Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Sexual coercion wikipedia , lookup
Slut-shaming wikipedia , lookup
Human female sexuality wikipedia , lookup
Human male sexuality wikipedia , lookup
Human mating strategies wikipedia , lookup
Female promiscuity wikipedia , lookup
Body odour and sexual attraction wikipedia , lookup
Sexual attraction wikipedia , lookup
Sexual reproduction wikipedia , lookup
Lecture 5: Behavioral Ecology Principles of Ecology Eben Goodale… Guest Lecturer: Uromi Goodale College of Forestry, Guangxi University Today’s lecture • • • • 4 questions of behavioral ecology Nature vs. nurture Foraging ecology Charles Darwin’s two biggest problems: – Sexual Selection – Group Living and Altruism. • Looking at human behavior Why did the prize for physiology(生理学) / medicine go to these three men? Konrad Lorenz (1903-1989) ducks imprint on (被铭记为) human “parents” Niko Tinbergen (1907-1988) Worked on stimuli (刺激) that “release” behavior Karl Von Frisch (1886-1982) Discovered honeybee “dance language” Nobel prize 1973: study of behavior as a physiological process Tinbergen’s four questions • What stimulus elicits the behavior, and what physiological mechanisms mediate the response? • How does the animal’s experience during growth and development influence the response? • How does the behavior aid survival and reproduction? • What is the behavior’s evolutionary history? Tinbergen’s four questions • What stimulus elicits the behavior, and what physiological mechanisms mediate the response? Mechanistic(机械的) • How does the animal’s experience during growth and development influence the response? Developmental(发展的) • How does the behavior aid survival and reproduction? Ultimate Function • What is the behavior’s evolutionary history? Evolutionary history(进化历史) Nature versus nurture: the debate • Ethologists (like Tinbergen) see strong innate(先天 的) responses. • Psychologists (like B. F. Skinner) see everything can be learned. The super-stimulus: an incubating bird, given an extra big egg, will try to sit on it. Genetically innate. Cuckoos take advantage. The ‘Skinner box’: demonstration that by reinforcing ‘correct’ behavior with food, pigeons can be taught to do complex tasks. So nature(自然的) vs. nurture(后天培养 的): 2 camps. Is there a middle ground? Square on a flat surface: experience (the landscape) has no effect, Innate effects rule…wherever the square lands it stays. So nature vs. nurture: 2 camps. Is there a middle ground? Circle on a flat surface: circle can roll in any direction… experience rules. So nature vs. nurture: 2 camps. Is there a middle ground? Circle on a surface with a channel: there’s room to roll (= room for experience), but some places more likely than others. Channeled learning(引导学习): rats • Rats learning to associate bad smells to avoid foods. • But can’t learn to associate sound to avoid foods (but dogs can). Conclusion: all behavior a mix of genetically innate and learned components. It’s a continuum(连续的). Some behaviors mostly innate. Think of any human examples? Some behaviors mostly leaned. Today’s lecture • • • • 4 questions of behavioral ecology Nature vs. nurture Foraging ecology Charles Darwin’s two biggest problems: – Sexual Selection – Group Living and Altruism. • Looking at human behavior Foraging ecology • Do animals behave in a way that maximizes the amount of energy that they obtain? • “Optimal foraging ecology (最佳环境容量)” • What prey do animals select? • How long do they stay in one patch before moving to the next one? • How do they forage to use the least energy needed to obtain food? John Krebs tested birds on what prey they would select as it came by on a belt. Prey selection: minimizing “handling time(处理时间)” • The profitability(利 益率) of food = E / t (Energy/time) • Look at this experimentally by having different kinds of “prey” that are easier of harder to obtain (glue or tape) From Krebs et al. 1977 Minimizing travel: when to leave a patch? • When a patch(斑点) is first found, it has a lot of food, and feeding is quick. • But it becomes less rich over time. • The animal also needs to consider the energy required to find a new patch. The longer the travel time between patches, the longer the animal will stay in one patch. From Cowrie 1977 Ultimate function and Optimality Theory • An example … Crows drop whelks (snail in shell) against the ground. • Higher they go, the more successful … but the more time it takes. How high should they go? Zach (1978, 1979) The field evidence: Crows select largest whelks Crows drop whelks from ~ 5 m Minimizing energy spent: how to crack a shell N = Number of drops H = height Energy spent Height Crows end up going about as high as this model predicts (~ 2 m) Crows are such smart, cool birds: http://www.thewildclassroom.com/biodiversity/birds/aviantopics/optimalforagingtheory.html But do animals really behave optimally? • “Optimal foraging ecology” peaks in late 1970s. • People begin to realize that birds not following predictions particularly: when predators are present, when information is not perfect, where results are variable etc. Today’s lecture • • • • 4 questions of behavioral ecology Nature vs. nurture Foraging ecology Charles Darwin’s two biggest problems: – Sexual Selection – Group Living and Altruism. • Looking at human behavior Darwin’s Problems • Two difficult problems: – Sexual selection(性选择) Why do some animals have very elaborate ornaments that may be costly to their survival? – Altruism(偏利作用) Why do organisms help others at a cost to themselves? Worried Darwin. These are both potentially large problems for his theory of natural selection. These honeybee Workers help their queen but don’t reproduce themselves Darwin’s Problems • Two difficult problems: – Sexual selection Why do some animals have very elaborate ornaments that may be costly to their survival? – Altruism Why do organisms help others at a cost to themselves? Worried Darwin. These are both potentially large problems for his theory of natural selection. 1859 Origin of Species 1871 Descent of Man and Selection in Relation To Sex Natural selection What are the basic steps in this process: 1. Variation between individuals in traits 2. This variation is the trait is heritable 3. In every generation, there are more offspring produced than can survive. 4. Individuals with traits that fit the environment well survive and reproduce. 5. More individuals in the next generation will have the favored trait. Sexual selection What are the basic steps in this process: 1. Variation between individuals in traits 2. This variation is the trait is heritable 3. The trait in question affects the individual’s ability to mate. Individuals with traits that attract mates or beat rivals will leave more offspring. 4. More individuals in the next generation will have the favored trait. Natural selection and sexual selection collide Ever see a male peacock fly? With difficulty! How can we understand this from a Darwinian perspective….? Sexual selection Intrasexual(性内的) Two male elephant seals fight for access to females Intersexual A male sage-grouse displays for females Are females really using male ornaments to select mates? Famous experiment: Andersson 1982 Control I is unmanipulated birds. What is Control II and why do it? Idea of differences between sexes in investment in offspring Females produce a few, costly gametes(配子 – eggs Males produce many inexpensive gametes – sperm For females to reproduce, make best use of a few attempts Parental Investment Theory Formalized by Robert Trivers (1972) Male success can come from reproducing many times Females “choosy(挑剔的)” …note this is a generalization, not always true Some exceptions prove the rule about investment • General idea that female invest more per one offspring, so should be more choosy. • In species where males invest more, females are more colorful, fight; and males choose. In Jacanas, females mate with more than one male. Kill offspring male has with other females. In Pharalopes, males incubate Eggs; females brighter plumage In pipefish, males get pregnant Males choose females. Sexual selection: benefits for females What does the female (or in exceptional cases, the male) stand to gain by choosing good quality males (females)? Direct benefits: female gets nutrition or help rearing young Scorpion Fly: male gives the female a “nuptial gift” before meeting Sexual selection: benefits for females • Direct benefits very important for animals where a lot of parental care is necessary… Like birds where both parents are needed to feed chicks (“altricial young(成雏期)”)… But what about those lekking birds?? The males provide no parental genes. All they do is show off. http://www.youtube.com/watch?v=uVSxEkCU Ag0&feature=related What about the male peacocks that Petrie 1994 writes about? How do females benefit from selecting well-ornamented males? Sexual selection • So why would a female chose a male when parenting skills are not an issue? The “sexy son(性感儿子)” hypothesis: female choses male in hopes that her own male offspring will be attractive to females. The “good genes(优良基因)” / “handicap(阻碍)” hypothesis: A male peacock is announcing through his feathers, “I’m in such good condition and have such good genes that I can survive despite this ridiculous (crazy) tail”. Amotz Zahavi (1928-) Sexual selection • So why would a female chose a male when parenting skills are not an issue? Problem with these theories… why wouldn’t all males evolve to the same appearance (i.e., their phenotype) … why wouldn’t we run out of genetic variation? One solution: appearance is an indicator of resistance to pathogens(病原体) or parasites (寄生虫). Pathogens/parasites are constantly changing, so appearance can be an honest signal of genetic quality. Idea propounded By Marlene Zuk At UCRiverside (1956- ) Sexual selection And may be there isn’t an adaptive reason… Ronald Fisher hypothesized that if male and female sexual preference was genetically linked, males could evolve more of trait at same time females evolve preference for it Their sons have longer tail Males with long tail successful Their daughters really like long tails This process, called “run-away(逃跑者)” sexual selection, might lead to a cycle of trait elaboration. Sexual selection Stalk-eyed flies: evidence that female preference(优先权) evolves at same time as male trait. Wilkonson and Reillo 1994 Today’s lecture • • • • 4 questions of behavioral ecology Nature vs. nurture Foraging ecology Charles Darwin’s two biggest problems: – Sexual Selection – Group Living and Altruism. • Looking at human behavior Types of Animal Groups • Non-related: groups at a scarce resource: incidental groups (aggregations(聚 集)) • Non-related groups: herds, flocks, schools, swarms… • Related groups: colonies (bees, ants), family groups of animals (cooperative breeding birds)….. The selfish herd Start with non-related groups: individuals should join them to reduce their own risk “Geometry for the Selfish Herd” W. D. Hamilton (1971) 1) Marginal animals more vulnerable(脆 弱). 2) Animals move towards middle of group. Benefits/costs to groups: predation (捕食) • Vigilance (警觉) • Dilution of risk(降低 风险) • Confusion effect • Threaten predator …. But costs • More obvious to predators 1 2 4 8 12 1 2 4 8 12 Group Size Vigilance by skinks: Downes and Hoefer 2004 Benefits/costs to groups: foraging • Hidden food found more easily due to copying • Disturbance of food But costs… • Increased competition • Aggression or Kleptoparasitism (stealing) # Birds % of birds find food in 15 min 1 25% 2 40% 4 75% Krebs et al. 1972 Group size … what’s optimal(最理想 的)? Factors Increasing Group Size: Factors Decreasing Group Size: Vigilance, increased feeding Aggression Caraco 1980 Group size … what’s optimal? Daily survival rate Dail Covey size Quail coveys: Williams (2003) Cooperative breeders Now let’s talk about special kinds of groups in which the members are related. In cooperative breeders (繁殖), Only one male and one female breed, whereas others (usually juveniles (小的)) help raise young. Green wood-hoopoes Why do the helpers help? Kin selection = an explanation for altruism W. D. Hamilton (1936-2006) suggested that “altruistic” behaviors could be explained as an animal helping closely related individuals, and thereby perpetuating their genes. This is known as “kin selection”. Kin selection Hamilton’s rule: rB – C > 0 mate r = Relatedness B = Benefit C = Cost of helping How do we calculate r? For diploid(二倍体) organisms, You get ½ your alleles From mother, ½ from father. r = is percent of genes that are shared children Kin selection Hamilton’s rule: rB – C > 0 mate r = Relatedness B = Benefit C = Cost of helping How do we calculate r? For diploid organisms, You get ½ your alleles From mother, ½ from father. What is r for Mother and daughter? 50% children Kin selection Hamilton’s rule: rB – C > 0 mate r = Relatedness B = Benefit C = Cost of helping How do we calculate r? For diploid organisms, You get ½ your alleles From mother, ½ from father. What is r for 2 sisters? 100 + 50 + 50 + 0 / 4 = 50% children Cooperative(协同) behavior Why do the helpers help? They stay because by helping raise Their kin, they are increasing their Genes in the next generation. Lion pride: Males only form group of 3 or more if related… Eusocial animals What characteristics do eusocial(社会性的) animals have? 1) Individuals of more than one generation living together 2) cooperative care of young 3) division of individuals into non-reproductive and reproductive castes Naked mole rat Leaf cutter ant queen How did eusocial animals evolve? • Again kin-selection… • All naked mole rats Are close relatives b/c Of inbreeding(近亲交配). • Ants/bees are haploidDiploid(二倍体循环): fertile eggs are female, nonfertilized eggs are male. mate Children All female Don’t Mate = Male offspring How did eusocial animals evolve? • Again kin-selection… • All naked mole rats Are close relatives b/c Of inbreeding. • Ants are haploid-diploid: Fertile eggs are female Nonfertized eggs are male What is r for mother And daughter? 50% How did eusocial animals evolve? • Again kin-selection… • All naked mole rats Are close relatives b/c Of inbreeding. • Ants are haploid-diploid: Fertile eggs are female Nonfertized eggs are male What is r for Two sisters? 100 + 100 + 50 + 50 / 4 = 75% Kin selection = an explanation for altruism . W. D. Hamilton (1936-2006) Haploidiploidy High relatedness among female workers Eusociality? One of most famous results of Behavioral Ecology. But doesn’t explain the termites that are also eusocial but not haplo-diploid. Today’s lecture • • • • 4 questions of behavioral ecology Nature vs. nurture Foraging ecology Charles Darwin’s two biggest problems: – Sexual Selection – Group Living and Altruism. • Looking at human behavior Kin selection in humans? Who would you help out of a burning fire? Tend to save related people 0.5 Save younger people who Have more chance of reproducing 0.25 0.12 0.0 Relatedness From Buss “Evolutionary Psychology” (2008) Kin selection in humans? A more subtle prediction: Because human fertilization internal, male paternity uncertain. Hypothesis: Maternal grandparents (外祖父母)should invest more because they are more sure of their genes are represented. Sexual selection in humans • Men are less choosy! • Women investment higher: 9 months + lactation can last in some cultures up to 4 years. Likelihood To have Sex Length know partner Sometime to consider: could this be cultural (文化的)rather than biological? … Could young men be taught that being sexually outgoing is appropriate, and women be taught it’s not so? Women’s options: long-term vs. short-term mating strategies(策略) • Advantages to marriage: – Resources, care given by father increase chances of success for children. • Advantages to short-term mating: - good gene models? - testing potential long-term partner? It takes two to tango! If men are opting for short-term Mating options, women are too Women’s presence for short-term mates: good genes over caretaking? Index of “Social Dominance(优势)”” From Buss 2008, After Gangestad et al. 2004 Women’s presence for short-term mates: good genes over caretaking? Symmetry(对称性) Women prefer symmetrical men particularly when they are fertile and not looking for long-term partners. From Little et al. 2007 Amazingly, women when they are fertile have been shown to prefer the smell (sweaty T-shirt) of symmetrical men! Gangestad and Thornhill 1998 Women’s presence for short-term mates: testing long-term mates? Care to dance? Better dancers are more symmetrical and women are more perceptive about men’s dancing than men are about women’s. From Brown et al. 2005 Women’s presence for short-term mates: testing long-term mates? Care to dance? From Brown et al. 2005 Homework • Chapters 9 and 10 for Saturday. • Read the “sweaty T-shirt” study (Gangestad and Thornhill 1998). Is their work convincing to you? What are the strengths(重点) of the paper? What are its weaknesses(缺点)? Be prepared to discuss. Key concepts • Animal behaviorists ask different kinds of questions: about how a behavior occurs, how it develops, what its adaptive functions are, and about its evolutionary history. • All behavior is a mix of genetic instructions and learning; but behaviors differ in the proportion with which they are genetically encoded. • Foraging theory is an example where researchers have tested whether animals make decisions that increase their energy intake and decrease how much energy they spend foraging. • Sexual selection can explain elaborate ornaments of one sex: these ornaments determine the animal’s reproductive success. Why “choosy” individuals select ornamented animals is more complicated, but perhaps they are selecting good genes for their offspring. • Animals are more likely to help their relatives than other individuals (“kin selection”). Because kin share the helpers’ genes, the helper is ensuring that more of its genes are found in the next generation.