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

• 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• Innate behavior: instinctive, does not

require learning

– Preset paths in nervous system

– Genetic: fixed action pattern

Example: goose replacing an egg from her nest

• Egg retrieval behavior is triggered by a sign stimulus

• Once pattern begins, it goes to completion; even if the egg is removed

Innate Behavior• 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

• 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 receptor sequence and location in brain different

Behavioral GeneticsVasopressin receptor

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

• 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

• 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

• 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

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

• 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

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

• 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

Orientation and Migratory Behavior

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

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

The waggle dance of honeybees

CommunicationCommunication facilitates group living

• 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

• 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

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

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...efficient strategies in a niche

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 (nutritive protein containing packet) for the female

• Mating systems reflect adaptations for reproductive success in a niche

• 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

• 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

• Kin selection: direct genetic advantage; selection favors relatives

• 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