CHAPTER 50 LECTURE NOTES
Behavior is influenced by innate and learned factors.
Innate = Inborn or present at birth.
Behavior = What an animal does and how it does it.
Fitness is a central concept in animal behavior. Since natural selection works on genetic variation caused by mutation and recombination, organisms should have features that maximize fitness over time. Animals are expected to engage in optimal behaviors.
Optimal behavior = A behavior that maximizes individual fitness.
Experiment: Two species of lovebirds were interbred. Female fischer's lovebirds cut long strips of nesting material which are carried individually to the nest. Female peach-faced lovebirds cut short strips and carries several at a time by tucking them into her back feathers.
Learned behaviors are typically based upon gene created neural systems that are receptive to learning.
Behavioral ecologists assume optimal behavior increases fitness.
Behavioral ecology: = A field of study that assumes animals increase fitness through optimal behavior.
Because behavior is assumed to increase fitness, questions about ultimate causation, or the reasons why behaviors exist are evolutionary questions.
Ultimate causation = The evolutionary reason for the existence of a behavior.
The immediate mechanism or how a behavior is expressed is the proximate cause. Proximate causes may be internal processes or environmental stimuli.
Proximate causation = The immediate cause and/or mechanism underlying a behavior.
Example: Behavior- Bluegill sunfish breed in spring and early summer.
Proximate cause: Breeding is triggered by the effect of increased day length on a fish's pineal gland.
Ultimate cause: Breeding is most successful when water temperatures and food supplies are optimal.
Example: Behavior- Human "sweet tooth".
Proximate cause: Sweet taste buds are a proximate mechanism that increases the chances of eating high-energy foods.
Ultimate cause: Sweet, high-energy , foods were rare prior to mechanized agriculture.
Increased fitness associated with consuming these foods is the ultimate reason for the natural selection of a "sweet tooth".
Ethology pre-dates behavioral ecology .Relying on descriptive studies, ethologists discovered many behaviors were innate.
Ethology = Descriptive science based on studies of animals in the natural environment.
Innate behaviors may seem purposeful, but animals with innate behaviors are unaware of the significance of their actions.
Konrad Lorenz, Niko Tinbergen and Karl von Frisch shared the 1973 Nobel Prize for physiology or medicine for their work in ethology.
A. Fixed-Action
Patterns
The most fundamental concept in classical ethology is the fixed-action pattern (F AP).
Fixed-action pattern = A highly stereotyped, innate, behavior.
Sign stimulus = An external sensory stimulus which triggers a fixed-action pattern.
Example: Niko Tinbergen noticed male three-spined stickleback fish responded aggressively to red trucks passing by their tank.
Fixed-Action Pattern: Male sticklebacks attack other males that enter their territories.
Sign stimulus: The red belly of the invading male. Sticklebacks attacked nonfish-like models with red on the ventral surface.
Example: Parent/young feeding behavior in birds.
Fixed-Action Pattern: The begging behavior of newly hatched chicks (raised heads, open mouths, loud cheeps).
Sign stimulus: Parent landing at the nest.
Example: Greylag goose egg retrieval behavior: (See Campbell, Figure 50.6)
Fixed-Action Pattern: Rolls the egg back to the nest using side-to-side head motions.
Sign stimulus: The appearance of an object near the nest.
Example: Protective behavior in hen turkeys:
Fixed-Action Pattern: Mothering behavior.
Sign stimulus: Cheeping sound of chicks.
Example: The human infant grasping response is a fixed-action pattern released by a tactile stimulus. Human babies smile when they hear certain sounds, or see a figure consisting of two dark spots on a circle (rudimentary representation of a face).
Example: Female digger wasps place a paralyzed cricket in their nests which serves as food for the young wasp after it hatches.
Fixed-Action Pattern: She places the cricket 2.5 cm from the nest.
Sign stimulus: Nest site.
Fixed-Action Pattern: She enters the nest and inspects it.
Sign stimulus: Presence of cricket 2.5 cm from nest.
Fixed-Action Pattern: She exits the nest and retrieves the cricket.
Sign stimulus: Presence of cricket 2.5 cm from nest.
B. The Nature of Sign
Stimuli
Sign stimuli are usually simple characteristics ( e.g. ultrasonic bat sounds trigger avoidance behavior in moths).
Sign stimuli may be specific choices from an array of possibilities.
Example: Herring gull chick feeding behavior. The adult lowers its head and moves its beak. The chick pecks the red spot on the beak, causing the adult to regurgitate.
Fixed-action pattern: Pecking the red spot on the beak.
Sign stimulus: Red spot swung horizontally at the end of a long, vertical object.
Natural selection favors cues associated with the relevant behavior or object. Some randomness is probable in fixing upon one of many possible sign stimuli for a F AP .
An animal's sensitivity to general stimuli and its sign stimuli are correlated.
A supernormal stimulus may elicit stronger responses than natural stimuli.
Supernormal stimulus = Artificial stimulus that elicits a stronger response than occurs naturally.
V. Learning is
experience-based modification of behavior
Learning = The modification of behavior by experience.
A. Nature Versus
Nurture
While European ethologists were discovering innate behaviors in nature, American psychologists were finding learning abilities in lab animals. Thus began the debate over nature versus nurture.
Nature versus nurture = The debate over whether instinct or learning is of primary importance in animal behavior.
Some behavioral aspects seem to be due primarily to either instinct or learning.
B. Learning Versus
Maturation
Individuals may improve behaviors over time. This is often attributed to learning but, in some cases, may be due to developmental changes in neuro-muscular systems as animals mature.
Maturation = Development of neuro-muscular systems that allows behavioral improvement.
C. Habituation
Animals stop responding to stimuli that do not provide appropriate feedback.
Habituation = Learning to ignore irrelevant stimuli or stimuli that do not provide proper feedback.
D. Imprinting
Imprinting is a form of learning closely associated with innate behavior.
Konrad Lorenz conducted an experiment with greylag geese. (See Campbell, Figure 50.8)
Experiment: A clutch of goose eggs was divided between the mother and an incubator.
Results: Goslings reared by the mother behaved normally and mated with other geese.
The incubator goslings spent their first hours of life with Lorenz and preferred
humans for the rest of their lives. They even tried to mate with humans.
Conclusions: Greylags have no innate sense of "mother" or "gooseness". They identify with and respond to the first object with certain characteristics they encounter. The ability or tendency to respond is innate.
Imprinting stimulus = An object in the environment to which the response is directed.
1. Critical Period
Critical period = A limited time during which imprinting can occur.
2. Song Development
in Birds: A Study of Imprinting
Song development is highly responsive to selective pressures.
In male white-crowned sparrows:
Song development may be more or less fixed in other species:
E. Classical
Conditioning
Associative learning = The learning process where animals associate one stimulus with another.
Classical conditioning is a type of associative learning where a specific, or conditioned, response is elicited by a specific stimulus.
Classical conditioning = A process in which an animal learns to respond to an external stimulus which does not normally elicit that response.
F. Operant
Conditioning
Operant conditioning, or trial-and-error learning, is another type of associative learning.
Operant conditioning = A process where an animal learns to associate one of its behaviors with a reward or punishment and then tends to repeat or avoid that behavior.
Operant conditioning is the basis for most animal training and is common in nature-
G. Observational
Learning
Observational learning = The ability of animals to learn by observing the actions of others.
H. Play
Play has no apparent goal but uses movements closely associated with goal-directed behaviors.
Play is potentially dangerous or costly.
What is the selective
advantage of play?
I. Insight
Insight learning is also called reasoning.
Insight learning = The ability of animals to perform appropriate behaviors on the first attempt in situations with which they have no prior experience.
J. Animal Cognition
Cognition = Knowing, including awareness and judgment.
Behaviorism = A mechanistic approach which describes behavior in terms of stimulus and response.
Cognitive ethologists think cognitive ability arises through natural selection and forms a
phylogenetic continuum stretching into evolutionary history .
Cognitive ethology = A view that sees conscious thinking as an inherent part of animal
behavior.
VI. Rhythmic
behaviors synchronize an animal's activities with daily changes in the
environment
Animals repeat behaviors at regular intervals (daily, seasonally).
Animals carry out behaviors when their particular ecological niches can be exploited most profitably from a survival and fitness standpoint. This can cause behavioral rhythms.
The proximate bases for rhythms are not obvious.
Experiment: Flying squirrels are normally active at night. Flying squirrels were placed in constant darkness and their activity monitored. (See Campbell, Figure 50.13)
Results: Rhythmic activity continued. Since normal cycles deviate from the 24 hour clock, the test squirrels eventually were out of phase with the environment.
Conclusions: Biological clocks are intrinsic, but the timing of rhythmic behavior must be adjusted to environmental cues to remain in sync.
Even when endogenous factors are present, the internal, proximate, timing mechanism is unknown. A biochemical, possibly molecular, clock has been hypothesized.
It is unclear if endogenous clocks are important in longer cycle rhythmic behaviors. Breeding and hibernation are partially based on physiological and hormonal changes linked to exogenous factors such as day length.
VII. Environmental
cues guide animal movement
Studies have concentrated on the proximate mechanisms animals use to detect and respond to external cues that guide movements.
The ultimate bases for oriented movements are related to animal adaptations to different environments and the development of behaviors that bring them to those environments at the proper time of the year.
A. Kinesis and Taxis
Animals use a variety of cues to guide them in their movements.
Kinesis involves a change in activity rate in response to a stimulus.
Kinesis = A randomly directed change in activity fate in response to an environmental stimulus.
Taxis is a directed movement toward or away from a stimulus.
Taxis = A semi-automatic, oriented, movement toward or away from a stimulus.
B. Migration Behavior
Migration is the most commonly known type of oriented animal movement.
Migration = The seasonal movement of animals over relatively long distances.
Migrating animals use three mechanisms: piloting, orientation and navigation.
Piloting = Movement of animals from one landmark to another.
Orientation = Movement of animals along a compass line.
Navigation = The ability of animals who can orient along compass lines to determine their location in relation to their destination.
VIII. Behavioral
ecologists are using cost/benefit analysis to study foraging behavior
Generalists feed on many items. They are not efficient collectors of any single food, but take advantage of multiple options when foods are scarce.
· Generalists concentrate on abundant prey.
· Generalists develop a search image for a favored item. If the item becomes scarce, a new search image is developed. Search images let generalists combine efficient short-term specialization with generalist flexibility .
Search image = The ability of a generalist feeder to learn the key visual characters of a prey item.
Specialists feed on specific items and usually have highly specific morphological and behavioral adaptations. They are extremely efficient foragers.
Food habits are fundamental to an animal's niche and may be shaped by interspecific competition and evolutionary factors.
Natural selection should favor foraging strategies that maximize gains and minimize costs in terms of calories gained and expended. Other criteria such as nutrient gain may be equally important.
· Foraging costs include: energy needed to locate, catch and eat food; the risk of being caught by a predator while feeding; time taken from other activities such as courtship and breeding.
· Behavioral ecologists analyze tradeoffs to predict optimal foraging strategies-
· Tradeoffs include density and size of prey versus foraging distances or prey catchability .
· For example, small mouth bass eat minnows and crayfish. Since no preference is shown, each may be optimal under different conditions. Minnows have more useable energy per unit weight than crayfish, but are harder to catch. Crayfish are easier to catch, but more difficult to subdue.
Animals modify behavior to keep the ratio of energy gain to loss high.
· This ability is probably innate, although learning may be involved.
Experiment: Bluegill sunfish eat small crustaceans. (See Campbell, Figure 50.16) Optimal foraging theory predicts the proportion of small to large prey will vary with the density of the prey population. At low densities, sunfish should not be selective but at high densities, they should concentrate on larger prey.
Results: Sunfish were more selective at higher prey densities, but not to the extent predicted. Young fish were less efficient than adults. Younger fish may be less able to judge size and distance due to incompletely developed neural systems.
Conclusion: Maturation and learning may result in increased foraging efficiency in adults.
Most sexually reproducing species must be social for part of their life cycle in order to reproduce; some species spend most of their lives in close association with conspecifics.
Social behavior = Any interaction between two or more animals, usually of the same species.
· Includes aggression, courtship, cooperation, and even deception.
· Has both costs and benefits to members of species that interact extensively.
Sociobiology = Study of social behavior that has evolutionary theory as its conceptual framework.
· In 1975, E.O. Wilson published Sociobiology: The New Synthesis which helped form sociobiology into a coherent method of analysis and interpretation.
· From the sociobiologist's point of view, the genetic basis of behavior and fitness can be used to analyze the evolution and maintenance of social behavior.
Because members of a population share a common niche, there is potential for conflict, especially among members of species that maintain densities near carrying capacity.
· Sometimes social behavior involves cooperative effort, as when a group accomplishes something more efficiently than a single individual.
· Even when cooperation seems to be mutually beneficial, each participant usually acts to maximize its fitness, even at a cost to the other participant.
Agonistic behavior = A contest of threat displays which continues until a participant submits and yields access to a resource (e.g. mate, food, territory).
· Ritual behaviors are prevalent so it is rare that participants are seriously injured. (See Campbell, Figure 50.18)
Ritual = Symbolic behavior that minimizes the possibility of serious injury to the antagonists.
· Natural selection favors ending a contest as soon as a winner is established because further conflict could injure the victor as well as the vanquished-
· Canines show agonistic behavior by trying to look larger. They bare teeth; erect ears, tail and fur; stand upright; and make eye contact. The loser submits by sleeking its fur, tucking its tail and looking away.
The top ranked member of a social group controls the behavior of the members of the group. The second ranked animal controls everyone except the top individual and so on down the line to the lowest ranked animal.
Dominance hierarchy = A linear social organization within a group.
· Top ranked animals are assured access to resources. Low ranked animals do not waste energy or risk harm in combat.
· Wolf packs typically have a female dominance hierarchy. The top female relies on food availability to control mating in the pack.
Territories are defended areas typically used for feeding, mating, rearing young etc.
Territory = An area defended from conspecifics.
· Territory size varies with the species, territory function, and the amount of resources available. (See Campbell, Figure 50.19)
· Some species defend territories during the breeding season and form social groups at other times of the year.
· Territories are not home ranges. Home ranges are areas which animals inhabit but do not defend. Territories and home ranges may overlap.
Territories are usually successfully defended by their owners.
· Owners usually win because a territory is more valuable to the owner since he is familiar with it.
· Ownership is continually proclaimed -a primary function of bird song, red squirrel chattering and the bellowing of sea lions. Others use scent marks or patrols to announce their presence. (See Campbell, Figure 50.20)
· Defense is usually directed at conspecifics who are most likely to compete directly for the same resources.
Dominance hierarchies and territoriality tend to stabilize population densities by assuring enough individuals reproduce to result in relatively stable populations from year to year.
The correlation between mating behavior and reproductive fitness is vital to behavioral ecology.
Species often have a complex courtship ritual unique to that species.
· Courtships are a series of fixed-action patterns alternately triggered by the participants.
· Ritual courtships probably evolved from behaviors that once had a direct meaning.
For example, male balloon flies spin oval silk balloons which they carry while flying in a swarm. The swarm is approached by females seeking mates. A female accepts a male's balloon when they fly off to copulate.
· In a related species, the male brings a dead insect for the female to eat while they mate.
· In another species, the insect is presented inside a silk balloon, possibly because silk helps subdue the insect or makes it look larger .
· Balloon flies eat nectar .The ritual has evolved into bringing something that was once associated with food.
· It is as if, over evolutionary time, a suitor wooed a lady with diamonds, then with a box containing diamonds and finally with an empty box.
Courtship assures each partner that the potential mate is not a threat, is the proper species, the proper sex and in the correct physiological condition.
· Courtship may allow one or both sexes to choose a mate from a number of candidates.
Females are usually more discriminating than males because they normally have a greater parental investment.
· Eggs are usually larger and more costly to produce than sperm-
· Gametes of placental mammals are closer in size, but females invest considerable time and energy carrying young before birth.
Parental investment = The time and resources an individual expends to produce an offspring.
Competition among individuals of the same sex (usually males) may determine which individuals of that sex will mate.
· Most inales mate with as many females as possible: They compete with other males for mates and may try to impress females.
· Males perform more intense courtship displays than females.
· Secondary sex characteristics may be highly developed in males (e.g. deer antlers, bird colors).
There are two ultimate bases for mate selection.
1. If the other sex gives parental care, it is best to choose the most competent mate.
· For example, male common terns bring fish to potential mates as part of the courtship ritual. This behavior may be a proximate indicator of his ability to feed the chicks.
· Some females prefer males with the most extreme and energetic courtship displays or secondary sex characteristics. These characteristics may be proximate indicators of the male's health.
2. Genetic quality is important when males provide no parental care and sperm are their only contribution to offspring.
· Lek species have a communal area where males display. Females visit the lek and choose a mate. The proximate basis for her choice is a preference for males that court the most vigorously and have the most extreme secondary sex characteristics.
It may be difficult to determine if differential mating success among males is due to male-male competition, female choice or both.
· Three-spined stickleback courtship is based on stereotyped releasers and F APs. (See Campbell, Figure 50.21) Despite this, the female can back out of the courtship anytime.
· Female choice is probably ultimately based on the quality of the male's parental care, because only male sticklebacks give parental care.
Promiscuous = A mating system with no strong pair-bonds or lasting relationships.
Monogamous = A mating system where one male mates with one female.
Polygamous = A mating system where an individual of one sex mates with several of the other.
· Polygyny is a mating sub-system where one male mates with multiple females.
· Polyandry is a mating sub-system where one female mates with multiple males.
The needs of the young are an important ultimate factor in the evolution of mating systems.
· Most birds are monogamous. Young birds often require significant parental care. A male may ultimately increase his reproductive fitness by helping a single mate rear a brood than by seeking additional mates.
· Polygyny is common in birds where the young are able to care for themselves soon after hatching. Males can maximize their fitness by seeking additional mates.
Another factor influencing mating systems and parental care is the certainty of paternity.
(See Campbell, Methods Box, page 1197)
· Young born or eggs laid by a female definitely contain the female's genes, but even in monogamous species, the young could have been fathered by a male other than the female's normal mate.
· The certainty of paternity is relatively low in species with internal fertilization because mating and birth ( or egg laying) are separated over time. Exclusive male parental care is rare in birds or mammals.
· Certainty of paternity is higher when egg laying and mating occur together, as in external fertilization. Parental care, when present, in fishes and amphibians is as likely to be by males as by females.
· When parental care is given by males, the mating system may be polygynous with multiple females laying eggs in a nest tended by a male.
Communication = The intentional transmission of information between individuals.
Behavioral ecologists assume communication has occurred when an act by a "sender" produces a change in the behavior of another individual, the "receiver".
Ethologists assumed communication evolved to maximize the quantity and accuracy of information. Behavioral ecologists argue that communication evolved to maximize the fitness of communicators.
Animals lie. Mimicry often is adaptive to the sender and maladaptive for the receiver.
· Male and female Photinus fireflies communicate by a characteristic pattern of flashes. Females of the predatory firefly genus PFioturus mimic the female Photinus flash pattern, attracting male Photinus fireflies which they kill and eat.
· In some mammals, a new dominant male kills young born too soon to be his offspring. Without dependent young, females ovulate sooner, allowing the new male to father their young. Hanuman langur females in the early stages of pregnancy solicit copulations from new dominant males. When they give birth shortly before young fathered by these males would appear, they may deceive the male into treating their young as his own.
An evolutionary consideration is the mode used to transmit information. Animals use visual, auditory, chemical, tactile and electrical signals.
The mode used to transmit information is related to an animal's lifestyle.
· Most mammals are nocturnal and use olfactory and auditory signals.
· Animals that communicate by odors emit chemical signals. called pheromones. Pheromones are important releasers for specific courtship behaviors and are the cues ant scouts release that guide other ants to food.
· Birds are mostly diurnal and use visual and auditory signals. Diurnal humans also use visual and auditory signals. If we could detect the chemical signals of mammals, then mammal sniffing might be as popular as bird watching.
A complex communication system is found in honeybees. (See Campbell, Figure 50.22)
· To maximize foraging efficiency, workers communicate the location of food sources which change as flowers bloom and new patches are found.
· Karl von Frisch studied honeybee communication. He found individual bees communicated to other bees when they returned to the hive.
· Returning bees "dance" to indicate the location of food.
· If the source is < 50m, the bee does the "round dance", moving rapidly sideways in tight circles and regurgitating nectar. Workers leave the hive and forage nearby.
· If the food is farther away, the bee does a "waggle dance", a half-circle swing in one direction, followed by a straight run and then a half-circle swing in the other direction. This dance indicates location in two ways:
1. The angle of the run in relation to the vertical surface of the hive is the same as the horizontal angle of the food in relation to the sun.
2. Distance to the food is indicated by variations in the speed at which a bee wags its abdomen during the straight run.
XIII. The concept of inclusive fitness can account for most altruistic behavior
Behavior that maximizes individual reproductive success will be favored by selection, regardless of how much damage such behavior does to another individual, local population, or species.
Animals occasionally exhibit apparently unselfish or altruistic behavior.
Altruistic behavior = A behavior that reduces an individual's personal welfare but benefits others.
· When parents sacrifice their well-being to produce and aid-offspring, they increase their fitness because it maximizes their genetic representation in the population.
· Like parents and offspring, siblings share 1/2 their genes, so selection might favor helping one's parents produce more siblings, or even helping siblings directly.
· Selection might result in animals increasing their genetic representation in the next generation by "altruistically" helping close relatives.
· Inclusive fitness includes assistance to relatives that maximizes individual fitness.
· Coefficient of relatedness is the proportion of genes that are identical in two individuals because of common ancestry .The higher the coefficient of relatedness, the more likely an individual is to aid a relative.
Inclusive fitness = The reproductive fitness of an individual as measured by its offspring and assistance to the reproductive efforts of close relatives.
Kin selection = The mechanism of increasing inclusive fitness.
· The contribution of kin selection to inclusive fitness varies among species. It may be rare or nonexistent in species that are not social or disperse widely.
· In predicting if an individual will aid relatives, behavioral ecologists have derived a formula that combines coefficients of relatedness, costs to the altruist and benefits to the recipient.
If kin selection explains altruism, then examples of unselfish behavior should involve close relatives.
· Belding's ground squirrels give alarm calls when danger appears. These calls alert other squirrels but increase the risk to the alarm givers. Females remain near their birth sites and are usually related to other members of the group. Only females give alarm calls. (See Campbell, Figure 50.23)
· Worker bees are sterile. They labor on behalf of a single fertile queen. Workers sting intruders, a behavior that defends the hive but results in the death of the worker. The queen is the mother of all the bees in the hive.
Altruistic behavior toward non-relatives sometimes occurs. This behavior is adaptive if there is a reasonable chance of the aid being returned in the future.
The book, Sociobiology by E.O. Wilson (1975) presented the thesis that social behavior has an evolutionary basis.
An example of the debate involves cultural taboos on incest.
Is there an innate aversion to incest or is this an
acquired behavior?