Behavior
Animal Types of behavior Inheritance of behaviors Selection on behaviors
Foraging Reproduction Social Behavior
Animals behave
Sexual selection
Male-male comptetion Female choice
Altruism
h ttp://plantsinmotion.bio.indiana.edu/plantmotion/movements/nastic/mimosa/strongmimosa.html
Do plants behave?
Proximate vs. Ultimate Causes of a Behavior
Behavioral ecologists distinguish between proximate and ultimate causes of behavior
Proximate causes: the immediate stimulus and mechanism for the behavior (proximate) Ultimate causes: How the behavior contributes to survival and reproduction (ultimate)
Some behaviors are hard-wired
A fixed action pattern (FAP)
Is a sequence of unlearned, innate behaviors that is unchangeable Once initiated, is usually carried to completion
In male stickleback fish, the stimulus for attack behavior
Is the red underside of an intruder
A FAP is triggered by an external sensory stimulus
Known as a sign stimulus
(a) A male three-spined stickleback fish shows its red underside.
Figure 51.3a
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When presented with unrealistic models
As long as some red is present, the attack behavior occurs
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.
(b) The realistic model at the top, without a red underside, produces no aggressive response in a male three-spined stickleback fish. The other models, with red undersides, produce strong responses.
PROXIMATE CAUSE: The red belly of the intruding male acts as a sign stimulus that releases aggression in a male stickleback.
Figure 51.3b
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.
Some behaviors have a learning component
Imprinting is a type of behavior
That includes both learning and innate components and is generally irreversible
Konrad Lorenz showed that
When baby geese spent the first few hours of their life with him, they imprinted on him as their parent
Imprinting is distinguished from other types of learning by a sensitive period
A limited phase in an animals development that is the only time when certain behaviors can be learned
There are proximate and ultimate causes for this type of behavior
BEHAVIOR: Young geese follow and imprint on their mother.
Conservation biologists have taken advantage of imprinting
In programs to save the whooping crane from extinction
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 Figure 51.6
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Migration
Many behaviors have a strong genetic component Biologists study the ways both genes and the environment
Influence the development of behavioral phenotypes
Many features of migratory behavior in birds
Have been found to be genetically programmed
Behavior that is developmentally fixed
Is called innate behavior and is under strong genetic influence
Figure 51.8
Birds placed in funnel cages
Left marks indicating the direction they were trying to migrate
Since the 1960s some Blackcaps from Europe have been wintering in Britain rather than their traditional wintering grounds in the western Mediterranean
N BRITAIN W
GER
E S MA NY N E S
Adults from Britain and F1 offspring of British adults
(a) B lackcaps placed in a funnel cage left marks indicating the direction in which they were trying to migrate.
(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.
Young from SW Germany
W
Mediterranean Sea
Figure 51.21a
Figure 51.21b
Animal Communication
In behavioral ecology
A signal is a behavior that causes a change in another animal s behavior
Auditory Communication
Experiments with various insects have shown that courtship songs are under genetic control
EXPERIMENT Charles Henry, Luca Martnez, and Kent H olsinger c rossed males and females of Chrysoperla plorabunda a nd C hrysoperla johnsoni, two morphologically identical species of lacewings that sing different courtship songs.
SONOGRAMS C hrysoperla plorabunda p arent
Communication
Is the reception of and response to signals
Volley period
Modes of communication
Visual, auditory, chemical, tactile, and electrical signals
Standard repeating unit crossed with Chrysoperla johnsoni p arent Volley period
Vibration volleys
The type of signal used to transmit information
Is closely related to an animals lifestyle and environment
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.
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Learning
RESULTS The F1 hybrid offspring sing a song in which the length of the standard repeating unit is similar to that sung by the C hrysoperla plorabunda p arent, but the volley period, that is, the interval between vibration volleys, is more similar to that of the Chrysoperla johnsoni p arent.
F1 hybrids, typical phenotype Volley period
Learning is the modification of behavior
Based on specific experiences
Standard repeating unit
CONCLUSION The results of this experiment indicate that the songs sung by C hrysoperla plorabunda and C hrysoperla johnsoni a re under genetic control.
Learned behaviors
Range from very simple to very complex
Operant conditioning is a type of associative learning
In which an animal learns to associate one of its behaviors with a reward or punishment
Cognition and Problem Solving
Cognition is the ability of an animals nervous system
To perceive, store, process, and use information gathered by sensory receptors
Figure 51.16
Problem solving can be learned
By observing the behavior of other animals
Behavior Evolves
Because of the influence of genes on behavior
Natural selection can result in the evolution of behavioral traits in populations
Food for thought: Can cultural traits evolve by natural selection?
Figure 51.17
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Behavioral Variation in Natural Populations
Coastal populations of garter snakes eat slugs Inland populations eat frogs, fish, etc. but no slugs Even newborn snakes follow this pattern
Rover - Sitter in Drosophila
Drosophila populations raised in high- and low-density conditions show a clear divergence in behavior linked to specific genes
Start with equal # rovers and sitters
Average path length (cm) 14 12 10 8 6 4 2 0 Low population density High population density
High/low density After 74 generations Evolution of behavior
(a) A garter snake (Thamnophis elegans)
Figure 51.20
(b) A banana slug (Ariolimus californicus); not to scale
L1
L2
L3
H1
H2
H3
H4
H5
Figure 51.18a, b
D. M elanogaster lineages
Foraging Behavior
Optimal foraging theory Views foraging behavior as a compromise between the benefits of nutrition and the costs of obtaining food Behaviors that maximize energy intake per unit time or per unit of energy spent will evolve
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
60 50 100 Average number of drops 40 30 Average number of drops Total flight height 20 10 0 Drop height preferred by crows 75 125 Total flight height (number of drops drop height)
Research on mule deer populations
Balancing Food Intake with Risk of Predation
Has shown that predation risk affects where the deer choose to feed
Relative deer use 70 60 Predation occurrence (%) 50 40 30 20 10 0 Open 0 Forest edge Habitat Forest interior 5 10 Predation risk 20
15 Relative deer use
50
2
Figure 51.22
3 5 Height of drop (m)
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15
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Figure 51.24
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Summary
There are proximate and ultimate causes of behaviors Behaviors often have a genetic basis Behaviors evolve to maximize fitness Foraging behavior maximizes energy intake while minimzing time, energy used, or predation risk
In many organisms, males and females different in or size ornamentation Sexual Dimorphism differences between sexes in traits not directly required for reproduction
peacocks
lions
spider
Why?
pheasants
Sexual Selection
Is a form of natural selection Concerns the evolution of traits that increase reproduction rather than survival In some cases, traits that increase reproductive success at the cost of reduced survival evolve. These are the traits Darwin thought of as sexually selected
Darwin asked, why is the peacocks tail so long?
The peacocks tail is long and showy The peahens isnt
How can the long tail evolve if it clearly makes the peacock more susceptible to predation? Why is it usually the case that the male is ornamented while, if the species is sexually dimorphic, the female is usually plain?
Batemans principle
Energetic cost of reproduction in males is low, relative to females
Sperm is cheap relative to eggs (anisogamy)
Males reproductive success generally increases with the number of mates Females reproductive success is limited by egg production and not by the number of mates Therefore, males should evolve traits that increase their access to females. Females should be choosy about with whom they will mate.
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Male-male competition may involve agonistic behavior
An often ritualized contest that determines which competitor gains access to a resource
Male-male competition (intrasexual selection) for access to females
Leads to large body size, antlers and other features useful in ritualized or real battles among males
Figure 51.30
Female choice (intersexual selection) leads to ornamentation of males,
Runaway sexual selection Good genes (honest signals)
Long-tailed widowbird extremely sexually dimorphic Why?
Long tails result of sexual selection
Purves figure p. 950
Experiment: lengthen tail shorten tail control Which males get mates? Conclusion - tail length result of sexual selection
Why would females choose such long tails? Offspring more vulnerable to predators? Many examples of sexual selection lead to weird, even deleterious (to survival) traits
Purves fig 53.3
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Female choice - why do females choose what they choose?
1. Good genes hypothesis 2. Runaway sexual selection
Good genes hypothesis: sexually selected trait is an honest indicator of overall good genes Females chose the mate they do because those mates are genetically superior, o ffspring will have higher fitness Example: Gray T ree frogs (Hyla versicolor) Eastern US
Breeding season - males call to attract females Some males have long songs with many trills, others - short calls Females choosy about calls
http://people.wcsu. edu/pinout/herpetology/hversicolor/difference.htm
play synthesized male songs for females in the lab
Female gray tree frogs strongly prefer males with longer songs Why? What is so great about long songs?
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Experimental test: Frogs have external fertilization researchers collected unfertilized eggs and controlled which males sperm fertilized them
Eggs got sperm from *long calling male, or * short calling male
Tadpoles got * high food diet, o r *low food diet Compare fitness of offspring
Measured components of fitness: growth
Conclusion - for all fitness measures, either no difference due to male parent or offspring of long callers (LC) did better
Gray tree frog females prefer males with longer songs Why? W hat is so great about long songs? Long songs are a honest indicator of overall good genes Support good genes hypothesis to explain why females choose mates they chose
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Different Types of Mating Systems 1. monogamy - one male and one female mate 2. polygamy - multiple mates a. polygyny - one male mates with multiple females b. polyandry - one female mates with multiple males
In monogamous relationships
One male mates with one female
(a) S ince monogamous species, such as these trumpeter swans, are often monomorphic, males and females are difficult to distinguish using external characteristics only.
Figure 51.25a
Monogamous species usually sexually m onomorphic. Both parents provide parental care.
In a system called polygyny
One male mates with many females The males are often more showy and larger than the females
In polyandrous systems
One female mates with many males
Each male incubates the eggs in his nest and cares for the young while the females go off in search of more males
The females are often more showy than the males
Figure 51.25b
(b) Among p olygynous species, such as elk, the male (left) is often highly ornamented.
Figure 51.25c
(c) I n polyandrous species, such as these Wilsons phalaropes, females (top) are generally more ornamented than males.
Sexual selection - s ummary 1. Why do males & females look so different? 2. Sexual selection - differential success in getting mates 3. Batemans principle - explains how sexual selection works When parental investment differs sex with greater investment - choosy (intersexual selection) sex with least investment - competes (intrasexual selection) 4. How do females choose? good genes runaway sexual selection 5. Mating systems - test of Bateman s principle
movie
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In naked mole rat populations
Altruism - how can it evolve?
Some animals help to rear offspring produced by others while not reproducing themselves Natural selection favors behavior
That maximizes an individuals survival and reproduction
Nonreproductive individuals may sacrifice their lives protecting the reproductive individuals from predators
How can helping evolve?
Follow the genes!
Figure 51.33
Florida Scrub Jays Helpers at the nest
Inclusive Fitness
Altruistic behavior can be explained by inclusive fitness
The total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables close relatives to produce offspring
Hamiltons Rule and Kin Selection
Hamilton proposed a quantitative measure
For predicting when natural selection would favor altruistic acts among related individuals Altruistic behavior will evolve when the benefit to the recipient, times its coefficient of relatedness to the giver, exceeds the cost to the giver. B = benefit = increase in reproductive success of the recipient C = cost = reduction in reproductive success of the giver r = coefficient of relatedness Condition favoring the evolution of altruistic behavior: rB > C
The three key variables in an altruistic act are
The benefit to the recipient The cost to the altruist The coefficient of relatedness
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The coefficient of relatedness
Is the probability that two relatives may share the same genes
Parent A Parent B
Natural selection favors altruism when the benefit to the recipient multiplied by the coefficient of relatedness exceeds the cost to the altruist This inequality (rB > C) is called Hamiltons rule Predictions:
Altruistic behavior should increase the reproductive success of the recipient
Experiment: compare productivity of nests with and without helpers
OR
Altruistic behavior more likely to evolve when giver and recipient are closely related
Experiment: are helpers related to those they help? Experiment: If a helper tries instead to reproduce, what is the outcome?
1
/2 (0.5) probability
Figure 51.34
1
/2 (0.5) probability Sibling 2
Cost to helper should be low
Sibling 1
Reciprocal Altruism
Kin selection is natural selection
That favors this kind of altruistic behavior by enhancing reproductive success of relatives Haldane remarked: I would gladly lay down my life for two brothers or eight cousins.
Altruistic behavior toward unrelated individuals
Can be adaptive if the aided individual returns the favor in the future
This type of altruism
Is called reciprocal altruism
Evolutionary psychologists, have found that women accord more importance to a man s financial prospects, social status, and age preferring men who are rich, of high social standing, and who are older than they are. Such men can make a greater parental investment and thus contribute to the success of their offspring. Men prefer women who are younger than they are (age being an indicator of fertility). Men also accord greater importance to physical beauty (an indicator of health) and to body shape (they prefer women with a waist-to-hip ratio of less than 70%, another fertility indicator). Of course, the human cortex, that generator and assimilator of human culture, adds other criteria for choosing a partner. But these predispositions from our evolutionary heritage can often still be discerned in our behaviour.
Human Sociobiology Proceed with caution!
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