Ethology

Ethology is a subdivision of biology that focuses on animal behavior that is innate—a study of animal behavior that holds the belief that most of what animals know is instinctive, not learned. Instincts are genetically programmed behaviors; they generally serve to galvanize the mechanisms that evoke the animal to act or react. Ethology, as a discipline, developed in Europe and became popular in the early 1900s. As a study of animal behavior, ethology also deals with the question of nurture versus nature, focusing on the natural environment and the physiological aspects in that environment. Unlike animal behaviorists, who are generally interested in learned behaviors, ethologists focus on innate behaviors—that is, the behavior developed during ontogenetic development. According to one theory, for example, ducks learn to “quack” like ducks and don't “honk” like geese because the chicks hear their parents while in the egg; thus, they learn to “quack.” Early ethologists noted for their work were Herbert Spencer, Charles Darwin,G. J. Romanes, and William James. Major modern ethologists include Konrad Lorenz, Nikolaas Tinbergen, and Karl von Frisch. These modern ethologists unveiled four basic strategies by which genetic programming directs the lives of animals: sign stimuli, motor programs, drive, and imprinting.

Sign Stimuli: A sign stimulus is an external sensory stimulus that triggers a typical, innate behavior (fixed-action pattern). It allows animals to recognize and react appropriately to important objects or individuals they interact with for the first time. For example, baby herring gulls know from birth to whom they direct their begging calls in order to be fed. They also know how to trigger the regurgitation action in their parents in order to receive the food. However, the chick does not recognize the parent itself. It solely relies on the sign stimulus of the vertical line of the herring gull bill and the red spot on the tip of the bill (pecked at to induce regurgitation). Almost any model presenting this visual image would evoke the same reactions from the chicks. Another example involves the graylag goose and its unaltered egg-retrieval pattern. If it sees an egg outside of the nest, the goose rolls the egg with its beak back to the nest using side-to-side head motions. However, the fixed-action pattern is such that any object resembling an egg is rolled to the nest even though it may not be incubated. Fixed-action patterns are innate behavioral patterns that are triggered by sign stimuli. They are carried out to completion even if other stimuli are present or if the behavior is inappropriate (the graylag goose and nonegg objects).

Sign stimuli aren't solely visual. They may be tactile or olfactory, such as in the case of pheromones. The most customary uses of sign stimuli in wildlife are in communication, food gathering, and in warning signals. The various types of communication include visual, chemical, and mechanical communications. Mechanical communication is primarily performed through vibrations through the ground or air. Chemical communication largely includes pheromones that one animal emits to influence the behavior of another species or that of the other gender. Sign stimuli are also used in courting and mating. They are especially prevalent among animals that are usually solitary except during the sexual part of their lives. Sticklebacks, for example, use a system of inter-locking releasers to organize their mating. When the sticklebacks' breeding season arrives, the male's underside turns bright red. While the color attracts females, it also provokes other males to attack. As a female approaches the “red” male, she reveals her belly, which is swollen with eggs. This rouses the male to perform the mating dance and then lead the female to his nest. Through a series of movements, the male induces the female to release her eggs so he can fertilize them. If the female is induced in any other way other than the specific movements of the fertilizing male, the male stickleback will not fertilize the resulting eggs, but will eat them instead.

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