Download Intro to Animal Behavior

--------------Intro to Animal Behavior-------------Behavior is action that alters the relationship between an organism and its environment.
Behavior may occur as a result of external stimuli (e.g., sight of a predator), internal stimuli (e.g., hunger) or a
mixture of the two (e.g., mating behavior: sight of a mate and the urge to mate). The study of animal behavior
involves investigating the relationships animals have with their physical environments and with other
organisms. Examples of animal behavior studies could include research to determine how animals find and
defend resources, communicate, avoid predators, choose mates, reproduce and care for their young.
It is often useful to distinguish between
 Innate behavior: Behavior determined by the "hard-wiring" of the nervous system. It is usually
inflexible, a given stimulus triggering a given response. A salamander raised away from water until long
after its siblings begin swimming successfully will swim every bit as well as they the very first time it is
placed in the water. Clearly this rather elaborate response is "built in" in the species and not something
that must be acquired by practice.
 Learned behavior: Behavior that is more or less permanently altered as a result of the experience of the
individual organism (e.g., learning to play baseball well).
 However, careful analysis often reveals that any particular behavior is a combination of innate and
learned components.
When studying behavior, it is important to identify both the behavior and the related stimulus (internal or
external) that initiates or controls it. Ultimately, this leads us to ask why the behavior exists, and what
evolutionary significance it might have (for example, how did it influence the species' survival and reproductive
success?).
--------------------Innate Behavior-------------------Types of innate behavior: Taxes, Reflexes, Instincts
Reflexes
Reflexes will not be discussed in detail here, but they are automatic, involuntary nervous responses to stimuli
involving one body part (for example, pulling a hand away from a hot stove).
Taxes
Some organisms respond to a stimulus by automatically moving directly toward or away from or at some
defined angle to it. These responses are called taxes. They are similar to tropisms in plants except that actual
locomotion of the entire organism is involved.
 Chemotaxis: Responding to chemical compounds
 Phototaxis: Responding to light
 Magnetotaxis: Responding to magnetic fields
Instincts
Instincts are complex behavior patterns that are inborn, inflexible
and valuable at adapting the animal to its environment. They differ from
reflexes in their complexity. The entire body participates in instinctive
behavior, and an elaborate series of actions may be involved.
The scratching behavior of a dog and a European bullfinch,
shown here, is part of their genetic heritage. The widespread behavior of
scratching with a hind limb crossed over a forelimb in common to most Drawing courtesy of Rudolf Freund
birds, reptiles, and mammals. Instincts are inherited just as the structure
and Scientific American, 1958
of tissues and organs are.
Another example:
 The African peach-faced lovebird carries nesting materials to the nesting site by tucking them
underneath their wings.
 Its close relative, the Fischer's lovebird, uses its beak to transport nesting materials.
 The two species can breed with one another. When they do so, the offspring try to tuck the nesting
materials under their wings, which they are incapable of doing due to the shape of the wing. After they
fail at tucking a few times, they carry nesting material in their beaks.
Foraging Behavior
Foraging for food is a crucial behavior for animals. Like all behavior, it requires the interaction of many
components. Nonetheless, it turns out that in some animals, at least, foraging behavior can be altered by a single
gene.
Foraging Behavior in Drosophila melanogaster (fruit flies)
The discovery of the genetic control of foraging in Drosophila began with the observations of Marla
Sokolowski when she was an undergraduate biology student at the University of Toronto.
She noticed that Drosophila larvae, feeding in her culture vessels, displayed one of two distinct feeding
patterns:
 rovers, who moved rapidly over the surface of the culture medium
 sitters, who fed at a much more leisurely pace
She went on to find that this pattern of behavior
 continued when the larvae became adults
 was present in populations of wild fruit flies, not just in her laboratory colonies
After further years of research, she has shown that the behavior is under the control of a single gene, named for
("foraging"). There are two alleles present in the population at almost equal frequencies.
 forR, which is dominant [rovers are either homozygous (forR/forR) or heterozygous (forR/fors)]
 fors, which is recessive [sitters are homozygous (fors/fors)]
 About 70% of natural populations are rovers
Both alleles encode a PKG, an enzyme that attaches phosphate groups to proteins. The enzyme encoded by the
forR allele is more active than that encoded by fors. PKG is activated by a molecule called cyclic GMP (cGMP).
She and her colleagues have succeeded in inserting forR DNA into sitters who promptly become rovers.
Why should alleles for two such different behaviors be maintained at such high frequency in the population?
One possible answer: it permits the population to thrive under varying food conditions:
 sitters are favored when food is abundant;
 rovers are favored when competition for food is strong, such as in crowded cultures.
Honeybees ( Apis mellifera)
Honeybees have their version of the for gene, called Amfor ("Apis mellifera for"). It, too, encodes the
cGMP-dependent protein, PKG.
When worker bees first hatch, they remain in the hive tending to various housekeeping chores, such as
feeding the larvae. But when they are 2–3 weeks old, they leave the hive and begin foraging for nectar and
pollen. This change in behavior coincides with the increased expression of Amfor.
When newly-hatched workers are treated with cGMP, the amount of PKG in their brains goes up and they
quickly begin foraging instead of doing housekeeping.
Releasers of Instinctive Behavior
So once the body is prepared for certain types of instinctive behavior, an
external stimulus may be needed to initiate the response. The stimulus need not
necessarily be appropriate to be effective.
 During the breeding season, the female three-spined stickleback normally
follows the red-bellied male (a in the figure) to the nest that he has prepared.
 He guides her into the nest (b) and then prods the base of her tail (c).
 She then lays eggs in the nest.
 After doing so, the male drives her from the nest, enters it himself, and
fertilizes the eggs (d).
 Although this is the normal pattern, the female will follow almost any small
red object to the nest, and once within the nest, neither the male nor any
other red object need be present.
 Any object touching her near the base of her tail will cause her to release her
eggs.
It is as though she were primed internally for each item of behavior and needed
only one specific signal to release the behavior pattern. For this reason, signals
that trigger instinctive acts are called releasers. Once a particular response is
released, it usually runs to completion even though the stimulus has been
removed. One or two prods at the base of her tail will release the entire sequence
of muscular actions involved in liberating her eggs.
Pheromones (chemical signals) serve as important releasers for the social
insects: ants, bees, and termites. Many of these animals emit several different pheromones which elicit, for
example, alarm behavior, mating behavior, and foraging behavior in other members of their species. The
mammary glands of domestic rabbit mothers emit a pheromone that releases immediate nursing behavior by
their babies. A good thing, too, as mothers devote only 5-7 minutes a day to feeding their pups so they had
better be quick about it.
A number of studies have shown that animals can often be induced to respond to inappropriate releasers.
For example, a male robin defending its territory will repeatedly attack a simple clump of red feathers but will
not attack a stuffed robin that lacks the red breast of the males. Although such behavior seems inappropriate to
our eyes, it reveals a crucial feature of all animal behavior: animals respond selectively to certain aspects of the
total sensory input they receive. Animals spend their lives bombarded by lots of sights, sounds, odors, etc. But
their nervous system filters this mass of data, and they respond only to those aspects that the evolutionary
history of the species has proved to be significant for survival.
Other Types of Instinctive Behavior
Migration
Migration is the periodic movement of an animal from the place where it has been living to a new area and its
subsequent return journey to the original home. When animals migrate, it is usually to find abundant food and a
good place to breed.
Hibernation
Hibernation is a time of inactivity in order to help an animal survive through the cold winter months. This
inactivity is not like human sleep where loud noises can wake you up. With true hibernation, the animal can be
moved around or touched and not know it.
Estivation
Estivation is a state of dormancy similar to hibernation, but during the months of the summer. Animals that
estivate spend a summer inactive and insulated against heat and dryness to avoid the potentially harmful effects
of the season, or to avoid contact with other species with which they may otherwise be in competition, or for
which they are prey.
--------------------Learned Behavior-------------------Habituation
Habituation is a reduction in a previously-displayed response when no reward or punishment follows.
If you make an unusual sound in the presence of the family dog, it will respond — usually by turning its head
toward the sound. If the stimulus is given repeatedly and nothing either pleasant or unpleasant happens to the
dog, it will soon cease to respond.
This lack of response is not a result of fatigue nor of sensory adaptation (an example of sensory adaptation is if
someone rests their hand on a table, they immediately feels the table's surface on their skin. Within a few
seconds, however, they cease to feel the table's surface. The sensory neurons stimulated by the table's surface
respond immediately, but then respond less and less until they may not respond at all). Habituation is longlasting; when fully habituated, the dog will not respond to the stimulus even though weeks or months have
elapsed since it was last presented.
Sensitization
Sensitization is an increase in the response to an
innocuous stimulus when that stimulus occurs after a
punishing stimulus.
An example:
When the siphon of the sea slug Aplysia is gently
touched, the animal withdraws its gill for a brief period
(1st bar). However, if the tail receives an electrical
shock beforehand, the same gentle touch to the siphon
will elicit a longer period of withdrawal (not shown).
The sensitization response to a single shock dies out
after about an hour (2nd bar), and returns to baseline
after a day (3rd bar). So it is an example of short-term
memory.
However, if the animal is sensitized with multiple
shocks given over several days, its subsequent response
to a gentle touch on the siphon is much larger and is
retained longer (4th & 5th bars). This is an example of
long-term memory and requires protein synthesis.
Imprinting
If newly-hatched geese are exposed to a moving object of reasonable size
and emitting reasonable sounds, they will begin to follow it just as they
would normally follow their mother. This is called imprinting.
The time of exposure is quite critical. A few days after hatching,
imprinting no longer occurs. Prior to this time, though, the results can be
quite remarkable. A gosling imprinted to a moving box or clucking person
will try to follow this object for the rest of its life. In fact, when the
gosling reaches sexual maturity, it will make the imprinted object, rather
than a member of its own species, the goal of its sexual drive.
Much of our knowledge of imprinting was learned from the research of
Konrad Lorenz, shown here with some of his imprinted goslings. Lorenz
shared a Nobel Prize in 1973 for his discoveries.
Male mice become imprinted with the odor of litter-mates during the first
three weeks of life. When they reach sexual maturity, they avoid mating
with close relatives.
The Conditioned Response (CR)
The conditioned response is probably the simplest form of learned behavior. It is a response that, as a result of
experience, comes to be caused by a stimulus different from the one that originally triggered it.
The Russian physiologist Ivan Pavlov found that placing meat powder in a dog's mouth would cause it to
salivate. The meat powder, an unconditioned stimulus (US), triggers a simple inborn reflex involving taste
receptors, sensory neurons, networks of interneurons in the brain, and autonomic motor neurons running to the
salivary glands producing an unconditioned response (UR).
Pavlov found that if he rang a bell every time he put the meat powder in the dog's mouth, the dog eventually
salivated upon hearing the bell alone. This is the conditioned response (CR). The dog has learned to respond to
a substitute stimulus, the conditioned stimulus (CS).
We assume that the physiological basis of the conditioned response is the transfer, by appropriate neurons, of
nervous activity in the auditory areas of the brain to the motor neurons controlling salivation. This involves the
development and/or strengthening of neural circuits, which, we may also assume, is characteristic of all forms
of learning.
The conditioned response has proven to be an excellent tool for determining the sensory capabilities of other
animals. For example, honeybees can be conditioned to seek food on a piece of blue cardboard . By offering
other colors to a blue-conditioned bee, Karl von Frisch (who shared the 1973 Nobel Prize with Lorenz) found
that honeybees can discriminate between different colors.
Instrumental Conditioning
Pavlov's dogs were retrained and the response being conditioned (salivation) was innate.
But the principles of conditioning can also be used to train animals to perform tasks that are not innate.
In these cases, the animal is placed in a setting where it can move about and engage in different activities.
The experimenter chooses to reward only one behavior, for example, turning to the left. By first rewarding (with
a pellet of food) even the slightest
movement to the left and then only more
complete turns, a skilled experimenter can
in about 2 minutes train a pigeon to make
a complete turn. A little more work and the
pigeon will pace out a figure eight.
In the example shown here, the pigeon,
presented with two spots of light, pecks at
the brighter and reaches down to pick up the grain of food that is its reward. Such training is known as
instrumental conditioning or operant conditioning. The latter term was coined by B. F. Skinner, whose skill
with the technique enabled him to train pigeons to play ping-pong and even a toy piano!
It is also called trial-and-error learning because the animal is free to try various responses before finding the
one that is rewarded.
Maze problems are a form of instrumental
conditioning in which the animal is faced with a
sequence of alternatives.
In this photo, Julia, a chimpanzee, uses a magnet
to move an iron ring through a maze. Julia is able
to solve mazes like this on her first attempt most
(86%) of the time and sometimes faster than
biology students can.
Concepts
Although most animals solve mazes and other problems by
trial and error, Julia (and biology students) usually make only
one or two random attempts at solving a problem and then, all
of a sudden, "get it." They have made an abstract
generalization about the specific problem; that is, have formed
a concept.
Oddity problems are an example. This young rhesus monkey
has learned that food will be found, not under any particular
object, but under whichever object is different from the others.
In monkeys (and probably humans as well), concept formation
depends on activity in the prefrontal cortex of the brain.
Recent research suggests that honeybees can also solve simple
oddity problems.
---------------------Social Behavior--------------------Social animals such as chimpanzees have a complex system of communicating and functioning in their groups
and scientists have shown chimpanzees display social behavior that is both innate and learned. Chimpanzees are
intelligent enough to adapt and learn not only from their own species, but from other animals in their habitat.
Because of this fluidity of influencing what chimpanzees observe and can learn from, many times their behavior
are learned from observing other animals (for example, searching for food sources). However, animals such as
ants or bees are usually more genetically “hard-wired”, and their interactions with other members of their
species can only evolve to a certain level of sophistication to serve their purpose (such as bee-dancing to
communicate with each other about a food source).
Patterns of Behavior
Social behaviors in animals can be related to courtship and mating, caring for young, defense, obtaining food,
establishing or maintaining territory or periodic cycles. Successful behaviors promote survival of the individual
animal and its future generations.
 Courtship consists of behaviors that help members of the same species identify and select potential
mates. Sexual selection is an evolutionary mechanism in which some traits increase an individual's
chance of mating and passing along its genetic information.
 Parental care, if present, is usually provided by the female. This may allow successful and perhaps
healthier males to maximize their reproductive output. Reproduction and care of offspring requires a
great deal of energy, and the number of offspring produced at any one time is usually inversely
proportional to the amount of energy invested in parental care (meaning if a lot of offspring are
produced, little energy is invested in parental care; if few offspring are produced, a lot of energy is
invested in parental care).
 Defensive behaviors involve protection of the individual. In some animals, it also involves protection of
offspring, mates and territory.
 Migration is the regular, recurrent, seasonal movement of populations from one geographic location to
another and back again. Many species of fish, mammals, and even insects take amazing migratory
journeys, but birds, as a group, are the most mobile creatures on Earth. In general, migrating animals use
one or more of three mechanisms: piloting, orientation and navigation. Piloting involves use of familiar
landmarks and usually is used to locate nearby destinations. In orientation, an animal detects compass
directions and travels in straight-line pathways. Navigation, which is the most complex mechanism,
involves being able to determine the present location, and then the use of compass direction to travel in
the desired direction. Some animals use the Earth's magnetic field, the sun, or the stars for navigation.
 Foraging behaviors relate to the ability of the animal to locate, obtain and consume food.
 Many animals respond to periodic changes in the environment with daily or seasonal cycles of
behavior. Daily patterns, such as sleep cycles, are referred to as circadian rhythms and are related to the
Earth's 24 hour day-night cycles. Other periodic behavior can be linked to changes in the length of day
and night, or of temperature.
 Territorial behavior typically relates to feeding, mating and/or caring for offspring. A territory can vary
widely from species to species. Territorial behavior is thought to lead to increased reproductive success
by defending a particular area containing critical resources.
 Example: Siamese Fighting Fish (Betta splendens) AKA Betta fish
 Male Betta fish are extremely aggressive towards males of their own species (though they
are total wimps when attacked by a different species), and will readily fight to complete
exhaustion. When fighting, males will nip at each others fins until one of them is too tired
to continue, though this usually takes so long that the fins of both combatants resemble
torn up rags by the time one of the fish concedes defeat by retreating.
 Male Betta fish will fight to claim territory, or to protect their eggs or protect their
offspring, but physical combat is always preceded by a display sometimes called
"flaring." When stimulated by the sight of a rival male (the releaser), a male Betta fish
will exhibit several types of genetically determined aggressive movements. The fish will
spread his fins, extend his gill opercula and membranes, and generally appear much larger
than his resting size. If this does not cause the rival male to retreat, fighting will ensue.
Communication
Communication occurs when one organism passes along some type of information (signal) to another,
generating a response. Animals may use visual, auditory (sound), tactile (touch), chemical or electrical signals
to communicate with one another. Transmitting and receiving these signals generates an external or internal
response in the organism. Some examples are:
 Pheromones, chemical signals used for communication, are especially common in mammals and insects.
Bees use pheromones to determine social rank and to initiate reproduction. The context of the signal is
important. For example, male honeybees will respond to the pheromones of the queen while they are
outside the hive (where they can mate), but are unaffected by the pheromones while inside the hive. Ants
also use pheromones to mark a trails to food sources.
 Karl von Frisch was awarded the Nobel Prize for physiology and medicine in 1973 for his theory that
honey bees communicate by a dance language. This theory was presented first by von Frisch in the
1940s. He suggested that worker bees are able to communicate direction and distance to a food source
through movements described as "round dances and waggle dances."
 Birds use song to recognize and attract other members of their species, to warn of predators and to
defend their territories. Some birds, such as killdeer, will leave the nest and perform an elaborate
"broken wing" display to attract a predator away from its nest.
 Niko Tinbergren demonstrated in his research that visual displays of stickleback fish initiate
reproduction. The red belly of the male stickleback attracts a female, who adopts a head up posture. In
response, the male makes a series of zigzag motions, leading the female to his nest where she deposits
her eggs. Finally, the male enters the nest and fertilizes the eggs.