Ethology, the scientific study of animal behavior, examines how animals interact with their environment and other organisms. Behavior is defined as a change in the activity of an organism, occurring in response to an internal or external stimulus. Understanding these actions requires researchers to explore the underlying mechanisms and evolutionary history of a behavior.
The Fundamental Questions of Behavior
Researchers categorize their inquiries using proximate and ultimate causation, a framework proposed by ethologist Niko Tinbergen. These two levels of analysis represent the “how” and “why” of any behavior. Proximate causation focuses on the immediate mechanisms that trigger and control an action in an individual animal, addressing the “how” questions.
These mechanisms include sensory, genetic, and physiological elements, such as neural pathways and hormonal changes. For example, a proximate explanation for a male bird singing involves rising testosterone levels and environmental stimuli, like increased daylight hours, activating the song center in its brain. Proximate causes explain the mechanics of the behavior, detailing the pathways that allow the animal to perform the action.
Ultimate causation addresses the evolutionary significance of the behavior, focusing on the “why” questions. This analysis explores how the behavior has been shaped by natural selection over time. The ultimate explanation concerns the survival value and reproductive success, or fitness, gained by exhibiting the behavior.
The ultimate reason for the male bird’s song is to attract a mate, increasing his chances of successful reproduction. Migration is another example, where the ultimate cause is the selective advantage of exploiting seasonal food resources and avoiding harsh winter conditions.
How Behaviors Originate
Animal behaviors originate from two major sources: those that are innate and those that are modified by experience. Innate behaviors, or instincts, are genetically programmed actions performed correctly the first time the animal encounters the appropriate stimulus. These behaviors are fixed within the species’ genetic code and are resistant to change.
A specific type of innate action is the fixed action pattern (FAP), a sequence of unlearned acts that is largely unchangeable and carried to completion once initiated. Examples include the intricate web-spinning of a spider or the egg-rolling retrieval behavior of a graylag goose. Simple reflexes, like the immediate withdrawal of a limb from a painful stimulus, also fall under the category of innate responses.
Learned behaviors are those an animal develops or modifies as a result of specific environmental experiences. This category includes distinct processes that allow animals to adapt their actions to changing conditions.
More complex learning includes:
- Habituation, where an animal decreases its response to a repeated stimulus that carries no meaningful information (e.g., prairie dogs ignoring human footsteps).
- Associative learning, where an animal links one environmental feature with another.
- Classical conditioning, which involves associating an arbitrary stimulus (like a bell) with a biological response (like salivation).
- Operant conditioning, which involves learning to associate a specific behavior with a reward or punishment.
- Imprinting, a rapid learning process that occurs during a narrow, sensitive period early in life, such as when a duckling bonds with the first adult it sees.
Observing and Measuring Behavior
The study of animal behavior depends on rigorous methods for observing and quantifying actions. The primary tool for systematic observation is the ethogram, a comprehensive catalog of all the discrete, species-typical behaviors an animal performs. Each entry provides a detailed description, ensuring researchers can accurately identify and record the same action.
Using the ethogram, researchers employ various sampling methods to collect quantitative data. Focal animal sampling involves recording all behaviors performed by one specific individual over a set period. Scan sampling involves surveying a group of animals at regular, brief intervals and noting what each individual is doing at that exact moment.
These methods allow scientists to measure key metrics like frequency, duration, and latency. By calculating the percentage of time an animal spends on different activities, researchers construct a time budget that provides insight into energy allocation. Ethologists also use controlled experiments, often incorporating technology like GPS tracking and video analysis, to test hypotheses about the causes and functions of behavior.