Fixed action pattern

Fixed action pattern (FAP) is a series of instinctive behavioral sequences that are innate and, once initiated, are run to completion. Fixed action patterns are unchangeable and, once initiated, will be carried out to completion without regard to changes in the original stimulus. They are a key concept in the study of ethology, the biological study of animal behavior.

Fixed action patterns are triggered by a very specific stimulus, known as a sign stimulus or releaser. Once the sign stimulus is detected, the fixed action pattern is invariably and automatically performed. For example, the stickleback fish exhibits a fixed action pattern where the male attacks other males that enter its territory during the breeding season. The sign stimulus for this behavior is the red belly of the intruding fish. Even a model with no other fish-like characteristics but with a red underside can trigger this aggressive behavior.

Characteristics

Fixed action patterns are characterized by several key features:

• Innate: They are genetically programmed behaviors that an animal is born with, not learned behaviors.
• Stereotyped: The sequence of actions within a fixed action pattern is performed in the same way each time, across individuals of a species.
• Inflexible: Once initiated, the sequence is carried out to completion, regardless of changes in the environment.
• Triggered: They are initiated by a specific external stimulus.

Examples

In addition to the stickleback fish's territorial aggression, other examples of fixed action patterns include:

• The egg-rolling behavior of the greylag goose, where a goose uses its beak to roll a wayward egg back to its nest, triggered by the visual stimulus of an egg-shaped object outside the nest.
• The web-spinning behavior of spiders, which is a complex sequence of movements performed in the same order each time to construct a web.
• The mating dance of many bird species, where a specific series of movements and sounds must be performed to attract a mate.

Significance in Ethology

Fixed action patterns are significant in the study of ethology for several reasons:

• They provide evidence for the genetic basis of some behaviors.
• They help in understanding how animals interact with their environment and other organisms.
• They offer insights into the evolutionary pressures that have shaped behavior.

Criticism and Limitations

While fixed action patterns provide a framework for understanding certain types of behavior, they have limitations. Critics argue that the concept does not account for the flexibility and adaptability of most animal behaviors in response to changing environmental conditions. Furthermore, the distinction between innate and learned behaviors is not always clear-cut, as both can influence each other.

See Also

• Ethology
• Innate behavior
• Behavioral ecology
• Sign stimulus

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  Three-spined stickleback
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  Greylag goose
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  Reed warbler feeding a cuckoo