What Are Fixed Action Patterns?
Fixed Action Patterns (FAPs) represent distinct, unlearned behavioral sequences characteristic of a particular species. These complex actions are innate, meaning they are genetically programmed and do not require prior experience or learning for their execution. The concept of FAPs emerged within the field of ethology, a discipline focused on the scientific study of animal behavior under natural conditions. Pioneers such as Konrad Lorenz and Niko Tinbergen significantly contributed to the understanding and definition of these patterned responses. FAPs are more elaborate than simple reflexes, involving a coordinated series of movements that contribute to survival or reproduction.
Distinctive Features of Fixed Action Patterns
Fixed Action Patterns are stereotyped and invariant. The behavior unfolds in a consistent, predictable manner with minimal variation among individuals of the same species. The sequence of actions remains largely identical each time it is performed, regardless of minor environmental changes.
FAPs are initiated by a specific external cue, known as a sign stimulus or releaser. This stimulus triggers the pre-programmed behavioral sequence. Its presence is often sufficient to elicit the entire pattern.
Once initiated, a Fixed Action Pattern is ballistic, meaning it runs to completion. The behavior continues through its entire sequence, even if the original sign stimulus is removed or the action’s goal becomes unattainable. This highlights their automatic, pre-programmed nature.
FAPs are unlearned and innate. Their capacity is genetically encoded, present from birth or a specific developmental stage. Animals do not need to practice or be taught these actions.
Illustrative Examples from the Animal Kingdom
A classic example of a Fixed Action Pattern is the egg-retrieving behavior of the Greylag Goose. If an egg rolls out of its nest, the goose will extend its neck and use its bill to roll the egg back into the nest. The sight of an egg outside the nest serves as the sign stimulus for this behavior.
Once the goose begins the rolling motion, it will continue the entire sequence, even if the egg is removed mid-retrieval. The goose will complete the head and neck movements as if still guiding the egg, demonstrating the ballistic nature of this FAP. This innate behavior ensures offspring safety, crucial for reproductive success.
Another well-documented example is the aggressive display of the male Three-spined Stickleback fish during its breeding season. Male sticklebacks develop a bright red belly when ready to mate and will aggressively attack other males entering their territory. The sign stimulus for this aggression is the sight of a red underside.
Even a crude model with a red underside triggers the aggressive FAP, while a realistic model without red will not. This behavior, involving charges and bites, defends nesting sites and attracts females. The stickleback continues its aggressive sequence even if the red object is quickly removed.
The parasitic Cuckoo chick also displays a Fixed Action Pattern shortly after hatching. Upon emerging from its egg in the nest of a host bird, the blind and naked cuckoo chick begins to push any other eggs or nestlings out of the nest. The tactile stimulus of an object in its back triggers this pushing behavior.
This action, despite the chick’s undeveloped state, ensures it receives all parental care and food from the unsuspecting host parents. The Cuckoo chick continues to eject items until it is the sole occupant.
Why Fixed Action Patterns Matter in Nature
Fixed Action Patterns hold evolutionary and ecological importance for many species. These innate behaviors allow animals to respond quickly and efficiently to environmental cues without learning. Rapid responses are essential for survival, especially in predator avoidance or prey capture.
For instance, a defensive FAP can be crucial when encountering a threat.
FAPs also play a role in reproductive success, guiding species-specific courtship rituals, mating behaviors, and parental care. These sequences ensure complex, multi-step reproductive actions are performed correctly, contributing to species fitness.
Studying FAPs helps scientists understand the genetic basis of behavior, revealing how actions are encoded in an animal’s biological blueprint. They highlight the interplay between internal programming and external environmental stimuli. Examining these behaviors provides insight into adaptive strategies that enable animals to thrive.