BI158 Chapter 51 Animal Behavior
The How and Why of Animal Activity
Fiddlers crabs feed with their small claw and wave their large claw
Why do male fiddler crabs engage in claw waving behavior? What triggers it?
Claw waving is used to repel other males and to attract females
A behavior is an action carried out by muscles under control of the nervous system
Behavior is involved with feeding, reproduction, and maintain homeostasis
An animal’s physiology contributes to behavior, and behavior influences physiology
Behavior is a trait subject to natural selection like any other trait
Producing and responding to signals, like fiddler crabs, is a part of every animal’s life history.
Concept 51.1 Discrete sensory inputs can stimulate both simple and complex behaviors
Niko Tibergen identified four questions that should be asked about animal behavior
What stimulus elicits the behavior, and what physiological mechanisms mediate the response?
How does the animal’s experience during growth and development influence the response?
How does the behavior aid survival and reproduction?
What is the behavior’s evolutionary history?
Proximate causation address “how” a behavior occurs or is modified, including Tibergen’s question 1 and 2
Ultimate causation address “why” a behavior occurs in the context of natural selection, including Tinbergen’s questions 3 and 4
Behavior ecology is the study of the ecological and evolutionary basis for animal behavior
Behavior ecology integrates proximate and ultimate explanations for animal behavior
Fixed Action Patterns
A fixed action pattern is a sequence of unlearned acts directly linked to a simple stimulus
Fixed action patterns are unchangeable and, once initiated, usually carried to completion
A fixed action pattern is triggered by an external cue known as a sign stimulus
Tinbergen’s work with 3-spined sticklebacks illustrates this concept and Q1.
He observed male stickleback fish responding to a passing red truck in his office - and showed these fish responded to red in some situations.
In male stickleback fish, the stimulus for attack behavior is the red underside of an intruder.
When presented with unrealistic models the attack behavior occurs as long as some red is present.
Migration
Environmental cues can trigger movement in a particular direction, such as migration.
Migration is a regular, long-distance change in location engaged in by many animals
How do they find their way in unfamiliar settings?
Animals can orient themselves using, e.g.,
The position of the sun and their circadian clock (an internal 24-clock that is an integral part of their nervous system)
The position of the North Star (nocturnal animals)
Earth’s magnetic field (birds & fishes)
Behavioral Rhythms
Some animal behavior is affected by the animal’s circadian rhythm, a daily cycle of rest and activity
Behaviors such as migration and reproduction are linked to changing seasons, or a circannual rhythm
Although food availability may be a reason for migrating, it isn’t necessarily a cue for migration.
Day lengths are common seasonal cues
Some behaviors are linked to lunar cycles, which affect tidal movements
E.g. Fiddler crabs courtship behavior is linked with the lunar cycle
They court more (=reproduce more) prior to new and full moon phases
Why?
At these times, tides are at their greatest fluctuations, which gives hatched larvae a greater chance to disperse to deeper waters
Animal Signals and Communication
A signal is a stimulus transmitted from one animal to another.
Often, a signal is a behavior that causes a change in another animal’s behavior
Communication is the transmission and reception of signals, and plays a role in proximate causation of behavior
Forms of Animal Communication
Animals communicated using visual, chemical, tactile, and auditory signals
Fruit fly (Drosphila melangaster) courtship follows a three step stimulus-response chain.
A male identifies a female of the same species and orients toward her
Chemical
The male alerts the female to his presence
Tactile communication: he touches
Animals Signals
A signal is a stimulus transmitted from one animal to another
Often, a signal is a behavior that causes a change in another animal’s behavior
Communication is the transmission and recoption of signals, and plays a role in the proximate causation of behavoir
Forms of Animal Communications:
Animals communicate using visual, chemical, tactile, and auditory signals
Example: Fruit fly (Drosphila melanogaster) courtship follows a three-step stimulus
A male identifies a female of the same species and orients toward her
Chemical communication: he smells a female’s chemicals in the air to confirm her identity
Visual communication: he sees the female and orients his body toward him
The male alerts the female of his presence
Tactile communication: he touches the female with a foreleg
The male produces a courtship song to inform the female of his species
Auditory communication: fe extends and vibrates his wing
If all three steps are successful, the female will allow the male to copulate
Example: Honeybees
Honeybees show complex communication with symbolic language
This was discovered by karl von Frisch in the early 1900s
He used glass-walled hives to observe bee behavior
A bee returning from the field peforms a dance to communicate information about the distance and direction of a food source
Returning honeybees get the attention of “followers” by performing a dance
If the food is 50m from the hive, the bee does a “round dance” by moving in tight circles while waving its abdomen back and forth
When food is further than 50m, the bee does a waggle dance
A half circle swing in one direction
A straight run with waggling abdomen
Another half circle swing in another direction
The angle of the straight run, relative to the hive’s vertical surface is the same as the horizontal angle of the food in relation to the sun
If 30 degrees to teh right of the vertical, then followers fly 30 degrees from the angle of the sun
They may use odor or other cues as they approach
Pheromones
Many animals that communicate through odors emit chemical substances called pheromones
Pheromones are common among mammals and insects, and often related to reproductive behavoir
They can be used over short or long distances
We use pheromone traps to control some insect pests
For example:
A female moth can attract a male moth several kilometers distant
A honeybee queen produces a pheromone that affects the development and behavior of female workers and male drones
When a minnow or catfish is injured, an alarm substance in the fish’s skin disperses in the water, inducing a fright response among fish in the area
Pheromones can be effective at very low concentrations
For example
A 1cm^2 of minnow skin has enough alarm phenomone for 58,000 L of water
Nocturnal anmals, such as most terrestrial mammals, depend on olfactory and auditory communication
Diurnal animals, such as humans, and most birds, use visual and auditory communciation
Concept 51.2 Learning establishes specific links between experience and behavior
Innate behavior is developmentally fixed and does no vary among individuals
FAP (fixed action pattern) is one example of this
Sometimes we call these “closed genetic program” behaviors
Other behaviors can vary with experience, and may differ among individuals
Open genetic program (because our experience influences it)
Experience and Behavior
TInbergen’s Q2 refers to the impact of development and experience on behavior
Cross-fostering studies help behavioral ecologists to identify the contribution of environment to an animal’s behavior
A cross-fostering study places the young from one species in the care of adults from another species
The extent of how behavior changes give us a measure of how environment influence behavior
Example:
Studies of California mice and white-footed mice have uncovered an infleunce of social environment on agressive and parental behaviors
Cross-fostered mice developed some behaviors that were consistent with their foster parents
Ex. Male behavior (aggressiveness and parental care) followed the experiential model, and they may be passed on to future generations
Example:
In humans, twin studies allow researchers to compare the relative influences of genetics and environment on behavior
When identical twins (who are effectively clones) are reared apart we can compare with those reared together
Ex. such studies looked at alcoholism, eanxiety disorders, schizophrenia
Learning
Learning is the modification of behavior based on specific experiences
Capcaity to learn is dependent on the development of an organized nervous system
Process of learning involves formation of neural connection for each memory
Research into learning seeks to understand the contribution of both nature (genes) and nurture (environment) in shaping learning
Usually learning and behavior itself is determined by influence of both
Genes <——> Environment
Imprinting
Imprinting is the establishment of a long-lasting behavioral response to a particular individual or object
Imprinting includes learning and innate components and is generally irreversible
It is distinguished form othe rlearning by a sensititve period
A sensitive peroid is a limited developmental phase that is the only time when certain behaviors can be learned
If bonding doesn’t occur, offspring may die, and parents lose reproductive success
In many species of waterfowl, young birds don’t have an innate way to recognize mother—and indentidy with the first thing they encounter with certain characteristics
In the 1930s, Konrad Lorenz showed that when baby geese spent the first few hours of their life with him, they improinted on him as their parent
The imprint stimulus in greylag geese is a nearby object that is moving away from the young geese
Conservation biologists have taken advantage of imprinting in programs to save the whooping crane from extinction
When raising them with foster sandhill cranes, they were unable to recognize whooping cranes as mating partners
Young whooping cranes can imprint on humans in “crane suits” who then lead crane migrations using ultralight aircraft
Spatial Learning and Cognitive Maps
Spatial learning is a more complex modification based on experience with the spatial structure of the environment
Niko Tibergen showed how digger wasps use landmarks to find nest entrances
Tibergen manipulated objects around nest entrances
He found that they used these landmarks to find their nest when they returned
Thus, they perform spatial learning
A cognitive map is an internal representation of spatial relationships between objects in an animal’s surroundings
For example, Clark’s nutcrackers can find food hidden in caches located halfway between particular landmarks
They find them months later after hiding them in the fall for winter food
Associative Learning
Learning often involves making associateions between experiences
In associative learning, animals associate on efeature of their environment with another
For example, a blue jay will avoid eating monarchs and similar-looking butterflies after an experience with a distateful monarch butterfly
Classical conditioning is a type of associative learning in which an arbitrary stimulus is asscoiated with a reward or punishment
For example, Pavlov’s Dog
A dog that repeatedly hears a bell before being fed will salivate in anticipation at the bell’s sound
Operant conditioning is a type of associative learning in which an animal learn s to associate one of its behaviors with a reward or punishment
It is also called trial-and-error learning
For example, a rat that is fed after pushing a lever will learn to push the lever in order to receive food
There is some restriction to the type of associations that can be formed between environmental stimulus and behavior
For example: rates can learn to avoid illness-inducing foods on the basis of smells, but not on the basis of sights or sounds
Why this? Perhaps thos associations that cannot be formed are unlikely to be an advantage in nature
Cognition and Problem Solving
Cognition is a process of knowing that may include awareness, reasoning, recollection, and judgement
This is relatively complex form of learning, and it is used to thorugh that only primates and cetaceans can do this
However, many other animals, even insects, seem to exhibit such learning in the lab
For example, honeybees can distinguish “same” from “different”
Two groups of honeybees were trained in the color maze. They learned to associate food reward with an entrance stimulus that was either the same of different color as the arm entrance
They were then put into a bar maze (b&w patterns) and correctly chose same or different pattern, based on the previous training with colors
Hence, they are cognizant of using same or different in different contexts to make decisions
Problem solving is the process of devising a strategy to overcome an obstacle
Examples:
Chimpanzees can stack boxes in order to reach suspended food
Ravens obtained food suspended from a branch by a string by pulling up the string
Problem solving appears to be highly developed in some mammals (espeically primates & dolphins) and present in some birds (corvids—crows and ravans)
Development of Learned Behaviors
Development of some behaviors occurs gradually & in distinct stages
For example, a w hite-crowned sparrow male memorizes the song if its species during an early sensitive period (50 days), but does not sing it
The bird then learns to tsing the song during a sexond learning phase, when it sings a “subsong”
It compares the song it sings with the song it memorized as it practices until it “crystallines”
Song-learning isn’t necessarily the same in other birds. Canaries for example, may modify their songs between mating seasons
Social Learning
Social learning is learning throught eh observaiton of others through the observation of others and forms the roots of culture
Examples:
Young chimpanzees learn to crack palm nuts with stones by copying older chimpanzees
Young vervet monkeys learn from older monkeys to give and respond to distinct alarm calls for different predators
Infant vervets give general alarm calls
Culture is a system of information transfer through observation or teaching that influences behavior of individuals in a populationn
Culture vs. Natural Selection
Culture can alter behavior and influence the fitness of individuals in relatively short time
Natural selection’s influence on behavior happens in relatively long time frames
Concept 51.3 Selection for individual survival and reproductive success can explain diverse behaviors
Behavior enhances surivial and reproductive success in a population (Q3)
Ex. Natural selection refines behaviors that enhance the efficieny of feeding
Foraging, or food-obtaining behavior, includes recognizing, searching for, capturing, and eating food items
capturing, and eating food items
Evolution of Foraging Behavior
In Drosophila, variation in a single gene (for^R & for^S) dictates foraging behavior in the larvae
Larvae with for^R allele travel farther while foraging than larvae with the for^S allele
Larvae in high-density populations benefit from foraging farther for food, while larvae in low-density populations benefit from short-distance foraging
Natural selection favor different alleles (for^R and for^S) depending on the density of the population
Under laboratory conditions, evolutionary changes in the frequency of these two alleles were observed over several generations
Optimal Foraging Model
Optimal foraging model view foraging behavior as a compromise between benefits of nutrition and costs of obtaining food (a cost-benefit analysis)
It’s an economic approach to look at ultimate causation
The costs of obtaining food include energy expenditure and the risk of being eaten while foraging
Natural selection should favor foraging behavior that minimizes the costs and maximizes the benefits
Evolution and Human Culture
Human culture is related to evolutionary theory in the distinct discipline of sociobiology
Human behavior, like that of other species, results from interaction 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
Another example of mate choice by females occurs in zebra finches
Female chicks who imprint on ornamented fathers are more likely to select ornamented mates
Experiments suggest that mate choice by female zebra finches has played a key role in the evolution of ornamentation in male zebra finches
Balancing Risk and Reward
Risk of predation affects foraging behavior
E.g., mule deer are more likely to feed in open forested areas where they are less likely to be killed by mountain lions
E.g., Northwestern crows choose a drop height which takes the fewest times to crack a whelk
Mating Behavior and Mate Choice
Mating behavior and mate choice play a major role in determining reproductive success
Mating behavior includes seeking or attracting mates, choosing among potential mates, competing for mates, and caring for offspring.
Who is the choosiest sex?
Which sex has the most to gain or lose by being choosy?
Mating Systems and Sexual Dimorphism
Mating relationships define a number of distinct mating systems
In some species, mating is promiscuous, with no strong pair-bonds or lasting relationships
Other species form monogamous relationships where one male mates with one female
Males and females with monogamous mating systems tend to have similar external morphologies
In polygamous relationships, an individual of one sex mates with several individuals of the other sex
Species with polygamous mating systems are usually sexually dimorphic: males and females have different external morphologies
Polygamous relationships can be either polygynous or polyandrous
In polygyny, one male mates with many females
The males are usually more showy and larger than the females
Polygyny is the most common mating system in animals - why?
In polyandry, one female mates with many males
The females are often more showy than the males
This is a very rare mating system in animals.
Mating Systems and Parental Care
Needs of the young are an important factor constraining evolution of mating systems
The amount of parental care needed (and who gives it) factors in mating systems.
Consider bird species where chicks need a continuous supply of food
A male maximizes his reproductive success by staying with his mate and helping care for his chicks (monogamy)
Consider bird species where chicks are soon able to feed and care for themselves
A male maximizes his reproductive success by seeking additional mates (polygyny)
Certainty of paternity influences parental care and mating behavior
Females can be certain that eggs laid or young born contain her genes; however, paternal certainty depends on mating behavior
Paternal certainty is relatively low in species with internal fertilization because mating and birth are separated over time
Male-only parental care is relatively rare in mammals & birds
Certainty of paternity is much higher when egg laying and mating occur together, as in external fertilization
In species with external fertilization, parental care is at least as likely to be by males as females
<10% of fishes & amphibians with internal fertilization have parental care.
>50% of those with external fertilization have parental care.
Certainty or paternity isn’t necessarily a conscious thing.
Sexual Selection and Mate Choice
Sexual dimorphism results from sexual selection, a special form of natural selection that deals with reproductive success
In intersexual selection, members of one sex choose mates on the basis of certain traits
Intrasexual selection involves competition between members of the same sex for mates
Mate Choice by Females
Female choice is a type of intersexual selection
Females can drive sexual selection by choosing males with specific behaviors or features of anatomy
For example, female stalk-eyed flies choose males with relatively long eyestalks
Ornaments, such as long eyestalks, often correlate with health and vitality.
Mate-choice copying is a behavior in which individuals copy the mate choice of others
For example, in an experiment with guppies, the choice of female models influenced the choice of other females
If a female guppy observed a model female courting a drab male, she often copied the preference of the model female
However, it didn’t occur when differences between males was more marked
Male Competition for Mates
Male competition for mates is a source of intrasexual selection that can reduce variation among males
Such competition may involve agonistic behavior, an often ritualized contest that determines which competitor gains access to a resource
Applying Game Theory
In some species, sexual selection has driven the evolution of alternative mating behavior and morphology in males.
The fitness of a particular phenotype (behavior or morphology) depends on the phenotypes of other individuals in the population
Game theory (John Nash, Beautiful Mind) evaluates alternative strategies where the outcome depends on each individual’s strategy and the strategy of other individuals
For example, each side-blotched lizard has a blue, orange, or yellow throat
Each color is associated with a specific strategy for obtaining mates
Orange-throat males are the most aggressive and defend large territories
Blue-throats defend small territories
Yellow-throats are nonterritorial, mimic females, and use “sneaky” strategies to mate
When blue are abundant, they can defend a few females in their territories from sneaky yellow throats, but orange throats can overwhelm them.
When orange are abundant, they have more females in their territories; the yellow throats can gain greater success by sneaking
When yellow are more abundant, blue have an advantage by being able to defend their territories and females
Like rock-paper-scissors, each strategy will outcompete one strategy but be outcompeted by the other strategy
The success of each strategy depends on the frequency of all of the strategies; this drives frequency-dependent selection
Concept 51.4: Genetic analyses and the concept of inclusive fitness provide a basis for studying the evolution of behavior
Animal behavior is governed by complex interactions between genetic and environmental factors
Selfless behavior can be explained by inclusive fitness (personal fitness plus that of close relatives)
Genetic Basis of Behavior
A master regulatory gene can control many behaviors
For example, a single gene (fru) controls many behaviors of the male fruit fly courtship ritual
If fru is mutated to an inactive form, males don’t court or mate with females.
If females express the male fru, they court other females
Hence, fru oversees a lot of male specific wiring of the nervous system
Variation in the activity or amount of a gene product can have a large effect on behavior
For example, male prairie voles pair-bond with their mates, while male meadow voles do not (and provide little care for pups)
The level of a specific receptor for a neurotransmitter (vaspressin) determines which behavioral pattern develops
Vasopressin is released during mating and binds to receptors in the male brain. More receptors, more pair-bonding
Genetic Variation and the Evolution of Behavior
When behavioral variation within a species corresponds to environmental variation (within populations), it may be evidence of past evolution and natural selection.
Case Study: Variation in Prey Selection
The natural diet of western garter snakes varies by population
Coast populations feed mostly on abundant banana slugs, while inaldn populations do not eat banana slugs, which are rare in their habitat
The differences in diet are genetic
The two populations differ in their ability to detect and respond to specific odor molecules produced by the banana slugs
Case Study: Variation in Migratory Patterns
Most blackcaps (birds) that breed in Germanyy winter in Africa, but some winter in Britain
Under laboratory conditions, each migratory population exhibits different migratory behaviors
The migratory behaviors reflect genetic differences between populations
Altruism
Natural selection favors behavior that maximizes an individual’s survival and reproduction
These behaviors are often selfish
On occasion, some animals behave in ways that reduce their individual fitness but increase the fitness of others
This kind of behavior is called altruism
E.g., under threat from a predator, an individual Belding’s ground squirrel will make an alarm call to warn others, even though calling increases the chances that the caller is killed
E.g., in naked mole rat populations, nonreproductive indivudals may sacrifice their lives protecting their reproductive queen and kinds from predators
Inclusive Fitness
The evolution of altruistic behavior can be explained by inclusive fitness
Inclusive fitness is the total effect of an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring
Hamitlon’s Rule and Kin Selection
William Hamiton proposed a quantitative measure for predicting when natural selection would favor altruistic acts among related individuals
Three key variables in an altruistic act
Benefit to the recipient (B)
Cost ot the altruistic ©
Coefficeint of relatedness (the fraction of genes that, on average, are shared, r)
Natural selection favors altruism when
rB>C
This inequality is called Hamilton’s rule
Hamilton’s rule is illustrated with the following example of a girl who risks her life to save her brother
Assume the average individual has two children; as a result of the sister’s action
The brother can now father two children so B=2
The sister has a 25% chance of dying and not being able to have two children, so C=0.25 x 2 = 0.5
The brother and sister share half their genes on average, so r = 0.5
If the sister saves her brother rB(=1) > C(=0.5)
Kin selection is the natural selection that favors this kind of altruistic behavior by enhancing reproductive success of relatives
An example of the relationship between kin selection and altruism is the warning behavior in Belding’s ground squirrels
In a group, most of the females are closely related to each other
Most alarm calls are given by females who are likely aiding close relatives
Another example of kin selection comes from naked mole rats - they live colonies and are closely related to each other.
One queen, 1-3 “kings who mate with her.
Non-reproductive individuals increase their inclusive fitness by helping the reproductive queen and kings (their close relatives) to pass their genes to the next generation
Reciprocal Altruism
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
Reciprocal altruism is limited to species with stable social groups where individuals meet repeatedly, and cheaters (who don’t reciprocate) are punished
Reciprocal altruism has been used to explain altruism between unrelated inidividuals in humans
In game theory, a tit-for-tat strategy has the following rules
Individuals always cooperate on first encounter
An individual treats another the same way it was treated the last time they met
That is, inidivudals will always cooperate, unless their opponent cheated them the last time they met
Tit-for-tat strategy explains how reciprocal altruism could have evolved
Individuals who engage in a tit-for-tat strategy hav a higher fitness than indiivduals who are always selfish
Evolution and Human Culture
No other species comes close to matching the social learning and cultural transmission that occur among humans
We are better at acquiring new skills than any animal
Not all of our activities seem to have a survival or reproduction role
Play behavior may improve our ability to use objects and develop social skill, or prepare us to handle unexpected events
Human culture is related to evolutionary theory in the distinct discipline of sociobiology
Human behavior, like that of other species, results from interaction 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