Behavior

The study of animal behavior is known as ethology. Ethologists investigate the mechanisms and evolution of behavior. Charles Darwin founded the scientific study of behavior, and showed by many examples that behavior, as well as morphology and physiology, is an adaptation to environmental demands, and can increase the chances of species survival.

Between 1930 and 1950, the Austrian naturalist Konrad Lorenz and the Dutch ethologist Niko Tinbergen found that certain animals show fixed-action patterns of behavior (FAPs), which are strong responses to specific stimuli. For example, male stickleback fish attack other breeding males that enter their territory. The defending male recognizes intruders by a red stripe on their underside. Tinbergen found that the male sticklebacks he was studying were so attuned to the red stripe that they would try to attack passing red British mail trucks visible through the glass of their tanks. Tinbergen termed the red stripe a behavioral releaser, a simple stimulus that brings about an FAP.

Once an FAP is initiated, it continues to completion even if circumstances change. If an egg rolls out of a goose's nest, the goose stretches her neck until the underside of her bill touches the egg. Then she rolls the egg back to the nest. If someone takes the egg away while she is reaching for it, the goose goes through the motions anyway without an egg. FAPs have innate components.

Complex programmed behavior involves several steps and is more complicated than FAP. When birds build nests and beavers build dams they are exhibiting complex programmed behavior.

Reflexes are also innate. A reflex is a simple, inborn, automatic response by a part of the body to a stimulus. At its simplest, a reflex involves receptor and sensory neurons and an effector organ, for example, when certain coelenterates withdraw their tentacles. More complex reflexes include processing interneurons between the sensory and motor neurons as well as specialized receptors. Complex reflexes occur when food in the mouth stimulates the salivary glands to produce saliva, or when a hand is pulled away rapidly from a hot object. Reflexes help animals respond quickly to a stimulus, thus protecting them from harm. Learned behavior results from experience, and enables animals to adjust to new situations. Unless an animal exhibits a behavior at birth, however, it is often difficult to determine if the behavior is learned or innate. For example, pecking, an innate behavior in chicks, gets more accurate as the chicks get older. The improvement in pecking aim does not occur because the chicks learn and correct their errors, but is due to a natural maturing of muscles and eyes. Scientific studies have shown that pecking is entirely innate.

The interaction of heredity and learning can be observed in a learning program known as imprinting, seen frequently in birds. Imprinting is the learning of a behavior at a critical period early in life that becomes permanent. Such behavior was studied in the 1930s by Lorenz. Newly hatched geese are able to walk at birth. They survive because they follow their parents. How do young geese recognize their parents from all the objects in the environment? Lorenz found that if he removed the parents from view the first day after hatching and he walked in front of the young geese, they would follow him. This tactic did not work if he waited until the third day after hatching. Lorenz concluded that during a critical period, the goslings follow their parents' movement and learn enough about their parents to recognize them. Since Lorenz found that young geese will follow any moving object, he determined that movement is their releaser for parental imprinting.

Habituation is a type of behavior in which an animal learns to ignore a stimulus that is repeated over and over. A snail will pull its head back into its shell when touched. When touched repeatedly with no subsequent harm, however, the withdrawal response ceases. Apparently, the snail's nervous system "learns" that the stimulus is not threatening and stops the reflex.

In classical conditioning, an animal's reflexes are trained to respond to a new stimulus. Ivan Pavlov, a Russian physiologist working in the early twentieth century, was the first to demonstrate this type of learning behavior. He placed powdered meat in a dog's mouth and observed that by reflex saliva flowed into the mouth. Then Pavlov rang a bell before he gave the dog its food. After doing this for a few times, the dog salivated merely at the sound of the bell. Many experiments of this type demonstrate that an innate behavior can be modified.

Further information about behavior modification came in the 1940s and 1950s with the work of B.F. Skinner, an American physiologist. He demonstrated operant conditioning, the training of certain behaviors by environmental rewards. This type of learning is also known as trial-and-error. During operant conditioning, a random behavior is rewarded and subsequently retained by an animal. If we want to train a dog to sit on command, all we have to do is wait until the dog sits. Then say "sit" and give the dog a biscuit. After a few times the dog will sit on command. Apparently, the reward reinforces the behavior and fosters its repetition.

Operant conditioning also occurs in nature. By watching their parents, young chimps learn to prepare a stick by stripping a twig and then using it to pick up termites from rotten logs. Their behavior is rewarded by the meal of termites, a preferred food. Operant conditioning lets animals add behaviors that are not inherited to their repertory.

Reasoning is a way to solve problems without trial-and-error. This is accomplished by thinking. Using reasoning or insight, we apply memories of past experiences to new situations to help find answers. Memory is the storing and retrieving of learned material. The two types of memory are short-term memory, the memory of recent events, and long-term memory, the memory of events that occurred in the past. When given a phone number, we quickly forget it. This is typical of short-term memory which is temporary. Long-term memory lasts longer, days or even a lifetime. Humans use reasoning more than other animals, but primates and others have been observed to solve problems by thought processes. Researchers recently discovered that black-capped chickadees develop new brain cells to improve their memory, which helps the birds locate buried seeds in winter.

In much of their behavior, animals interact with each other. In order to do this they communicate with each other, using their sense organs. Birds hear each other sing, a dog sees and hears the spit and hiss of a cornered cat, ants lay down scent signals (pheromones), to mark a trail that leads to food.

There are many kinds of interactive behavior. One of them is courtship behavior that usually takes place at the start of the mating season. During courtship, some animals leap and dance, others sing, still others ruffle their feathers or puff up pouches. The male peacock displays his glorious plumage to the female. Humpback whales advertise their presence under the sea by singing a song that can be heard hundreds of miles away. Courtship behavior enables an animal to find, identify, attract, and arouse a mate. During courtship, animals use rituals, a series of behaviors for communication that is performed the same way by all the males or females in a species. Territorial behavior is also interactive. Here, animals use signals such as pheromones and visual displays to claim and defend a territory.

Some animals live together in groups and display social behavior. The group helps protect individuals from predators, and allows cooperation and division of labor.

Insects, such as bees, ants, and termites live in complex groups in which some individuals find food, some defend the colony, and some tend to the offspring. A method of reducing fighting in a group is accomplished by a dominance hierarchy or ranking system. Chickens, for example, have a peck-order from the dominant to the most submissive. Each individual knows its place in the peck-order and does not challenge individuals of higher rank, thereby reducing the chances of fighting. Interactions among group members gets more complex with more intelligent species such as apes.