in groups of a certain size
What are the costs of living in groups?
- Increased competition (for mates, nest sites, territories, food)
- Increased conspicuousness to predators
- Increased chance of disease transmission
How does group lving create mating opportunities?
Lekking behaviour:
- leks are areas where males congregate to dispay to females
- males often defend tiny territories
- females visit and chose males to mate with
- no resource to defend (only the male)
- Male mating success +vely correlates with display activity, aggression rate and lek attendance. +ve correlation to ‘extravagent’ male traits (antlers, tails, colours)
- Males in central positions are often more successful (territory position)
What is eusocial behaviour?
- adults live in groups
- cooperative care of juveniles (individuals care for brood that is not their own)
- reproductive division of labour (not all individuals get to reproduce)
- overlap of generations
What are some examples of eusocial animal groups?
- Most are arthropods (mostly in class of insecta, + snapping shrimp)
- Some chordata (mammalia; african mole rats; naked mole rats and damaraland mole rat)
How do mole rats function (eusociality)?
Eusociality has evolved twice independently in mole rats
- Colonies of 75-80 individuals
- Complex burrows
- 1 female ‘queen’, breeds with 1-3 males
- Remaining members are workers
- If queen female is removed than new (previously non reproductive) female will fight and become queen
- Can live up to 28 years (both reproductive and non-reproductives)
Mole rats don’t show signs of aging (senesense) and they also do not get cancer.
- well protected environments
- extrinsic mortality very low so strong selection for long lives
What are two problems in social groups?
Altruism - particularly extreme reproductive altrisum - seems incompatible with natural selection
Cooperation - open to free-riding (cheating)
. individuals that enjoy the benefits but don’t cooperate (e.g. vigilance in groups
How does kin-selection help to explain altruism?
Helping individuals that share copies of the same gene.
Altruism will evolve if the benetit (b) received by the recipient multiplied by the relatedness (r) of the recipient to the donor (of the behaviour) is greater than the cost (c) of the behaviour to the recipient
rb>c (Hamilton’s rule)
relatedness is essential - if r=0 then it doesn’t work
e.g. parental care is altruistic (caring for young is costly)
What theories help to solve the problem of selfishness in cooperation?
- Kin selection (helping those with copies of the same gene)
- By-product benefits (cooperation as a by-product of an otherwise selfish act)
- Reciprocity (helping those that help you)
- Enforcement (rewarding cooperation and punishing free riding)
