Short & Sweet Male Intraspecific Competition

1. Short & SweetMale Intraspecific Competition

2. Male-Male Competition • Andersson, 1994 “Sexual Selection” • 5 fundamental areas of male-male competition • Scrambles • Endurance Rivalry • Contests • Sperm competition • Mate choice (Female choice)

3. Contest Competition • Combat Contests • Traits that improve success in fights • Large size • Strength • Weaponry • Agility • Strength signals • Favors Threat signals • Alternate tactics • Alternate mating tactics of inferior competitors, avoiding contests with superior rivals

4. Strength Signal Contests • Signals of strength or fighting ability used to assess each other to avoid direct combat • Adaptations • Visual • Auditory • Tactile • Chemical

5. Tactile Strength Signal • Rattlesnake • Ritualized wrestling to avoid deadly battles • http://www.youtube.com/watch?v=9_pbJXHuxPs&feature=related • http://www.youtube.com/watch?v=lUup6AdcKLw&feature=related

6. Auditory Strength Signal • Red deer in rutting season • Avoid conflict by signaling strength with auditory signals • Frequent & long bellows • Night & day • Prevents from feeding • Lose stamina • Signal stamina, size & confidence • http://www.youtube.com/watch?v=97ORGksHhKw&feature=related

7. Strength Signal • Elephants use visual, vocal, tactile & chemical strength signals to avoid conflict • Typical Male bull • Display with trunk • Lock tusks • “shove” match • Male bull in musth • Musth gland • Increased levels of testosterone • Temporal gland secretes • Urine dribbles • Posture- head high, chin tucked, long stride • Ear wave, tusk wave

8. Elephant Musth • http://www.youtube.com/watch?v=bIzvXsmW3qY

9. Strength Signal • Gorilla • Male signals dominant status • Silverback • Musk • Posture • Display • http://www.youtube.com/watch?v=HDxA8-01cp4

10. Strength Signal • Manakin • Ritualized display to avoid conflict • http://www.youtube.com/watch?v=RZc0x0f6_88&feature=related

11. Alternative Contests • When it pays to be a wimp • Poor competitors avoid direct contests by using alternative behaviors • Adaptations that promote • Sneaky behaviors • Hermaphrodites • Dwarfism • Coersion & forced copulations • Infanticide

12. Sneaker • Alternate strategy used by non dominant & immature males (small) • Short term & long term strategy • Strategies involve taking advantage of dominant males distraction • Selection favors small & inconspicuous males • Cost benefit analysis • Dominant aggressive lifestyle is risky & expensive

13. Male Sneakers • http://www.youtube.com/watch?v=zj8istSAMoY

14. Sneakers Smaller payoff, but it’s better than nothing!

15. Slide Blotched Lizard

16. Rock-Paper-scissors

17. 3 color Morphs

18. 3 Reproductive Strategies

19. Yellow Throated Sneaker • Mimic the throat color of receptive females • Also mimic female behavior • Female rejection bob, nips & chase • High reproductive success rate • When a dominant male is encountered the sneaker mimics a female • Behavior only effective on Orange males • http://bio.research.ucsc.edu/~barrylab/classes/animal_behavior/IMAGES6.DIR/Y_VS_O.HTM

20. Blue Throated Monogomous • Mate guard a female • Ensure paternity • Moderate testosterone levels • Moderate life ~7 • Aggressive with other blue males over territory • Display to maintain territory • Typically avoid battle • Recognize sneaker males • Drive out sneakers • Low sneaker success • http://bio.research.ucsc.edu/~barrylab/classes/animal_behavior/IMAGES6.DIR/B_VS_Y.HTM

21. Orange Throated Dominant • High levels of testosterone & aggression level • Short lived ~2yrs • Defends territory & multiple females • Invade blue male territory to gain paternity in blue clutches • Vulnerable to sneakers • http://bio.research.ucsc.edu/~barrylab/classes/animal_behavior/IMAGES6.DIR/B_VS_O.HTM

22. Rock-Paper-Scissors • Multiple polymorphism exist in unison • Each polymorphism dominates in 6 yr cycle • Yellows can fool oranges • Blues attack yellows • Orange defeat challenging males, but fooled by yellows

23. Bluegill Sunfish • Nest in dense colonies • Territorial males build nests • 15% of males have territories • Females arrive & lay eggs • Male tends eggs & nest

24. Dense Colonies

25. Males Establish Territory

26. Males Build & Guard Nests

27. Mating Pair

28. Bluegill Sunfish • 3 male reproductive tactics w/ 3 polymorphisms • Age independent • Parental Male • Reproductive maturity at 7 yrs • Large size • Build & defend nests • Satellite male • Sexual maturity 2-5 yrs ave 4 yrs • Die early (less than 7yrs), if persists remain as satellite • Intermediate size • Mimic females • Sneaker • Small & inconspicuous • Sexual maturity 2-3 yrs

29. Parental Male • Grows rapidly & steadily until reaches maturation • 7 yrs • Immature males stay away from mating colony & focus on growth • “Stayaways” • Immature males have relatively small testes per body size

30. Satellite Male • Average male in colony ~4 yrs • Grow fast initially then slows growth rate • Large testes relative to body size • Hovers above colony • When female visits parental male nest satellite drops down into nest • Satellite mimics female sinks down slowly into nest while female is present & releases sperm • Confuses parental male • Achieves reproductive success without having to care for young • Will never mature into parental type

31. Parental Male- Female- Satellite

32. Sneaker Male • Small & inconspicuous male • Ave age in colony 2-3 yrs • Grow fast initially then slows growth rate • Large testes relative to body size • Darts rapidly into nest while parent male & female are mating • Releases sperm onto eggs • High risk of injury from attack • Sneaker male will mature into satellite male

33. Understanding Warriors & Wimps

34. Game Theory • Maynard Smith & George Price, 1973 • “The Logic of Animal Conflict” • Genetic equilibrium between alternate strategies • One strategy can’t be completely invaded by an alternate strategy • Game Theory used to understand patterns of conflict • Which strategy provides highest fitness • Warrior vs. Wimp • Hawk & Dove

35. Hawk & Dove • Competing for a limited resource • Hawk • Initiates aggressive behavior • Aggression continues until injured or opponent is down • Dove • Retreats immediately if opponent initiates aggressive behavior

37. Contest Results • Dove-Dove • Resource shared equally • Neither injured • Hawk-Hawk • Both injured badly • Hawk-Dove • Dove immediately retreats • Hawk gains resource No single best strategy, each strategy is the best answer to the other

38. Hermaphrodites • An organism with both male & female reproductive organs • Common in invertebrates & fishes • 2 hermaphroditic strategies • Individual persists as hermaphrodite throughout lifetime • Sequential hermaphrodites • Individual transitions from one sex to another within lifetime

39. Hermaphrodite as a lifestyle http://bio.research.ucsc.edu/grad/weaver/Pages/project.html

40. Flatworms Penis Fencing

41. Sequential Hermaphrodites have Sex Change • Change sex in response to size, age, environment • Size advantage hypothesis • Reproductive success increases with body size differently in males & females • By altering sex over lifespan can maximize reproductive success • 2 modes • Protandry • Protogynous

43. Protandry Sex Change • Adults change from male to female as grow • Sex change favored when female reproduction capacity increases faster with body size than does the number of eggs produced by the male • Large females produce lots of eggs • Small males produce lots of sperm • Start out as male, then as reach large size switch to female • Found in species that have no direct male-male competition • Examples mollusks, crustaceans, fish & some plants

45. Protandry Sex Change • Example Amphiprion Anemone fishes • Live in or near sea anemones w/o being injured • Protected by anemone stinging cell in a symbiotic relationship • Males don’t have to fight to maintain territory • Group contains 1 monogomous pair & juveniles • Females larger produce more eggs • Smaller individual of pair is male • Increased reproductive fitness for both

47. Anemone Fishes

48. Protogynous Sex Change • Adults change from female to male as grow • Opposite pattern of sex change favored when males protect spawning site or territory • Large males have increased fertility as they are able to monopolize multiple females • Start out as females & change sex into males as grow large enough to defend a territory • Examples some fish

49. Protogynous Sex Change • Dascyllus damselfish • Social groups of several males & females • Male-male competition is high • Selection favors large males • Individuals start as female & become male as become large enough to compete for females

50. Dascyllus Damselfish