Lavc f10 lecture 11 primate reproductive strategies


Published on

Anthro 101: Human Biological Evolution lecture on Primate Reproductive Strategies - Rebecca Frank @ LAVC Fall 2010

Published in: Education
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide
  • Why does food matter so much to females? Why don’t they pass the buck or spend their time finding more mates like males do?
  • Hi low, different estimates at different sites. All white bar = 1 estimate, All grey bar = 0 at one site higher at other site
  • Preying mantis females eat their mates during sex…
  • Lavc f10 lecture 11 primate reproductive strategies

    1. 1. Anthro 101: Human Biological Evolution Lecture 11: Primate Reproductive Strategies Office Drop-in Hours AHS 308 Tutoring Lab Hours AHS 232 T 5:30 - 6:30 M & T 1 - 4 Th 11:15 - 12:15, 1:15 - 3:15 Student ID required F 12 - 1:30 by appointment
    2. 2. Attendance survey <ul><li>What are the three benefits of living in a social group? </li></ul><ul><li>What is one cost of living in a social group? </li></ul>
    3. 3. Studying Primate Behavior <ul><li>An evolutionary approach to behavior </li></ul><ul><li>Female Reproductive Strategies </li></ul><ul><li>Parental Investment </li></ul><ul><li>Sexual Selection </li></ul><ul><li>Male Reproductive Strategies </li></ul>
    4. 4. Behaviors are adaptations to particular social environments <ul><li>Behavioral strategies </li></ul><ul><ul><li>Course of action under certain circumstances </li></ul></ul><ul><ul><li>Does not imply conscious reasoning, deliberate planning, or intent </li></ul></ul><ul><li>How does the behavior effect and individual’s fitness </li></ul><ul><ul><li>Costs vs. Benefits of an action </li></ul></ul>
    5. 5. Mammalian females are committed to invest in offspring <ul><li>Internal gestation </li></ul><ul><li>Lactation </li></ul><ul><li>Maternal investment obligatory </li></ul><ul><li>Paternal care optional </li></ul>
    6. 6. Costs of Maternal Care <ul><li>Energy </li></ul><ul><ul><li>Lactation, gestation </li></ul></ul><ul><ul><li>Calories & nutrients </li></ul></ul><ul><li>Time </li></ul><ul><ul><li>Callitrichids - twins 2x per year </li></ul></ul><ul><ul><li>Monkeys - one infant every 2 - 4 years </li></ul></ul><ul><ul><li>Apes - one infant every 5 - 7 years </li></ul></ul>
    7. 7. Primate females invest heavily in each infant and produce few total offspring <ul><li>Litter size = 1 (max 2) </li></ul><ul><li>Long inter-birth intervals </li></ul><ul><li>Lifespan < 20 yrs </li></ul><ul><li>Not all infants survive </li></ul><ul><li>Each infant represents big fraction of females’ reproductive output </li></ul>Golden monkey
    8. 8. What strategies do females use to enhance reproductive success? 1. Care 2. Competition 3. Cooperation
    9. 9. 1. Female primates provide many types of care for their offspring <ul><li>Nourishment </li></ul><ul><li>Transportation </li></ul><ul><li>Warmth </li></ul><ul><li>Protection from predators </li></ul><ul><li>Protection from harassment </li></ul>
    10. 10. How much care should females give offspring? <ul><li>More care  higher chance of survival </li></ul><ul><li>BUT care for present infant, reduces ability to care for older infants AND future infants </li></ul><ul><ul><li>Females have finite reproductive career </li></ul></ul><ul><ul><li>Care for infants taxes maternal resources </li></ul></ul><ul><li>Mothers must make tradeoff </li></ul><ul><ul><li>Few very high quality offspring </li></ul></ul><ul><ul><li>Many very low quality offspring </li></ul></ul><ul><li>Primate mothers invest heavily in each offspring and have only a few </li></ul>Golden monkey
    11. 11. 2. Female reproduction is limited by access to food: <ul><li>Competition </li></ul><ul><ul><li>Scramble </li></ul></ul><ul><ul><li>Contest </li></ul></ul>Silver leaf monkey
    12. 12. 3. Competition sometimes favors cooperation among females <ul><li>Between group competition </li></ul><ul><ul><li>Territorial species </li></ul></ul><ul><ul><li>Females in the same troop cooperate to confront females from other groups </li></ul></ul><ul><ul><li>Larger groups will get access to more resources than smaller groups </li></ul></ul>
    13. 13. 3. Competition sometimes favors cooperation among females <ul><li>Within group competition </li></ul><ul><li>females form alliances in some species </li></ul><ul><ul><li>affect access to resources </li></ul></ul><ul><ul><li>affect rank acquisition </li></ul></ul><ul><li>Alliances often composed of kin </li></ul><ul><li>Social bonds (friends) may also enhance reproductive success </li></ul><ul><ul><li>Not about rank </li></ul></ul><ul><ul><li>Not about fighting for resources </li></ul></ul>
    14. 14. Cooperation: In marmosets and tamarins, female RS depends on helpers
    15. 15. Selection shapes male reproductive strategies of males, too <ul><li>Parental investment is costly </li></ul><ul><li>Mammalian females are obligated to invest heavily in offspring </li></ul><ul><li>Mammalian males have more options than females </li></ul><ul><li>Females are limited in the number of offspring they can have </li></ul><ul><li>Females are a limiting resource for males </li></ul>
    16. 16. 1. Males can increase RS by investing in offspring <ul><li>Expect males to invest when </li></ul><ul><ul><li>Finding additional mates difficult </li></ul></ul><ul><ul><ul><li>Females spaced out (time) </li></ul></ul></ul><ul><ul><ul><li>Female mate synchronously </li></ul></ul></ul><ul><ul><li>Fitness of kids raised by one parent low </li></ul></ul><ul><ul><ul><li>infants are very big </li></ul></ul></ul><ul><ul><ul><li>litter size > 1 </li></ul></ul></ul><ul><ul><ul><li>high risk of predation/infanticide </li></ul></ul></ul>
    17. 17. 2. Males can increase RS by competing <ul><li>Sexual Selection favors traits that increase success in competition for mates </li></ul><ul><li>more pronounced in sex with limited access to mates </li></ul><ul><li>= MALES (in mammals… usually) </li></ul><ul><li>Intra-sexual selection = male-male competition for access to mates </li></ul><ul><li>Inter-sexual selection = female selection of males with the most attractive traits </li></ul>
    18. 18. Intra-sexual selection in primate males <ul><li>Male-male competition favors </li></ul><ul><ul><li>Large body size </li></ul></ul><ul><ul><li>Large canines </li></ul></ul><ul><ul><li>Mate guarding </li></ul></ul>
    19. 19. Inter-sexual selection in primate males <ul><li>Inter-sexual selection = </li></ul><ul><li>Female choice favors </li></ul><ul><ul><li>Flashy colors </li></ul></ul><ul><ul><li>Energetic displays </li></ul></ul><ul><ul><li>Friendly behavior </li></ul></ul><ul><ul><li>Paternal care </li></ul></ul>mandrill tamarin
    20. 20. Pair-bonded species: Marmosets & Tamarins <ul><li>Male RS tied to his mate’s RS </li></ul><ul><li>Males invest in offspring </li></ul><ul><ul><li>Carry infants </li></ul></ul><ul><ul><li>Share food with infants </li></ul></ul><ul><li>Males guard females vs. rivals </li></ul><ul><li>Closely bonded to mate </li></ul>Dusky titi monkeys
    21. 21. Pair-bonede species: Gibbons and siamangs Males are attentive to mates Sing duets in territorial displays Females have priority of access Males help care for infants
    22. 22. Competitive males & distant fathers: multi-male groups <ul><li>Male RS tied to number of different females he can mate with </li></ul><ul><li>Males compete for dominance rank </li></ul><ul><ul><li>Male dominance rank is function of size & strength </li></ul></ul><ul><li>Rank orders change frequently </li></ul><ul><li>High ranking males monopolize conceiving females </li></ul><ul><li>Male rank is correlated with reproductive success </li></ul>
    23. 23. Multi-male groups <ul><li>Baboons </li></ul><ul><li>Langurs </li></ul><ul><li>Chimpanzees </li></ul> The Bone Room 2010
    24. 24. More intense male-male competition leads to greater sexual dimorphism
    25. 25. Baboon males are twice as big as females
    26. 26. Males are well-armed for conflict
    27. 27. Males fight over access to receptive females
    28. 28. These fights can be very costly to males
    29. 29. High rank enhances male reproductive success Baboons
    30. 30. Intense male-male competition can also lead to sperm competition….and larger testes…in species where females mate promiscuously Monogamous 1- ♂, Multi-♀ Multi- ♂, Multi-♀ Observed/Expected Size 0.5 1.0 1.5 2.0
    31. 31. In multi-male groups, some males provide low cost care <ul><li>Males usually tolerant of juveniles </li></ul><ul><li>Males support juveniles in aggressive interactions </li></ul><ul><li>Some evidence that males selectively help own offspring </li></ul>
    32. 32. One-male groups: Competition to gain access to females is intensified <ul><li>Males compete for access to groups of females </li></ul><ul><li>Outsiders exert constant pressure on resident males </li></ul><ul><li>Tenure of resident males often short </li></ul>
    33. 33. Infanticide is a sexually-selected male reproductive strategy <ul><li>Females nurse infants for many months </li></ul><ul><li>If unweaned infant dies, female resumes cycling immediately </li></ul><ul><li>Death of infant makes females available for mating sooner </li></ul><ul><li>Infanticidal males gain immediate mating opportunities </li></ul><ul><li>If male tenure is short , infanticide enhances male mating opportunities </li></ul>
    34. 34. If infanticide is a sexually-selected male reproductive strategy, we predict: <ul><li>Infanticide will be linked to changes in male residence or status </li></ul><ul><li>Males will kill unweaned infants </li></ul><ul><li>Males won’t kill their own infants </li></ul><ul><li>Infanticidal males will gain reproductive benefits </li></ul><ul><li>Evidence supports all four predictions </li></ul>
    35. 35. 1. Infanticide is associated with changes in male status: Males don’t kill unless they GAIN reproductive access they did not have before
    36. 36. 1. Males begin to kill infants soon after they join group Hanuman langurs, Borries & Koenig 2000
    37. 37. 2. Males kill unweaned infants Probability of surviving presence of infanticidal male Langurs Howlers 0-3 3-6 6-9 > 9 Age (mos)
    38. 38. 3. Males don’t kill own infants
    39. 39. 4. Infanticidal males gain reproductive benefits <ul><li>Infanticide brings females back into estrus </li></ul><ul><li>Infanticidal males often mate with mother of dead infant </li></ul>
    40. 40. Infanticide is a major cause of mortality % deaths due to infanticide
    41. 41. Counterstrategies to thwart infanticide <ul><li>Defend victims of attack </li></ul><ul><ul><li>Mothers </li></ul></ul><ul><ul><li>Female kin </li></ul></ul><ul><ul><li>Males present at conception </li></ul></ul><ul><ul><li>Fathers </li></ul></ul><ul><li>Confuse paternity </li></ul><ul><ul><li>Estrus swellings </li></ul></ul><ul><ul><li>Mate with many males </li></ul></ul><ul><ul><li>Mate with newcomers </li></ul></ul>
    42. 42. In baboons, male-female ties may be response to infanticide <ul><li>In some populations, infanticide is common when new males join group or males rise in status </li></ul><ul><li>New mothers form associations with particular males </li></ul><ul><ul><li>possible father of current infant </li></ul></ul><ul><li>Males protect females’ infants </li></ul>
    43. 43. Sexually-selected infanticide has now been documented in a number of taxa <ul><li>All the major groups of primates </li></ul><ul><ul><li>Prosimians </li></ul></ul><ul><ul><li>New World monkeys </li></ul></ul><ul><ul><li>Old World monkeys </li></ul></ul><ul><ul><li>Apes </li></ul></ul><ul><li>Lions </li></ul><ul><li>Rodents </li></ul><ul><li>Birds </li></ul>Many still think its pathological and not adaptive
    44. 44. Controversy persists because people confuse “is” and “ought” <ul><li>This is called the “naturalistic fallacy” </li></ul><ul><ul><li>assume that natural phenomena are right, just, unchangeable, good </li></ul></ul><ul><li>Worry that if infanticide is adaptive for langurs or lions, it would be justified in humans </li></ul><ul><li>But this reasoning is wrong </li></ul><ul><li>we can’t extract moral meaning from behavior of other animals or what is natural </li></ul>
    45. 45. In-Class Activity #5 <ul><li>Write a personal ad seeking a mate from the perspective of a male or female of any primate species you choose. </li></ul><ul><li>Include details that are specific to that species and sex </li></ul><ul><li>Do NOT say what species you are writing the ad for </li></ul><ul><li>May work in small groups - write everyone’s name down </li></ul>