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BEHAVIORAL ECOLOGY Chapter 51 Behavior behavior = everything an animal does and how it does it behavioral response to threat = erect fins behaviors generate 2 types of questions: proximate = HOW? do environmental stimuli trigger the behavior? are there genetic, physiological, and anatomical mechanisms underlying the behavioral act ? ultimate does = WHY? the behavior have evolutionary significance? Ethology ethology = the scientific study of how animals behave, particularly in their natural environments questions at the core of ethology: What is the mechanistic basis of the behavior, including chemical, anatomical, and physiological mechanisms? How does development of the animal, from zygote to mature individual, influence the behavior? What is the evolutionary history of the behavior? How does the behavior contribute to survival and reproduction (fitness)? Fixed Action Pattern (FAP) a FAP is a sequence of unlearned behavioral acts that is essentially unchangeable and, once initiated, is usually carried to completion this type of behavior is studied extensively by the ethologists a FAP is triggered by an external sensory stimulus known as a sign stimulus (ex) the red underside of a male intruder triggers the male three–spined stickleback fish to attack FAP Example the red underside of a male intruder triggers the male three–spined stickleback fish to attack Imprinting imprinting is a type of behavior that includes both learning and innate components and is generally irreversible involves a sensitive period = a limited phase in an animal′s development that is the only time when certain behaviors can be learned this type of behavior is also studied by ethologists Imprinting Example In species that provide parental care, parent– offspring bonding is a critical part of the life cycle. During the period of bonding, the young imprint on their parent and learn the basic behaviors of their species, while the parent learns to recognize its offspring Nature vs. Nurture behavioral traits are the result of complex interactions between genetic and environmental factors thus, in biology, nature vs. nurture is not a debate biologists study how both genes and the environment influence the development of phenotypes, including behavioral phenotypes Innate Behavior behavior that is developmentally fixed under strong genetic influence examples: directed movements (kinesis, taxis, migration) animal signals & communication mating & parental behaviors Directed Movements kinesis = a simple change in activity or turning rate in response to a stimulus taxis = an automatic, oriented movement toward (+) or away from (–) some stimulus bird migration Signals & Communication signal = a behavior that causes a change in another animal′s behavior (aka: display) (ex) pheromones – chemical substances in odors communication = the transmission of, reception of, and response to signals reception can be visual, auditory, chemical (olfactory), tactile, or electrical Mating & Parental Behaviors prairie voles are monogamous male prairie voles form a strong pair–bond with a single female after they mate male prairie voles also help their mates care for young they spend a great deal of time hovering over their young, licking them, and carrying them around Environment & Behavior environmental factors, such as the following, can influence the development of behaviors quality of the diet nature of social interactions opportunities for learning Diet diet can influence mate choice (ex) mate choice by females in some Drosophila species is strongly influenced by the dietary environment in which larvae develop Social Environment cross–fostered California & white–footed mice adopt some of the behaviors of their foster parents this suggests that experience during development can lead to changes in parental and aggressive behaviors (in these rodents) that can be passed from one generation to the next Learning learning = the modification of behavior based on specific experiences types of learning include: habituation – the loss of responsiveness to stimuli that convey little or no information spatial learning – the modification of behavior based on experience with the spatial structure of the environment cognitive mapping – an internal representation of the spatial relationships between objects in an animal′s surroundings associative learning - ability of many animals to associate one feature of the environment (a stimulus, such as color) with another (bad taste) classical conditioning – an arbitrary stimulus is associated with a reward or punishment operant conditioning – trial-and-error learning cognition – the ability of an animal′s nervous system to perceive, store, process, and use information gathered by sensory receptors (associated with problem solving) Evolution of Behavioral Traits natural selection can result in the evolution of behavioral traits in populations one source of evidence = behavioral variation between and within species (ex) prey selection & aggressive behavior when behavioral variation within a species corresponds to variation in environmental conditions, it may be evidence of past evolution natural selection favors behaviors that increase survival and reproductive success (ex) foraging & mate choice behaviors Foraging Behavior foraging includes eating and any mechanisms an animal uses to recognize, search for, and capture food items natural selection should favor foraging behavior that minimizes the costs of foraging and maximizes the benefits this is based on the optimal foraging theory which views foraging behavior as a compromise between the benefits of nutrition and the costs of obtaining food Mating Behavior includes seeking or attracting mates, choosing among potential mates, and competing for mates how mating behavior enhances reproductive success depends on the species′ mating system (promiscuous, monogamous, polygamous) mate preferences by females may play a central role in the evolution of male behavior and anatomy male competition for mates can reduce variation among males competition for mates (or other resources like food) may involve agonistic behavior – a ritualized contest that determines which competitor gains access to the resource Game Theory a way of thinking about behavioral evolution in situations where the fitness of a particular behavioral phenotype is influenced by other behavioral phenotypes in the population (ex) side-blotched lizards the relative mating success of each male type is not fixed but changes with the relative abundance of the other male types in the populations Altruism some animals behave in ways that reduce their individual fitness but increase the fitness of other individuals in the population inclusive fitness can account for most altruistic social behavior inclusive fitness = the total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables other close relatives, who share many of those genes, to produce offspring natural selection that favors this enhancement of the reproductive success of relatives is called kin selection Hamilton’s Rule a quantitative measure for predicting when natural selection will favor altruistic acts among related individuals the three key variables in an act of altruism are: B = benefit to the recipient C = cost to the altruist how many fewer offspring the altruist produces r = coefficient of relatedness the average number of extra offspring that the beneficiary of an altruistic act produces the probability that if two individuals share a common parent or ancestor, a particular gene present in one individual will also be present in the second individual natural selection favors altruism when rB > C Reciprocal Altruism altruistic behavior between unrelated individuals, whereby the current altruistic individual benefits in the future when the current beneficiary reciprocates commonly invoked to explain altruism between unrelated humans; rare in other animals limited largely to species (such as chimpanzees) with social groups stable enough that individuals have many chances to exchange aid Social Learning social learning = learning through observing others forms the roots of culture = a system of information transfer through social learning or teaching that influences the behavior of individuals in a population cultural transfer of information has the potential to alter behavioral phenotypes and, in turn, to influence the fitness of individuals in many species, mate choice is strongly influenced by social learning (mate choice copying) Sociobiology sociobiology = the study of social behavior based on evolutionary theory main premise is that certain behavioral characteristics exist because they are expressions of genes that have been perpetuated by natural selection
