Lecture 11- Conflict and aggression I Flashcards
hamilton’s rule
rB-c>0
types of inter-family conflict
sexual conflict (e.g. over parental care)
sibling conflict
parent-offspring conflict
shape of the cost/benefit/parental investment curve in a harsh environment
sigmoidal, benefit of some parental care is quite high but there are diminishing returns + a little bit of care doesn’t seem important
shape of the parental investment care/cost benefit curve in a more benign environment
benefits are higher at a lower extent of care, less investment required for decent benefits
how might cost of reproduction to the parents impact parental care
more parental care as producing another offspring may be less viable, more important that this one survives
parental optimism example
acting as though an environment will be beneficial even if it may not, e.g. snowy owls laying large clutches, if there is not good food availability, siblings can cannibalise- creates high sibling conflict
parental pessimism example
obligate siblicide in chicks- associated with low hatching success, producing 2 eggs so you will likely get 1, and if 2 hatch, you still end up with 1 actual offspring
triver’s model of parent-offspring conflict
fitness/parental investment curves for offspring and parent
levels off in offspring, levels off at half the height for parents, cost to parents increases linearly- can locate optima for different parties from these
example of a trade-off in investment in lambs
high birth weight is better for offspring, but less good for mothers
better from the mothers pov to have 2, smaller lambs- creates stabilising selection due to conflict of interest
conditions that can create additional parent-child conflict
addition of another father to a brood, lower overall relatedness so easier to reach a conflict threshold
example of a dishonest signal of need
begging in birds regardless of true need, competition with siblings? may help in future competition
conditions where sibling aggression is more common
longer nesting periods- relationships last longer so it pays to be dominant in them, can help in situations such as bouts of food shortage to be dominant
smaller broods- easier to outcompete a smaller number, makes it more beneficial to try in terms of energy tradeoff
stable biparental care model
both parents providing equal-ish amount of care, evolutionarily stable state where both parents want to be investing a bit less than the other one
sealed bid model
responses occur over revolutionary, ratjer than behavioural, time- changes in investment don’t come from changes in conditions in real time
examples of how you can experimentally modify parental care
removing a parent and watching for a response
changing costs of parental care, e.g. adding weights to make finding food more costly
