Behavioral Ecology

Chapter 37

Nature vs. Nurture

Behavior To what degree do our

genes (nature) and environmental influences (nurture) affect behavior?

Nature versus Nurture: Genetic Influences

Lovebird Nesting Behavior Genetic role in nest

making: Fischer lovebirds,

Agapornis fischeri Peach-face

lovebirds, Agapornis roseicollis

Hybrid lovebirds exhibit intermediate behavior

Nature versus Nurture: Genetic Influences

Garter Snake Experiments Genetic role in food

preference In the wild:

Inland populations of garter snakes are aquatic

Coastal populations are terrestrial

In the laboratory: Inland snakes refused

slugs Coastal snakes readily

accepted them Hybrid snakes exhibited

intermediate acceptance of slugs as food

Nature versus Nurture: Genetic Influences

Garter Snake Experiments Sensory receptors are

specific for prey Presented baby snakes

with slug extract on cotton swabs

Coastal Inland

Genetic difference – physiological difference

Nature versus Nurture: Genetic Influences

Experiments with Humans Twin Studies

Look at characteristics of twins raised apart

Many share common preferences in food, activity patterns, and mate selection

Nature versus Nurture: Environmental Influences Fixed Action Patterns (FAP)

Specific behaviors elicited by a sign stimulus

Learning A durable change in

behavior brought about by experience

Nature versus Nurture: Environmental Influences

Learning in Birds Imprinting: a simple

form of learning Sensitive period Social interactions

between parent and offspring during the sensitive period are important

Nature versus Nurture: Environmental Influences

Learning in Birds Song Learning

White-crowned sparrows Species-specific song with different dialects

Three groups: Birds that heard no songs

Sang an undeveloped song as adults Birds that heard White-crowned sparrows

Sang in that dialect as long as tape was played during a sensitive period

Birds that had adult tutor Sang the tutor’s song even if a different species

and no matter when tutoring began

Nature versus Nurture: Environmental Influences

Associative learning 1. Classical Conditioning

The presentation of two different types of stimuli at the same time

Causes an animal to form an association between them

2. Operant Conditioning A stimulus-response

connection is strengthened Training an animal by

rewarding it

Other means of learning….

Animals may learn through insight, imitation, and habituation Insight learning

An animal suddenly solves a problem without any prior experience with the problem

Habituation An animal no longer

responds to a repeated stimulus

Mating Behaviors

Sexual Selection Adaptive changes that increase ability to

attract a mate Influences fitness

Three influences on mating: Female Choice Male Competition Human Mating

1. Female Choice

Two Hypotheses: Good Genes Hypothesis

Females choose mates on basis of traits that improve survival

Run-away Hypothesis Females choose mates on

basis of traits that improve appearance

2. Male Competition

Males can produce many offspring because continuously produce sperm in large numbers Less time and energy invested in reproduction Males compete to inseminate as many

females as possible Cost-benefit analyses

Is the benefit of access to mating worth the cost of competition among males??

2. Male Competition

Males and females have separate dominance hierarchies Higher-ranking animal

has greater access to resources than a lower-ranking animal

Dominance is decided by confrontations

3. Mating in Humans

Human Males Compete Humans are dimorphic

Men are larger and stronger likely as result of past selection by females

Males pay a price - the average life span is seven years less than females!

Sociobiology

Applies the principles of evolutionary biology to the study of social behavior in animals

Hypothesis Living in a society has a greater reproductive benefit

than reproductive cost Benefits of Group Living

Helps an animal avoid predators, rear offspring, and find food

Disadvantages to Group Living Competition among members of the group for

resources Exposes group members to illnesses and parasites

Sociobiology

Helpers at the Nest Minimal short-term

reproductive sacrifice made to maximize future reproductive potential

Helper contributes to survival of kin

Sociobiology and Human Culture

Humans live in organized societies Culture of a human society involves a wide

spectrum of customs Earliest organized societies may have been

the “hunters-gatherers” Predatory lifestyle likely encouraged the

evolution of intelligence and the development of language

Animal Communication

Communication 4 types communication signals:

Chemical Auditory Visual Tactile

Animal Communication

Chemical Communication Pheromones

Powerful chemical signals passed in low concentration

May be released into the air or used in territory marking

Animal Communication

Auditory Communication Very rapid and can be

modified for specific situations

Animal Communication

Visual Communication Most used by diurnal

species-must be able to be seen

Plumage, courtship “dances”, aggressive displays, etc

Animal Communication

Tactile Communication Occurs when one

individual touches another