Psychology 351 – Animal Behavior

Alcock, Chapter 6 – Behavioral Adaptations for Survival
Summary by Kris Mattox


Introduction
- Hard to pass on genes if you are dead. Most animals are strongly motivated to stay alive (survive) long enough to reproduce.
- Selection Pressure : favoring those individuals with attributes that postpone death until they have reproduced at least once.
- Main Goal of Chapter : to establish what is meant by an adaptation and to show how one can use a cost-benefit approach to produce hypotheses on the possible adaptive value of a behavioral trait while using the comparative method to test those hypotheses.

Mobbing Behavior and the Evolution of Adaptations
- Mobbing Behavior : animals such as gulls swooping, diving, and calling loudly at predators that are getting too close to their youngsters, helping them survive. This behavior increases their reproductive success, passing on the hereditary basis for their willingness to join groups of other gulls in mobbing on those who might eat their eggs and youngsters.
- Adaptionist Approach (Hans Kruuk) : studying the evolutionary, ultimate causes of a behavior (an adaptive product of natural selection).
  • Selection cannot create the best genes for a particular task, but has to wait for mutations to occur by chance. Then it can get rid of the less effective alleles, leaving the ones that are better at promoting reproduction in place. If a “better” allele does not come along, there is nothing selection can do about it (keep “good” alleles, get rid of “negative” alleles).
- Fitness : higher reproductive success or higher genetic success.
- Adaptation: a hereditary trait that either (1) spread because of natural selection in the past and has been maintained by selection to the present OR (2) is currently spreading relative to alternative traits because of natural selection.
  • Test hypotheses about possible adaptations by focusing on the current benefits of a given trait.
- Cost – Benefit Approach : to analyze phenotypes (behaviors) in terms of their fitness benefits and fitness costs.
- Fitness Benefit : the positive effect of a trait on the number of surviving offspring produced by an individual or the number of copies of its alleles it contributes to the next generation.
- Fitness Cost : the damaging effects of the trait on these measures of individual genetic success (Example – Gulls time & energy spent mobbing).

The Comparative Method for Testing Adaptionist Hypotheses
- Comparative Method : testing predictions about the evolution of an interesting trait by looking at animals other than the species whose characteristics are under investigation.
- Divergent Evolution : when the evolutionary result shifts away from the ancestral behavior pattern.
- Convergent Evolution : species from different evolutionary lineages that live in similar environments, and therefore experience similar selection pressures, can be predicted to evolve similar traits.

The Cost Benefit Approach to Antipredator Behavior
- All behaviors have fitness costs and benefits, but only those whose benefits exceed their costs can be directly selected for.
- There are benefits of getting together with others, including the potential for group attack on a shared enemy, which could prevent it from doing damage.

The Costs and Benefits of Camouflage
- Benefits : able to hide from predators, able to sneak up on prey.
- Costs : even organisms that have camouflage are susceptible to predators. Predators can track prey down by their odor.

Some Darwinian Puzzles
- Darwinian Puzzles : traits whose costs seem likely to exceed their benefits.
  • Example – a species whose orange and black wing pattern makes it easy to spot.
- Alarm Signal Hypothesis : warn co specifics, particularly offspring, that a predator is dangerously near.
- Social Cohesion Hypothesis : able to form groups and flee in a coordinated manner, making it harder for a predator to cut one out of the herd.
- Confusion Effect Hypothesis : individuals in a fleeing herd are able to confuse and distract a following predator.
- Pursuit Deterrence Hypothesis : announce to a pursuing predator that the individual was in excellent condition and therefore unlikely to be captured.

Optimality Theory and Antipredator Behavior
- Optimality Theory : looking at the costs and benefits of four alternative hereditary behavioral phenotypes in a hypothetical species. One of the (4) phenotypes generates a net loss, the other (3) are linked to net fitness gain. Only (1) is an adaptation, because it produces the greatest net benefit of the (4). Optimal trait is an adaptation.

Game Theory Applied to Social Defenses
- Game Theory : focus on cases in which individuals are competing with one another in such a way that the fitness consequences of a given behavioral option depend on the actions of the other competitors.
- Selfish Herd : all the individuals were hiding behind others to reduce the probability of being selected by a predator.