Download Organismal Ecology Organismal Ecology = Autecology

Organismal Ecology
–  Studies how an organism’s structure,
physiology, and behavior (animals) meet the
challenges posed by the environment
Organismal Ecology = Autecology
•  Organismal Ecology = Autecology: self ecology
–  the initial focus of ecology: an organism’s
home life
•  Emphasis on Habitat & Niche
–  Where an organism is found
–  It’s role in the environment
–  What limits its distribution
Figure 50.3a
–  How it responds to environmental challenges
(a) Organismal ecology. How do humpback whales select their
calving areas?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Organisms and the Environment
Abiotic Factors and Organismal Ecology
• 
•  The n-dimensional niche was developed for
Organismal Ecology
Recall: Environmental factors that affect
organisms can be divided into two classes:
1.  Abiotic, or nonliving factors
e.g. Temperature, Precipitation, Salinity, etc.
2.  Biotic, or living factors
e.g. Conspecifics, Predators/Prey,
Competitors, Symbionts, etc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Focus on Abiotic Factors more than Biotic
Factors
–  A three-dimensional niche might include:
•  Temperature, rainfall, nitrogen
–  An n-dimensional niche includes all other
environmental factors
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Survival, Growth and Reproduction
Niche: Survival, Growth and Reproduction
•  For an organism’s species to live in a habitat
over time
•  For any single abiotic factor, conditions must
be appropriate at some time (e.g. season) for:
–  It not only needs to survive,
–  Growth and Reproduction
–  It must also be able to
–  And always for Survival, or:
•  Grow, and
•  Migration
•  Reproduce
•  Hibernation, or other resistant stage
•  Seed, spore, endospore, etc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1
Environmental Factors as Limiting Resources
Response to Environmental Challenges
•  A Limiting Resource limits the distribution or
abundance of organisms
•  Organismal responses to the environment
effect their ability to tolerate environmental
challenges
–  Abiotic factors
•  Nutrients: nitrogen, phosphorus, etc.
•  Nest sites, refugia, anchorage, etc.
–  May be experimentally demonstrated by
•  Addition and Removal experiments
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
•  Organismal Responses include:
–  Behavioral (animals)
–  Physiological
–  Morphological
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Response to Environmental Challenges
Response to Environmental Challenges
•  Behavior is the coordinated movement of
muscles (and glands) by neurons
•  Physiological responses also may be rapid
•  Is the most rapid response to the environment
–  If conditions are unfavorable, Move!
•  Daily or Seasonal Migration
•  Huddling by mammal social groups to
conserve body warmth
•  Avoidance of Predator (biotic factor)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Vasoconstriction of peripheral blood vessels
conserves heat
–  Acclimation to changing seasons/elevations:
•  Alternative forms of enzymes
–  Acclimation to changing elevations:
•  Increase concentration of hemoglobin
–  Salmon osmoregulation in fresh vs. saltwater
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Response to Environmental Challenges
Response to Environmental Challenges
•  Morphological changes occur more slowly
•  Morphological changes occur more slowly
–  Acclimation to changing seasonal
temperatures
•  Winter ‘coats’ in mammals and birds
–  Leaf morphology of plants vary with shading
–  Plants vary with wind patterns
•  Usually not reversible
–  Usually reversible
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
2
Response to Environmental Challenges
Costs and Benefits of Homeostasis
•  Over longer time frames
•  As organisms respond to the environment
–  Natural Selection affects organismal responses
–  they must balance costs and benefits
•  Major trade-offs occur between
–  Conformers vs. Regulators
•  Osmoconformers vs. Osmoregulators
•  Ectotherms/Poikilotherms vs.
Endotherms/Homeotherms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Osmoregulation
Osmoregulation
•  Organisms need to manage their water
balance, particulary aquatic organisms
•  Most marine fishes are osmoregulators
–  May live in freshwater or saltwater
–  They constantly drink seawater, and
–  Excrete small amounts of salty urine
•  Hagfish are osmoconformers
–  Their bodies conform to the osmotic
concentration of the deep ocean
–  Environment is fairly constant
•  Hagfish adapted to these conditions
•  Low cost
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Osmoregulation
Osmoregulation
•  Freshwater fishes osmoregulate
•  Osmoregulation by most marine and
freshwater fishes is energetically costly
–  They do not drink water
–  Excrete large volumes of dilute urine
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  but it favors the rest of their metabolic
processes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
3
Trade-Off: Poikilothermy vs. Homeothermy
Trade-Off: Poikilothermy vs. Homeothermy
•  Poikilotherms: allow their body temperatures to
fluctuate with the environment
•  Homeotherms: maintain a constant, warm
body temperature
–  Benefit: inexpensive
•  70% of energy budget used for basic
metabolism
•  30% of energy budget available for growth
and reproduction
–  Cost: slower metabolism
Note: ancestral
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Benefit: higher metabolism, rapid chemical
reactions, including locomotion
•  Early bird gets the warm! Able to gain
much more energy
–  Cost: Energetically expensive
•  97.5-99.5% of energy budget used for
basic metabolism
•  0.5-2.5% of energy budget available for
growth and reproduction
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Trade-Off: Poikilothermy vs. Homeothermy
Principle of Allocation
•  Many poikilotherms can behaviorally regulate
temperature
•  There are always trade-offs between an
organism’s ecological strategies
–  Lizards can bask in the sun
–  Cost: Increased risk of predation
•  Regardless of the ‘strategy’
–  Organisms are constantly faced with trade-offs
–  Impossible to maximize both energy intake and
efficiency of energy use, other risks, etc.
–  Which is better? Both successful today!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Organismal Ecology Today
•  Rather than Organismal Ecology, modern
ecologists tend to specialize
–  Behavioral Ecology
–  E.g. Conformers vs. Regulators
•  Similarly, there are finite resources & costs in
acquiring resources
•  The Principle of Allocation states that
organism’s cannot simultaneously maximize
survival, growth & reproduction
–  Rather, they must allocate their available
resources
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Chapter 51
Behavioral Ecology
–  Physiological Ecology
–  Functional Morphology
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4
Animal Behavior
•  Humans have probably studied animal
behavior
–  For as long as we have lived on Earth
•  As hunters
•  Cranes are birds that have captivated people’s
interest
–  Possibly because they are large and their
behavior is easily observed
–  Knowledge of animal behavior was essential to
human survival
Figure 51.1
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
What Is Behavior?
Animal Behavior
•  Behavior
•  Classically, Animal Behavior studied
–  Is what an animal does and how it does it
–  Includes muscular and nonmuscular activity
–  Behavior Patterns: coordinated movement of
muscles by neurons
•  Animal Behavior also includes
Dorsal fin
–  Learning
–  Chemical communication between animals
–  Related processes that may affect behavior
Anal fin
Figure 51.2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Behavioral Ecology
Proximate & Ultimate Causes
•  Behavioral Ecology is a modern discipline of
animal behavior
•  Behavioral ecologists distinguish between
proximate and ultimate causes of behavior
–  Extends observations of animal behavior by
studying how such behavior is controlled, how
it develops, its evolution and how it contributes
to survival and reproductive success
–  Proximate causes focus on the immediate
stimulus and mechanism for the behavior
–  Ultimate causes explain how the behavior
contributes to survival and reproduction
–  Conducted in the light of Evolutionary theory
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
5
Proximate and Ultimate Questions
Proximate and Ultimate Questions
• 
• 
Proximate, or “how,” questions about
behavior have two foci
–  The environmental stimuli that trigger a
behavior, e.g. a ‘Sign Stimulus’
–  The genetic, developmental, physiological,
and anatomical mechanisms underlying a
behavioral act
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ultimate, or “why,” questions about behavior
address the evolutionary significance of a
behavior
–  It’s evolutionary history, and
–  Current affect on fitness: via increased
survival and/or reproduction
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Anthropomorphism
Early Animal Behavior
•  Animal Behavior studies are particularly prone
to observer bias
•  From the time of Darwin
–  We tend to ascribe purpose and feelings to the
actions of animals
–  Anthropomorphism is the attribution of humanlike qualities to animals, e.g. consciousness
•  To avoid bias, behavioral biologists avoid terms
that suggest purpose & use parsimony:
–  Many biologists studied behavior from an
evolutionary viewpoint, e.g.
•  Ethologists
–  Other scientists, mostly from psychological
backgrounds, focused on learning, e.g.
•  Behaviorists
–  The simplest explanation is more likely true
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ethology
Classical Ethologists
•  Ethology is a branch of animal behavior
•  Three Ethologists shared a Nobel Prize (1973)
–  Particularly focused on the natural history of
animals and their behavior in the natural
environments in which they evolved
–  Karl von Frisch, Austrian
–  Assumed that behavior was adaptive
–  Niko Tinbergen, Dutch
–  Konrad Lorenz, Austrian
–  Developed a conceptual framework defined by
the set of Proximate and Ultimate questions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
6
Ethology
Fixed Action Patterns
•  Ethologists focused on behavior patterns that
were essentially
•  A fixed action pattern (FAP)
–  Innate, or instinctual
–  Is an unlearned, innate behavior pattern that is
unchangeable
–  Innate behavior is determined in large part by
genes
–  Usually occurs in a stereotypical sequence
with other behavior patterns (Ethogram)
–  Innate behavior is often stereotypical or ‘fixed’
–  Once the sequence is initiated, it is usually
carried to completion
–  Is triggered by an external sensory stimulus
•  a Sign Stimulus
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Sign Stimulus
•  In male stickleback (fish)
–  the stimulus for attack behavior is the red
underside of an intruder
•  A male stickleback in breeding condition will
attack even unrealistic models
–  If red is present on their underside
(a) A male three-spined stickleback fish shows its red underside.
Figure 51.3a
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 51.3b
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ethogram
•  Proximate and ultimate causes for the FAP
attack behavior in male stickleback fish
BEHAVIOR: A male stickleback fish attacks other male sticklebacks that invade its nesting
territory.
PROXIMATE CAUSE: The red belly of the intruding male acts as a sign stimulus
that releases aggression in a male stickleback.
Figure 51.4
ULTIMATE CAUSE: By chasing away other male sticklebacks, a male decreases
the chance that eggs laid in his nesting territory will be fertilized by another male.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
7
Imprinting
Young Geese ‘Imprint on’ & follow their Mother
•  Imprinting is a type of behavior
•  There are proximate and ultimate causes for
this type of behavior
–  That includes both learning and innate
components; is generally irreversible
BEHAVIOR: Young geese follow and imprint on their mother.
•  Imprinting is distinguished from other types of
learning by a ‘sensitive period’
–  A limited phase in an animal’s development
that is the only time when certain behaviors
can be learned
PROXIMATE CAUSE: During an early, critical developmental stage, the young
geese observe their mother moving away from them and calling.
ULTIMATE CAUSE: On average, geese that follow and imprint on their mother
receive more care and learn necessary skills, and thus have a greater chance of
surviving than those that do not follow their mother.
Figure 51.5
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Young Geese will Imprint on any large body
•  Konrad Lorenz
showed
–  When baby geese
spent the first few
hours of their life
with him
•  Conservation biologists have taken advantage
of imprinting
–  In programs to save the whooping crane from
extinction
–  They imprinted on
him as their parent
Figure 51.6
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Comparative Ethology
Directed Movements
•  Ethologists also demonstrated the relationships
between organisms and their similar behavior
patterns
•  Many animal movements
–  Geese and Ducks share similar sequences of
courtship behavior patterns
–  Are under substantial genetic influence
•  These types of movements
–  Are called directed movements
–  Behavior patterns are useful characters for
determining evolutionary relationships
(cladograms)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
8
Migration
Behaviorists and Learning
•  Many features of migratory behavior in birds
•  Behaviorists focused on learned behavior
–  Have been genetically programmed
•  Learning is the modification of behavior
–  Based on specific experiences with their
environment
•  Learned behavior
–  Ranges from very simple to very complex
Figure 51.8
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Associative Learning
•  In associative learning
–  Animals associate one feature of their
environment with another
–  Includes both
•  Classical Conditioning
•  Classical conditioning is a type of associative
learning
–  In which an arbitrary stimulus is associated
with a reward or punishment
–  Was pioneered by Ivan Pavlov (Russian)
•  Operant Conditioning
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pavlov and Classical Conditioning
Operant Conditioning
•  Pavlov paired
•  Operant conditioning is another type of
associative learning
–  An unconditioned stimulus: food
–  To a conditioned stimulus: a bell
–  In which an animal learns to associate one of its
behavior patterns with a reward or punishment
•  Dogs salivate when presented food,
–  An unconditioned response
•  Over time, the dogs began to salivate upon
hearing the bell
–  A conditioned response
Figure 51.16
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
9
Operant Conditioning
Genetic and Environmental Interaction in Learning
•  BF Skinner (American)
•  By the mid-20th Century
–  Shaped behavior by reinforcement:
•  Pigeons learned to peck keys in a complex
series of strikes against left and right keys
to receive a reward (usually food)
–  Claimed he could shape nearly any sequence
of behavior
–  Ethologists and Behaviorists were completely
at odds
•  Ethologists studied innate behavior,
determined in large part by their genes
•  Behaviorists studied learned behavior,
dependent on their environment
–  Nature vs. Nurture debate
–  Studies tested the importance of genes &
environment
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Limitations of Learning
Selection Shapes the ability to Learn
•  Some Conditioning studies produced odd
results
•  Subsequent studies demonstrated constraints
on behavior
•  Racoons are good ‘learners’
–  Quickly learn to put coins in a piggy bank to
earn a food reward
•  But instead of getting better with more trials
–  As raccoons associated the coins with food,
the less they would put the coins in the bank!
–  They rubbed them in their paws over & over
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Likely based on natural selection
•  Rats can associate food with nausea,
•  But not food with pain
–  Can associate sound with pain,
•  But not sound with nausea
•  Garcia et al 1974 (handout)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Dogs and Squirrels: differential learning
•  Dogs and Squirrels differ in their ability to find a
new pathway when the direct path is blocked
–  Dogs generally considered more ‘intelligent’
•  But cannot perform this task
–  Squirrels are expert in the task
–  Natural context
•  Dogs/wolves rarely limited in direct path
•  Squirrels regularly test possible paths along
branches between trees
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
10
Experience Shapes Behavior Patterns
Genetics and Learning Affect Behavior
•  Ethologists also became aware that many
‘Fixed Action Patterns’ may be modified, or
improved over time
•  Hybrid crosses in Lovebirds demonstrate
alternate forms of genes that determine how to
carry nest materials
•  ‘Modal Action Patterns’ describe the central
tendency of innate behavior patterns, but
•  Over time, hybrids learn to carry nest materials
(overhead, attached)
–  acknowledge small changes due to
environmental experience: learning
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
•  Conclude: Both Nature and Nurture affect
behavior (and most aspects of biology)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nature and Nurture influence Animal Behavior
•  Biologists concluded:
•  Environment, interacting with an animal’s
genetic makeup, influences the development of
behavior patterns
•  Research has revealed
–  That environmental conditions modify many of
the same behavior patterns, for example:
–  Diet affects mate selection by female
Drosophila mojavensis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Larval diet affects mate choice by D. mojavensis
EXPERIMENT
William Etges raised a D. mojavensis population from Baja California
and a D. mojavensis population from Sonora on three different culture media: artificial
medium, agria cactus (the Baja host plant), and organ pipe cactus (the Sonoran host
plant). From each culture medium, Etges collected 15 male and female Baja D.
mojavensis pairs and 15 Sonoran pairs and observed the numbers of matings between
males and females from the two populations.
RESULTS
When D. mojavensis had been raised on artificial medium, females
from the Sonoran population showed a strong preference for Sonoran males (a). When D.
mojavensis had been raised on cactus medium, the Sonoran females mated with Baja
and Sonoran males in approximately equal frequency (b).
100
With Baja males
(a)
Proportion of matings by
Sonoran females
With Sonoran
males
75
Modern Animal Behavior: Behavioral Ecology
•  Behavioral traits evolve by natural selection
–  Many behavior patterns have a strong genetic
component
–  Selection may also shape the way behavior
responds to the environment (e.g. learning)
(b)
•  Behavioral Ecologists study
50
25
0
Artificial
Organ pipe cactus
Agria cactus
Culture medium
–  How genes and the environment influence the
development and expression of behavioral
phenotypes
CONCLUSION
The difference in mate selection shown by females that developed on
different diets indicates that mate choice by females of Sonoran populations of D.
mojavensis is strongly influenced by the dietary environment in which larvae develop.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Under past and current selection pressure
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
11
Behavioral Variation allows for Selection
Behavioral Variation in Natural Populations
•  Behavioral traits can evolve by natural
selection
•  When behavioral variation within a species
–  Corresponds to variation in the environment,
it may be evidence of past evolution
•  Because of the influence of genes on behavior
–  But, correlation does not equal causation
–  Natural selection can result in the evolution of
behavioral traits in populations
–  Recall: Variation is necessary for selection
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Variation in Prey Selection
Variation in Predation Behavior
•  Differences in prey selection in populations of
garter snakes correlate with prey availability
•  Funnel spiders living in different habitats
–  Exhibit differing speed of attack at prey items
–  Evidence of behavioral evolution
Desert
grassland
population
Time to attack (seconds)
50
60
Riparian
population
40
30
20
10
0
Figure 51.18a, b
(a) A garter snake (Thamnophis
elegans)
(b) A banana slug (Ariolimus
californicus); not to scale
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Field
Lab-raised
generation 1
Lab-raised
generation 2
Population
Figure 51.19
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Behavioral Ecology
Behavioral Ecology: Four behavioral ‘needs’
•  Natural selection favors behavior that
increases 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, or the four ‘F’s’
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Behavioral Ecologists often group behavior
based on four ‘needs’:
1.  Feeding (foraging)
2.  Fleeing (predator avoidance)
3.  Fighting (over resources, mates, status)
4.  Reproduction: the ultimate measure of fitness
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
12
Modeling Behavior
Behavioral Models
•  Behavioral Ecologists assume that natural
selection has shaped behavior to maximize
fitness
•  Optimality models
•  Two common models used:
–  Optimality models
–  Assume organisms behave to maximize
some outcome, minimize some cost, or
achieve the most cost effective Trade-off
•  Game theory
–  Game theory models
–  Both evaluate the Trade-offs between Costs &
Benefits of behavioral alternatives
–  Evolutionarily Stable Strategies (ESS)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Evaluates alternative behavioral strategies
in situations where the outcome depends
on each individual’s strategy as well as the
strategy of other individuals (Sociobiology)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Foraging Behavior
Energy Costs and Benefits
•  Animals need to find and consume food items
to gain energy and other nutrients
•  Reto Zach
•  Optimal foraging theory
–  Views foraging behavior as a compromise
between the benefits of nutrition and the costs
of obtaining food:
–  Conducted a cost-benefit analysis of feeding
behavior in crows
•  The crows eat whelks (snails, molluscs)
–  But must drop them from the air to crack the
shells
•  Energy costs
•  Wear and tear of body parts
•  Risks of predation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Risk of Predation
–  indicating a trade-off between energy gained
(food) and energy expended
Average number of drops
30
75
Total flight height
20
Drop height
preferred
by crows
10
2
Figure 51.22
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
3
5
Height of drop (m)
50
7
15
25
Predation occurrence (%)
100
40
Predation
risk
Relative deer use
70
Total flight height (number of drops × drop height)
50
Average number of drops
–  Has shown that predation risk affects where
the deer choose to feed
125
60
0
•  Research on mule deer populations
60
20
15
50
40
10
30
20
Relative deer use
•  Zach found that the optimal flight height in
foraging behavior minimized ‘total flight height’
5
10
0
0
Open
Figure 51.24
Forest edge
Habitat
Forest interior
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
13
‘Fleeing’ - Predator Avoidance
Fleeing, or Predator Avoidance
•  The risk of predation affects feeding, fighting
and reproduction
•  The benefits of avoiding predation are obvious
•  Animals may flee out right:
•  The costs of fleeing = ‘time-out’ from other
activities
–  Swim, run, fly away
•  Or hide in grasses, trees, burrows, etc
–  Continued life vs. death (for most animals)
•  Optimal trade-offs:
–  How close to allow predator before avoidance?
–  If cryptic: need to behave like grass, tree, rock,
etc.
–  How long to ‘hide’ before returning to other
activity?
•  School & herd behavior
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Hermit Crabs as model systems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Fighting: Intraspecifc Conflict, Agonistic Behavior
Fighting: Trade-offs
•  Fighting occurs between conspecifics (mostly)
• 
–  Agonistic behavior
•  Animals fight over resources (benefits)
–  Food, Mates, other limiting resources, and
–  Status (social organisms; Sociobiology) determines access to other resources
Fights often Highly Ritualized
–  To reduce costs: energy and bodily harm
1.  Assessment:
• 
Size determines 90% of contests
2.  Escalation to full combat
3.  Appeasement
•  Costs range from minimal to extreme
–  Energetic expense, Debilitating injury, Death
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Fighting & Game Theory
Fighting: Trade-offs
•  Game theory
•  Game Theory: Hawks vs. Doves
–  Evaluates alternative behavioral strategies
in situations where the outcome depends
on each individual’s strategy as well as the
strategy of other individuals (Sociobiology)
–  Hawks vs. Doves
Payoff: Hawk
Dove
Hawk
-0.1
0
Dove
1.0
0.5
–  Hawks do better than doves, if hawks are rare
–  If hawks are common, the cost of fighting may
favor doves
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
14
Territoriality
Territories: Economic Defensibility
•  Many animals are Territorial
•  Because territories are defended spaces
•  A territory is any defended space
•  Various types of territories
–  Feeding territories
–  Mating territories
–  All purpose territories
–  They must ‘cost’ something
•  Models suggest territories will only occur if they
are
•  Economically Defensible, i.e. if: B > C
–  The benefit of holding the territory (resources)
is greater than the cost of defending it
–  Herbivorous fishes: parrotfish vs. damselfish
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mating Behavior and Mate Choice
Mating Systems and Mate Choice
•  Reproduction and Mating behavior
•  Mating relationships between males & females
–  Is shaped by both natural & sexual selection
•  Recall Anisogamy Theory
–  Different gametes lead to different strategies
Males are eager, Females are choosy
•  Other factors affect these patterns:
–  Population dispersion
–  Parental care of offspring (Parental Investment)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Varies a great deal from species to species
–  Depends on the interaction of mating
strategies by both sexes
•  Polygamy refers to ‘many gametes’ or multiple
partners:
–  Promiscuous, polygynous, polyandrous, or
polygynandrous
•  Monogamy refers to ‘single gametes’
–  Exactly one male and one female together
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Polygamy: Promiscuous
Polygamy: Polygyny
•  In many species, mating is promiscuous
•  Another common mating system is polygyny
–  With no strong pair-bonds or lasting
relationships
–  One male mates with many females
–  Males often showy and larger than females
–  Many marine animals are broadcast spawners
–  ‘Group grope’
–  Promiscuous mating systems are a form of
Polygamy:
•  some individuals mate with multiple partners
Figure 51.25b
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
(b) Among polygynous species, such as elk, the male (left) is
often highly ornamented.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
15
Polygamy: Polyandry
Polygynandry
•  Polyandrous systems are rare
•  Anisogamy theory suggests Polygyny should
be the most common mating system
–  One female mates with many males
–  The females are often more showy than the males
–  Note some males very successful (by sexual
selection), but others do not mate at all
•  Polygynandry is probably more common
–  Successful males mate with multiple females,
–  Females mate (over time) with multiple males,
As the ‘best’ male changes over time
Figure 51.25c
(c) In polyandrous species, such as these Wilson’s phalaropes, females
(top) are generally more ornamented than males.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Monogamy
Monogamy
•  Monogamous mating systems are rare
•  Exclusive Monogamy refers to repeated rounds
of reproduction with one mate for both sexes
–  One male mates with one female
•  Social Monogamy refers to species that
commonly occur in pairs
–  Commonly: Biparental-care Monogamy
–  Genetic studies have found that many Socially
Monogamous species are actually
Polygynandrous, e.g. most birds & humans
(a) Since monogamous species, such as these trumpeter swans, are
often monomorphic, males and females are difficult to distinguish
using external characteristics only.
–  Extra Pair Copulations sought by both sexes
Figure 51.25a
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Constraints on Mating: The Limiting Sex
•  Anisogamy theory is based on both the cost
and availability of gametes
•  However, in some cases males provide care
•  Which most affects mating strategies?
–  Energetic costs or Availability?
•  Pipefish Study:
–  Males are the Limiting Sex
•  The needs of the young
–  Are an important factor constraining the
evolution of mating systems
•  The certainty of paternity influences parental
care and mating behavior
–  Paternal care is rare with internal fertilization
(egg is fertilized in female’s reproductive tract)
–  Male’s cannot be certain of their paternity
–  Sex-role Reversal
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
16
Applying Game Theory
•  In species with external fertilization
–  Parental care is as likely to be carried out by
males as females
•  Game theory evaluates alternative behavioral
strategies in situations
–  Where the outcome depends on an individual’s
strategy and the strategy of other individuals
•  Alternative Reproductive Strategies are
wonderful examples of game theory in action
Eggs
–  Strategies may be genetically fixed, or
–  Conditional, the behavioral phenotype is
shaped by its environment
–  What alternative might evolve successfully?
Figure 51.26
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Game Theory & Mating Success
Alternative Reproductive Strategies: Fishes
•  Mating success of male side-blotched lizards is
influenced by male polymorphism (behavior &
color) and their relative abundance
•  Alternative Reproductive Strategies have been
studied in various fishes
- Orange dominates Blue dominates Yellow (sneaks)
–  Bluegill sunfish:
•  Males may be territorial, or
•  Sneakers: Satellites or Female mimics
–  Salmon: Hooknose males vs. Jacks
–  Many fishes are hermaphrodites
•  Sequential hermaphrodites (change sex)
•  Simultaneous hermaphrodites
Figure 51.32
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Why Change Sex?
Why Change Sex?
•  Selection will favor sex change if reproductive
success is greater as one sex when small, but
increases in the other sex at larger size
•  Graph: Reproductive Sex x Size
–  Protogyny
•  First Female, then Male
RS
–  Protandry
•  First Male, then Female
Body Size
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17
Sociobiology
Altruistic Behavior: Benefit to another, at some Cost
•  Sociobiology studies the behavior of social
animals
–  Similar in assumptions to Behavioral Ecology
–  Behavior is shaped by selection
•  Genes and Environment effect Phenotype
•  Natural selection normally favors selfish
behavior: passes on more genes
•  Kin Selection can explain some ‘unselfish’
behavior (altruism)
•  Hamilton’s rule: br > c
–  When the ‘benefit’ to the recipient
–  Multiplied by the coefficient of ‘relatedness’
–  Exceeds the ‘cost’ to the altruist
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Kin Selection vs. Altruism
•  The warning behavior observed in Belding’s
ground squirrels increases survival of kin
Reciprocal Altruism
•  Reciprocal Altruism is helping behavior toward
unrelated individuals
–  Can be adaptive if the aided individual returns
the favor in the future
–  Is rare and susceptible to cheating
Mean distance
moved from
natal burrow
(m)
300
Male
200
100
Female
0
0
2
3
4
Figure 51.35
12
13
14
15
25
26
Age (months)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Reciprocal Altruism
Social Learning
•  Reciprocal Altruism requires a set of four
conditions to allow its evolution & maintenance
(selection):
•  Social learning
–  Ability to Recognize Specific Individuals
–  Repeated Interactions with same Individuals
–  Many Opportunities to Help and be Helped
–  Ability to Punish Cheaters
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
18
Social Learning & Cultural Transmission
Sociobiology, Evolution and Human Culture
•  No other species comes close to the social
•  Human culture and evolutionary theory
learning & cultural transmission among humans
–  Is studied by the 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, e.g.
cultural transmission via books
•  We also exhibit much Reciprocal Altruism: Money
Figure 51.38
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Anthropomorphism
Anthropomorphism in Human Studies
•  Animal Behavior studies are particularly prone
to observer bias
•  The greatest bias may be in studies of human
behavior
–  We tend to ascribe purpose to the actions of
animals
–  Anthropomorphism is the attribution of humanlike qualities to animals, e.g. consciousness
–  Do we also ‘anthropomorphize’ ourselves?
–  We tend to ascribe consciousness to human
behavior patterns
•  However: consider how we make food choices
–  What thought processes led to your choice of
breakfast foods? The balance of amino acids?
•  How do we make our mate choices?
–  Teen pregnancy
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Human Sociobiology and Environmentalism
Sustainability
•  Much of our current environmental concerns are based
on over use of environmental resources and release of
waste: pollution
•  Sustainability is to meet the needs of the
present without compromising the ability of
future generations to meet their own needs.
(United Nations)
–  Overuse of Water: aquatic habitats & water tables
–  Loss of Agricultural land: limits food production
–  Overfishing: particularly ocean fishes (who regulates?)
–  Pollution: DDT/PCB’s, Metals, Nuclear Waste, etc.
–  Greenhouse gases & Global Climate Change
•  Most of these problems reflect choices that
–  Maximize Immediate Benefits (selfish)
–  But ignore longterm Costs (Altruism/Kin Selection)
–  Unsustainable!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
–  Reciprocal altruism?
•  Sustainability is achieved when all people on
Earth can live well without compromising the
quality of life for future generations. We do not
inherit the earth from our ancestors; we borrow
it from our children. (Native American Proverb)
–  Kin Selection?
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
19
Human Sociobiology and Environmentalism
Reciprocal Altruism & Fair Use
•  Reductions in resource use & pollution require
•  Enactment and Enforcement of Fair Laws can
and will Protect our Environment
–  Coordinated efforts by diverse human
populations and cultures must limit own use,
find/share alternate technology
•  But, Reciprocal Altruism is prone to Cheating
–  Tragedy of the Commons, Malthus
•  The solution to Cheating is Punishment
–  Charge for excess use of resources
–  Fine/punish cheaters
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
20