Optimal theory The theory used to generate hypotheses about the adaptive value of characteristics which analyzes the costs and benefits of alternative decisions in terms of their fitness payoffs

Decision variable – behavioral options

Currency – often related to fitness

Constraints – intrinsic vs. extrinsic

Advantages

Make assumption explicit

Generate testable prediction

Suggest new hypothesis if model does not fit

Criticism

Behavior may not always optimal

Optimal diet E1 E2 E2 E1 E1h2

----- > ----- , if ----- > ------- => S1 > -------- - h1

h1 h2 h2 S1+h1 E2

Always eat the most profitable prey type

Include less profitable prey only if S1 > (E1h2/E2) - h1

Inclusion of the less profitable prey does not depend on its abundance, only on the abundance of the more profitable prey

Specialist on prey 1 will switch and become generalist both suddenly and completely when prey 1 become rare

Multiple prey choice

Rank all prey by profitability

To decide whether to include a prey item when encounter, its profitability must exceed the net profitability of all higher ranking prey

E3 > (E1 + E2)/(h1 + s1 + h2 + s2)

Reasons for partial preference

Discrimination error

Lack of complete information

Variation in predator or prey

Simultaneous encounter of multiple prey

Short term sampling rule for estimating encounter rate

Patch choice modelWhen is the optimal time to leave a patch?

e.g. hummingbird or bee visiting flowers

Constraints

Time spent searching in patches and traveling between patches are independent

Perfect knowledge

Energy gain in patches show diminishing gain

Marginal value theorem – patch residence time

Great titMeal worm hidden in sawdust in pots hanging from trees

Long and short travel time achieved by making lids hard or easy to remove

Actual patch resident time ~ prediction

Central place foraging

Starling travel between feeder and nest

Load curve shows diminishing return because it becomes harder to probe as bill fills

Observation fits MVT prediction

What if optimality failsNutrients, predation, competition, risk of starvation, age, experience, etc.

Consider currency other than profitability

Efficiency, Egain/Espent

Nectar load of bee shows diminishing return because larger loads take more energy

Fit maximize efficiency model but not maximize profitability

Selection on hives favor efficiency

Foraging in a variable environment

Immediate responseRisk sensitive foraging

Long-term responseTopor or hibernation

Fat storage

Caching or hoarding

agriculture

Risk sensitive foraging

Choose to forage in constant or variable (unpredictable) environment

Risk averse vs risk prone

Foraging in Juncos Two pans: one with a non-variable modest reward and the other with a variable but higher pay-off reward

The birds that were non-energy limited chose the lower payoff pan over the higher payoff, but risky pan. When food was limited, they opted for the higher payoff but risky pan.

Why hoarding instead of fat storage

Fat increase body mass and predation risk

If food is super-abundant, not all can be stored as fat

Large store provide food supply for a group over winter

Can be more easily transferred to offspring

Anti-predator strategies making detection less likely

egg-shell removalcamouflage & cryptic behaviorindustrial melanism in mothFreezingremoving evidence of presencebroken-winged display

Cost of cryptic behaviorTime lost for other activities

Belding’s ground squirrels respond to alarm call: hiding in underground burrows = time not spent feeding

Cost of time lost for feeding varies among individuals depending on their nutritional status. Well-fed individuals should have less to gain from additional feeding

Trinidadian guppies

Males court most vigorously at moderate light intensity (low light, not visible to females; high light, too visible to predators)

Small males court more vigorously , especially at high light intensity

making attack less likely

physical and chemical repellents and weapons

warning coloration & behavior

bright color wings under dull color wings, big eye-spots

hiss sound, inflation and increase body size, tail of rattlesnake, stripes and hand-stand of skunks

mimicry

stotting--hypotheses alarm signal hypothesissocial cohesion hypothesisconfusion effect hypothesispursuit-deterrent (un-profitability advertisement hypothesis)anti-ambush hypothesishandicap principlestartle effect

making capture less likelyvigilance, e.g. moth-bat

misdirecting a predator's attack

fleeing

Cooperative defense

vigilance

selfish herd

dilution effect

group mobbing

Key prediction of selfish herd hypothesis

Individuals should compete for access to safest spots in the herd

Individuals in least safe spots in the herd should be safer than are solitary individuals

e.g. blue-gill sunfish breeds in colony. Males compete for central territory which is preferred by females and lower in predation risk. Solitary males experiencing higher rate of infestation/predation than edge males

Cooperative defense: mobbing

Hypothesis: If mobbing protects eggs and young, the degree of protection should be proportional to the intensity of the mobbing

Test: placing eggs along a transect from inside to outside the border of the colony

Results: mobbing rates increased toward center of colony and predation rate decreases as mobbing rates increased

Hypothesis: comparative method

Related species nesting in habitats less vulnerable to terrestrial predation should not exhibit the behavior – kittiwake

Unrelated species nesting in similar habitats should demonstrate mobbing – swallow, ground squirrels

Alarm call

Ideal free distributionAnimal sequentially fill available habitat staring with best patches

Assumption

“ideal” by possessing perfect info about resource quality

“free” to disperse appropriately

Expectation – animals disperse to equalize energy intake or reproduction

Deviation from IFD16/20 studies show too many in poor habitat or too few in rich habitat

Perception error

Differences in competitive abilityDominants exclude subordinates

Dominance – how?Resource holding potential - ability of control access to a resource

Correlate w/ body size, experience, matrilineal relationship, fat reserves, prior success or failure, etc.

Require recognition or status badge

Economics of territorialityResource must be defendable

Renewable, not ephemeral or super-abundant

Benefit > cost of defense

Energetic cost increase w/ # of intruders, territory size

Benefit accrue by increasing energy intake rate, reducing energy cost and starvation risk

If nectar level increase from 2 to 3 ul per flower, the bird save 1.3 hr per day foraging time and save

(1000x1.3) – (400x1.3) = 780 cal

But the bird spent 0.28 hr per day defending and the cost of defending =

(3000x0.28) – (400x0.28) = 728 cal

Economically defendable