Animal Behavior

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Slide 58

Appearance / variation of male zebra finches in nature

Slide 59

Male Competition for Mates

Male competition for mates is a source of intrasexual selection that can reduce variation among males.

Such competition may involve agonistic behavior, an often ritualized contest that determines which competitor gains access to a resource.

Slide 60

Males Compete - Agonistic interaction

Slide 61

Applying Game Theory

In some species, sexual selection has driven the evolution of alternative mating behavior and morphology in males.

The fitness of a particular phenotype (behavior or morphology) depends on the phenotypes of other individuals in the population.

Game theory evaluates alternative strategies where the outcome depends on each individual’s strategy and the strategy of other individuals.

Slide 62

For example, each side-blotched lizard has a blue, orange, or yellow throat, and each color is associated with a specific strategy for obtaining mates. There is a genetic basis to throat color and mating strategy.

Like rock-paper-scissors, each strategy will outcompete one strategy, but be outcompeted by the other strategy. The success of each strategy depends on the frequency of all of the strategies; this drives frequency-dependent selection.

Slide 63

Male polymorphism in the side-blotched lizard (Uta stansburiana)

Slide 64

Inclusive fitness can account for the evolution of altruistic social behavior

Natural selection favors behavior that maximizes an individual’s survival and reproduction.

These behaviors are often selfish.

On occasion, some animals behave in ways that reduce their individual fitness but increase the fitness of others.

This kind of behavior is called altruism, or selflessness.

Slide 65

Altruism

Example of altruism / selfless behavior for the good of the group:

Under threat from a predator, an individual Belding’s ground squirrel will make an alarm call to warn others, even though calling increases the chances that the caller is killed.

Slide 66

Inclusive Fitness

Altruism can be explained by inclusive fitness.

Inclusive fitness is the total effect an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring.