ETHOLOGY

Ethology is the biological study of animal behavior. It derives from the Greek root ethos, which, in normal English usage, refers to the manner of living, or customary behavior, of a social entity. One may therefore speak of the ethos of a particular sports club, small town, or professional organization, for example. By the same token, ethologists are concerned with the ethos of animals: their way of behaving.

Ethology traces its history to the early decades of the twentieth century, especially the work of the Austrian physician Konrad Lorenz (1903–1989), Dutch biologist Niko Tinbergen (1907–1988), and German entomologist Karl von Frisch (1886–1982); in recognition of their achievements, these three shared the Nobel Prize in physiology or medicine in 1973. The characteristics of ethology as a scientific discipline can be appreciated by comparing it to one of its well-known counterparts, comparative psychology.

Whereas comparative psychology is primarily concerned with understanding human behavior, such that animal research is conducted with an eye to better understanding Homo sapiens, ethology focuses specifically on the behavior of animals for its own sake. Similarly, comparative psychologists study a small range of animal species—particularly laboratory rats, macaque monkeys, and pigeons—as easily manipulated substitutes for human beings. By contrast, ethologists study the diversity of animal species, especially invertebrates, fish, and birds. Because of their underlying concern with understanding human behavior, researchers in comparative psychology are especially interested in examining the various concomitants of learning (which have a notable impact on human beings). Ethologists pay considerable attention to behavior that is loosely described as "instinctual," which tends to be more prevalent in the species with simpler nervous systems that are typically the subject of ethological research. Ethologists also emphasize the study of animal behavior in its natural context; that is to say, under field conditions where the organisms normally live and to which they are adapted by natural selection. By contrast, comparative psychologists typically conduct their research in a laboratory setting within which they can carefully control for extraneous factors while focusing on the role of various aspects of experience.

Some Aspects of Classical Ethology

Ethology, as the study of how organisms conduct their lives, long has been especially concerned with compiling careful, detailed descriptions of actual behavior patterns, known as ethograms. These detailed records (including verbal descriptions, photographs, and sonograms of vocal communications, for example) are not generally considered ends in themselves, but are fundamental to a rounded, ethological understanding of any species: Ethologists emphasize that they must first know what the animals in question do before they can pose meaningful questions.

According to Niko Tinbergen, those questions are especially concerned with the following:

1. How does the behavior in question influence the survival and success of the animal? In modern evolutionary terms, what is its adaptive significance; or, how does it contribute to the inclusive fitness of the individual and the genes responsible, recognizing that inclusive fitness involves not only personal, Darwinian reproductive success but also the effect of each behavior on the fitness of other genetic relatives.
2. What actually makes the behavior occur at any given moment? This might include the role of hormones, brain mechanisms, prior learning, and so forth.
3. How does the behavior in question develop as the individual grows and matures? What is its developmental trajectory, or ontogeny?
4. How has the behavior evolved during the course of the species' evolutionary history? In short, what is its phylogeny?

It is worth noting that of these, question a has become the special province of sociobiology, a research discipline closely allied to ethology and that emphasizes matters of adaptive significance and evolutionary—often called ultimate—causation. By contrast, question b is associated in the public mind with research into animal behavior more generally; it is often called proximate causation. Ideally, a complete understanding of animal behavior will involve both ultimate and proximate considerations, as well as attention to matters of ontogeny and phylogeny.

Through their research, early ethologists developed a number of concepts now considered part of "classical ethology." These include, but are not limited to, the following. Fixed action patterns are the fundamental building blocks of behavior, consisting of simple, relatively unvarying movements that are more or less independent of prior experience. Once initiated, fixed action patterns generally continue to completion even if the initiating stimulus is no longer present; this emphasizes the unthinking nature of these acts, which are the products of natural selection rather than complex cognition or daily experience. Fixed action patterns, in turn, are evoked by releasers, features of the environment or other animals to which the receiving animal is delicately attuned. The situation is analogous to a lock-and-key mechanism: a lock is carefully adjusted (in the case of animal behavior, by natural selection rather than by a locksmith) to the specific characteristics of a key. In ethological terminology, the lock is an innate releasing mechanism, a characteristic of the receiving animal—usually but not necessarily located in the animal's central nervous system—that responds to the traits of the releaser. Continuing the analogy, when the key fits the lock, a door opens; this is equivalent to the fixed action pattern. And, just as a door moves along a fixed, predetermined pathway, so do the behavior patterns with which ethologists have traditionally been most concerned.

Although it may appear that this schema is only capable of generating simple behaviors (a simple releaser evokes a comparably simple fixed action pattern), ethologists demonstrated that these connections can be "chained," such that fixed action patterns by one individual, for example, can serve as a releaser for another, whose fixed action pattern, in turn, serves as a releaser for another fixed action pattern in the first; and so on. In the process, complex sequences of courtship, parental care, or communication can be constructed.

In the courtship behavior of the three-spined stickleback fish—a species that has been intensively studied by ethologists—males develop a bright red abdomen in response to the warming water and increased day length of spring; females react to this releaser by their own fixed action pattern, a "head-up" display which in turn reveals their abdomens, swollen with eggs; the male, in turn, responds by his own fixed action pattern, a "zigzag dance," which involves swimming rapidly toward a nest made of algae that he would have previously constructed and then swimming quickly toward the female; the female responds by following the male; the male lays on his side in a characteristic posture "showing" the nest entrance to the female; she enters; he rhythmically prods the base of her tail with his snout, whereupon she deposits her eggs; she swims away; he enters the nest, fertilizes the eggs, and continues to care for them until they hatch. Throughout this complex sequence, each situation or behavior by one animal serves as a releaser for a fixed action pattern by the other, and so on in turn.

Ethologists also developed descriptive models for the control of behavior. Two notable models are the hydraulic model of Lorenz and Tinbergen's hierarchical schema. Lorenz proposed that a kind of motivational pressure—which he labeled action specific energy—builds up within the central nervous system of an individual. This energy is dissipated when the appropriate fixed action pattern is performed. In some cases, if the behavior in question is blocked, the motivational energy spills over into another channel, generating a seemingly irrelevant behavior, known as a displacement activity. For example, shorebirds known as avocets, when engaged in a dispute at a territorial boundary, may tuck their heads into their wing feathers, in a posture indistinguishable from that normally assumed during sleep.

Lorenz's scheme is also consistent with vacuum activities, whereby an animal may suddenly perform a fixed action pattern in the absence of any suitable releasing stimulus; in this case, presumably the energy associated with a given fixed action pattern has built up to such a level that it essentially overflows its neuronal banks and the relevant brain centers discharge in an apparent vacuum. Although the hydraulic model does not have many current devotees, it still serves as a useful heuristic model.

Tinbergen proposed a similar perspective, one somewhat more consistent with known neurobiological mechanisms. He suggested that various major instinctive tendencies (e.g., reproduction, migration, food-getting) were organized hierarchically, such that reproduction, for instance, was subdivided into fighting, nest-building, mating, and care of offspring, each of which, in turn, was further subdivided. Thus, depending on the species, fighting might involve chasing, biting, and threatening, whereas care of offspring might involve provisioning the young, feeding them, defending them from predators, and providing various kinds of learning opportunities.

Ethology in the Twenty-first Century

Despite the ethological focus on animal behavior that can loosely be labeled "instinctive," an important realization characterizes all studies of behavior, whether conducted by ethologists, sociobiologists, or comparative psychologists: Behavior always derives from the interaction of genetic and experiential factors. Variously labeled instinct/learning, genes/experience, or nature/nurture, contemporary researchers widely acknowledge that these dichotomies are misleading. Just as it is impossible for an organism to exist or behave without some influence from its environment (the extreme case of "pure instinct"), it is impossible for environmental factors acting alone to produce behavior (the extreme case of "pure learning"). Every situation must involve both factors: there must always be an organism to do the behaving, and, moreover, organisms with different experiences exposed to the same situations always respond somewhat differently.

Ethologists have branched out substantially from their earlier focus on careful naturalistic descriptions of animal behavior, increasingly blurring the distinction between ethology and various related disciplines. Thus, neuroethologists concern themselves with the brain regions and precise neuronal mechanisms that govern, for example, animal communication as well as the reception of auditory, olfactory, visual, and even tactile signals. Behavior genetics incorporates an amalgam of ethology and precise genetic techniques to unravel the genetic influence on various behavior patterns; such research may range from the creation of cross-species hybrids to the detailed analysis of DNA sequences in identified genes responsible for specific behavioral tendencies. Behavioral endocrinology investigates the role of hormones in predisposing animals toward courtship, aggressive, migratory, and other behaviors, as well as the environmental and social situations responsible for releasing the relevant hormones. Mathematically inclined ethologists have been increasingly interested in applying concepts derived from game theory in seeking to understand how behavior has evolved, especially in situations such that the benefit to each individual depends not only on what he or she does, but also on the behavior of another individual.

Ethology and Ethics

Researchers increasingly have been applying the basic ethological techniques of detailed, objective, nonjudgmental observation to human behavior as well. Human ethology is essentially an organized form of "people watching," whereas human sociobiology (sometimes called evolutionary psychology) seeks to apply the principles of evolution by natural selection to Homo sapiens. Critics assert that the former approach consists of a kind of empty empiricism, lacking powerful theoretical roots; others attack the latter for being overly driven by theory, occasionally lacking in adequate empirical findings.

The conduct of ethology occasionally raises ethical issues concerning the treatment of animal subjects, but generally such matters are more controversial in the laboratory-oriented disciplines such as comparative psychology and neuroethology. Because ethologists study undisturbed, natural populations, or—when conducting laboratory research—strive to maintain their subjects under naturalistic conditions, the major ethical dilemma facing ethologists tends to center around whether or not to intervene in the events of the normal lives of their study animals. For example, is it appropriate to prevent a forthcoming act of predation? (Ethologists nearly always answer in the negative, because they are typically committed to nonintervention on the lives of their subjects.) Moreover, because the goal of ethological research—unlike that of comparative psychology—is to understand behavior rather than to control it, and because—unlike evolutionary psychology—ethologists generally do not directly employ controversial assumptions about evolutionary factors currently operating on human behavior, ethology is generally free of the moral conundrums often attending its sister disciplines.

DAVID P. BARASH

SEE ALSO Aggression;Animal Tools;Dominance;Nature versus Nurture;Selfish Genes;Sociobiology.

BIBLIOGRAPHY

Alcock, John. (2001). Animal Behavior: An Evolutionary Approach. Sunderland, MA: Sinauer. The standard college textbook of animal behavior, which includes a good, if brief, treatment of ethology.

Barash, David P. (1982). Sociobiology and Behavior. New York: Elsevier. A wide-ranging introduction to sociobiology, emphasizing its distinction from classical ethology.

Goodenough, Judith; Betty McGuire; and Robert A. Wallace. (1993). Perspectives on Animal Behavior. New York: Wiley. A solid introduction to animal behavior that seeks to introduce both ethological and sociobiological approaches.

Gould, James L. (1982). Ethology: The Mechanisms and Evolution of Behavior. New York: Norton. A technical but rewarding early account of animal behavior, especially strong on physiological mechanisms.

Lorenz, Konrad Z. (1982). The Foundations of Ethology. New York: Simon and Schuster. Technical articles by one of the founders of ethology.

Tinbergen, Niko. (1989). The Study of Instinct. Oxford, UK: Clarendon Press. An early and now-classic account of ethology as a scientific discipline distinct from comparative psychology.