Chapter 34 Animal Behavior
I. Elements of Behavior
Do you wash your vegetables before you eat them? If so, you have something in common with a
troop of Japanese monkeys that live on the Pacific island of Koshima. Many years ago, biologist
in Koshima began leaving sweet potatoes on a sandy beach to entice the resident monkeys into
the open. The monkeys ate their potatoes with sand still stuck to them. One day, a young female
member of the troop dunked her potato into a nearby pool and scrubbed the sand off it with her
hand. They young monkey, apparently preferring to eat a washed potato, repeated this technique
each day. Soon, another monkey in the troop started to imitate her. Months later, her mother
began to copy her, also. Eventually, all troop members came to wash their potatoes in the pool.
To this day, the descendants of the monkeys on the island of Koshima wash their sweet potatoes
before eating them.
A. Stimulus and Response
1. What kind of behavior is the monkey in the story exhibiting? This
is a learned behavior.
2. Biologists define behavior as the way an organism reacts to
changes in its internal condition or external environment.
a)
What are some examples of behaviors?
3. Usually, behaviors are performed when an animal reacts to a
stimulus. A stimulus (plural: stimuli) is any kind of signal that carries
information and can be detected.
a)
What are some stimuli that provoke the behaviors above?
4. A single, specific reaction to a stimulus—such as waking up when
you hear an alarm—is called a response.
5. Types of Stimuli
Animals respond to many types of external stimuli, such as
light, sound, odors, and temperature. But can every animal detect
all of these stimuli?
a)
Other animals have different senses and may respond to
stimuli that you are not equipped to sense.
b)
6. How Animals Respond
When an animal responds to a stimulus, body systems—
including the sense organs, nervous system, and muscles—interact
to produce the resultant behavior.
a)
Once an animals senses have detected an external stimulus that
information is passed along nerve cells to the brain.
b)
The brain and other parts of the nervous system process the
information and direct the body’s response.
c)
B. Behavior and Evolution
1. Animal behavior is as important to survival and reproduction as
any physical characteristic, such as teeth or claws.
2. Behaviors, like physical characteristics, may evolve under the
influence of natural selection.
3. Organisms with an adaptive behavior will survive and reproduce
better than organisms that lack the behavior.
4. After natural selection has operated for many generations, most
individuals in the population will exhibit the adaptive behavior.
C. Innate Behavior
1. Why do newly hatched birds beg for food within moments after
hatching?
These animals are exhibiting an innate behavior, also called an
instinct, or inborn behavior.
a)
2. Innate behaviors appear in fully functional form the first time they
are preformed, even though the animal may have had no previous
experience with the stimuli to which it responds.
Examples: weaving of a spider web and building of hanging
nest by weaver birds
a)
3. All innate behaviors depend on internal mechanisms that develop
as a result of complex interactions between an animal’s genes and its
environment.
D. Learned Behavior
1. Animals often live in unpredictable environments, so their
behavior must be flexible enough to deal with uncertainty and
change.
2. Many animals can alter their behavior as a result of experiences.
Such changes are called learning.
3. Acquired behavior is another name for learning, because these
behaviors develop over time.
4. Many animals have the ability to learn. The four major types of
learning are habituation, classical conditioning, operant conditioning,
and insight learning.
Habituation—The simplest type of learning is habituation. It
is a process by which an animal decreases or stops its response to
a repetitive stimulus that neither rewards nor harms the animal.
a)
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Example: common shore ragworm
Classical conditioning—Any time an animal makes a mental
connection between a stimulus and some king of reward or
punishment, it has learned by classical conditioning.
b)
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Example: Pavlov’s dog
Operant Conditioning—This occurs when an animal learns to
behave in a certain way through repeated practice, in order to
receive a reward or avoid punishment.
c)
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Example: Skinner box
Insight Learning—The most complicated form of learning is
insight learning, or reasoning. Insight learning occurs when an
animal applies something it has already learned to a new
situation, without a period of trial and error.
d)
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Example: Math problems
E. Instinct and Learning Combined
1. Most behaviors result from a combination of innate ability and
learning.
2. Young white-crowned sparrows have an innate ability to recognize
their own species’ song. To sing the complete version, however, the
young birds must first hear it sung by the adults. This process is
called imprinting.
3. Once imprinting has occurred, the behavior cannot be changed.
4. Imprinting involves both innate and learned behavior.
II. Patterns of Behavior
A. Behavioral Cycles
1. Many animals respond to periodic changes in the environment
with daily or seasonal cycles of behavior.
2. Another type of behavior that is influenced by changing seasons
is migration, the periodic movement from one place to another and
then back again.
3. Behavioral cycles that occur in daily patterns are called circadian
rhythms. The fact that you sleep at night and attend school during
the day is an example of a circadian rhythm.
B. Courtship
1. To pass along its genes to the next generation, any animal that
reproduces sexually needs to locate and mate with another member
of its species at least once. Courtship behavior is part of an overall
reproductive strategy that helps many animals identify healthy mates.
2. In courtship, an individual sends out stimuli—such as sound,
visual displays, or chemicals—in order to attract a member of the
opposite sex.
C. Social Behavior
1. Whenever animals interact with members of their own species, as
in courtship, they are exhibiting social behavior.
2. Many animals go beyond courtship in their social behavior and
form societies.
3. Often, members of a society are closely related to one another.
Related individuals share a large proportion of each other’s genes.
Therefore, helping a relative survive increases the change that the
genes an individual shares with that relative will be passed along to
offspring.
D. Competition and Aggression
1. Some animals have behaviors that help prevent others from using
limited resources.
2. Such patterns involve a specific area, or territory, that is occupied
and protected by an animal or group of animals.
3. Territories contain resources, such as food, water, nesting sites,
shelter, and potential mates that are necessary for an animal’s
survival and reproduction.
4. When two or more animals try to claim limited resources, such as
a territory or food, competition occurs.
5. During competition, animals may also show aggression, a
threatening behavior that one animal uses to gain control over
another.
E. Communication
1. Often, when animal behavior involves more than one individual,
some form of communication—the passing of information from one
organism to another—in involved.
2. Animals may use visual sound, touch, or chemical signals to
communicate with one another.
a)
Visual Signals
Cuttlefish, for example have large eyes that are as sophisticated
as those of vertebrates. In a matter of second, a single cuttlefish
can undergo changes in the color and patterns on its body. Its skin
will pucker into bumps and spines, and then suddenly become very
smooth.
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b)
Chemical Signals
Animals with well-developed senses of smell, including insects,
fishes, and many mammals, may communicate with chemicals.
Some animals release pheromones, chemical messengers that
affect the behavior of other individuals.
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c)
Sound Signals
Some animals that use sound have evolved elaborate
communication systems. Dolphins rely mainly on sound signals in
the dark and often murky ocean depths.
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d)
Language
The most complicated form of communication is language.
Language is a system of communication that combines sounds,
symbols, or gestures according to sets of rules about word order
and meaning, such as grammar.
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