Lecture 5: Behavioral Ecology Principles

1. Lecture 5:Behavioral Ecology Principles of EcologyEben Goodale… Guest Lecturer: Uromi GoodaleCollege of Forestry, Guangxi University

2. 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

3. Why did the prize for physiology（生理学） / medicine go to these three men? Karl Von Frisch (1886-1982) Discovered honeybee “dance language” 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 Nobel prize 1973: study of behavior as a physiological process

4. 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?

5. 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? Mechanistic（机械的） Developmental（发展的） Ultimate Function Evolutionary history（进化历史）

6. 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.

7. 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.

8. So nature vs. nurture: 2 camps.Is there a middle ground? Circle on a flat surface: circle can roll in any direction… experience rules.

9. 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.

10. 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.

11. 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

12. 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.

13. 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

14. 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. From Cowrie 1977 The longer the travel time between patches, the longer the animal will stay in one patch.

15. 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

16. 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

17. 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.

18. 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

19. 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

20. 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

21. Natural selection What are the basic steps in this process: • Variation between individuals in traits • This variation is the trait is heritable • In every generation, there are more offspring produced than can survive. • Individuals with traits that fit the environment well survive and reproduce. • More individuals in the next generation will have the favored trait.

22. Sexualselection What are the basic steps in this process: • Variation between individuals in traits • This variation is the trait is heritable • The trait in question affects the individual’s ability to mate. Individuals with traits that attract mates or beat rivals will leave more offspring. • More individuals in the next generation will have the favored trait.

23. Natural selection and sexual selection collide Ever see a male peacock fly? With difficulty! How can we understand this from a Darwinian perspective….?

24. Sexual selection Intrasexual（性内的） Two male elephant seals fight for access to females Intersexual A male sage-grouse displays for females

25. 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?

26. Idea of differencesbetween sexes in investment in offspring Females produce a few, costly gametes（配子 – eggs Males produce many inexpensive gametes – sperm Parental Investment Theory Formalized by Robert Trivers (1972) For females to reproduce, make best use of a few attempts Male success can come from reproducing many times Females “choosy（挑剔的）” …note this is a generalization, not always true

27. 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 Pharalopes, males incubate Eggs; females brighter plumage In Jacanas, females mate with more than one male. Kill offspring male has with other females. In pipefish, males get pregnant Males choose females.

28. 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

29. 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=uVSxEkCUAg0&feature=related What about the male peacocks that Petrie 1994 writes about? How do females benefit from selecting well-ornamented males?

30. 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-)

31. 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- )

32. Sexual selection Their sons have longer tail 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 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.

33. Sexual selection Stalk-eyed flies: evidence that female preference（优先权） evolves at same time as male trait. Wilkonson and Reillo 1994

34. 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

35. 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)…..

36. 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) • Marginal animals more vulnerable（脆弱）. • Animals move towards middle of group.

37. 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

38. Benefits/costs to groups: foraging • Hidden food found more easily due to copying • Disturbance of food But costs… • Increased competition • Aggression or Kleptoparasitism (stealing) Krebs et al. 1972

39. Group size … what’s optimal（最理想的）? Factors Increasing Group Size: Vigilance, increased feeding Factors Decreasing Group Size: Aggression Caraco 1980

40. Group size … what’s optimal? Dail Daily survival rate Covey size Quail coveys: Williams (2003)

41. 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?

42. Kin selection = an explanation foraltruism 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”.

43. mate children Kin selection Hamilton’s rule: rB – C > 0 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

44. 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. children What is r for Mother and daughter? 50%

45. 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. children What is r for 2 sisters? 100 + 50 + 50 + 0 / 4 = 50%

46. Lion pride: Males only form group of 3 or more if related… 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.

47. Naked mole rat Leaf cutter ant queen 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

48. 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 haploid- Diploid（二倍体循环）: fertile eggs are female, nonfertilized eggs are male. mate Don’t Mate = Male offspring Children All female

49. 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%

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%