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Organismal Ecology – Studies how an organism’s structure, physiology, and behavior (animals) meet the challenges posed by the environment Organismal Ecology = Autecology • Organismal Ecology = Autecology: self ecology – the initial focus of ecology: an organism’s home life • Emphasis on Habitat & Niche – Where an organism is found – It’s role in the environment – What limits its distribution Figure 50.3a – How it responds to environmental challenges (a) Organismal ecology. How do humpback whales select their calving areas? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Organisms and the Environment Abiotic Factors and Organismal Ecology • • The n-dimensional niche was developed for Organismal Ecology Recall: Environmental factors that affect organisms can be divided into two classes: 1. Abiotic, or nonliving factors e.g. Temperature, Precipitation, Salinity, etc. 2. Biotic, or living factors e.g. Conspecifics, Predators/Prey, Competitors, Symbionts, etc. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Focus on Abiotic Factors more than Biotic Factors – A three-dimensional niche might include: • Temperature, rainfall, nitrogen – An n-dimensional niche includes all other environmental factors Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survival, Growth and Reproduction Niche: Survival, Growth and Reproduction • For an organism’s species to live in a habitat over time • For any single abiotic factor, conditions must be appropriate at some time (e.g. season) for: – It not only needs to survive, – Growth and Reproduction – It must also be able to – And always for Survival, or: • Grow, and • Migration • Reproduce • Hibernation, or other resistant stage • Seed, spore, endospore, etc. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1 Environmental Factors as Limiting Resources Response to Environmental Challenges • A Limiting Resource limits the distribution or abundance of organisms • Organismal responses to the environment effect their ability to tolerate environmental challenges – Abiotic factors • Nutrients: nitrogen, phosphorus, etc. • Nest sites, refugia, anchorage, etc. – May be experimentally demonstrated by • Addition and Removal experiments Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Organismal Responses include: – Behavioral (animals) – Physiological – Morphological Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Response to Environmental Challenges Response to Environmental Challenges • Behavior is the coordinated movement of muscles (and glands) by neurons • Physiological responses also may be rapid • Is the most rapid response to the environment – If conditions are unfavorable, Move! • Daily or Seasonal Migration • Huddling by mammal social groups to conserve body warmth • Avoidance of Predator (biotic factor) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Vasoconstriction of peripheral blood vessels conserves heat – Acclimation to changing seasons/elevations: • Alternative forms of enzymes – Acclimation to changing elevations: • Increase concentration of hemoglobin – Salmon osmoregulation in fresh vs. saltwater Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Response to Environmental Challenges Response to Environmental Challenges • Morphological changes occur more slowly • Morphological changes occur more slowly – Acclimation to changing seasonal temperatures • Winter ‘coats’ in mammals and birds – Leaf morphology of plants vary with shading – Plants vary with wind patterns • Usually not reversible – Usually reversible Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 Response to Environmental Challenges Costs and Benefits of Homeostasis • Over longer time frames • As organisms respond to the environment – Natural Selection affects organismal responses – they must balance costs and benefits • Major trade-offs occur between – Conformers vs. Regulators • Osmoconformers vs. Osmoregulators • Ectotherms/Poikilotherms vs. Endotherms/Homeotherms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Osmoregulation Osmoregulation • Organisms need to manage their water balance, particulary aquatic organisms • Most marine fishes are osmoregulators – May live in freshwater or saltwater – They constantly drink seawater, and – Excrete small amounts of salty urine • Hagfish are osmoconformers – Their bodies conform to the osmotic concentration of the deep ocean – Environment is fairly constant • Hagfish adapted to these conditions • Low cost Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Osmoregulation Osmoregulation • Freshwater fishes osmoregulate • Osmoregulation by most marine and freshwater fishes is energetically costly – They do not drink water – Excrete large volumes of dilute urine Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – but it favors the rest of their metabolic processes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3 Trade-Off: Poikilothermy vs. Homeothermy Trade-Off: Poikilothermy vs. Homeothermy • Poikilotherms: allow their body temperatures to fluctuate with the environment • Homeotherms: maintain a constant, warm body temperature – Benefit: inexpensive • 70% of energy budget used for basic metabolism • 30% of energy budget available for growth and reproduction – Cost: slower metabolism Note: ancestral Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Benefit: higher metabolism, rapid chemical reactions, including locomotion • Early bird gets the warm! Able to gain much more energy – Cost: Energetically expensive • 97.5-99.5% of energy budget used for basic metabolism • 0.5-2.5% of energy budget available for growth and reproduction Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Trade-Off: Poikilothermy vs. Homeothermy Principle of Allocation • Many poikilotherms can behaviorally regulate temperature • There are always trade-offs between an organism’s ecological strategies – Lizards can bask in the sun – Cost: Increased risk of predation • Regardless of the ‘strategy’ – Organisms are constantly faced with trade-offs – Impossible to maximize both energy intake and efficiency of energy use, other risks, etc. – Which is better? Both successful today! Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Organismal Ecology Today • Rather than Organismal Ecology, modern ecologists tend to specialize – Behavioral Ecology – E.g. Conformers vs. Regulators • Similarly, there are finite resources & costs in acquiring resources • The Principle of Allocation states that organism’s cannot simultaneously maximize survival, growth & reproduction – Rather, they must allocate their available resources Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 51 Behavioral Ecology – Physiological Ecology – Functional Morphology PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4 Animal Behavior • Humans have probably studied animal behavior – For as long as we have lived on Earth • As hunters • Cranes are birds that have captivated people’s interest – Possibly because they are large and their behavior is easily observed – Knowledge of animal behavior was essential to human survival Figure 51.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What Is Behavior? Animal Behavior • Behavior • Classically, Animal Behavior studied – Is what an animal does and how it does it – Includes muscular and nonmuscular activity – Behavior Patterns: coordinated movement of muscles by neurons • Animal Behavior also includes Dorsal fin – Learning – Chemical communication between animals – Related processes that may affect behavior Anal fin Figure 51.2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Behavioral Ecology Proximate & Ultimate Causes • Behavioral Ecology is a modern discipline of animal behavior • Behavioral ecologists distinguish between proximate and ultimate causes of behavior – Extends observations of animal behavior by studying how such behavior is controlled, how it develops, its evolution and how it contributes to survival and reproductive success – Proximate causes focus on the immediate stimulus and mechanism for the behavior – Ultimate causes explain how the behavior contributes to survival and reproduction – Conducted in the light of Evolutionary theory Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5 Proximate and Ultimate Questions Proximate and Ultimate Questions • • Proximate, or “how,” questions about behavior have two foci – The environmental stimuli that trigger a behavior, e.g. a ‘Sign Stimulus’ – The genetic, developmental, physiological, and anatomical mechanisms underlying a behavioral act Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ultimate, or “why,” questions about behavior address the evolutionary significance of a behavior – It’s evolutionary history, and – Current affect on fitness: via increased survival and/or reproduction Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anthropomorphism Early Animal Behavior • Animal Behavior studies are particularly prone to observer bias • From the time of Darwin – We tend to ascribe purpose and feelings to the actions of animals – Anthropomorphism is the attribution of humanlike qualities to animals, e.g. consciousness • To avoid bias, behavioral biologists avoid terms that suggest purpose & use parsimony: – Many biologists studied behavior from an evolutionary viewpoint, e.g. • Ethologists – Other scientists, mostly from psychological backgrounds, focused on learning, e.g. • Behaviorists – The simplest explanation is more likely true Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ethology Classical Ethologists • Ethology is a branch of animal behavior • Three Ethologists shared a Nobel Prize (1973) – Particularly focused on the natural history of animals and their behavior in the natural environments in which they evolved – Karl von Frisch, Austrian – Assumed that behavior was adaptive – Niko Tinbergen, Dutch – Konrad Lorenz, Austrian – Developed a conceptual framework defined by the set of Proximate and Ultimate questions Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 6 Ethology Fixed Action Patterns • Ethologists focused on behavior patterns that were essentially • A fixed action pattern (FAP) – Innate, or instinctual – Is an unlearned, innate behavior pattern that is unchangeable – Innate behavior is determined in large part by genes – Usually occurs in a stereotypical sequence with other behavior patterns (Ethogram) – Innate behavior is often stereotypical or ‘fixed’ – Once the sequence is initiated, it is usually carried to completion – Is triggered by an external sensory stimulus • a Sign Stimulus Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sign Stimulus • In male stickleback (fish) – the stimulus for attack behavior is the red underside of an intruder • A male stickleback in breeding condition will attack even unrealistic models – If red is present on their underside (a) A male three-spined stickleback fish shows its red underside. Figure 51.3a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 51.3b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ethogram • 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. PROXIMATE CAUSE: The red belly of the intruding male acts as a sign stimulus that releases aggression in a male stickleback. 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. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 7 Imprinting Young Geese ‘Imprint on’ & follow their Mother • Imprinting is a type of behavior • There are proximate and ultimate causes for this type of behavior – That includes both learning and innate components; is generally irreversible BEHAVIOR: Young geese follow and imprint on their mother. • Imprinting is distinguished from other types of learning by a ‘sensitive period’ – A limited phase in an animal’s development that is the only time when certain behaviors can be learned 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Young Geese will Imprint on any large body • Konrad Lorenz showed – When baby geese spent the first few hours of their life with him • Conservation biologists have taken advantage of imprinting – In programs to save the whooping crane from extinction – They imprinted on him as their parent Figure 51.6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparative Ethology Directed Movements • Ethologists also demonstrated the relationships between organisms and their similar behavior patterns • Many animal movements – Geese and Ducks share similar sequences of courtship behavior patterns – Are under substantial genetic influence • These types of movements – Are called directed movements – Behavior patterns are useful characters for determining evolutionary relationships (cladograms) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 8 Migration Behaviorists and Learning • Many features of migratory behavior in birds • Behaviorists focused on learned behavior – Have been genetically programmed • Learning is the modification of behavior – Based on specific experiences with their environment • Learned behavior – Ranges from very simple to very complex Figure 51.8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Associative Learning • In associative learning – Animals associate one feature of their environment with another – Includes both • Classical Conditioning • Classical conditioning is a type of associative learning – In which an arbitrary stimulus is associated with a reward or punishment – Was pioneered by Ivan Pavlov (Russian) • Operant Conditioning Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pavlov and Classical Conditioning Operant Conditioning • Pavlov paired • Operant conditioning is another type of associative learning – An unconditioned stimulus: food – To a conditioned stimulus: a bell – In which an animal learns to associate one of its behavior patterns with a reward or punishment • Dogs salivate when presented food, – An unconditioned response • Over time, the dogs began to salivate upon hearing the bell – A conditioned response Figure 51.16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 9 Operant Conditioning Genetic and Environmental Interaction in Learning • BF Skinner (American) • By the mid-20th Century – Shaped behavior by reinforcement: • Pigeons learned to peck keys in a complex series of strikes against left and right keys to receive a reward (usually food) – Claimed he could shape nearly any sequence of behavior – Ethologists and Behaviorists were completely at odds • Ethologists studied innate behavior, determined in large part by their genes • Behaviorists studied learned behavior, dependent on their environment – Nature vs. Nurture debate – Studies tested the importance of genes & environment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Limitations of Learning Selection Shapes the ability to Learn • Some Conditioning studies produced odd results • Subsequent studies demonstrated constraints on behavior • Racoons are good ‘learners’ – Quickly learn to put coins in a piggy bank to earn a food reward • But instead of getting better with more trials – As raccoons associated the coins with food, the less they would put the coins in the bank! – They rubbed them in their paws over & over Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Likely based on natural selection • Rats can associate food with nausea, • But not food with pain – Can associate sound with pain, • But not sound with nausea • Garcia et al 1974 (handout) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dogs and Squirrels: differential learning • Dogs and Squirrels differ in their ability to find a new pathway when the direct path is blocked – Dogs generally considered more ‘intelligent’ • But cannot perform this task – Squirrels are expert in the task – Natural context • Dogs/wolves rarely limited in direct path • Squirrels regularly test possible paths along branches between trees Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 10 Experience Shapes Behavior Patterns Genetics and Learning Affect Behavior • Ethologists also became aware that many ‘Fixed Action Patterns’ may be modified, or improved over time • Hybrid crosses in Lovebirds demonstrate alternate forms of genes that determine how to carry nest materials • ‘Modal Action Patterns’ describe the central tendency of innate behavior patterns, but • Over time, hybrids learn to carry nest materials (overhead, attached) – acknowledge small changes due to environmental experience: learning Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Conclude: Both Nature and Nurture affect behavior (and most aspects of biology) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nature and Nurture influence Animal Behavior • Biologists concluded: • Environment, interacting with an animal’s genetic makeup, influences the development of behavior patterns • Research has revealed – That environmental conditions modify many of the same behavior patterns, for example: – Diet affects mate selection by female Drosophila mojavensis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Larval diet affects mate choice by D. mojavensis EXPERIMENT William Etges raised a D. mojavensis population from Baja California and a D. mojavensis population from Sonora on three different culture media: artificial medium, agria cactus (the Baja host plant), and organ pipe cactus (the Sonoran host plant). From each culture medium, Etges collected 15 male and female Baja D. mojavensis pairs and 15 Sonoran pairs and observed the numbers of matings between males and females from the two populations. RESULTS When D. mojavensis had been raised on artificial medium, females from the Sonoran population showed a strong preference for Sonoran males (a). When D. mojavensis had been raised on cactus medium, the Sonoran females mated with Baja and Sonoran males in approximately equal frequency (b). 100 With Baja males (a) Proportion of matings by Sonoran females With Sonoran males 75 Modern Animal Behavior: Behavioral Ecology • Behavioral traits evolve by natural selection – Many behavior patterns have a strong genetic component – Selection may also shape the way behavior responds to the environment (e.g. learning) (b) • Behavioral Ecologists study 50 25 0 Artificial Organ pipe cactus Agria cactus Culture medium – How genes and the environment influence the development and expression of behavioral phenotypes CONCLUSION The difference in mate selection shown by females that developed on different diets indicates that mate choice by females of Sonoran populations of D. mojavensis is strongly influenced by the dietary environment in which larvae develop. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Under past and current selection pressure Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 11 Behavioral Variation allows for Selection Behavioral Variation in Natural Populations • Behavioral traits can evolve by natural selection • When behavioral variation within a species – Corresponds to variation in the environment, it may be evidence of past evolution • Because of the influence of genes on behavior – But, correlation does not equal causation – Natural selection can result in the evolution of behavioral traits in populations – Recall: Variation is necessary for selection Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Variation in Prey Selection Variation in Predation Behavior • Differences in prey selection in populations of garter snakes correlate with prey availability • Funnel spiders living in different habitats – Exhibit differing speed of attack at prey items – Evidence of behavioral evolution Desert grassland population Time to attack (seconds) 50 60 Riparian population 40 30 20 10 0 Figure 51.18a, b (a) A garter snake (Thamnophis elegans) (b) A banana slug (Ariolimus californicus); not to scale Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Field Lab-raised generation 1 Lab-raised generation 2 Population Figure 51.19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Behavioral Ecology Behavioral Ecology: Four behavioral ‘needs’ • Natural selection favors behavior that increases survival and reproductive success • • The genetic components of behavior – Evolve through natural selection • Behavior can affect fitness – Through its influence on foraging and mate choice, or the four ‘F’s’ Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Behavioral Ecologists often group behavior based on four ‘needs’: 1. Feeding (foraging) 2. Fleeing (predator avoidance) 3. Fighting (over resources, mates, status) 4. Reproduction: the ultimate measure of fitness Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 12 Modeling Behavior Behavioral Models • Behavioral Ecologists assume that natural selection has shaped behavior to maximize fitness • Optimality models • Two common models used: – Optimality models – Assume organisms behave to maximize some outcome, minimize some cost, or achieve the most cost effective Trade-off • Game theory – Game theory models – Both evaluate the Trade-offs between Costs & Benefits of behavioral alternatives – Evolutionarily Stable Strategies (ESS) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Evaluates alternative behavioral strategies in situations where the outcome depends on each individual’s strategy as well as the strategy of other individuals (Sociobiology) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Foraging Behavior Energy Costs and Benefits • Animals need to find and consume food items to gain energy and other nutrients • Reto Zach • Optimal foraging theory – Views foraging behavior as a compromise between the benefits of nutrition and the costs of obtaining food: – Conducted a cost-benefit analysis of feeding behavior in crows • The crows eat whelks (snails, molluscs) – But must drop them from the air to crack the shells • Energy costs • Wear and tear of body parts • Risks of predation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Risk of Predation – indicating a trade-off between energy gained (food) and energy expended Average number of drops 30 75 Total flight height 20 Drop height preferred by crows 10 2 Figure 51.22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3 5 Height of drop (m) 50 7 15 25 Predation occurrence (%) 100 40 Predation risk Relative deer use 70 Total flight height (number of drops × drop height) 50 Average number of drops – Has shown that predation risk affects where the deer choose to feed 125 60 0 • Research on mule deer populations 60 20 15 50 40 10 30 20 Relative deer use • Zach found that the optimal flight height in foraging behavior minimized ‘total flight height’ 5 10 0 0 Open Figure 51.24 Forest edge Habitat Forest interior Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 13 ‘Fleeing’ - Predator Avoidance Fleeing, or Predator Avoidance • The risk of predation affects feeding, fighting and reproduction • The benefits of avoiding predation are obvious • Animals may flee out right: • The costs of fleeing = ‘time-out’ from other activities – Swim, run, fly away • Or hide in grasses, trees, burrows, etc – Continued life vs. death (for most animals) • Optimal trade-offs: – How close to allow predator before avoidance? – If cryptic: need to behave like grass, tree, rock, etc. – How long to ‘hide’ before returning to other activity? • School & herd behavior Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Hermit Crabs as model systems Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fighting: Intraspecifc Conflict, Agonistic Behavior Fighting: Trade-offs • Fighting occurs between conspecifics (mostly) • – Agonistic behavior • Animals fight over resources (benefits) – Food, Mates, other limiting resources, and – Status (social organisms; Sociobiology) determines access to other resources Fights often Highly Ritualized – To reduce costs: energy and bodily harm 1. Assessment: • Size determines 90% of contests 2. Escalation to full combat 3. Appeasement • Costs range from minimal to extreme – Energetic expense, Debilitating injury, Death Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fighting & Game Theory Fighting: Trade-offs • Game theory • Game Theory: Hawks vs. Doves – Evaluates alternative behavioral strategies in situations where the outcome depends on each individual’s strategy as well as the strategy of other individuals (Sociobiology) – Hawks vs. Doves Payoff: Hawk Dove Hawk -0.1 0 Dove 1.0 0.5 – Hawks do better than doves, if hawks are rare – If hawks are common, the cost of fighting may favor doves Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 14 Territoriality Territories: Economic Defensibility • Many animals are Territorial • Because territories are defended spaces • A territory is any defended space • Various types of territories – Feeding territories – Mating territories – All purpose territories – They must ‘cost’ something • Models suggest territories will only occur if they are • Economically Defensible, i.e. if: B > C – The benefit of holding the territory (resources) is greater than the cost of defending it – Herbivorous fishes: parrotfish vs. damselfish Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mating Behavior and Mate Choice Mating Systems and Mate Choice • Reproduction and Mating behavior • Mating relationships between males & females – Is shaped by both natural & sexual selection • Recall Anisogamy Theory – Different gametes lead to different strategies Males are eager, Females are choosy • Other factors affect these patterns: – Population dispersion – Parental care of offspring (Parental Investment) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Varies a great deal from species to species – Depends on the interaction of mating strategies by both sexes • Polygamy refers to ‘many gametes’ or multiple partners: – Promiscuous, polygynous, polyandrous, or polygynandrous • Monogamy refers to ‘single gametes’ – Exactly one male and one female together Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Polygamy: Promiscuous Polygamy: Polygyny • In many species, mating is promiscuous • Another common mating system is polygyny – With no strong pair-bonds or lasting relationships – One male mates with many females – Males often showy and larger than females – Many marine animals are broadcast spawners – ‘Group grope’ – Promiscuous mating systems are a form of Polygamy: • some individuals mate with multiple partners Figure 51.25b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) Among polygynous species, such as elk, the male (left) is often highly ornamented. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 15 Polygamy: Polyandry Polygynandry • Polyandrous systems are rare • Anisogamy theory suggests Polygyny should be the most common mating system – One female mates with many males – The females are often more showy than the males – Note some males very successful (by sexual selection), but others do not mate at all • Polygynandry is probably more common – Successful males mate with multiple females, – Females mate (over time) with multiple males, As the ‘best’ male changes over time Figure 51.25c (c) In polyandrous species, such as these Wilson’s phalaropes, females (top) are generally more ornamented than males. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monogamy Monogamy • Monogamous mating systems are rare • Exclusive Monogamy refers to repeated rounds of reproduction with one mate for both sexes – One male mates with one female • Social Monogamy refers to species that commonly occur in pairs – Commonly: Biparental-care Monogamy – Genetic studies have found that many Socially Monogamous species are actually Polygynandrous, e.g. most birds & humans (a) Since monogamous species, such as these trumpeter swans, are often monomorphic, males and females are difficult to distinguish using external characteristics only. – Extra Pair Copulations sought by both sexes Figure 51.25a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Constraints on Mating: The Limiting Sex • Anisogamy theory is based on both the cost and availability of gametes • However, in some cases males provide care • Which most affects mating strategies? – Energetic costs or Availability? • Pipefish Study: – Males are the Limiting Sex • The needs of the young – Are an important factor constraining the evolution of mating systems • The certainty of paternity influences parental care and mating behavior – Paternal care is rare with internal fertilization (egg is fertilized in female’s reproductive tract) – Male’s cannot be certain of their paternity – Sex-role Reversal Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 16 Applying Game Theory • In species with external fertilization – Parental care is as likely to be carried out by males as females • Game theory evaluates alternative behavioral strategies in situations – Where the outcome depends on an individual’s strategy and the strategy of other individuals • Alternative Reproductive Strategies are wonderful examples of game theory in action Eggs – Strategies may be genetically fixed, or – Conditional, the behavioral phenotype is shaped by its environment – What alternative might evolve successfully? Figure 51.26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Game Theory & Mating Success Alternative Reproductive Strategies: Fishes • Mating success of male side-blotched lizards is influenced by male polymorphism (behavior & color) and their relative abundance • Alternative Reproductive Strategies have been studied in various fishes - Orange dominates Blue dominates Yellow (sneaks) – Bluegill sunfish: • Males may be territorial, or • Sneakers: Satellites or Female mimics – Salmon: Hooknose males vs. Jacks – Many fishes are hermaphrodites • Sequential hermaphrodites (change sex) • Simultaneous hermaphrodites Figure 51.32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Why Change Sex? Why Change Sex? • Selection will favor sex change if reproductive success is greater as one sex when small, but increases in the other sex at larger size • Graph: Reproductive Sex x Size – Protogyny • First Female, then Male RS – Protandry • First Male, then Female Body Size Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 17 Sociobiology Altruistic Behavior: Benefit to another, at some Cost • Sociobiology studies the behavior of social animals – Similar in assumptions to Behavioral Ecology – Behavior is shaped by selection • Genes and Environment effect Phenotype • Natural selection normally favors selfish behavior: passes on more genes • Kin Selection can explain some ‘unselfish’ behavior (altruism) • Hamilton’s rule: br > c – When the ‘benefit’ to the recipient – Multiplied by the coefficient of ‘relatedness’ – Exceeds the ‘cost’ to the altruist Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Kin Selection vs. Altruism • The warning behavior observed in Belding’s ground squirrels increases survival of kin Reciprocal Altruism • Reciprocal Altruism is helping behavior toward unrelated individuals – Can be adaptive if the aided individual returns the favor in the future – Is rare and susceptible to cheating Mean distance moved from natal burrow (m) 300 Male 200 100 Female 0 0 2 3 4 Figure 51.35 12 13 14 15 25 26 Age (months) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reciprocal Altruism Social Learning • Reciprocal Altruism requires a set of four conditions to allow its evolution & maintenance (selection): • Social learning – Ability to Recognize Specific Individuals – Repeated Interactions with same Individuals – Many Opportunities to Help and be Helped – Ability to Punish Cheaters Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Forms the roots of culture • Culture can be defined as a system of information transfer through observation or teaching – That influences the behavior of individuals in a population Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 18 Social Learning & Cultural Transmission Sociobiology, Evolution and Human Culture • No other species comes close to the social • Human culture and evolutionary theory learning & cultural transmission among humans – Is studied by the discipline of sociobiology • Human behavior, like that of other species – Is the result of interactions 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, e.g. cultural transmission via books • We also exhibit much Reciprocal Altruism: Money Figure 51.38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anthropomorphism Anthropomorphism in Human Studies • Animal Behavior studies are particularly prone to observer bias • The greatest bias may be in studies of human behavior – We tend to ascribe purpose to the actions of animals – Anthropomorphism is the attribution of humanlike qualities to animals, e.g. consciousness – Do we also ‘anthropomorphize’ ourselves? – We tend to ascribe consciousness to human behavior patterns • However: consider how we make food choices – What thought processes led to your choice of breakfast foods? The balance of amino acids? • How do we make our mate choices? – Teen pregnancy Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Human Sociobiology and Environmentalism Sustainability • Much of our current environmental concerns are based on over use of environmental resources and release of waste: pollution • Sustainability is to meet the needs of the present without compromising the ability of future generations to meet their own needs. (United Nations) – Overuse of Water: aquatic habitats & water tables – Loss of Agricultural land: limits food production – Overfishing: particularly ocean fishes (who regulates?) – Pollution: DDT/PCB’s, Metals, Nuclear Waste, etc. – Greenhouse gases & Global Climate Change • Most of these problems reflect choices that – Maximize Immediate Benefits (selfish) – But ignore longterm Costs (Altruism/Kin Selection) – Unsustainable! Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Reciprocal altruism? • Sustainability is achieved when all people on Earth can live well without compromising the quality of life for future generations. We do not inherit the earth from our ancestors; we borrow it from our children. (Native American Proverb) – Kin Selection? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 19 Human Sociobiology and Environmentalism Reciprocal Altruism & Fair Use • Reductions in resource use & pollution require • Enactment and Enforcement of Fair Laws can and will Protect our Environment – Coordinated efforts by diverse human populations and cultures must limit own use, find/share alternate technology • But, Reciprocal Altruism is prone to Cheating – Tragedy of the Commons, Malthus • The solution to Cheating is Punishment – Charge for excess use of resources – Fine/punish cheaters Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 20