Animal instincts

Instincts are patterns of behavior found in animals that are exhibited from the beginning of life. They are not learned but inherited through successive generations of the species. Ethologists call these stereotyped behaviors fixed action patterns (FAPs). Over time, such patterns are shaped by evolution, but at any given moment, a species maintains a range of instincts that are unique to its members. A number of categories of stereotyped behavioral responses exist that apply to all organic forms. These include the basic drives such as reproduction, feeding, and protection from predators. The term “instinctive behavior” is generally reserved for animals and insects while excluding plants, bacteria, and viruses. Simple forms of stereotyped responses include a variety of reflex actions in which sensory nerve cells are affected by conditions such as heat and light. The more complex forms of responses are studied to understand the sequence of responses and the process of evolution that selected these patterns.

The Study of Instincts

The study of instinctive behavior began in the nineteenth century with the development of clinical psychology. Scientists noticed a direct link between animal and human behavior. Clinical experimentation of human subjects was not always possible or desirable, so experiments were carried out on monkeys, mice, and guinea pigs. Experiments focused on the responses of test subjects to specific environmental conditions. An example of this type of experiment would be investigating the puzzle-solving ability of rats in a maze. The flexibility and nature of these responses were seen as part of a study of learning processes.

The field of ethology later began to formulate a different view of animal behavior. A European group, including Konrad Lorenz, Nikolaas Tinbergen, and Karl von Frisch, noticed that animals possess a specific innate capacity to perform complex activities in response to the environment. As a result, modern ethology shifted the study of animal behavior from learned responses to inherited patterns of behavior. Ethologists did this by observing the courtship behaviors of birds, as well as nest building, rearing of young, and territorial ownership. From their beginning as “bird watchers,” ethologists collected a body of scholarship that came to represent a respected field of study. A number of subfields have been created, ranging from neurology and genetics of behavior to ecology of species behavior. One element that links these diverse and distinctive fields of study is that of signals, language, and communications.

Charles Darwin gave the scientific world a theory of evolution, but he was also an avid observer of instinctive behavior. He observed domesticated pigeons and described how emotions are expressed by humans and animals. Other early pioneers in this field included Charles Whitman, who studied the family tree of a group of pigeons in Massachusetts, and Oskar Heinroth, who observed several species of waterfowl in Germany. Their observations led to the conclusion that members of a species share the same body functions, bone structures, and behavior patterns.

The next progression was to compare instinctive behavior across several closely related species. This work was accomplished between 1940 and 1960 by Lorenz and Tinbergen. Lorenz chose as his subject the courtship sequences of mallards, teals, and gadwalls. Recognition signals among ducks are a specific sequence of behaviors that include tail shaking, head flicking, and whistling. The exact sequence for different species is different, yet the components are the same. Through these studies, it is possible to conclude that courtship sequences originated in a single ancestral form and crossbreeding between duck species produced variations in the pattern. Tinbergen arrived at a similar conclusion with his work on the calls, body postures, and movements of gulls. His study of the signaling behavior of more than fifteen species of gulls showed that their system of signals is similar. As a result of their work, Lorenz and Tinbergen provided a scientific basis both for the biological source of behavior and for an evolutionary source of instinctive reaction.

The Nature Versus Nurture Debate

Although few scientists of the time had objected to the notion that genetics contributed to instinctive behavior, there was an ongoing debate as to the extent of the genetic contribution. The scientific bias was on the side of learned behavior patterns in such areas as language, signals, and body postures. It seemed clear that higher animals learn how to transfer information among themselves. One example was that an isolated songbird denied access to parental teaching, does not instinctively know the songs of its species. Consequently, the genetic component may play only a small part in the overall development of behavior. In this debate, the contribution of Karl von Frisch shifted the balance to the side of inheritance. Von Frisch showed that honeybees communicate both the direction and the distance of a source of nectar through a sequence of dance patterns. A scouting bee returning to the hive can provide exact information to other bees. While it was argued that the larger brain sizes of higher animals contributed substantially to learning a system of communication, it was difficult to make the same argument for insects.

The debate on nature versus nurture produced extensive efforts to determine the extent to which instinctive behavior is shaped by inheritance or by learning. In the study of seagull chicks, Jack Hailman created a series of experiments that added evidence to the side of learned behavior. The parent of a seagull chick can elicit pecking from the chick either by pointing its bill downward or by swinging its bill from side to side. The chick will respond not only to a parent’s action. However, but also to a model that has the shape of the parent. The initial feeding behavior of a newly hatched chick is a “hit and miss” affair. With growth, the chick responds more precisely to the figure of the parent and acquires greater coordination. Thus, the initial instinct is for the chick to peck at a variety of motions, but with maturity, a learning component takes place to create greater discrimination. Further research indicates that several behaviors that scientists believed to be instincts are learned or acquired behaviors. Sea turtles likely possess an internal magnetic compass that guides them during their migrations. Because the Earth's magnetic field plays a role in the behavior, it is not considered an instinct, but a behavior guided by an external force present before birth.

Sequences of Behavior

During the 1950s and 1960s, researchers in instinctive behavior studied several types of animals and insects. Scientists began to understand that instincts are not a simple response to the environment but are a complex sequence of behavior. Scientists also began to find evidence suggesting that natural selection acts on behavior patterns as well as on an organism’s biological makeup. The result of this research came to be categorized into three broad groups of instinctive behavior. One was the response of a simple instinct on the part of a single organ to some stimulus. An example is a nerve cell responding to light that triggers a reflex response. Other reflex reactions include locomotion and movement. Another type of stereotyped behavior is called fixed action patterns (FAPs). For example, the courting behavior of ducks can be classified as FAPs, where the pattern and timing of the responses are invariable for all members of the species. Similar FAPs are found in spiders, crabs, and a number of other insects and lower animals. A final group of instinctive behaviors was described as modifiable action patterns (MAPs) and included fixed patterns that could be modified by the environment or by learning. For example, in species of birds, the core of nest-building behavior is fixed, but actual nest-building depends on the availability of preferred building materials, which can be altered by location and setting.

With the deciphering of the genetic code during the 1950s, research in instinctive behavior shifted toward the genetic basis of innate behavior. Research has shown that one group of chemicals called neuropeptides are produced by specific genes. Within the brain, these peptides have the ability to govern stereotyped behavior. For example, a specific peptide (angiotensin II), when injected into vertebrates, causes spontaneous drinking activity. Research on neuroactive chemicals that influence behavior patterns is still in its infancy; research on brain functions and neuron pathways has only begun. In the future, biochemists expect to isolate the link between the genetic code and brain function.

One area of stereotyped behavior that has puzzled scientists since the time of Darwin is altruistic behavior. Scientists have struggled to explain behaviors such as ants drowning themselves in a stream so that others can cross over them or a parent animal risking its life so that offspring can survive. W. D. Hamilton, among others, began to use probability models, which show that cooperative behavior, which may risk the lives of individuals, results in greater survival of the rest of the group. Altruistic behavior is not only “for the good of the species” but also provides a greater probability that large numbers of that group will reproduce and, therefore, gain an advantage.

The Fieldwork of Ethology

The early students of ethology were often called “birdwatchers” because they began their work by observing the behavior of birds. Fieldwork involves repeated observations of a subject over long periods of time. Eventually, a sequence of behavior emerges, and then it is possible to read the language of the behavior. For example, Lorenz observed that the courtship sequence of the mallard duck involved some ten segmented parts, such as bill-shake, head-flick, tail-shake, and grunt-whistle.

In certain instances, fieldwork with insects and lower animals offers the possibility of direct experimentation. In his attempt to translate the dancing motion of bees, von Frisch made the food source available. Consequently, he was able to vary the distance of the food source, change its location, and alter the quantity of food. Each change in the variables produced some variation in the dance—perhaps a new “phrase” added to the language. In other areas of research, the test subject can be modified for direct experimentation. When William Keeton attempted to explain how pigeons found their way home, he used contact lenses to cover the eyes of the pigeon to block out the position of the sun. He also created secondary magnetic fields around the pigeon to test the subject’s sensitivity to the earth’s magnetic field.

While all studies of stereotyped behavior begin with observation, either in the field or in controlled settings, further exploration usually requires laboratory research. In Jack Hailman’s study of the learning component of seagull chicks, he constructed models of gull parents and correlated pecking accuracy with growth. He also modified features of the model seagull to study possible changes in responses from the chicks. As the search for the causes of instinctive behavior moves further into the organism, the methodology follows—into areas of brain function (neuroethology), the chemistry of innate behavior, and the genetic component of behavior. Investigating the source of egg-laying behavior of a species of a large marine snail (Aplysia), Richard Scheller and Richard Axel found three genes that produce a number of peptides that govern this behavior.

Instincts and Genes

Instincts are a part of all living organisms, and observable instinctive responses are only a small part of an intricate pattern. The genetic makeup of an organism dictates specific unlearned patterns of responses and variations that, in turn, determine a favorable selection of individuals within a species. Clearly, instincts in sexual selection, reproduction, food gathering, and other basic needs are critical for the survival of members of a species. In higher animals, instinctive activities are often overshadowed (and sometimes disguised) by learned patterns of responses. For example, in dogs, the pulling back of facial muscles and the showing of teeth is a response to fear and attack. In humans, laughter is a similar response to surprise, embarrassment, and uneasiness. Because of social adaptation, however, laughter takes on additional behavioral conventions.

Until the early twentieth century, instincts were thought to be learned responses to specific situations. Consequently, if aggression were learned, then it could be modified, changed, and unlearned. With the establishment of a genetic and biochemical foundation for instincts, research in stereotyped behavior has become part of a heated debate. In 1975, Edward O. Wilson published Sociobiology: The New Synthesis. This highly technical work found a surprisingly large audience. Wilson attempted to place all social behavior on a biological basis. Although the work emphasized animal behavior, Wilson implied that all human history was also part of evolutionary biology and that his work would synthesize all the social sciences with biology. Since instincts such as aggression, selection of sexual partners, and care of the young play a prominent part in cultural activities, Wilson seems to suggest that in the future, the study of society will be grounded in neurobiology and sociobiology.

In 2016, author Mark S. Blumberg suggested that the word instinct had become a catch-all phrase to account for adaptive and complex abilities in animals that do not form from learning or experience. Blumberg listed a number of these instincts, such as survival, migratory, herding, maternal, or language instincts. Blumberg argued that instead of such behaviors originating as “inborn, pre-programmed, hardwired, or genetically determined,” these activities were instead developed through species-typical experiences and under environmental contexts.

In 2017, an argument was put forth by Professors Gene Robinson and Andrew Barron that learned behaviors in animals had long ago migrated into DNA. This became the mechanism for these behaviors to become instinctive as they were transmitted through generations. This process, called epigenetics, involves the modification of genetic material and may occur because of environmental stress, starvation, significant pain, or coming into contact with a pathogen. These experiences are likely built into DNA to improve species longevity. The mechanisms by which learned behaviors and psychological responses are inherited are poorly understood, but hormones and RNA are believed to contribute. Conversely, inherited and acquired behaviors can be altered or reversed under particular conditions. Wild animals in captivity, even well-cared-for animals, experience depreciating decision-making and memory skills. The capillaries that deliver blood to the brain’s neurons shrink over time, neurons decrease in size, and the cerebral cortex thins. This alters many animal instincts, including hunting, mating, communication, warnings, and more. Understanding this process is important for animal rehabilitation canters and for conservation efforts of endangered animals.

Principal Terms

Altruism: a high degree of devotion to the interest of others that often includes self-sacrifice

Ethology: a branch of biology that studies behavior

Fixed action pattern (FAP): a behavior whose timing and duration are invariable for all members of a species

Innate: denotes an inherited and unalterable condition or ability in an organism

Neurobiology: the study of the biology of the brain

Neuroethology: the study of behavior as it relates to brain functions

Peptide: a chemical combination of certain amino acids

Signal: information transmitted through sound, such as bird calls, or through sight, such as body posture

Stereotyped behavior: an unlearned and unchanging behavior pattern that is unique to a species

Bibliography

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