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Explore the fascinating world of animal behavior, from innate instincts to learned behaviors, communication methods, and evolutionary influences. Learn about proximate and ultimate causes, social structures, and survival strategies in this insightful guide.
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Ch. 51 Warm-Up • What is something that you can do that you have been able to do since birth? • What is one behavior that you learned by watching someone else? • List some ways that animals communicate. • Define: • Circadian rhythms • Pheromones • Learned behaviors • Imprinting • Associative learning • Classical conditioning • Operant conditioning
Ch. 51 Warm-Up • What is the difference between proximate and ultimate causes of behavior? • Explain the difference between kinesis and taxis. • What are the 4 common modes of animal communication? • Define: • Optimal foraging model • Sexual Selection • Promiscuous • Monogamous • Polygamous • Altruism • Inclusive fitness • Kin selection
Ch. 51 Warm-Up • What do you think is the advantage for a species to be: • Monogamous? • Polygamous? • Describe an example of when you have participated in reciprocal altruism.
You Must Know: How behaviors are the result of natural selection How innate and learned behaviors increase survival and reproductive fitness How organisms use communication to increase fitness The role of altruism and inclusive fitness in kin selection
Introduction • Ethology: study of animal behavior • Behavior: what an animal does and how it does it • Both genetic & environmental factors • Essential for survival and reproduction • Subject to natural selection over time
Understanding behavior • Proximate cause: “how” a behavior occurs or is modified • Ultimate cause: “why” a behavior in context of natural selection A courting pair of East Asian red-crowned cranes.
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. 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.
Innate behaviors: developmentally fixed and are not learned • Fixed action patterns (FAPs):sequence of unlearned acts that are unchangeable and usually carried to completion • Triggered by sign stimulus • Ensures that activities essential to survival are performed correctly without practice • Eg. goose & egg
Directed Movements • Kinesis: simple change in activity or turning rate in response to a stimulus • Taxis: automatic movement, oriented movement +/- from stimulus(eg. phototaxis, chemotaxis, geotaxis) Kinesis increases the chance that a sow bug will encounter and stay in a moist environment. Positive rheotaxis keeps trout facing into the current, the direction from which most food comes.
Circadian Rhythm: internal biological clock • More on Clock Genes: http://learn.genetics.utah.edu/content/inheritance/clockgenes/ The circadian clock in the hamster brain signals a change in coat color according to season by releasing the hormone melatonin. The Suprachiasmatic nuclei (SCN) region is located in the hypothalamus of the brain. The SCN sends signals throughout the body in response to dark and light. Plants can have two internal clocks: one sensitive to light and the other sensitive to temperature
Migration • Regular, long-distance change in location • Environmental cues: sun, stars, earth’s magnetic field, landmarks
Signal: stimulus that causes a change in behavior; basis of animal communication • Pheromones– chemicals emitted by members of one species that affect other members of the species (eg. Queen bee, fruit fly, fish, termites, trees, humans) • Visual signals – eg. Warning flash of white of a mockingbird's wing • Tactile(touch) – eg. Male fruit fly taps female fly • Auditory signals – screech of blue jay or song of warbler Courtship behavior of fruit flies
Honeybee dance language • Used to inform other bees about distance and direction of travel to food sources
Learned behaviors: behaviors that are modified based on specific experiences
Types of Learning • Habituation: loss of responsiveness to stimuli that convey little or no information • Simple form of learning • Imprinting: learning + innate components • Limited to sensitive period in life, generally irreversible • ie. Lorenz’ imprinting in greylag geese
BEHAVIOR: Young geese follow and imprint on their mother. 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.
Captive breeding programs for endangered species must provide proper imprinting models Pilot wearing crane suit acts as a surrogate parent to teach young whooping cranes a migration route
3. Spatial Learning • Cognitive Map: internal representation of spatial relationship among objects in an animal’s surroundings Birds use spatial maps to relocate nut caches
Some organisms move in response to a recognized object or environmental cue, a landmark. Nest No nest Nest
4. Associative Learning: ability to associate one stimulus with another (eg. monarchs = foul taste) A. Classical conditioning: arbitrary stimulus associated with particular outcome (eg. Pavlov’s dogs: salivate with ringing bell)
B. Operant conditioning: another type of associative learning • Trial-and-error learning • Associate its own behavior with reward or punishment
5. Cognition: process of knowing that involves awareness, reasoning, recollection, judgment • Problem-solving behavior relies on cognition
6. Social learning: learning by observing others Vervet monkeys learning correct use of alarm calls.
Examples of learned animal behavior • Nut-cracking crow (2:16) • TED Talk: Amazing intelligence of crows (11:34) • Chimpanzee problem solving (1:02) • Chimpanzee problem solving by cooperation (2:14)
Concept 51.4: Selection for individual survival and reproductive success can explain most behaviors • Genetic components of behavior evolve through NATURAL SELECTION!!!!! • Behavior can affect fitness by influencing foraging and mate choice • Natural selection refines behaviors that enhance efficiency of feeding • Foraging:food-obtaining behavior; includes recognizing, searching for, capturing, and eating food items • Drosophila melanogaster,variation in gene dictates foraging behavior in larvae • Larvae with one allele travel farther while foraging than larvae with other allele • Larvae in high-density populations benefit from foraging farther for food • Larvae in low-density populations benefit from short-distance foraging • Natural selection favors different foraging behavior depending density of the population
Optimal Foraging Model • Optimal foraging model:views foraging behavior as compromise between benefits of nutrition and costs of obtaining food • costs of obtaining food include energy expenditure and risk of being eaten while foraging • Natural selection should favor foraging behavior that minimizes costsand maximizes benefits • Optimal foraging behavior demonstrated by Northwestern crow • crow will drop whelk (a mollusc) from height to break shell and feed on soft parts • crow faces trade-off between height from which it drops whelk and number of timesit must drop whelk • Researchers determined experimentally that total flight height (which reflects total energy expenditure) minimized at drop height of 5 m AND… • average flight height for crows is 5.2 m. BOOM. SCIENCE.
Mating Behavior & Mate Choice • Sexual selection: seeking and attracting mates, choosing and competing for mates
Mating Behavior and Mate Choice • Mating behavior includes seeking or attracting mates, choosing among potential mates, and competing for mates • Mating behavior results from type of natural selection called sexual selection • Promiscuous: no strong pair-bonds or lasting relationships; many animals • Monogamous relationships: one male mates with one female • Males and females with monogamous mating systems have similar external morphologies • Polygamous relationships:individual of one sex mates with several individuals of other sex; species usually sexually dimorphic: males and females have different external morphologies • Polygyny: one male mates with many females • Males usually more showy and larger than females • Polyandry: one female mates with many males; RARE • Females often more showy than males
Needs of young important factor constraining evolution of mating systems • Ex: Bird species chicks need continuous supply of food • A male maximizes his reproductive success by staying with his mate, and caring for his chicks (monogamy) • Ex: Bird species chicks soon able to feed and care for self • A male maximizes his reproductive success by seeking additional mates (polygyny) • Females certain eggs laid / young born contain her genes; however, paternal certainty depends on mating behavior • Paternity certainty influences parental care and mating behavior • Paternal certainty relatively low species with internal fertilization • mating and birth separated over time • Paternal certainty much higher when egg laying and mating occur together, as in external fertilization • parental care is at least as likely to be by males as by females
Sexual Selection and Mate Choice • Intersexual selection: members of one sex choose mates on basis of certain traits • Female Choice • Intrasexualselection:involves competition between members of same sex for mates Mate Choice by Females • Females drive sexual selection by choosing males with specific behaviors or features of anatomy • Ex: female stalk-eyed flies choose males with relatively long eyestalks • Ornaments, such as long eyestalks, often correlate with health and vitality • Ex: Female zebra finch chicks who imprint on ornamented fathers are more likely to select ornamented mates • Experiments suggest mate choice by female zebra finches play key role in evolution of ornamentation in male zebra finches
Fig. 51-24 Experimental Groups of Parental Pairs Control Group Females ornamented Both parents ornamented Males ornamented Parents not ornamented Offspring Offspring Mate preference of female offspring: ornamented male Mate preference of female offspring: none
Male Competition for Mates • source of intrasexual selection that can reduce variation among males • may involve agonistic behavior • often ritualized contest that determines which competitor gains access to resource (lady or land that lady likes)
Applying Game Theory • Sexual selection driven evolution of alternative mating behavior and morphology in males • Fitness of particular phenotype (behavior or morphology) depends on phenotypes of other individuals in population • Game theory:evaluates alternative strategies where outcome depends on each individual’s strategy and strategy of other individuals • Ex: each side-blotched lizard has blue, orange, or yellow throat • each color associated with specific strategy for obtaining mates • genetic basis to throat color and mating strategy • Like rock-paper-scissors, each strategy will outcompete one strategy, but be outcompeted by other strategy • THUS! success of each strategy depends on frequency of all of strategies; • THIS drives frequency-dependent selection
Sexual selection • Ornaments correlate in general with health and vitality
Agonistic behavior: threats, rituals, and sometimes combat; settles disputes over resources (mates)
Behaviors can be directed by genes • Certain behaviors in prairie voles are under relatively strong genetic control • ADH (vasopressin) triggers pair-bond formation and aggression by male voles
Differences in oxytocin (a hormone) receptors in 2 species of voles • Monogamous prairie voles vs. promiscuous montane voles High oxytocin levels in prairie voles Low oxytocin levels in montane voles
Concept 51.3: Both genetic makeup and environment contribute to the development of behaviors • Animal behavior governed by complex interactions between genetic and environmental factors • Cross-fostering studies help behavioral ecologists identify contribution of environment to animal’s behavior • Cross-fostering study:places young from one species in care of adults from another species • California mice and white-footed mice study uncovered influence of social environment on aggressive and parental behaviors • Cross-fostered mice developed some behaviors that were consistent with their foster parents • Humans: twin studies allow researchers to compare relative influences of genetics and environment on behavior
Regulatory Genes and Behavior • Master regulatory gene can control many behaviors • Ex: single gene controls many behaviors of male fruit fly courtship ritual • Multiple independent genes can contribute to a single behavior • Ex: Green lacewings: courtship song unique to each species; multiple independent genes govern different components of courtship song
Genetically Based Behavioral Variation in Natural Populations • Behavioral variation within species corresponds to environmental variation evidence of past evolution • Example: Most blackcaps (birds) that breed in Germany winter in Africa, but some winter in Britain • two migratory populations are genetically distinct • Example: Natural diet of western garter snakes varies by population • Coastal populations feed mostly on banana slugs, while inland populations rarely eat banana slugs • Studies show differences in diet are genetic • two populations differ in ability to detect and respond to specific odor molecules produced by banana slugs!
Influence of Single-Locus Variation • Differences at single locus can sometimes have a large effect on behavior • Ex: male prairie voles pair-bond with their mates, while male meadow voles do not • level of specific receptor for neurotransmitter determines which behavioral pattern develops
Altruistic social behavior • Altruism = selfless behavior • Reduce individual fitness but increase fitness of others in population • i.e. bee societies; naked mole rats • Inclusive fitness: total effect of producing own offspring (pass on genes) + helping close relatives • Kin selection: type of natural selection; altruistic behavior enhances reproductive success of relatives
Concept 51.5: Inclusive fitness can account for the evolution of altruistic social behavior • Natural selection favors behavior that maximizes individual’s survival and reproduction • These behaviors are often selfish Altruism: • Occasionally some animals behave in ways that reduce their individual fitness but increasefitness of others AKA selflessness • Ex: under threat from predator, individual Belding’s ground squirrel make alarm call to warn others, even though calling increases chances that caller is killed • Ex: naked mole rat populations, nonreproductive individuals sacrifice lives protecting their reproductive queen and kings from predators
Inclusive Fitness • Altruism explained by inclusive fitness • Inclusive fitness: total effect individual has on proliferating its genes by producing offspring and helping close relatives produce offspring
Hamilton’s Rule and Kin Selection • William Hamilton proposed quantitative measure for predicting when natural selection would favor altruistic acts among related individuals • Three key variables in altruistic act: • Benefit to recipient (B) • Cost to altruist (C) • Coefficient of relatedness (fraction of genes that, on average, are shared; r) • Natural selection favors altruism when: rB > C • Hamilton’s rule: thisinequality • Kin selection:natural selection that favors this kind of altruistic behavior by enhancing reproductive success of relatives • Ex: warning behavior in Belding’s ground squirrels • In group, most of females closely related to each other • Most alarm calls given by females who aiding close relatives • Ex: Naked mole rats living within colony are closely related • Nonreproductive individuals increase their inclusive fitness by helping reproductive queen and kings (their close relatives) to pass their genes to the next generation
Fig. 51-29 300 Male 200 Mean distance (m) moved from birthplace 100 Female 0 1 2 3 4 12 13 14 15 25 26 Age (months)
