Group Living Flashcards
What did Williams and Hamilton suggest about group behaviour?
It’s the benefit to the individual that drives aggregation behaviour
Aggregation will reduce the risk of predation (dilution)
What is predator swamping?
The idea that synchronised emergence can ‘swamp’ predators reducing capacity to catch prey
What is the selfish herd effect?
Individuals around the edge of a group are more at risk, therefore individuals will move around to gain a safer position in the aggregation
What is the confusion effect?
It is hard to focus on one individual when many others are moving within line of sight
What is the oddity effect?
Predators prefer to attack odd looking individuals because they are easier to focus on
High saliency individuals will be more easily noticed by predators
Give an example of communal defence
Study on nesting birds showed that artificial nests placed near the colonies suffered lower predation then the nests placed near solitary nests
How does group vigilance benefit an individual?
Higher chance of a predator being spotted when in a larger group
Spend less time looking around for predators and more time feeding
How might group vigilance be a problem?
Dilution reduces the vigilance of the individual but the overall vigilance of the group may be reduced, especially when there is competition over food resources
What is the ‘Trafalgar effect’?
Individuals know when the predator is approaching before it is even in sight
Usually due to alarm calls
What are the advantages to not cheating in a group?
More vigilant individuals are less likely to be targeted by predators, also more vigilant individuals will spot alarm flights etc. quicker
What are sentinels?
A small number of individuals watching from a look out point for predators while the rest forage in relative safety knowing they are being watched over
E.g. meerkats
Why do some animals take the role of sentinels?
Predation risk for sentinels is reduced as they tend to be the first to spot the predator and therefore the first to respond - could be a selfish reason
How could information sharing on food availability/patches be beneficial to an individual?
Could be the dilution effect to reduce the risk of predation and allows more time for the individual to feed instead of looking out for predators
Give an example of when information sharing benefits an individual
Ravens feeding on a carcass could fight off juveniles
However when it reached 6 or more they would give way
Therefore juvenile ravens call out to other ravens to gain access to the carcass
