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52
What, How, and Why Questions
• What questions focus on the stimuli that elicit a
behavior; such stimuli are the proximate causes of
the behavior.
• How questions focus on the development of a
behavior and the neural and hormonal mechanisms
that underlie a behavior.
• Why questions are concerned with the function and
evolution of a behavior; the selective pressures that
shape a behavior are considered ultimate causes.
52
Behavior Shaped by Inheritance
• Stereotypic behaviors are performed in the same
way every time. If there is little difference in the
way different individuals perform the behavior it is
said to be species-specific.
• Ex. Web spinning by spiders.
Figure 52.1 Spider Web Designs Are Species-Specific
52
Behavior Shaped by Inheritance
• Ethologists study the behavior of animals in their
natural environments.
• The parallel field of comparative psychology
focuses on learning by animals in laboratory
environments.
• Central Question: To what extent are behaviors
determined by inheritance and to what extent are
they modified by experience.
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Behavior Shaped by Inheritance
• Deprivation and hybridization experiments were
used to determine whether a behavior is inherited.
• In deprivation experiments, animals were raised
in conditions the behavior being studied.
• If the behavior was displayed in its entirety, then it
was described as inherited.
• Ex. Squirral story.
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Behavior Shaped by Inheritance
• In hybridization experiments, closely related
species that differ in aspects of a behavior are bred
to produce hybrid offspring.
• Konrad Lorenz did hybridization experiments with
duck species that can interbreed, but rarely do so
because of the specificity of their courtship displays.
• His results showed that motor patterns of courtship
displays are inherited.
52
Behavior Shaped by Inheritance
• Releasers are stimuli that trigger many inherited
behaviors.
• Releasers are usually a simple sensory signal.
 What they see, hear, etc.
• Ex. Herring gulls, bulls.
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Behavior Shaped by Inheritance
• Today, behavioral biologists believe that most
behaviors develop through an interaction of
inheritance and learning.
• For example, begging in herring gull chicks also
has a learned component: Over time, gull chicks
learn the characteristics of their parents, refine
their parental image, and eventually beg only from
their own parents.
52
Behavior Shaped by Inheritance
• Imprinting is a type of learning in which animals
learn, during a critical period, a complex set of
stimuli that later act as a releaser.
• Lorenz showed that newly hatched goslings
imprint on the image of the first object they see
(normally their parent, but under experimental
conditions, Lorenz or his assistants).
• Subsequent exposure to the object releases the
goslings’ following behavior.
Figure 52.5 Imprinting Enables an Animal to Learn a Complex Releaser
52
Behavior Shaped by Inheritance
• The ability to learn and modify behavior based on
experience can change behaviors often.
• In species with non-overlapping generations,
opportunities to learn from parents are not
available, so inherited behaviors are very
important.
 Spiders and their webs.
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Behavior Shaped by Inheritance
• Inherited behaviors also occur when there are
opportunities for learning the wrong behavior,
when mistakes would be costly or dangerous.
• The behavior must be performed correctly the
first time; there may be no second chance.
 Ex. Predator avoidance
52
Hormones and Behavior
• Differences in behaviors of males and females are
an example of genetic influence on behavior.
• Action of the sex steroids on the brain determine
sex differences in behavior.
• The sexual behavior of rats differs between males
and females.
• Receptive female rats display lordosis, a posture
in which the hindquarters are slightly raised.
• Male rats, on the other hand, display mounting
and copulatory behavior.
52
Hormones and Behavior
• Sex steroids present early in life determine which
pattern of sexual behavior an adult rat will display.
Figure 52.7 Hormonal Control of Sexual Behavior (Part 1)
Figure 52.7 Hormonal Control of Sexual Behavior (Part 2)
52
The Genetics of Behavior
• Behavior has genetic determinants. Genes code
for proteins; there are then many complex steps
between this starting point and the expression of
a behavior.
• There is no behavior for which we know the
precise series of steps from gene to behavior.
52
Communication
• Communication is behavior that influences the
actions of other individuals.
• The displays or signals of communication
convey information, and the transmission of this
information benefits the sender and the receiver.
• There are five channels of communication:
chemical, visual, auditory, tactile, and electric.
These channels differ in their effectiveness in
different environments.
52
Communication
• Pheromones are molecules used in chemical
communication between individuals.
• Pheromones can convey very specific messages
with large amounts of information. An example is
the pheromone released by female silkworm
moths.
• Territory marking by cats and other mammals
provides information on the species, individual
identity, reproductive status, size, and when the
animal was last in the area.
• Pheromones remain in the environment for a
while, in contrast to vocal or visual signals.
Figure 52.11 Many Animals Communicate with Pheromones
52
Communication
• The speed of diffusion of pheromone molecules is
determined by the size and chemical nature of the
molecules.
• Sex attractants tend to be small molecules that
diffuse rapidly; such messages travel great
distances and quickly disappear.
• Scent marking pheromones tend to be large
molecules that create relatively localized, longlasting messages.
52
Communication
• The advantages of visual signals include ease of
production, diversity, flexibility, speed, and a clear
indication of the position of the signaler.
• The disadvantages of visual signals include failure
to get the attention of the receiver, who may not
be focused on the sender, and limitations on the
details that can be transmitted.
• Visual communication also works poorly at night
and in complex or low-light environments.
52
Communication
• Unlike visual signals, auditory signals can be used
at night or low-light environments. In addition, the
receiver does not have to be focused on the
sender of an auditory signal to get the message.
• Sound can provide directional information as long
as the receiver has at least two receptors with
some space between them.
• Communicating with sound works well over long
distances; an extreme example is the song of
humpback whales, which can be heard hundreds
of kilometers away.
• However, visual signals are better than auditory
signals at rapidly conveying complex information.
52
Communication
• Communication by touch is very common among
animals, particularly when conditions are poor for
visual communication.
• Studies by Karl von Frisch revealed the role of
tactile communication in the dance of honeybees.
• A successful forager returns to the hive and
communicates by dancing in the dark on a vertical
surface within the hive.
• As she dances, her hivemates monitor her
movements through touch and interpret her
message.
52
Communication
• If the food source is more than 80 m away, the
waggle dance is used to convey information
about distance and direction to the food source.
• The round dance conveys information about the
distance of food if it is within about 80 m.
• The odor on the bee’s body also provides
information about the kind of flower to look for.
Figure 52.12 The Waggle Dance of the Honeybee
52
Communication
• Some fish emit electric pulses and generate
electric fields in the water around them. Such
signals can be used to detect objects in the
environment and to communicate.
• Glass knife fish emit electric signals that convey
information about the sex, identity, and position
within the dominance hierarchy of the sender.
• Resident individuals adjust the frequencies of
their signals to prevent overlap with a new fish
introduced into their tank.
52
The Timing of Behavior: Biological Rhythms
• Circadian rhythms are rhythms that are about 24
hours long but do not depend on the cycle of light
and dark.
• Animals in constant darkness demonstrate daily
cycles of sleep and activity; they are said to have an
endogenous (internal) clock.
• A rhythm is a series of cycles and the length of one
cycle is the period.
• Any point in the cycle is called a phase; two rhythms
that completely match are said to be in phase.
• Rhythms that are shifted so as to be out of phase are
described as phase-advanced or phase-delayed.
52
The Timing of Behavior: Biological Rhythms
• Entrainment is the process of resetting the
circadian rhythm by exposure to environmental
cues.
• Animals in constant light or dark will not be
entrained to the 24-hour cycle of the environment;
their circadian clock is described as free-running.
• The free-running circadian rhythm is under
genetic control.
• Free-running circadian rhythms of animals can be
entrained in the laboratory by short pulses of light
or dark every 24 hours.
Figure 52.13 Circadian Rhythms
52
The Timing of Behavior: Biological Rhythms
• In mammals, the master circadian clock is located
in the suprachiasmatic nuclei (SCN).
• The SCN is found only in vertebrates; in some
vertebrates, the SCN is the master clock
(mammals), and in others the master clock is the
pineal gland (birds).
• In some invertebrates (mollusks), the cells driving
circadian rhythms are in the eyes.
• In protists and fungi, rhythmicity is a property of
individual cells.
Figure 52.14 Where the Clock Is (Part 1)
Figure 52.14 Where the Clock Is (Part 2)
52
The Timing of Behavior: Biological Rhythms
• The clock genes that regulate circadian rhythms
are homologous across a wide range of
organisms.
• In fruit flies, the genes period (per) and timeless
(tim) are clock genes.
• Mutations of the per gene cause flies to have
either short or long free-running circadian periods,
and mutations of the tim gene result in loss of
circadian rhythms.
• The transcription and translation of these two
genes have a circadian rhythm, and the rhythm
appears to be controlled by negative feedback of
the PER and TIM proteins on two other clock
genes, clock (clk) and cycle (cyc).
Figure 52.15 Circadian Rhythms Are Generated by a Molecular Clock
52
The Timing of Behavior: Biological Rhythms
• This molecular negative feedback loop is the
basic model for a clock mechanism.
• Genes produce products that shut down their own
expression, with a delay.
• The mammalian clock has a similar circuit design
and some homologous genes, but their molecular
interactions and functions are different.
52
The Timing of Behavior: Biological Rhythms
• Day length, or photoperiod, is a reliable indicator
of upcoming seasonal changes. Animal species
are described as photoperiodic if their behavior
or physiology is influenced by day length.
• Some animals, such as those that hibernate,
cannot rely on day length as a cue of upcoming
seasonal change and instead have endogenous
annual rhythms called circannual rhythms.
• Circannual rhythms are usually shorter than 365
days.
• The neural mechanisms of circannual rhythms are
unknown.
52
Finding Their Way: Orientation and Navigation
• Piloting is a simple means of navigation involving
the use of landmarks.
• Gray whales use landmarks along the west coast
of North America to find their way between the
Bering Sea and the coastal lagoons of Mexico.
52
Finding Their Way: Orientation and Navigation
• Homing is the ability of an animal to return to its
nest site or burrow.
• In many animals, homing involves piloting, the
use of landmarks in a familiar environment.
• Incredible examples of homing are also found
among marine birds that can return home after
flying great distances over open ocean with few, if
any, landmarks.
• Albatrosses, for example, return to the island on
which they were raised after spending 8 or 9
years flying over southern oceans.
Figure 52.16 Coming Home
52
Finding Their Way: Orientation and Navigation
• In other species, including homing pigeons,
individuals released at a location they have never
been before can still find their way home.
• Homing pigeons do not fly randomly until
encountering familiar landmarks. Instead, they fly
in a fairly direct route to their home loft.
• Experiments have shown that these birds can
navigate without visual cues from the landscape.
Birds fitted with frosted contact lenses so that they
could only see the degree of light and dark could
still find their way home.
52
Finding Their Way: Orientation and Navigation
• Seasonal movement between breeding and
nonbreeding grounds is called migration.
• Many homing and migrating species are able to
take direct routes to their destinations, even
through environments they have never
experienced before.
• Two types of navigation include distance-anddirection navigation (knowing direction to the
destination, and how far it is) and bicoordinate
or true navigation (knowing latitude and
longitude of current position and destination).
52
Finding Their Way: Orientation and Navigation
• Experiments with starlings showed that naive
juvenile birds were using distance-and-direction
navigation.
• Experienced adult birds were not disrupted by
geographic displacement.
Figure 52.17 Distance-and-Direction Navigation
52
Finding Their Way: Orientation and Navigation
• Biological rhythms may be involved in determining
distances for some migratory species.
• Birds held in captivity show increased and
oriented activity, termed migratory restlessness,
at about the time they would normally migrate.
• The duration of migratory restlessness correlates
with the typical duration of migration for the
species.
• This suggests that the duration of migratory
restlessness could set the distance for migration.
52
Finding Their Way: Orientation and Navigation
• Animals may use the sun and the stars to
determine direction.
• The sun is an excellent compass, provided the
time of day is known. Animals can determine time
of day from their circadian clocks.
• Clock-shifting experiments have shown that birds
are capable of using their circadian clocks to
determine direction from the position of the sun.
52
Finding Their Way: Orientation and Navigation
• In a clock-shifting experiment, a bird is placed in a
circular cage from which it can see the sun and
sky but no other visual cues.
• After training the bird to expect food from a certain
direction, scientists were able to phase-advance
the bird’s circadian rhythms by 6 hours. Once
under normal conditions, the bird looked for food
in the wrong direction.
• These birds are using a time-compensated solar
compass.
Figure 52.18 The Time-Compensated Solar Compass (Part 1)
Figure 52.18 The Time-Compensated Solar Compass (Part 2)
52
Finding Their Way: Orientation and Navigation
• Many species are active at night, or simply
migrate at night, and thus cannot use the sun for
directional information. These species appear to
use stars for direction.
• Species that rely on stars for directional
information can use the North Star, a fixed point
that always indicates north, or constellations,
collections of stars that move as Earth rotates.
• Animals need to use their circadian clock with the
moving constellations.
52
Finding Their Way: Orientation and Navigation
• Stephen Emlen tested the orientation abilities of
birds in a planetarium in which the star patterns
were projected on the domed ceiling. The star
patterns could be rotated to simulate rotation of
Earth.
• Wild-caught birds could orient in the planetarium
when the star patterns were either stationary or
rotated more quickly than normal.
• These results showed that the birds were using
the North Star, the fixed point in the sky, for
directional information, rather than the
constellations.
52
Finding Their Way: Orientation and Navigation
• Birds raised in the planetarium under a stationary
sky and tested with a stationary sky could not
orient well.
• However, birds raised in the planetarium under a
rotating sky oriented well when tested with a
rotating sky.
• Thus, birds could learn to use constellations for
orientation as long as the sky rotated during the
time the birds were maturing.
52
Finding Their Way: Orientation and Navigation
• Use of the sun and stars for directional
information is not possible during overcast
conditions.
• Some birds, such as pigeons, can orient well
under overcast skies, apparently using their ability
to sense Earth’s magnetic field and thus gain
directional information.
• When small magnets were attached to the heads
of pigeons and the birds were displaced under
overcast skies, they could not find their way back
to their home loft.
52
Finding Their Way: Orientation and Navigation
• It now appears that homing pigeons use the sun
when available, magnetic cues when the sun is
unavailable, and landmarks when close to home.
• There appears to be considerable redundancy in
the means by which animals determine direction.
• Other sources of directional information include
the plane of polarized light, low-frequency sound,
and weather patterns.
52
Human Behavior
• Culture is the transmission of learned behavior
from one generation to another and is characteristic
of humans.
• Human behavior is also influenced by genetic
factors.
• Some motor patterns appear to be programmed
into the human nervous system.
• For example, similar facial expressions are
displayed by human populations that have had little
or no contact. Blind infants smile and frown
although they have never seen these expressions
in others.
52
Human Behavior
• As we acknowledge that human behavior has
both learned and genetic components, we also
find examples of culture, once thought to be a
uniquely human characteristic, in other animals.
• Japanese macaques, for example, developed
new methods of food preparation, and these
methods were transmitted to other individuals in
the population via imitative learning.
• Chimpanzees also display culturally transmitted
behaviors including tool using and courtship.
Populations have distinct behavioral repertoires or
culture.