Competing for resources

Competition for resources important for how animals distribute

- Competition is the main process shaping distribution of individuals - Competition varies with amount of resources in time and space - exploitation competition vs. resource defence

Ideal Free Distribution (IFD)

- Competitors adjust their distribution proportionally to the amount of resources available in each patch - Competition by exploitation Ideal: - Animals have information about patch qualities animals have equal competitive abilities Free: - No territoriality - No travel costs between patches - Move to wherever their intake ishighest

Game theory - Hawks and Doves

- Individuals compete for a resource that can not be shared - Two strategies in a population - "Hawks" fight to death - risk of injury - "Doves" never fight - no injury - Two players in a game - The winner is decided by contest If Hawks is exclusive strategy (-25) a mutant Dove can invade (0) - If Doves is exclusive strategy (+25), a mutant Hawk can invade (+50) - Neither pure strategy is ESS - ESS: Mixed strategy where the average pay-off of either strategy is equal - pay-off of +25 if all played doves

Escalated fights

- When the value of the resource exceeds the cost of injury V > C Hawk strategy is ESS (fx. mating chance)

Evolutionarily Stable Strategy (ESS)

- the best strategy - ESS denotes the strategy taken by most individuals of a population that cannot be beaten by any different strategy - No mutant strategy can 'invade' and do better

Economic defendability

Competition by exploitation

Dispersal

Movement away from a previous range to a new one

Game theory

modelling of strategies to understand and predict ESS

Different fighting strategies are expected:

when gain < cost: not worth it when gain > cost: individuals risk more

competitors

when individuals both exploit a limited resource