Transcript Behavior

Behavioral Biology
Chapter 54
Approaches
• Behavior: the way an animal responds
to stimulus in its environment
• Two components of behavior
– Immediate cause
– Evolutionary origin
• Proximate causation:“how” of behavior
– Measure: hormone level testosterone
– Impulse of nerve signal
Approaches
• Ultimate causation: “why” of behavior
• Determine how behavior influences
reproductive success or survival
• Controversy:
– Is behavior determined by individual’s
genes
– Or by learning and experience
• Nature or nurture
Approaches
• Innate behavior: instinctive, does not
require learning
– Preset paths in nervous system
– Genetic: fixed action pattern
Example: goose replacing an egg from
her nest
Approaches
• Egg retrieval behavior is triggered by a
sign stimulus
• Innate releasing mechanism or fixed
action pattern is the stereotyped act
• Not very specific: anything round will
trigger the goose’s reaction
• Once pattern begins, it goes to
completion; even if the egg is removed
Approaches
• Male stickleback fish will attack anything
with a red underside
– Does not need to be a fish
– Supernormal stimuli: given a
choice: animals respond to a larger
stimuli over a normal size stimuli
Behavioral Genetics
• Artificial selection data has shown that
behavioral differences among individuals
often result from genetic differences
• Genetics of learning
Behavioral Genetics
Human twin study
• Identical twins: identical genetically
• 50 sets, twins raised separately
– Similarity in personality,
temperament, leisure time activities
• Indicates that genetics plays a role in
determining behavior even in humans
Behavioral Genetics
• Single gene: Drosophila
– Alternative alleles for feeding
behavior as larvae
• One type moves around to eat
• Second type remain in same area
to eat
– Courtship behavior also affected by a
mutation in a single gene
Behavioral Genetics
• Mice: fosB gene
• Determines whether female mice
nurture their young
– Both fosB alleles disabled: ignore
young
– Normal mothers: protective maternal
behavior
• Protein expressed by fosB activates
other enzymes and genes that affect
neural circuitry within the hypothalamus
Behavioral Genetics
• fosB present: mother
cares for her young
• fosB absent: young
are ignored and
eventually die
Behavioral Genetics
• Prairie voles are
monogamous
• Montane voles
mate and do not
work together to
raise young
• Different response
to oxytocin and
vasopressin
• Peptide receptors
different
Learning
• Learning: altered behavior as a result
of previous experiences
• Nonassociative learning: does not
require an animal to form an association
between two stimuli or between a
stimulus and response
– Habituation: decrease in response
to a repeated stimulus
– No positive or negative
consequences
Learning
• Associative learning: association
between two stimuli or between a
stimulus and a response
– Conditioned behavior through
association
– Two major types:
• Classical conditioning
• Operant conditioning
– Differ in the way associations are
established
Learning
Associative learning is involved in
predator-prey interactions: after being
stung the toad learns not to eat
bumblebees.
• Classical conditioning: the paired
presentation of two different kinds of stimuli
with an association formed between them
– Pavlovian conditioning
• Unconditioned stimulus: meat
• Unconditioned response: salivating
• Conditioned stimulus: bell ringing
• Conditioned response: After time, the
dog salivates with only the ringing of the
bell
Learning
• Operant conditioning: animal learns to
associate its behavior response with a
reward or punishment
– B.F. Skinner
– Trial and error learning
• Today it is believed that instinct guides
learning by determining what type of
information can be learned through
conditioning
Learning
• Instinct and learning
– Innate predispositions toward forming
certain associations
– Pigeons can learn to associate food
with colors, but not with sound
– Learning is possible only within the
boundaries set by instinct
– In nature, adaptation by learning is
important to survival
Learning
• Clark’s
nutcracker can
remember the
locations of up to
2000 seed
caches months
after hiding them
• Uses spatial
memory
Development of Behavior
• Parent-offspring interactions influence
cognition and behavior
• Imprinting: formation of social
attachment to other individuals or
develop preferences that will influence
behavior later in life
• Filial imprinting: attachment between
parents and offspring
– Konrad Lorenz
Development of Behavior
• Goslings follow
Konrad Lorenz
as if he were
their mother
• 1973 Nobel
Prize
Development of Behavior
• Instinct and learning may interact as
behavior develops
– White-crowned sparrow males sing
species-specific courtship song during
mating
– Genetic template: innate program to
learn the appropriate song
– Can not learn the song unless they hear
it at a critical period in development
Development of Behavior
a. Exposed to
own species
song during
development
b. Not exposed
to song
Development of Behavior
• Cuckoos are
raised by a
different species
• Learn their own
song: innate
Animal Cognition
• Do animals show cognitive behavior
• What type of behavior demonstrates
cognition?
• Japanese macaques learned to wash
sand off potatoes
• Chimps pull the leaves of off a tree
branch to use it as a tool for picking
termites
• Some birds learn to take off milk caps
from bottles
Animal Cognition
Orientation and Migratory
Behavior
• Orientation: goal-oriented movements
– Track stimuli in the environment
– Homing instinct
– Taxis: movement toward or away
from a stimulus
– Kineses: more or less active when
stimulus intensity increases
Orientation and Migratory
Behavior
• Migration involves population moving
large distances
– Monarch butterflies fly from North
America to Mexico
Orientation and Migratory
Behavior
It takes 2 - 5 generations for the migration
Orientation and Migratory
Behavior
Bobolinks have
changed their
migration by
adding a new
segment
Orientation and Migratory
Behavior
• Migrating animals must be capable of
orientation and navigation
• Navigation: the ability to set or adjust
a bearing
– Sun and stars: general direction
– Earth’s magnetic field: specific path
– Information from the stars overrides
the magnetic information if they
conflict
Orientation and Migratory
Behavior
Migratory
behavior of
starlings
Communication
• Communication can play a key role in
behaviors
– Among members of the same species
– Between species
• Successful reproduction depends on
appropriate signals and responses
– Stimulus-response chain: behavior
of one individual releases a behavior
by another individual
Communication
Long-distance communication
– Pheromones: chemical messengers
• Sex attractant
• Males have sensory receptors
• Some insect pheromones can be
detected as far as 7km away
– Acoustic signals
• Vocal calls, wing clicking
– Light signals: firefly
Communication
Bioluminescent
displays of
lampyrid beetles
are speciesspecific. Each
number represents
the flash pattern of
a male of a
different species
Communication
Communication facilitates group
living
– Guards: set off an alarm call so
group can seek shelter
– Social insects produce
pheromones that trigger attack
behavior
– Ants deposit trail pheromones
between nest and food source
Communication
The waggle dance of honeybees
Communication
• James L. Gould devised an experiment to
trick hive members into going in the wrong
direction
– Supported von Frisch’s explanation of
the bees using the Sun as their
reference position
– Eliminated Wenner’s challenge that it
was flower odor that drew the bees to the
food location
– Robot bees are now being used
Communication
Primate
language:
Vocabulary to
communicate
identity of
specific
predators
Communication
• Chimpanzees and gorillas can learn to
recognize a large number of symbols
and use them to communicate abstract
concepts
• Complexity of human language
– Differences are superficial
– 3000 languages draw from the same
set of 40 consonant sounds
Communication
• Signals vary in their degree of specificity
• Level of specificity: relates to the
function of a signal
– Mark territories with pheromones
– Species and other species specific
• Pursuit-deterrent signals: predator has
been seen and should not waste time
chasing the prey
Communication
Cleaner Fish. The grouper has entered
the cleaner fish’s “station” and adopted a
posture that allows the cleaner fish to
enter the mouth and gills and feed on
attached parasites
Behavioral Ecology
• Niko Tinbergen
divided the
investigation of
behavior into the
study of
– Development
– Physiological basis
– Function: including
evolutionary
significance
Behavioral Ecology
• Evolutionary analysis: survival value of
behavior
• Tinbergen observed gull nestlings hatch
and parents remove the shells of the eggs
• Placed broken eggs by the nests
– Predators (crows) found nests with
broken eggs and ate the hatchlings
– Nests without egg shells had less
predation
Behavioral Ecology
• Behavioral ecology: study of how
natural selection shapes behavior
– Adaptive significance of behavior
– Reproductive success, fitness
• Questions asked
– Is behavior adaptive
– How is it adaptive
• Enhance energy intake, increase
mating success, decrease
predation
Behavioral Ecology
Foraging behavior can directly influence
individual fitness
• Foraging involves a trade-off between
food’s energy content and the cost of
obtaining the food
• Optimal foraging theory: natural
selection favors individuals whose
foraging behavior is energetically
efficient
Behavioral Ecology
Optimal foraging makes two assumptions
1. Natural selection will only favor
behavior that maximizes energy
acquisition if the increased energy
reserves lead to increases in
reproductive success
– Avoid predators
– Find mates
Behavioral Ecology
2. Optimal behavior has evolved by
natural selection
• Female zebra finches that were
successful foraging had successful
offspring
• Removed offspring to ensure
learning not a part of the foraging
success
Behavioral Ecology
Optimal diet. The shore crab selects a
diet of energetically profitable prey
Behavioral Ecology
Territorial behavior secures resources
• Home range: where the animal lives
and forages; defends territory
• Defense against intrusion by other
individuals
• Birds sing or display to signal their
territory; energetically costly
• Benefit: increased food intake
Behavioral Ecology
Competition for space. Territory size in
birds is adjusted according to the
number of competitors
Behavioral Ecology
The benefit of territoriality. Sunbirds and
hummingbirds protect their food source
by attacking others that approach
flowers in their territory
Behavioral Ecology
• In some species, exclusive access to
females is a more important
determinant of territory size for males
than food
• Several females in territory are
defended vigorously
• Nonbreeding season
– Male territory size decreases
– Aggression decreases
Sexual Selection
• Reproductive strategies: decisions
about mating
– How many mates to have
– How much time devoted to rearing
offspring
– How much energy devoted to rearing
offspring
• Evolved partly in response to cost of
reproduction
Sexual Selection
Sexes often have different reproductive
strategies
• Females do not mate with the first male
they encounter
• Mate choice: evaluate a male’s quality
– Peahens mate with males with more
eyespots in their tail
– Frogs mate with males that have
complex calls
Sexual Selection
Products of sexual selection.
Attracting mates with long feathers is
common in bird species
Sexual Selection
• Males engage in mate choice less
frequently than females
• Parental investment: contributions each
sex makes in producing and rearing
offspring
– Females have higher investment
– Eggs larger than sperm
– Females are usually responsible for
gestation and lactation, or yolk
production
Sexual Selection
• Consequences of disparities in
reproductive investment - sexes face
different selective pressures
• Male fitness rarely limited by sperm count
• Number of eggs produced often does
limit reproductive success
• Females are choosey because it is costly
for them to reproduce
Sexual Selection
Advantage of male mate choice. Male
Mormon crickets choose heavier
females as mates, larger females have
more eggs
Sexual Selection
• Male Mormon crickets use 30% of their
body weight making up a
spermatophore for the female
• Male seahorses brood and care for the
young
• Females compete for males when
males are choosey
Sexual Selection
• Sexual selection involves both:
– Intrasexual selection: interactions
between members of one sex
– Intersexual selection: interactions
between members of opposite sex
(mate choice)
• Sexual selection leads to the evolution
of structures used in combat with other
males. Ex. Antlers, horns
Sexual Selection
• Secondary sexual characteristics:
horns, long feathers, coloration
Sexual Selection
• Intrasexual selection
– Males compete for
opportunity to mate
– Males defend their
territory & females
– Dominant males mate
with many females:
polygyny
– Sexual dimorphism:
males look different from
the females
Sexual Selection
Sperm competition
– Females mate with multiple males
– Males evolved features to maximize
sperm success
– Testes large to produce many sperm
per mating
– Sperm large and swim more rapidly
Sexual Selection
Intersexual selection
• Direct benefits of mate choice
– Females benefit by choosing males that
help raise offspring
– Males that do not help raise young;
provide territories, nesting sites, food,
predator refuges
Sexual Selection
Indirect benefits of mate choice
• Choose male that is healthiest or oldest
• Guppies and birds: coloration reflects
quality of diet and health
– Less likely to carry disease
– Good genes
• Handicap hypothesis: genetically
superior mates can survive a handicap
Sexual Selection
Alternative Theory
• Sensory exploitation: evolution in males
of an attractive signal that “exploits”
sound or colors
• Túngara frog
• Cluck sound
Sexual Selection
• Mating systems reflect adaptations for
reproductive success
• Energy costs, food resources, nest
sites, distribution of opposite sex
• Mating systems
– Monogamy: one male one female
– Polygyny: one male many females
– Polyandry: one female many males
Sexual Selection
• Mating systems influenced by ecology
– Territory size
– Needs of offspring
• Both parents: monogamy
• Altricial: offspring require long care
• Precocial: little care required
• Polyandrous systems: males usually care
for the young, females mate with many
males
Sexual Selection
The study of paternity. a) DNA
fingerprinting gel, b) results of DNA
fingerprinting study in red-winged
blackbirds
Sexual Selection
Extra-pair copulations (EPCs)
• Red-winged blackbirds study
– Half of all nests contained at least one
hatchling fertilized b a male not
defending the territory
• Evolutionary advantage of EPCs:
– Males: increased reproductive success
– Females: genetically superior individual
mated with, even if paired with another
male
Sexual Selection
Alternative mating strategies
• Fish
– Two genetic classes of males
• Large and small
• External fertilization: small males
“sneak” in to fertilize females
• Dung beetles
– Territorial males have large horns
– Small males do not have horns or
territories, intercept females in tunnels
Sexual Selection
Male fish fertilizing a female’s eggs
Altruism
• Altruism: the performance of an action
that benefits another individual at a cost to
the actor
• Question: if altruism imposes a cost to an
individual, how could an allele be favored
by natural selection?
• Group selection: rare
– Among groups: leads to a decrease in
allele’s frequency
– Within groups: may favor the allele
Altruism
• Reciprocal altruism: Partnerships in
which mutual exchanges of altruistic acts
occur because they benefit both
participants
– Cheaters are discriminated against
– Vampire bats
• Share blood
meal
Altruism
• Kin selection: direct genetic
advantage; selection favors relatives
• William Hamilton: explanation in 1964
– Brothers: 50% of alleles
– First cousin: 1/8th of alleles
• Hamiltons’s rule: altruistic acts are
favored when rb > c
• b and c are benefits and costs, r is the
coefficient of relatedness
Altruism
Altruism
Kin selection in white-fronted bee-eater
Altruism
Haplodiploidy and Hymenopteran social
evolution
• Bee hive: eusocial society
– single queen lays eggs
– 50,000 workers, no eggs
– Cooperative care of the brood: workers
propagate more of their own alleles by
giving up their own reproduction to assist
their mother in rearing their sisters (75%)
Altruism
Reproductive division of
labor in honeybees
Female workers share
75% of alleles with each
sister
Males are haploid
Queen shares 50% of
alleles with offspring
Social Systems
• Society: a group of organisms of the
same species that are organized in a
cooperative manner
• Advantages
– Kin selection: greater odds of alleles
surviving in the gene pool
– Greater protection from predators
– Increase feeding and mating success
Social Systems
Flocking behavior decreases predation
Social Systems
• Insect societies include individuals
specialized for different tasks
• Castes: groups of individuals that differ in
size and morphology and perform different
tasks
• Workers and soldiers
– Honeybees
– Leaf-cutter ants
– Fire ants
Social Systems
• Foraging and predator avoidance
• Meerkat sentinel on duty
• Take turns to act as lookout