Behavioral Ecology

How evolutionshapes behavior

Optimality

Organisms behave to maximize benefit and minimize cost

Optimal Foragingmaximize nutritional benefits minimize energetic/survival costs

Zach, 1978

Zach, 1978

Crows generally fly5 meters high

Zach, 1978

Higher than 5 meters does not increase the chance of the shell breaking

Benefits < Costs

Territory

TerritoryBenefits: exclusive access to food, matesCosts: energy required to defend

Reproductive Behavior

Optimized Reproductionmaximize offspringminimize energetic/survival costs

Energetic/survival costs are typically unequal between males and females

“Battle of the vs Sexes”

Mate Choice

Parental Investment TheoryThe sex with the most energetic costs from parenting

will be more selective

Which sex has higher parental costs?

Birds female produce large eggsand may lay 50 to over 100% of their body weight eachseason

Mammalsonly females can becomepregnant and lactate

Generally, females invest more in eggs than males do in sperm

Females are usually more selective

Mate Choice causes Sexual Selection

Intrasexual: traits that give a competitive advantage

Intersexual: traits that are preferred by the chooser sex

Intrasexual Selection

Intersexual Selection

Fig. 37.12Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Mating systems

Polyandry: multiple malesPolygyny: multiple femalesPromiscuous: multiple males & femalesMonogamy: one male, one female

Jacana

Elephant seal Dunnock

Black vulture

Clumped food (fruit tree): Polygyny/Polyandry

Random/uniform food (insects): Monogamy

Socialbehavior

From simple social groups………

…. To complex societies

Altruism

Behavior that benefits others at a cost to the individual

Cost may be minor…

…or extreme!

Optimality

maximize benefitminimize cost

So how could altruism evolve?

Reciprocity

“You scratch my back, I’ll scratch yours.”

Vampire bats

Benefit = survival (as a recipient)Cost = small amount of food loss (as a donor)

Benefit > Cost in the long term

Kin Selection

Helping your relatives

Siblings: share 1/2 of your genesCousins: share 1/8 of your genes

"Would I lay down my life to save my brother?

No, but I would to save two brothers or eight cousins.”

-J.B.S. Haldane

Fig. 37.17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Belding’s ground squirrels

Benefit = protect relatives who share genesCost = increased predation risk to self

Benefit > Cost if relatives near by

Communication

Fig. 37.15

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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a: © S. Osolinski/OSF/Animals Animals-Earth Scenes