Animal Behavior Exam 2

Lectures 8-14

Benefits of foraging:

E = energy gain (calories)

Costs of foraging:

s = time spent searching for a prey item.

h = time spent handling a prey item (capture and consumption)

Profitability (P) =

E_new / h_new

R_average =

E_average / h_average + s_average

Rate-Maximizing Diet Model

E(new) / h(new) ≥ E(average) / h(average) + S(average)

Life-dinner principle

reduced activity means less foraging.

Reduced predation risks:

1. Dilution effect

2. selfish herd effect

3. improved detection

4. confusion effects

5. mobbing behavior

What do male animals fight over?

Females, territories, food, non-food resources.

Payoff matrix

determines behavioral strategies that evolve based on benefits and costs.

Evolutionary Stable Strategy (ESS)

Strategy that cannot be bettered and, therefore, cannot be replaced by any other strategy when most of the members of the population have adopted it.

Mixed ESS

the mixture of strategies is stable and departures from the stable mixture cannot invade.

Pure ESS

All individuals adopt the same strategy and no other strategy can invade.

Payoff asymmetry

Owners place a higher value on the resource than do rivals

Conventional rule

A rule to settle a contest (Ex: coin flip, “I was here first”)

Resource Holding Potential (or Power)

the ability to acquire and defend resources through greater strength, fighting ability, energy reserves, and motivation to fight.

Bateman’s principle

variability in reproductive success is greater in males than in females.

Intra-sexual selection

members of one sex (usually males) compete among themselves for access to members of the other sex (male-male competition).

Inter-sexual selection

Members of one sex (usually females) prefer to mate with members of the other sex that have particular traits (female choice).

Types of Intra-sexual selection

1. Direct fighting

2. endurance rivalry

3. sperm competition

4. mate-guarding

5. alternative mating tactics - behavioral/genetic polymorphism

Direct benefits = benefits that accrue to females in the current generation:

1. nutrition

2. male parental care

3. territory resources

4. protection/decreased harrassment

5. more or better sperm/increased fertilizationIi

Indirect benefits = benefits that accrue to females in the next generation:

1. “Good genes” in offspring

2. “Sexy sons” attractive to females

3. Higher genetic compatibility.

Direct Parental Care:

1. care of fertilized eggs

2. feed offspring

3. protect offspring

4. care following nutritional independence

Indirect Parental Care

1. Invest in gamete production

2. prepare the natal environment (maintain nests or dens)

Parental care costs to females:

1. increased predation risk

2. reduced foraging time

3. reduced future fecundity

4. physiological costs

Parental care costs to males

1. increased predation risk

2. reduced foraging time

3. reduced future fecundity

4. reduced opportunities to seek additional mates

5. uncertainty of paternity

Parental care benefits to males and females

Increased survival of individual offspring.

Hypotheses for evolution of elaborate traits:

1. Sensory exploitation

2. Honest advertisement

3. Runaway sexual selection

4. Chase away selection

Sensory exploitation hypothesis

• trait exploits a pre-existing bias of the female.

• may explain origin of many elaborate male traits

Honest advertisement hypothesis

trait indicates some heritable aspect of a male’s genetic or physiological quality (selected male trait is costly).

Runaway selection hypothesis

trait and preference become genetically correlated and co-evolve in a positive feedback loop that “runs away” (sexy sons).

Chase away selection

trait evolves through a co-evolutionary “arms-race” between male ardor and female resistance (males benefit more often than females).