PrepTest 52, Section 4, Question 13

Traditional theories of animal behavior assert that animal conflict within a species is highly ritualized and does not vary from contest to contest. This species-specific model assumes that repetitive use of the same visual and vocal displays and an absence of escalated fighting evolved to prevent injury. The contestant that exhibits the "best" display wins the contested resource. Gal�pagos tortoises, for instance, settle contests on the basis of height: the ritualized display consists of two tortoises facing one another and stretching their necks skyward; the tortoise perceived as being "taller" wins.

In populations of the spider Agelenopsis aperta, however, fighting behavior varies greatly from contest to contest. In addition, fighting is not limited to displays: biting and shoving are common. Susan Riechert argues that a recently developed model, evolutionary game theory, provides a closer fit to A. aperta territorial disputes than does the species-specific model, because it explains variations in conflict behavior that may result from varying conditions, such as differences in size, age, and experience of combatants. Evolutionary game theory was adapted from the classical game theory that was developed by von Neumann and Morgenstern to explain human behavior in conflict situations. In both classical and evolutionary game theory, strategies are weighed in terms of maximizing the average payoff against contestants employing both the same and different strategies. For example, a spider may engage in escalated fighting during a dispute only if the disputed resource is valuable enough to warrant the risk of physical injury. There are, however, two major differences between the classical and evolutionary theories. First, whereas in classical game theory it is assumed that rational thought is used to determine which action to take, evolutionary game theory assumes that instinct and long-term species advantage ultimately determine the strategies that are exhibited. The other difference is in the payoffs: in classical game theory, the payoffs are determined by an individual's personal judgment of what constitutes winning; in evolutionary game theory, the payoffs are defined in terms of reproductive success.

In studying populations of A. aperta in a grassland habitat and a riparian habitat, Riechert predicts that such factors as the size of the opponents, the potential rate of predation in a habitat, and the probability of winning a subsequent site if the dispute is lost will all affect the behavior of spiders in territorial disputes. In addition, she predicts that the markedly different levels of competition for web sites in the two habitats will affect the spiders' willingness to engage in escalated fighting. In the grassland, where 12 percent of the habitat is available for occupation by A. aperta, Riechert predicts that spiders will be more willing to engage in escalated fighting than in the riparian habitat, where 90 percent of the habitat is suitable for occupation.

Traditional theories of animal behavior assert that animal conflict within a species is highly ritualized and does not vary from contest to contest. This species-specific model assumes that repetitive use of the same visual and vocal displays and an absence of escalated fighting evolved to prevent injury. The contestant that exhibits the "best" display wins the contested resource. Gal�pagos tortoises, for instance, settle contests on the basis of height: the ritualized display consists of two tortoises facing one another and stretching their necks skyward; the tortoise perceived as being "taller" wins.

In populations of the spider Agelenopsis aperta, however, fighting behavior varies greatly from contest to contest. In addition, fighting is not limited to displays: biting and shoving are common. Susan Riechert argues that a recently developed model, evolutionary game theory, provides a closer fit to A. aperta territorial disputes than does the species-specific model, because it explains variations in conflict behavior that may result from varying conditions, such as differences in size, age, and experience of combatants. Evolutionary game theory was adapted from the classical game theory that was developed by von Neumann and Morgenstern to explain human behavior in conflict situations. In both classical and evolutionary game theory, strategies are weighed in terms of maximizing the average payoff against contestants employing both the same and different strategies. For example, a spider may engage in escalated fighting during a dispute only if the disputed resource is valuable enough to warrant the risk of physical injury. There are, however, two major differences between the classical and evolutionary theories. First, whereas in classical game theory it is assumed that rational thought is used to determine which action to take, evolutionary game theory assumes that instinct and long-term species advantage ultimately determine the strategies that are exhibited. The other difference is in the payoffs: in classical game theory, the payoffs are determined by an individual's personal judgment of what constitutes winning; in evolutionary game theory, the payoffs are defined in terms of reproductive success.

In studying populations of A. aperta in a grassland habitat and a riparian habitat, Riechert predicts that such factors as the size of the opponents, the potential rate of predation in a habitat, and the probability of winning a subsequent site if the dispute is lost will all affect the behavior of spiders in territorial disputes. In addition, she predicts that the markedly different levels of competition for web sites in the two habitats will affect the spiders' willingness to engage in escalated fighting. In the grassland, where 12 percent of the habitat is available for occupation by A. aperta, Riechert predicts that spiders will be more willing to engage in escalated fighting than in the riparian habitat, where 90 percent of the habitat is suitable for occupation.