According to Konrad Lorenz, Charles Otis Whitman and Oskar Heinroth, the first American and the other German, were two significant precursors of the modern study of animal behaviour. Active in the early 1900s, they were interested in birds. While Whitman wrote a monumental work on the pigeon (Columba livia), ducks held no secrets for Heinroth. Completely independently, the two scholars concluded that the expressive movements (displays) underlying communication between conspecifics, as well as those related to behaviors fundamental to the species (reproductive, agonistic, or parental care), were remarkably consistent in form.
If we stop to observe a male pigeon courting a female on the street, we will always see the same movement: the male, calling, bows before her, pirouetting repeatedly. This movement is called a “bowing display” in the ethogram of wild, domestic, and urban pigeons. All males perform it the same way, but what is interesting is that all known pigeon species perform it in a very similar manner.
From this evidence, our two researchers concluded that the behavioral elements of a species are equally valid, just like anatomical characteristics, in systematically defining it. Likewise, if a series of movements is common to a group of species, this is a sure sign of phyletic closeness. They were the first to recognize that the behavioural expressions of a species, like the shape of a wing, a leg, or a beak, are part of its phenotype. That is to say, I recognize a pigeon by its appearance but also by the way it courts the female.
K. Lorenz fully embraced these findings, introducing into ethology the key concept of the formal stability of the expressive movements of various species, referring to them as “Fixed Action Patterns” (FAPs).
Their formal stability derives from the fact that FAPs constitute inherited motor coordinations that an individual does not need to learn, being among the innate abilities that form the set of behaviors with which they are born. Lorenz defined these innate behaviors as instincts, though it was not an ideal choice… The term instinct is often given a negative connotation, sometimes implying actions done against one’s will, so much so that even Shakespeare has one of his characters say, “Beware of instinct!”
In ethology, however, instinct carries no negative meaning. In Lorenz’s view, it is identified with what is innate, visibly expressed through a complex movement or action, controlled and guided by a rigid implementation program in the central nervous system: a FAP, in fact, the best way to exemplify instinct in the ethological sense.
We could cite many fixed action patterns (FAPs) depicted in every ethology textbook, starting with the construction of spider webs, which is species-specific (images 1 and 2). However, a young spider that has never had contact with its parents knows how to spin them correctly, thread by thread, after its first molt. The territorial male stickleback assumes a “head-down” position when faced with an intruder threatening its privacy. Without ever having done so before, nor even seen it done, it builds its “sleeve” nest on the bottom of ponds and springs, as all sticklebacks have done for generations.
Frogs can capture an insect in flight by shooting their long tongues, which are held forward rather than backward in their mouths (fig. 3). The aiming mechanism is a variable, visually guided orientation action, while the tongue firing is a fixed, inherited motor coordination skill. The same process occurs with the egg retrieval mechanism in ground-nesting birds: the retraction movement of the egg with the beak is the fixed action pattern (FAP); the lateral adjustments to prevent it from slipping are orientation reflexes that depend primarily on the slope of the ground.
The stability of inherited motor coordination is demonstrated by the fact that it can manifest even without any clear utility, especially if the subject’s internal disposition matches an appropriate stimulating situation. For example, a dog hiding a bone in a room makes the gesture of covering it with dirt using its nose, an innate element of the corresponding fixed action pattern (FAP). Similarly, it will repeatedly turn around before curling up in its comfortable bed, as if flattening vegetation. Another example is the “kiss” of a pigeon, which reinforces the pair bond (image 4).
In ethology, there is no consensus-based definition of FAP, although some characteristic elements are recognized, in addition to the obvious fact of being innate: 1) the sequence of movements and actions of a FAP is unchangeable; 2) a FAP can be triggered by inappropriate stimuli; 3) a FAP is performed in the same manner by all members of a given species; 4) it is part of and is usually linked to a specific behavioural system (agonistic, territorial, reproductive).
A strong critique of Lorenz’s concept of FAP was launched in the late 1960s by George Barlow (University of California, Berkeley), a cichlid fish expert. He argued that many innate motor coordination patterns were not as fixed and stereotyped as Lorenz believed. Instead, in many FAP patterns, it was difficult to separate truly stereotyped, internally driven actions from those influenced by environmental conditions. He therefore proposed replacing the term Fixed with the less biased term Modal (MAP rather than FAP). Lorenz was not a strong advocate of statistics and paid little attention to minor differences in the expression of FAP patterns. Furthermore, specific research on the motor coordination patterns of mallards during reproductive behavior demonstrated perfect consistency in the expression of various FAP patterns involved. As a result, the traditional term was not abandoned, although some did so with reluctance.
Credits
Author: N. Emilio Baldaccini Former Professor of Ethology and Conservation of Zoocenotic Resources at the University of Pisa. He has published over 300 scientific papers in national and international journals. Actively engaged in scientific education, he is also a co-author of academic textbooks on Ethology, General and Systematic Zoology, and Comparative Anatomy.
Translated by Maria Antonietta Sessa
