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51 Behavioral Biology
• Statistical analysis
Pearson Behavior Lab
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What Is Behavior?
• Behavior
– Is what an animal does and how it does it
– Includes muscular and nonmuscular activity
Dorsal fin
Anal fin
Figure 51.2
2. Behavioral has both proximate
and ultimate causes
• Proximate questions are mechanistic, concerned
with the environmental stimuli that trigger a
behavior, as well as the genetic and physiological
mechanisms underlying a behavioral act.
• Ultimate questions address the evolutionary
significance for a behavior and why natural
selection favors this behavior.
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3. Behavior results from both
genes and environmental factors
• In biology, the
nature-versusnurture issue is not
about whether
genes or
environment
influence behavior,
but that both are
involved.
Fig. 51.1
Two Categories of Behavior
• Innate or Unlearned Behavior
• Learned Behavior or Conditioning
4. Innate behavior is
developmentally fixed
• These behaviors are due to genetic programming.
• The range of environmental differences among
individuals does not appear to alter the behavior.
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5. Classical ethology presaged an
evolutionary approach to
behavioral biology
• Ethology is the study of how animals behave in
their natural habitat.
– Karl von Frisch, Konrad Lorenz, and Niko
Tinbergen are three individuals who were
foremost in the initial stages of this field.
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• Fixed action pattern (FAP)
– A sequence of behavioral acts that is essentially
unchangeable and usually carried to completion
once initiated.
• The FAP is triggered by an external sensory stimulus
known as a sign stimulus (stimuli are usually obvious).
• The FAP usually occurs in a series of actions the same
way every time.
• Many animals tend to use a relatively small subset of the
sensory information available to them and behave
stereotypically.
The terms sign stimulus and
releaser are sometimes used
interchangeably. However ..
•Strictly speaking the term
releaser is used for stimuli that
have evolved to facilitate
communication between animals
of the same species
•Sign stimuli are features of an
animal's environment to which it
reacts in a particular way. For
example, the fly orchid is a plant
that looks like an insect which
helps it attract pollinators.
Sign stimuli
• In male stickleback fish, the stimulus for attack
behavior
– Is the red underside of an intruder
(a) A male three-spined stickleback fish shows its red underside.
Figure 51.3a
Sign stimuli
Sign stimuli
Fig. 51.2
Sign stimuli
Bee pollination movie
Sign stimuli
Super
Normal
Sign
Stimulus
Super Normal
Sign Stimulus
Sign stimuli
6. Behavioral ecology emphasizes
evolutionary hypotheses
• Behavioral ecology is the research field that
views behavior as an evolutionary adaptation to
the natural ecological conditions of animals.
• We expect animals to behave in ways that
maximize their fitness (this idea is valid only if
genes influence behavior).
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Many forms of sexual
advertising involve the
males displaying their blood
colour, often by expanding
the throat with air. Blood
colour is a good indicator of
health and so provides the
females with a guide to
male's fitness when it
comes to choosing a mate.
• Songbird repertoires
provide us with
examples.
– Why has natural
selection favored
a multi-song
behavior?
Fig. 51.5
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• It may be advantageous for males attracting
females.
Larger repertoire
results in earlier
pairing dates
Fig. 51.6
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1. Learning is experience-based
modification of behavior
• Learning (conditioning) is
the modification
of behavior resulting from
specific experiences.
– The alarm calls of vervet
monkeys provide an
example of how animals
improve their
performance of behavior.
Fig. 51.8
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• Learning versus maturation.
– Maturation is the situation in which a
behavior may improve because of ongoing
developmental changes in neuromuscular
systems, for example, flight in birds.
• As a bird continues to develop its muscles and
nervous system, it is able to fly.
• It is not true learning.
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Maturation causes tighter pecking group, but
learning is not involved
• Habituation.
– This involves a loss of responsiveness to
unimportant stimuli or stimuli that do not
provide appropriate feedback.
• For example, some animals stop responding to
warning signals if signals are not followed by a
predator attack (the “cry-wolf” effect).
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Habituation
“What’s so scary
about these old
scarecrows?”
2. Imprinting is learning limited to
a sensitive period
• Imprinting is the recognition, response, and
attachment of young to a particular adult or
object.
• Konrad Lorenz experimented with geese that
spent the first hours of their life with him and
after time responded to him as their “parent.”
– Lorenz isolated geese after hatching and found
that they could no longer imprint on anything.
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Imprinting
– What is innate
in these birds is the
ability to respond
to a parent figure;
while the outside
world provides
the imprinting
stimulus.
– The sensitive period
is a limited phase in
Fig. 51.9
an individual animal’s
development when learning
particular behaviors can take place Imprinting
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Imprinting
Imprinting occurs
only during a short
sensitive period early
in life
• Conservation biologists have taken advantage of
imprinting
– In programs to save the whooping crane from
extinction
Figure 51.6
With eyes on their spawning ground, Atlantic salmon swim upstream
during their spawning run. These wild Atlantic salmon (Salmo salar) are a
rarity, as most Atlantic salmon today spend their time on fish farms.
Directed Movements
• Many animal movements
– Are under substantial genetic influence
• These types of movements
– Are called directed movements
Kinesis
• A kinesis
– Is a simple change in activity or turning rate in
response to a stimulus
• Sow bugs
– Become more active in dry areas and less active in
humid areas
Moist site
under leaf
Dry open
area
(a) Kinesis increases the chance that a sow bug will encounter and stay in
a moist environment.
Figure 51.7a
Taxis
• A taxis
– Is a more or less automatic, oriented movement
toward or away from a stimulus
• Many stream fish exhibit positive rheotaxis
– Where they automatically swim in an upstream
direction
Direction
of river
current
(b) Positive rheotaxis keeps trout facing into the current, the direction
from which most food comes.
Figure 51.7b
Migration
• Many features of migratory behavior in birds
– Have been found to be genetically programmed
Figure 51.8
Animal Signals and
Communication
• In behavioral ecology
– A signal is a behavior that causes a change in another
animal’s behavior
• Communication
– Is the reception of and response to signals
• Animals communicate using
– Visual, auditory, chemical, tactile, and electrical
signals
• The type of signal used to transmit information
– Is closely related to an animal’s lifestyle and
environment
• When a minnow or catfish is injured
– An alarm substance in the fish’s skin disperses in the
water, inducing a fright response among fish in the
area
(a) Minnows are widely dispersed in an aquarium
before an alarm substance is introduced.
Figure 51.9a, b
(b) Within seconds of the alarm substance being introduced,
minnows aggregate near the
bottom of the aquarium and reduce their movement.
Auditory Communication
• Experiments with various insects
– Have shown that courtship songs are under genetic
control
EXPERIMENT Charles Henry, Lucía Martínez, and ent Holsinger crossed males and females of Chrysoperla plorabunda and Chrysoperla johnsoni, two
morphologically identical species of lacewings that sing different courtship songs.
SONOGRAMS
Chrysoperla plorabunda parent
Standard
repeating
unit
Volley
period
Vibration
volleys
crossed
with
Chrysoperla johnsoni parent
Volley period
Standard repeating unit
The researchers recorded and compared the songs of the male and female parents with
those of the hybrid offspring that had been raised in isolation from other lacewings.
RESULTS
The F1 hybrid offspring sing a song in which the length of the standard repeating unit is
similar to that sung by the Chrysoperla plorabunda parent, but the volley period, that is, the interval
Volley
between vibration volleys, is more similar
period to that of the Chrysoperla johnsoni parent.
F1 hybrids, typical phenotype
Standard repeating unit
CONCLUSION
The results of this experiment indicate that the songs sung by
Chrysoperla plorabunda and Chrysoperla johnsoni are under genetic
control.
Bird song provides a model system for
understanding the development of behavior
• Some songbirds have a sensitive period for
developing their songs.
– Individuals reared in silence performed abnormal
songs, but if recordings of the proper songs were
played early in the life of the bird, normal songs
developed.
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Imprinting
Fig. 51.10a
• Canaries exhibit open-ended learning where
they add new syllables to their song as the get
older.
Fig. 51.10b
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Imprinting
Genetic Influences on Mating and Parental Behavior
• A variety of mammalian behaviors
– Are under relatively strong genetic control
• Research has revealed the genetic and neural basis
– For the mating and parental behavior of male prairie voles
Figure 51.11
• Concept 51.3: Environment, interacting with an
animal’s genetic makeup, influences the
development of behaviors
• Research has revealed
– That environmental conditions modify many of the
same behaviors
4. Many animals can learn to
associate one stimulus with another
• Associative learning is the ability of many
animals to learn to associate one stimulus with
another.
• Classical conditioning is a type of associative
learning.
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Conditioning
– Pavlov’s dog is a good example.
• Ivan Pavlov exposed dogs to a bell ringing and at the
same time sprayed their mouths with powdered meat,
causing them to salivate.
• Soon, the dogs would salivate after hearing the bell
but not getting any powdered meat.
Classical
Conditioning
Pavlov’s
Dog
Training
• Operant conditioning.
– This is called trial-and-error learning - an
animal learns to associate one of its own
behaviors with a reward or a punishment.
Operant
Conditioning
Fig. 51.11
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Operant
conditioning
Skinner Box
Insight
1. The study of cognition connects nervous
system function with behavior
• Cognition is the ability of
an animal’s nervous system
to perceive, store, process,
and use information
gathered by sensory
receptors.
Fig. 51.13
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• Problem solving can be learned
– By observing the behavior of other animals
Figure 51.17
Genetic and Environmental
Interaction in Learning
• Genetics and environment can interact
– To influence the learning process
• Concept 51.4: Behavioral traits can evolve by
natural selection
• Because of the influence of genes on behavior
– Natural selection can result in the evolution of
behavioral traits in populations
Behavioral Variation in Natural
Populations
• When behavioral variation within a species
– Corresponds to variation in the environment, it may
be evidence of past evolution
Variation in Prey Selection
• Differences in prey selection in populations of
garter snakes
– Are due to prey availability and are evidence of
behavioral evolution
the natural diet of this species differs
widely across its range in California.
Coastal populations feed on
salamanders, frogs, and toads, but
predominantly on slugs. Inland
populations feed on frogs, leeches, and
fish, but not on slugs. In fact, slugs are
rare or absent in the inland habitats of T.
elegans
(a) A garter snake (Thamnophis
elegans)
Figure 51.18a, b
(b) A banana slug (Ariolimus
californicus); not to scale
Experimental Evidence for
Behavioral Evolution
• Laboratory and field experiments
– Can demonstrate the evolution of behavior
Variation in Aggressive Behavior
• Funnel spiders living in different habitats
– Exhibit differing degrees of aggressiveness in
defense and foraging behavior
Desert
grassland
population
60
Time to attack (seconds)
50
Riparian
population
40
30
20
10
0
Field
Lab-raised
generation 1
Population
Figure 51.19
Lab-raised
generation 2
Desert grassland
population less
aggressive
Laboratory Studies of Drosophila Foraging Behavior
• Studies of Drosophila populations raised in high- and
low-density conditions
– Show a clear divergence in behavior linked to specific
genes
14
12
Average path length (cm)
High density
flies foraged for
a longer length
Low population
density
High population
density
10
8
6
4
2
0
L1
L2
L3
H1
D. Melanogaster lineages
Figure 51.20
H2
H3
H4
H5
Migratory Patterns in Blackcaps
• Field and laboratory studies of Blackcap birds
– Have documented a change in their migratory
behavior
• Birds placed in funnel cages
– Left marks indicating the direction they were trying
to migrate
(a) Blackcaps placed in a funnel cage left marks indicating the
direction in which they were trying to migrate.
Figure 51.21a
• Migratory orientation of wintering adult birds
captured in Britain
– Was very similar to that of laboratory-raised birds
N
BRITAIN
W
E
S
(b) Wintering blackcaps captured in Britain and their laboratory-raised
offspring had a migratory orientation toward the west, while
young birds from Germany were oriented toward the southwest.
N
Young
from SW
Germany
Mediterranean
Sea
Figure 51.21b
E
W
S
Adults from
Britain and
F1 offspring
of British
adults
• Concept 51.5: Natural selection favors behaviors
that increase survival and reproductive success
• The genetic components of behavior
– Evolve through natural selection
• Behavior can affect fitness
– Through its influence on foraging and mate choice
Foraging Behavior
• Optimal foraging theory
– Views foraging behavior as a compromise between
the benefits of nutrition and the costs of obtaining
food
Energy Costs and Benefits
• Reto Zach
– Conducted a cost-benefit analysis of feeding
behavior in crows
• The crows eat molluscs called whelks
– But must drop them from the air to crack the shells
• Zach determined that the optimal flight height in
foraging behavior
– Correlated with a fewer number of drops, indicating
a trade-off between energy gained (food) and energy
expended
The optimal foraging
theory states that natural
selection will benefit
animals that maximize
their energy intake-toexpenditure ratio
Average number of drops
100
40
Average number of drops
30
75
Total flight height
Height X trials
20
Drop height
preferred
by crows
10
50
0
Figure 51.22
2
Height of drop (m)
25
3
5
7
15
Total flight height (number of drops
50
drop height)
125
60
What conclusion
can you make
about the effect
of prey density
on the size of
prey eaten?
At
high
At low
densities
densities large
all 3
prey
sizes is
eaten
preferred
equally
Risk of Predation
• Research on mule deer populations
– Has shown that predation risk affects where the deer
choose to feed
Predation
risk
Relative deer use
70
15
50
40
10
30
20
5
10
0
0
Open
Figure 51.24
Forest edge
Habitat
Forest interior
Relative deer use
Predation occurrence (%)
60
20
Mating Behavior and Mate
Choice
• Mating behavior
– Is the product of a form of natural selection call
sexual selection
Mating Systems and Mate Choice
• The mating relationship between males and
females
– Varies a great deal from species to species
• In many species, mating is promiscuous
– With no strong pair-bonds or lasting relationships
• In monogamous relationships
– One male mates with one female
(a) Since monogamous species, such as these trumpeter swans, are often
monomorphic, males and females are difficult to distinguish using
external characteristics only.
Figure 51.25a
• In a system called polygyny
– One male mates with many females
– The males are often more showy and larger than the
females
Figure 51.25b
(b) Among polygynous species, such as elk, the male (left) is
often highly ornamented.
• In polyandrous systems
– One female mates with many males
– The females are often more showy than the males
(c) In polyandrous species, such as these Wilson’s phalaropes, females (top)
are generally more ornamented than males.
Figure 51.25c
Colonial species of mole rats – one
queen, several kings
• The needs of the young
– Are an important factor constraining the evolution of
mating systems
– If little care is needed promiscuity is favored, is a lot
then monogamy is favored
• The certainty of paternity
– Influences parental care and mating behavior
• In species that produce large numbers of
offspring
– Parental care is at least as likely to be carried out
by males as females
Eggs
Figure 51.26
Sexual Selection and Mate
Choice
• In intersexual selection
– Members of one sex choose mates on the basis of
particular characteristics
• Intrasexual selection
– Involves competition among members of one sex for
mates
• Mate Choice by Females
• Male zebra finches
– Are more ornate than females, a trait that may affect
mate choice by the females
Figure 51.27
• Imprinting of female chicks on males with more
ornamentation
Experimental Groups
– Affects mate
selection as
adults
Both parents
ornamented
Males
ornamented
Control Group
Females
ornamented
Parents not
ornamented
Results
Females reared by
ornamented parents
or ornamented fathers
preferred ornamented
males as mates.
Females reared by
ornamented mothers or
nonornamented parents
showed no preference
for either ornamented or
nonornamented males.
Males reared by all experimental groups showed no
preference for either ornamented or nonornamented
female mates.
Figure 51.28
• The size of eyestalks in stalk-eyed flies
– Affects which males the females choose to mate with
Figure 51.29
• Male Competition for Mates
• Male competition for mates
– Is a source of intrasexual selection that can reduce
variation among males
• Agonistic behavior is a contest involving
threats.
– Submissive behavior.
An often ritualized contest that determines
which competitor gains access to a resource
– Generally, no harm is done.
• Morphology affects the mating behavior
– In isopods of the same species that are genetically
distinct
Large Paracerceis males
defend harems of females
within intertidal sponges.
Tiny males are
able to invade
and live within
large harems.
Figure 51.31
males mimic female morphology and
behavior and do not elicit a defensive
reponse in males and so are able to
gain access to guarded harems.
Applying Game Theory
• Game theory evaluates alternative behavioral
strategies in situations
– Where the outcome depends on each individual’s
strategy and the strategy of other individuals
• Mating success of male side-blotched lizards
– Was found to be influenced by male polymorphism
and the abundance of different males in a given area
Figure 51.32
• Concept 51.6: The concept of inclusive fitness
can account for most altruistic social behavior
• Many social behaviors are selfish
• Natural selection favors behavior
– That maximizes an individual’s survival and
reproduction
Altruism
• On occasion, some animals
– Behave in ways that reduce their individual fitness
but increase the fitness of others
• This kind of behavior
– Is called altruism, or selflessness
• In naked mole rat populations
– Nonreproductive individuals may sacrifice their lives
protecting the reproductive individuals from
predators
Figure 51.33
–Inclusive fitness: How can a naked
mole rat enhance its fitness by helping other
members of the population?
• How is altruistic behavior maintained by
evolution?
• If related individuals help each other, they are in
affect helping keep their own genes in the
population.
• Inclusive fitness is defined as the affect an
individual has on proliferating its own genes by
reproducing and helping relatives raise offspring.
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– Hamilton’s Rule and kin selection.
• William Hamilton proposed a quantitative
measure for predicting when natural selection
would favor altruistic acts.
• Hamilton’s rule states that natural selection
favors altruistic acts.
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• The three key variables in an altruistic act are
– The benefit to the recipient
– The cost to the altruist
– The coefficient of relatedness
• The coefficient of relatedness
– Is the probability that two relatives may share the
Haploid
same genes
50% of offspring share same
chromosome instead of 25%
• Natural selection favors altruism when the
benefit to the recipient
– Multiplied by the coefficient of relatedness exceeds
the cost to the altruist
• This inequality
– Is called Hamilton’s rule
– Kin selection is the mechanism of inclusive fitness,
where individuals help relatives raise young.
– Reciprocal altruism, where an individual aids other
unrelated individuals without any benefit, is rare, but
sometimes seen in primates (often in humans).
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Fig. 51.31
Social Learning
• Social learning
– Forms the roots of culture
• Culture can be defined as a system of
information transfer through observation or
teaching
– That influences the behavior of individuals in a
population
Mate Choice Copying
• Mate choice copying
– Is a behavior in which individuals in a population
copy the mate choice of others
• This type of behavior
– Has been extensively studied in the guppy Poecilia
reticulata
Control Sample
Male guppies
with varying
degrees of
coloration
Female guppies prefer
males with more orange
coloration.
Experimental Sample
Female model
engaged in
courtship with
less orange
male
Figure 51.36
Female guppies prefer less
orange males that are associated
with another female.
Social Learning of Alarm Calls
• Vervet monkeys
– Produce a complex set of alarm calls
• Infant monkeys give undiscriminating alarm
calls at first
– But learn to fine-tune them by the time they are
adults
Figure 51.37
• No other species
– Comes close to matching the social learning and cultural
transmission that occurs among humans
Figure 51.38
Evolution and Human Culture
• Human culture
– Is related to evolutionary theory in the distinct
discipline of sociobiology
• Human behavior, like that of other species
– Is the result of interactions between genes and
environment
• However, our social and cultural institutions
– May provide the only feature in which there is no
continuum between humans and other animals
Sociobiology connects evolutionary theory
to human culture
Fig. 51.32
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