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20.4: Overview of Animal Behavior

Created by: CK-12

Lesson Objectives

  • Describe how and why ethologists study animal behavior.
  • Explain how animal behaviors evolve.
  • Define innate behavior.
  • State ways that animals learn.
  • Identify types of animal behavior.

Vocabulary

  • aggression
  • animal behavior
  • circadian rhythm
  • cooperation
  • ethology
  • innate behavior
  • instinct
  • learning
  • nature-nurture debate
  • reflex
  • social animal
  • society
  • stimulus

Introduction

Did you ever see a dog sit on command? Have you ever watched a cat trying to catch a mouse? These are just two examples of the many behaviors of animals. Animal behavior includes all the ways that animals interact with each other and the environment. Examples of common animal behaviors are pictured in Figure below.

Examples of Animal Behavior. Can you think of other examples of animal behavior besides the three shown here?

Studying Animal Behavior

The branch of biology that studies animal behavior is called ethology. Ethologists usually study how animals behave in their natural environment, rather than in a lab. They generally try to answer four basic questions about the behaviors they observe:

  1. What causes the behavior? What is the stimulus, or trigger, for the behavior? What structures and functions of the animal are involved in the behavior?
  2. How does the behavior develop? Is it present early in life? Or does it appear only as the animal matures? Are certain experiences needed for the behavior to develop?
  3. Why did the behavior evolve? How does the behavior affect the fitness of the animal performing it? How does it affect the survival of the species?
  4. How did the behavior evolve? How does it compare with similar behaviors in related species? In what ancestor did the behavior first appear?

As you read about animal behavior in the rest of this lesson, think about these four questions. Try to answer the questions for different types of animal behavior.

Evolution of Animal Behavior

To the extent that behaviors are controlled by genes, they may evolve through natural selection. If behaviors increase fitness, they are likely to become more common over time. If they decrease fitness, they are likely to become less common.

Nature vs. Nurture

Some behaviors seem to be controlled solely by genes. Others appear to be due to experiences in a given environment. Whether behaviors are controlled mainly by genes or by the environment is often a matter of debate. This is called the nature-nurture debate. Nature refers to the genes an animal inherits. Nurture refers to the environment that the animal experiences.

In reality, most animal behaviors are not controlled by nature or nurture. Instead, they are influenced by both nature and nurture. In dogs, for example, the tendency to behave toward other dogs in a certain way is probably controlled by genes. However, the normal behaviors can’t develop in an environment that lacks other dogs. A puppy raised in isolation from other dogs may never develop the normal behaviors. It may always fear other dogs or act aggressively toward them.

How Behaviors Evolve

It’s easy to see how many common types of behavior evolve. That’s because they obviously increase the fitness of the animal performing them. For example, when wolves hunt together in a pack, they are more likely to catch prey (see Figure below). Therefore, hunting with others increases a wolf’s fitness. The wolf is more likely to survive and pass its genes to the next generation by behaving this way.

Wolves Hunting Cooperatively. Wolves hunt together in packs. This is adaptive because it increases their chances of killing prey and obtaining food.

The evolution of certain other types of behavior is not as easy to explain. An example is a squirrel chattering loudly to warn other squirrels that a predator is near. This is likely to help the other squirrels avoid the predator. Therefore, it could increase their fitness. But what about the squirrel raises the alarm? This squirrel is more likely to be noticed by the predator. Therefore, the behavior may actually lower this squirrel’s fitness. How could such a behavior evolve through natural selection?

One possible answer is that helping others often means helping close relatives. Close relatives share many of the same genes that they inherited from their common ancestor. As a result, helping a close relative may actually increase the chances that copies of one’s own genes will be passed to the next generation. In this way, a behavior that puts oneself at risk could actually increase through natural selection. This form of natural selection is called kin selection.

Innate Behavior

Behaviors that are closely controlled by genes with little or no environmental influence are called innate behaviors. These are behaviors that occur naturally in all members of a species whenever they are exposed to a certain stimulus. Innate behaviors do not have to be learned or practiced. They are also called instinctive behaviors. An instinct is the ability of an animal to perform a behavior the first time it is exposed to the proper stimulus. For example, a dog will drool the first time—and every time—it is exposed to food.

Significance of Innate Behavior

Innate behaviors are rigid and predictable. All members of the species perform the behaviors in the same way. Innate behaviors usually involve basic life functions, such as finding food or caring for offspring. Several examples are shown in Figure below. If an animal were to perform such important behaviors incorrectly, it would be less likely to survive or reproduce.

Examples of Innate Behavior. These innate behaviors are necessary for survival or reproduction. Can you explain why each behavior is important?

Intelligence and Innate Behavior

Innate behaviors occur in all animals. However, they are less common in species with higher levels of intelligence. Humans are the most intelligent species, and they have very few innate behaviors. The only innate behaviors in humans are reflexes. A reflex is a response that always occurs when a certain stimulus is present. For example, a human infant will grasp an object, such as a finger, that is placed in its palm. The infant has no control over this reaction because it is innate. Other than reflexes such as this, human behaviors are learned–or at least influenced by experience—rather than being innate.

Learned Behavior

Learning is a change in behavior that occurs as a result of experience. Compared with innate behaviors, learned behaviors are more flexible. They can be modified to suit changing conditions. This may make them more adaptive than innate behaviors. For example, drivers may have to modify how they drive (a learned behavior) when roads are wet or icy. Otherwise, they may lose control of their vehicle.

Animals may learn behaviors in a variety of ways. Some ways are quite simple. Others are more complex. Several types of learning are described in Figure below.

Types of Learning. Five different ways that animals may learn behaviors are shown here. What have you learned in each of these ways?

Insight learning, which is based on past experience and reasoning, is a hallmark of the human animal. Humans have used insight learning to solve problems ranging from starting a fire to traveling to the moon.

Types of Animal Behavior

Different types of behavior evolved in animals because the behaviors helped them survive or reproduce. Several different types of animal behavior are described below.

Social Behavior and Cooperation

In many species, animals live together in a close-knit group with other members of their species. Such a group is referred to as a society. Animals that live in a society are known as social animals. They live and work together for the good of the group. This called cooperation. Generally, each member of the group has a specific role that it plays in the society. Cooperation allows the group to do many things that a lone animal could never do. Look at the ants in Figure below. By working together, they are able to carry a large insect back to the nest to feed other members of their society.

Cooperation in a Social Insect. These ants are cooperating in a task that a single ant would be too small to do alone.

Communication

For individuals to cooperate, they need to communicate. Animals can communicate with sounds, chemicals, or visual cues. For example, to communicate with sounds, birds sing and frogs croak. Both may be communicating that they are good mates. Ants communicate with chemicals called pheromones. For example, they use the chemicals to mark trails to food sources so other ants can find them. Male dogs use pheromones in urine to mark their territory. They are “telling” other dogs to stay out of their yard. You can see several examples of visual communication in Figure below.

Visual Communication in Animals. Many animals use visual cues to communicate.

Cyclic Behaviors

Many animal behaviors occur in a regular cycle. Two types of cyclic behaviors are circadian rhythms and migration.

  • Circadian rhythms are regular changes in biology or behavior that occur in a 24-hour cycle. In humans, for example, blood pressure and body temperature change in a regular way throughout each 24-hour day.
  • Migration refers to seasonal movements of animals from one area to another. Migrants typically travel long distances. Usually, the migrants move to another area in order to find food or mates. Many birds, fish, and insects migrate. Mammals such as whales and caribou migrate as well. Figure below shows the migration route of a bird called a godwit.

Godwit Migration Route. Godwits make this incredibly long journey twice a year. In the fall, they migrate from the Arctic to Antarctica. They make the return flight in the spring.

KQED: Flyways: The Migratory Routes of Birds

For thousands of years and countless generations, migratory birds have flown the same long-distance paths between their breeding and feeding grounds. Understanding the routes these birds take, called flyways, helps conservation efforts and gives scientists better knowledge of global changes, both natural and man-made. See http://www.kqed.org/quest/television/the-great-migration for additional information.

Aggression

Aggression is behavior that is intended to cause harm or pain. It may involve physical violence against other individuals. For example, two male gorillas may fight and use their canine teeth to inflict deep wounds. Expressing aggression this way may lead to serious injury and even death.

In many species, display behaviors—rather than actual physical attacks—are used to show aggression. This helps prevent injury and death. Male gorillas, for example, are more likely to put on a display of aggression than to attack another male. In fact, gorillas have a whole series of display behaviors that they use to show aggression. They beat on their chest, dash back and forth, and pound the ground with their hands.

Competition

Aggressive behavior often occurs when individuals compete for the same resources. Animals may compete for territory, water, food, or mates. There are two basic types of competition: intraspecific and interspecific.

  • Intraspecific competition occurs between members of the same species. For example, two male deer may compete for mates by clashing their antlers together.
  • Interspecific competition occurs between members of different species. For example, one species of ant may attack and take over the colony of another ant species.

Mating and Courtship

Mating refers to the union of a male and female of the same species for reproduction. The relationship between mates varies by species. Adults may have many mates, or they may mate with just one individual. Mates may stay together only while mating. Or they may stay together for an entire breeding season or even for life.

Females are likely to be more selective than males in choosing mates. In many species, males put on courtship displays to encourage females to choose them as mates. For example, to attract a mate, a male bowerbird builds an elaborate nest decorated with hundreds of small blue objects (see Figure below). Other examples were described above and in previous lessons.

Bowerbird Decorating His Nest. A male bowerbird spends many hours collecting bits of blue glass and other small blue objects to decorate his nest. A female bowerbird inspects the nests of many males before choosing as a mate the male with the best nest.

Parental Care

In most species of fish, amphibians, and reptiles, parents provide no care to their offspring. In birds and mammals, on the other hand, parental care is common. Most often, the mother provides the care. However, in some species, both parents or just the father may be involved.

Parental care is generally longest and most involved in mammals. Besides feeding and protecting their offspring, parents may teach their offspring skills they will need to survive on their own. For example, meerkat adults teach their pups how to eat scorpions. They show the pups how to safely handle the poisonous insects and how to remove the stingers.

Lesson Summary

  • The branch of biology that studies animal behavior is called ethology. Ethologists usually study how animals behave in their natural environment. They try to determine the cause of behaviors, how behaviors develop, and how and why behaviors evolve.
  • Most animal behaviors are controlled by both genes and experiences in a given environment. To the extent that behaviors are controlled by genes, they may evolve. Behaviors that improve fitness increase through natural selection.
  • Innate behaviors are instinctive. They are controlled by genes and always occur in the same way. They do not have to be learned or practiced. Innate behaviors generally involve basic life functions, so it’s important that they be performed correctly.
  • Learning is a change in behavior that occurs as a result of experience. Learned behaviors are adaptive because they are flexible. They can change if the environment changes. Behaviors can be learned in several different ways, including through play.
  • Types of animal behavior include social behaviors such as cooperation, communication such as facial expressions, and cyclic behaviors such as migration. Competition may lead to aggressive behaviors or displays of aggression. Behaviors relating to reproduction include mating, courtship, and parenting behaviors.

Lesson Review Questions

Recall

1. Define animal behavior.

2. What is the nature-nurture debate?

3. What are innate behaviors? Give an example.

4. What is the relationship between intelligence and learning?

5. Name three types of learning in animals.

6. Describe an example of courtship behavior in animals.

Apply Concepts

7. Assume you are an ethologist. Apply lesson concepts to develop a hypothesis about a particular animal behavior. As an ethologist, how would you study the behavior in order to test your hypothesis?

8. Create a bulletin board or brief video to demonstrate the role of facial expressions in human communication.

Think Critically

9. Infer how and why cooperative hunting in female lions evolved.

10. Compare and contrast instinct and learning.

11. Explain why communication is needed for social living.

Points to Consider

In this lesson, you learned some of the ways that humans differ from other mammals. For example, humans have a larger and more complex brain than other mammals. That’s why they are also the most intelligent mammals. The next chapter introduces the biology of the human animal.

  • Besides their big brain and intelligence, how else might humans differ from other mammals?
  • What organs and organ systems do you think make up the human body?

For Table above, from top to bottom,

For Table above, from top to bottom,

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