CurrencyCurrency –What is to be maximized Strategy set (decision)Strategy set (decision) –What the animal can do ConstraintsConstraints –The limits of the model

CurrencyCurrency –Net energy intake per time Strategy setStrategy set –Add another prey type to diet or don’t Key constraintsKey constraints –Searching and handling are mutually exclusive –Prey are encountered sequentially –Animal has perfect information –Prey of a given type are identical

E = EnergyE = Energy T = TimeT = Time λ = Encounter frequencyλ = Encounter frequency h = Handling timeh = Handling time Math TimeMath Time

All-or-nothing ruleAll-or-nothing rule The inclusion of a less profitable item depends only on the absolute abundance of the more profitable prey typesThe inclusion of a less profitable item depends only on the absolute abundance of the more profitable prey types –Increased overall abundance will lead to diet narrowing

Absolute abundance of large prey mattersAbsolute abundance of large prey matters Birds do not abide by “all-or- nothing” ruleBirds do not abide by “all-or- nothing” rule –Why not? ErrorError SamplingSampling

CurrencyCurrency –Net energy intake per time Strategy setStrategy set –Stay or leave Key constraintsKey constraints –Density of prey in a patch decreases exponentially because predator searches at random Energy gain decreases over time in patchEnergy gain decreases over time in patch –Predator has complete knowledge of landscape

The expected travel time correlates positively with the time spent in each patch and the level at which each patch is exploitedThe expected travel time correlates positively with the time spent in each patch and the level at which each patch is exploited The effect of patch richness depends on the shape of the exploitation functionThe effect of patch richness depends on the shape of the exploitation function

Central place foragingCentral place foraging –Travel time PredictionsPredictions –Load time and load size increase with distance to patch

ConclusionsConclusions –Animals make subtle distinctions to optimize behavior But why isn’t the fit better?But why isn’t the fit better? –Predation risk –Sampling Why don’t we just add more terms?Why don’t we just add more terms?

Animals can learn about patch qualityAnimals can learn about patch quality Animals are BayesiansAnimals are Bayesians

Ecological riskEcological risk The fitness value of a food item depends on one’s energetic stateThe fitness value of a food item depends on one’s energetic state Predicts risk-sensitivity when foragingPredicts risk-sensitivity when foraging