The biology behind antipredator behavior is unique in that mistakes with respect to this type of behavior can lead to an animal having a future fitness of zero. This striking fact suggests that natural selection should operate very strongly on antipredator behavior. Indeed, the array of antipredator tactics used in nature is dazzling. Consider, for example, antipredator behaviors in schooling species of fish. In addition to the potential hydrodynamic and the foraging benefits accrued by living in groups, fish in schools display a wide assortment of antipredator tactics. When a predator is sighted, schooling fish school more tightly, allowing for the following antipredator tactics:
1. Fountain effect. Schools maximize their speed, split around a stalking predator, and then reassemble behind the putative danger.
2. Trafalgar effect. When animals school tightly, information about a predator spreads from individual to individual more quickly than in loose schools. This has been coined the 'Trafalgar effect' because it resembles the quick transfer of information of battle signals in Lord Nelson's fleet at the battle of Trafalgar.
3. Flash explosion. Schools of fish 'explode', with individuals swimming off in all directions. This may confuse a predator and allow for the prey species to escape. Schooling fish often add to this effect by moving around in very erratic patterns.
4. Predator inspection. A small number of individuals break away from a school and approach a predator to gain various types of information (e.g., is the predator hunting?), and then return to the school, where this information may spread across individuals.
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