What is ethology? |

Introduction

Ethology, from the Greek ethos (“behavior" or "manner”), is the study of animal behavior.
It is concerned primarily with the accurate description and rigorous experimental evaluation of animals’ behavior under natural conditions. Unlike the field of behaviorism, which traditionally emphasized the sole importance of the environment on behavior, ethology also recognizes the genetic and physiological mechanisms that regulate behavioral processes. Ethologists operate under the primary assumption that much of behavior is hereditary and thus strongly influenced by the forces of natural selection. Natural selection is the process of differential survival and reproduction that leads to heritable characteristics that are best suited for a particular environment.

In their search for a common, unifying explanation of behavioral processes, ethologists have sought to address three specific issues: the accurate, nonanthropomorphic description of behavior under natural conditions; the underlying mechanisms that regulate and control behavior; and the adaptive significance of various behavior patterns.

Descriptive Approach

In its earliest stages, ethology was characterized by a highly descriptive approach. Early ethologists were concerned primarily with accurate and objective accounts of behavior. Behavior, however, unlike other aspects of an organism’s biology (such as morphology or physiology), was a difficult and elusive thing to characterize and thus required careful, unbiased approaches to understanding the ways in which animals responded to stimuli in their environment. Konrad Lorenz, one of the early founders of the field, insisted that the only way to study behavior was to make objective observations under completely natural field conditions. This approach, most evident in his classic studies on aggression and imprinting (the innate behavioral attachment that a young animal forms with another individual such as its mother, with food, or with an object during a brief critical period shortly after birth), greatly enhanced understanding of communication in the animal kingdom. In contrast to Lorenz’s very subjective approach, the rigorous field experiments of Nikolaas Tinbergen and Karl von Frisch
were similar to those that later would characterize modern ethology.

The classic work of all three of these early ethologists helped demonstrate how an animal’s sensory limitations and capabilities can shape its behavior. For example, in a series of classic learning experiments, von Frisch convincingly documented the unusual visual capabilities of the honeybee. He first trained honeybees to forage at small glass dishes of sugar water and then, by attaching different visual cues to each dish, provided the animals with an opportunity to learn where to forage through the simple process of association. From these elegant but simple experiments, he found that bees locate and remember foraging sites by the use of specific colors, ultraviolet cues, and polarized light, a discovery that revolutionized the way in which humans view the sensory capabilities of animals.

Mechanistic Behavior

With the classic work of Lorenz, Tinbergen, and von Frisch came an increasing appreciation for the ways in which physiological limitations define behavioral differences between species. This awareness eventually gave way to a mechanistic approach to behavior, in which ethologists sought to determine how internal factors such as physiology, development, and genetics regulate and control behavior. The physiologically oriented ethologists, for example, focused on the influence of neuronal pathways and sensory organs on behavior. They were concerned with topics such as the control of feeding in insects, echolocation in bats, electric field detection in fish, and infrared detection in snakes. Similarly, neurobiologists attempted to show how behavioral changes are linked to modifications in the function of nerves and neuronal pathways. By observing the response of individual nerves, neurobiologists can observe changes that occur in the nerves when an animal modifies its behavior in response to some stimulus. In a similar way, they can show how learning and behavior are affected when specific nerve fibers are experimentally cut or removed.

Adaptive Behavior

The third and perhaps most significant area in ethology is that which deals with the evolutionary (adaptive) significance of behavior. Since the seminal work of Charles Darwin, ethologists have maintained that a species’ behavior is controlled largely by its genes. Darwin argued that an animal’s behavior was no different from any other phenotypic characteristic (physical expression of the genes) in that it was heritable and therefore subject to the same kinds of selective processes that lead to evolutionary change among organisms. He considered instinctual (or innate) behavior a tremendous adaptation that frees some organisms from the risky and sometimes costly business of trial-and-error learning. At the same time, he recognized the adaptive plasticity that accompanies the more complex behaviors that involve various degrees of learning.

Both Lorenz and Tinbergen also recognized the importance of evolutionary questions in behavior, but Tinbergen was the first to put such hypotheses to rigorous experimental tests. In a classic experiment on the evolutionary significance of spines in sticklebacks, he tested predation rates by pike on several species of these fish. He found predation rates to be lowest on the three-spined stickleback (a conspicuous species with large horizontal spines), moderate on the more cryptic ten-spined stickleback (which possesses ten smaller vertical spines on its dorsal surface), and highest for unarmored minnows.

Mechanisms of Heredity

More recently, behavioral geneticists have shown that much of learning, and of behavior in general, is intimately tied to mechanisms of heredity. The results of hybridization experiments and artificial breeding programs, as well as studies on human twins separated at birth, clearly demonstrate a strong genetic influence on behavior. In fact, it has been well documented that many animals (including both invertebrates and vertebrates) are genetically programmed (or have a genetic predisposition) to learn only specific kinds of behaviors. Such is the case for song learning in birds.

Thus, ethology places tremendous importance on the evolutionary history of an organism. It emphasizes the adaptive significance of the various types of behaviors, and it assumes that an animal’s behavior is constrained largely by its genetic and evolutionary background.

Learning Process Research

The field of ethology has contributed markedly to the understanding of several psychological and behavioral phenomena. One such area is the learning process. Learning is defined as any modification in behavior (other than that caused by maturation, fatigue, or injury) that is directed by previous experience.

The early experiments of the behaviorist psychologists on conditioning (the behavioral association that results from the reinforcement of a response with a stimulus) led to the notion that all behavior is learned. Traditionally, behaviorists maintained that all complex behaviors are learned by means of either classical or operant conditioning. Classical conditioning, first demonstrated by the Russian psychologist Ivan Petrovich Pavlov, is a form of associative learning in which an animal responds to an unrelated, novel stimulus after it is repeatedly paired with a more relevant stimulus. Operant conditioning, also a form of associative learning, occurs when an animal learns by manipulating some part of its environment (for example, the animal might ring a bell to receive a reward). This form of learning usually improves with experience and is therefore referred to as trial-and-error learning.

The primary objective of the approaches employed by the early behaviorists was to eliminate or control as many variables as possible and thereby remove any uncertainty about the factors that may influence the learning process. These approaches were especially successful at identifying the external mechanisms responsible for learning. Such techniques focused only on the input (stimulus) and output (response) of an experiment, however, and consequently deemphasized the importance of proximate mechanisms such as physiology and genetics. In addition, these approaches generally ignored the evolutionary considerations that ethologists considered so fundamental to the study of behavior.

Innate Behavior

In contrast, studies by the early ethologists suggested that much of behavior was dominated by innate processes that were constrained by the physiological and genetic design of the organism. Lorenz and Tinbergen, for example, demonstrated that many behavioral responses in the animal kingdom are fixed or stereotyped (instinctive) and are often elicited by simple environmental stimuli. They referred to such responses as fixed action patterns and to the stimuli that triggered them as sign stimuli.

The egg-rolling behavior of the greylag goose is perhaps one of the most widely cited examples of this kind of innate behavior. When one of these ground-nesting birds notices an egg outside its nest, it stands, walks to the egg, extends its bill in a very characteristic manner, and proceeds to roll the egg back to the nest. Although at first glance this may seem to represent a simple learned response, Lorenz and Tinbergen found this to be a highly ritualized behavior that was initiated by a very specific environmental stimulus. Through a series of clever experiments, Tinbergen showed that this behavior could be elicited by an egglike object (a ball) or even any object with a convex surface (a bottle or can), and that objects larger than eggs caused a more vigorous (supernormal) response. He also found that once the behavior was initiated, it always ran to completion. In other words, even when the egg was removed, the goose would continue with the motions as if it were returning the egg to the nest.

This and countless other examples of very ritualized behaviors, such as the avoidance response of ducklings to hawk models, the imprinting of young vertebrates on their mothers, the aggressive displays of male stickleback fish to the red bellies of other males, and the various courtship displays of a wide range of species, led early ethologists to conclude that much of behavior is governed by instinct.

These opposing views of ethologists and behaviorist psychologists eventually led to the misconception that learned behavior is governed entirely by the animal’s environment, whereas instinct is completely controlled by the genes. It is now widely accepted, however, that nearly all forms of behavior and learning involve certain degrees of both processes. Countless studies, for example, have demonstrated that numerous animals are genetically programmed to learn only certain behaviors. In contrast, it has been shown that instinct need not be completely fixed, but instead can be modified with experience.

Sociobiology

A second area of ethology that has received much attention from a variety of behavioral researchers and in some cases has sparked considerable controversy is sociobiology. In the early 1970s, Edward O. Wilson
and Robert Trivers of Harvard University initiated a new area of behavioral research when they began their investigations of the evolutionary basis of social behavior in animals. Their attention focused on the evolutionary enigma presented by altruistic
behaviors—acts that one organism performs (often at its own expense) to benefit another. Examples include alarm calls in the presence of a predator and nest-helping behavior. The most extreme cases of such behavior are found in those insect societies in which only a few individuals reproduce and others work to maintain the colony. Through careful experimentation and observation, it was soon determined that such unselfish behaviors are directed toward related individuals and that such behaviors probably evolve because they promote the survival of other individuals who also possess the genes for those same altruistic acts.

Although they initially sparked much debate, studies of the evolutionary basis for social behavior eventually strengthened the ethologists’ long-held notion that much of behavior is coded in the genes.

Research Debates

Although ethology had its beginnings with the work of Darwin and other early naturalists, it was von Frisch, Lorenz, and Tinbergen who conducted the first formal ethological studies and who received a joint Nobel Prize for their pioneering work in 1973. Their approach represented a considerable departure from that of behaviorist psychologists, and the differences between the two fields sparked a heated debate during the 1950s and 1960s, often referred to as the nature-versus-nurture controversy. Although this debate eventually led to the decline and virtual demise of behaviorism, it also helped shape modern ethology into a rigorous biological discipline that now holds a compatible niche within the realm of psychology.

Although the early ethologists argued that behaviorists treated their study organisms as “black-boxes” and ignored the genetic, physiological, and evolutionary backgrounds of their subjects, the behaviorists leveled several criticisms in return. In addition to their disbelief in the genetic control of behavior, they were most critical of the methodological approaches employed by ethologists. In contrast with the rigorously controlled laboratory experiments of psychologists, in which blind observers (observers unaware of the experimenters’ hypotheses or experimental design) were often used to collect data, behaviorists held that early ethologists conducted nearly all their studies under natural conditions without any regard for experimental control. In addition, their observations were often highly subjective and almost never quantified. Even when attempts were made to quantify the behavior, they never involved the rigorous statistical and analytical techniques of the behaviorists.

Furthermore, although the early ethologists argued that much of behavior is shaped by evolution and constrained by an organism’s physiological hardware, little evidence was initially available to support these contentions. Behaviorists, for example, held that ethologists often observed a behavior and casually assigned some adaptive significance to it without testing such evolutionary hypotheses.

These criticisms forced early ethologists to improve their approaches to data collection, experimental design, and data analysis, and as their approaches to the study of behavior were strengthened, so were their original hypotheses about the underlying control of behavior. Thus, as ethologists gained ground, behaviorism began to fall out of favor with most of the scientific community.

The basic views of early ethologists are still well preserved in all prominent areas of ethological research. In fact, the work of nearly all modern ethologists can best be characterized by the two basic sets of questions they seek to answer: the “how questions,” concerning underlying proximate causes, and the “why questions,” concerning ultimate causes (or evolutionary bases). The first of these is pursued by traditional ethologists and neurobiologists, while the latter is primarily the realm of behavioral ethologists. The fields of ethology and comparative psychology have begun to complement each other, and, increasingly, researchers from the two areas are merging their efforts on a diversity of research topics.

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