Lecture 10 - Social Behaviour Flashcards
What are the patterns of social organisation in animal societies and the underlying mechanisms?
- Stable closed social groups
- Fission fusion social groups with individual recognition
- Fission fusion social groups without individual recognition
What are closed groups?
Group memberships are closed and they protect they territory.
What kind of breeding occurs in closed groups?
- Cooperative breeding - females give birth around similar time
- Synchronise birth to confuse territory as multiple people take care of the offspring - no confidence over maternal relationships
How does cooperative breeding in closed groups cause evictions?
- As number of breeding females increase, evictions happen as the territory can only cope with a few at a time so females get pushed out - they then go and find a new group for themselves
- Females initiate the intergroup warfare means they can sneak away and mate with people from other groups to increase gene pool ans gain reproductive benefits
What are fission fusion social groups?
- Individuals join and leave - there are no barriers
- Dilution of risk by being in a large group
How are fission fusion groups assorted?
On phenotypic traits
How are phenotypic traits assorted?
Segregation in the habitat of high predation areas and active choice of individuals
Segregation in the habitat of high predation areas
- No shoals in mid zone as more at risk
- Larger fish at bottom, smaller at top
- Habitats they are in are constrained by who you are with over space and time
- This is passive
Active choice of individuals
- Who do they choose to join during fusion events?
- Fish choose to actively separate and choose who they wish to be with during these size sortive patterns of grouping
What is the confusion effects?
Time taken to successfully attack predator differs between when foraging in a group or individual of prey
- Confusion effect if there is more than one - more time
What are multilevel societies?
Stable subgroups which act dynamically at different levels of society
What is an example of a multilevel society?
Killer wales
- Matrilineal groups based around female
- Sons and daughters stay with their mum
- Mums form matronliness so there is a family unit
- Males mate with females from other matronliness
- Matronliness form pods which come together to form a community
- Form cooperative benefits within and between groups to reap the benefits e.g. share prey
What is the selfish herd?
Individual behaviour is often selfish – individuals often behave in ways that increase their own fitness at costs to others.
- Hamilton did a thought experiment where he theorised that to be selfish, frogs jump to the middle of the group to avoid the predation of snakes - this is selfish and not to protect the group as a whole
How do animals not behave selfishly all the time?
Ground squirrels get predated upon by weasels and live in tight nit groups
- use alarm calls in response to approaching predators
- Alerting predator it has been seen - may be less likely to attack as know they have been seen
- Squirrels go into burrows to hide and continue to call - potential cost as predator can find location now
Why do females give the alarm calls?
- Male biased dispersal
- Females stay in their natal areas
What does kinship promote?
prosocial behaviour (i.e. voluntary actions intended to help or benefit another individual or group of individuals)
What is inclusive fitness?
an individual’s total fitness as based on both the number of offspring it produces and the reproductive success of its relatives.
What is kin selection?
- Inclusive fitness models consider the effect of the gene not only on the individual that carries it but also on genetic kin carrying identical genes by decent
- The concept of inclusive fitness can be captured by Hamilton’s rule
What is Hamilton’s Rule?
Genes should increase in frequency when RxB>C
What is the R in Hamilton’s Rule?
R = the genetic relatedness of the recipient to the actor (i.e. the probability that a gene picked randomly from each at the same locus is identical by descent.)
What is the B in Hamilton’s Rule?
B = the additional reproductive benefit gained by the recipient of the altruistic act
What is the C in Hamilton’s Rule?
C = the reproductive cost to the individual of performing the act
What are the two kinds of kin selection required for kin to interact?
Kin fidelity and kin choice
What is kin fidelity?
Associations between kin based on spatial proximity
What is kin choice?
Discrimination between potential patterns based on relatedness?
What can kin fidelity lead to?
Recognition
What is the Major Histocompatibility Complex?
- Group of genes that code for proteins found on the surfaces of cells that help the immune system recognize foreign substances.
- MHC genes influence odour.
What kin recognition does the major histocompatibility complex play a critical role in?
- Social preferences - group composition.
- Mate selection - offspring viability.
How to MHC influence mate choice?
- Mating with close kin can result in reduced longevity, fewer offspring reaching maturity, and a weakened immune system – inbreeding depression.
- Individuals in some species prefer mates carrying dissimilar MHC genes, which may function to reduce inbreeding and increase genetic diversity.
What is the Green Beard Effect by Dawkins?
- Suppose that a gene appears that has two effects: its owners have green beards and help others with green beards.
- If it is impossible to cheat the system the gene would spread.
- There is some evidence for this effect in nature.
Example of Dawkins’ Green Beard Effect in the Red Fire Ant
- Nest in multiple queen colonies
- Egg-laying queens are Bb heterozygotes at the locus Gp-9
- BB queens initiating reproduction are killed by workers
- Bb rather than BB workers that are responsible for these executions.
- The mechanism for recognition seems to be an odor cue
