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Cgs Talk Jan 2009

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Gregarious behavior of spiny lobsters

Gregarious behavior of spiny lobsters

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  • 1. Cooperative Defense by Non-Kin Related Caribbean Spiny Lobsters Under Attack by Cooperating Predators Kari Lavalli CGS, Division of Natural Science, Boston University William F. Herrnkind Dept. of Biological Science, Florida State University
  • 2. Natural Selection
    • Main process responsible for evolutionary change
    • Produces adaptation by elimination of less fit genotypes
      • Maladaptive traits should be eliminated
      • Certain genes gain representation in the following generations at a greater frequency to that of other genes located at the same chromosome positions
    • Is compatible with most patterns/phenomena seen in nature, including behavioral traits
  • 3. Natural Selection & Evolution
  • 4. Natural Selection is a “Selfish” Process in Many Respects It acts on individuals to maximize their own reproductive output Paradox? We see LOTS of animals living in cohesive social groups, cooperating, and appearing to behave “altruistically”
  • 5. Behaviors that Seem to Violate Natural Selection Principles
    • Darwin recognized one behavioral trait that was not compatible with Natural Selection
      • It posed, “one special difficulty, which at first appeared to me insuperable, and actually fatal to my whole theory.”
      • Evolution of sterile castes in social insects
        • termites, ants, bees, wasps
        • sterile individuals forego reproduction to raise queen’s offspring
        • Darwin suggested that natural selection might operate on the level of the family here, rather than on the individual
    Explained by Kinship
  • 6. Seemingly Cooperative Activities
    • Food Giving – Altruistic? Kinship?
    • Food Sharing – Altruistic? Kinship?
    • Prey Capture – Cooperative? Selfish?
    • Parasite Removal – Altruistic? Selfish?
    • Predator Vigilance & Warning – Cooperative? Selfish?
    • Defense Against Predators – Cooperative? Selfish?
    • Heat Retention – Cooperative? Selfish?
    • Helping to Rear Offspring (skip reproduction) – Kinship? Selfish?
    • Care-giving Behavior (for sick/injured individuals) – Kinship?
  • 7. Living in Groups for Predation Avoidance
    • More efficient predator detection
    • May be more difficult to detect than scattered individuals (encounter effect)
    • May be more difficult to target (confusion effect)
    • Less likely to be victim of predator’s attack (dilution effect)
    • Possibility for coordinated group defense (if you possess weaponry)
  • 8. Examples of Arthropod Groups
  • 9. Phalanx of musk ox formed when threatened by wolves (calves and cows on the inside, bulls on the outside rim) The phalanx can also initiate coordinated counterattacks upon attacking wolves
  • 10. Aspects of Study
    • Grouping of prey
      • Cause & Function
      • Survival success
      • Cooperation?
    • Group attack by predator
      • Affect of Dominance Hierarchies
      • Degree of cooperation
    Subject of today’s talk
  • 11. Why Lobsters?
    • Two families of lobsters have gregarious species
      • Scyllaridae (slipper or shovel-nosed lobsters)
      • Palinuridae (spiny lobsters)
        • Stridentes
        • Silentes
    • Both families have:
      • species that communally den
      • species that migrate communally
      • solitary species
      • long, dispersive larval lives
        •  unlikely adults share kinship
    • First we examined slipper lobsters (weaponless); then spiny lobsters (have weaponry)
  • 12. Prey Life Cycle
  • 13. Methods 1: Weaponless Slipper Lobsters
    • Tethered 8 single lobsters and scattered them, at least 2 m apart, on a limestone reef at a depth of 20 m off Haifa, Israel
    • Tethered 8 lobsters together
    • Repeated 6 times
    • Examined differences in relative predation rates of solitary and grouped lobsters
    • Examined differences in attack behavior of predator (triggerfish)
    Lavalli & Spanier, 2001. Mar. Freshwat. Res. 52 : 1133-1143.
  • 14. Tethering Technique Lavalli & Spanier, 2001. Mar. Freshwat. Res. 52 : 1133-1143.
  • 15. Aspects Examined: Slipper Lobsters
    • Individual attack rate on lobsters
    • Capture risk per individual lobster
    • Fish capture success
    • Group attack rate
    Lavalli & Spanier, 2001. Mar. Freshwat. Res. 52 : 1133-1143.
  • 16. Results: Slipper Lobsters
    • Grouped lobsters:
      • At 3 hours: 1 dead/ 1 injured
      • At 24 hours: 16 dead/ 8 injured
    • Solitary lobsters:
      • At 3 hours: 3 dead / 1 injured
      • At 24 hours: 12 dead / 6 injured
    • No significant difference (Wilcoxin sum rank test) in:
      • individual attack probabilities at 3 hrs or 24 hrs
      • individual lobster capture risk at 3 hrs or 24 hrs
      • or fish capture success at 3 hrs or 24 hrs
      • group attack probability at 3 hours
    • Significant difference at 24 hours , with groups having a higher attack probability; P < 0.016 (Wilcoxin sum rank test)
    Lavalli & Spanier, 2001. Mar. Freshwat. Res. 52 : 1133-1143.
  • 17. Differences Seen in Predator Behavioral Circuits at 3 Hours Solitary Lobsters Grouped Lobsters
  • 18. Conclusion: Confusion Effect Operates only in Short-Term
    • Time to identify the individual to be attacked increases in a group because individuals are hard to delineate.
    BUT, over time, fish figures out individuals within a group and then concentrates on group members.
  • 19. Conclusion: Dilution Effect Not Seen in Short- or Long-Term
    • Dilution Effect predicts that:
    • chance of death = 1/N where N = number of individuals in group
    Solitary lobsters had <50% chance of death or injury; grouped lobsters had a 50% chance of death or injury 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/1
  • 20. Lobsters with Weapons
    • Possession of weapons allows for cooperative defense above and beyond a simple dilution or confusion effect
  • 21. Grouping in Panulirus spp. Codenning and emerging en masse is common in some spiny lobster species Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
  • 22. Panulirus argus Lobsters Queue to Move Across Featureless Terrain Most (95%) queues have 5-20 members Few solitary lobsters or small groups (5%) Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
  • 23. Queues Coil into “Rosettes” If Disturbed Antennae directed outward Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
  • 24. Questions
    • In the open, how are outcomes of encounters of lobsters and their piscine predators influenced by:
      • # of lobsters within the queue/rosette?
      • # of attacking predators?
    Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
  • 25. Predictions
    • Group Size of Lobsters
      • As group size increases:
        • Per capita risk of death should 
        • Fewer lobsters should be killed
    • Group Size of Predator*
      • As group size increases:
        • Per capita risk of death of prey should 
        • More lobsters should be killed
        • Time needed to subdue lobster should 
    • * presupposes that predators cooperate and don’t interfere with others’ attacks
    Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
  • 26. Methods 2: Group Sizes of Spiny Lobsters
    • Group Size of Lobsters
      • Field Studies off FSUML, Gulf of Mexico
        • Tethered solitary or a group of 5 lobsters on reefs
        • No difference in size among lobsters
        • 90 min trials
        • No control over fish group size or fish species
        • No control over fish hunger level
    Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
  • 27. Field Studies
  • 28. Field Studies
  • 29. Description of Fish Behaviors APPROACH (APR): Triggerfish swims to between one and two lobster antenna lengths ATTACK (AT): Triggerfish moves to within one lobster antennae length BITE (B): Triggerfish makes contact with the lobster by either smashing the shell with its mouth or by using the mouth to remove antennal tips or eyes SWIM OVER (SO): Triggerfish turns on side while swimming over lobsters at a distance of approximately 2 antennal lengths Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
  • 30. Description of Lobster Behaviors ANTENNA POINT (AP): Antennae moved and directed at approaching triggerfish ANTENNA WHIP (AW): Lobster uses one or both antennae to lash at fish LUNGE (L): Lobster rapidly thrusts antennae against fish TAIL FLIP (TF): Rapid abdominal flexion causing backward movement PIROUETTE (P): Animal spins rapidly, pointing antennae towards fish that are approaching in all directions Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
  • 31. Pointing by An Individual Lobster
  • 32. Pointing by All Group Members
  • 33. Whipping Behavior
  • 34. Lunging Behavior
  • 35. Field Studies: Results
    • Predators present on reefs included both triggerfish and sheepshead
      • also octopus, but saw no attacks
    Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
  • 36. Field Studies: Results
    • 40% of solitary lobsters killed
    • 0% of grouped lobsters killed
    • significant difference in size of survivors and victims
    t -test, P < 0.001
  • 37. Field Studies: Results N=10 solitary N=4 groups * ANOVA, p <0.001 Bonferoni post-hoc test, p <0.001
  • 38. Field Studies: Results N=10 solitary N=4 groups * ANOVA, p < 0.001 Tukey test, p < 0.001
  • 39. Methods 3: Group Sizes of Lobsters and Fish
    • Group Size of Lobsters
      • Does it change in response to predator presence?
        • 20 lobsters tested in 1999
          • With no fish present
          • With fish present
    • Group Size of Fish
      • Free-ranging lobsters
        • 1, 3, 5, 10, 20 in 2000
        • 1, 5, 10 in 2001
      • Used groups of 5 (2000) or 2 (2001) triggerfish
      • Controlled fish hunger level
    Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
  • 40. Mesocosm Studies
  • 41. Mesocosm Studies
  • 42. Mesocosm Studies
  • 43. Fish Collection
    • 1 group collected off FSUML reefs
    • 1 group collected off Big Pine Key
  • 44. Hourly Changes in Lobster Group Sizes Observed with No Fish Present % Observed Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
  • 45. Hourly Changes in Lobster Group Size Observed with Fish Present % Observed Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
  • 46. Hourly Changes in Lobster Group Size Observed (20 Lobsters Total) % Observed Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
  • 47. Hourly Changes in Lobster Group Size Observed (10 Lobsters Total) % Observed Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
  • 48. Mesocosm Results
    • 2000 Group Sizes
      • No difference in size among intact, injured, or victims
  • 49. Mesocosm Results
    • 2001 Group Sizes
      • No difference in size among intact, injured, or victims
  • 50. Solitary Lobsters have Greater per Capita Death Risk, but No Difference for Grouped Lobsters Regardless of # of Fish N=13 N=13 * * ANOVA, p < 0.001 Actual death risk close to risk predicted by dilution
  • 51. Time to Kill Not Affected by # Lobsters or # of Predators N=13 ANOVA, p = 0.55
  • 52. Removal of Stridulating Organ Has an Effect on Attacks/Kills by Naïve Fish N =15 fish per lobster treatment Pearson’s  2 , p < 0.01
  • 53. Types of Injuries Seen in Mesocosm
    • Solitary lobsters
      • 87.5% killed when fish targeted eyestalks
      • 12.5% killed by a directed attack on abdomen (generally biting huge hole through it or tearing it off)
    • Grouped lobsters
      • 3L: 80% eyestalks removed; 20% abdomen attacks
      • 5L: 76% eyestalks removed; 8% destruction of carapace and removal of vital organs; 8% 1 eyestalk and tailfan removed; 8% 1 eyestalk removed and abdomen attacked
      • 10L: 92% eyestalks removed; 8% abdomen attacked
      • 20L: 93% eyestalks removed; 7% entire antenna removed with subsequent attacks on abdomen
  • 54. Discussion
    • Grouping does not confer much of an advantage to slipper (weaponless) lobsters
    • Solitary spiny lobsters are at greater risk for predation than grouped lobsters
      • predation may be major evolutionary force driving gregarious behavior of P. argus
    • Size of lobster group confers an advantage to individuals that is close to that predicted by dilution effect
    •  number of predators does not impact predation rate (either per capita rate or time needed to make a kill)
      • Likely the result of interference among fish individuals
    • Stridente lobsters may use sound as a deterrent to attacks
  • 55. True Cooperation?
    • Unlikely in lobsters
      • Most likely due to selfish herd behavior
  • 56. Acknowledgements
    • Israeli group:
      • Divers: Stephen Breitstein, Rami Israelov, Amir Yurman, Oz Goffman, Yossi Tur-Caspa, Yossi Zilbiger, Micha Dadon, Joe Breman, Avinoam Breitstein, Dani Kerem, Diana Barshaw
      • Statistical Advice: Efrat Yaskil
    • Florida group:
      • Mark W. Butler, Jason Schratwieser, Scott Andree, Melissa Classon, Scott Donahue, Damon Karras, Sarah Kelly, Kent Smith, Jennifer Zimmerman
    • SWT group:
      • Videoanalysis: Andrea Miller, Jennifer Duran, Greg Cryer, Jeff Foerster, Cassie Malcom, Lisa Quintanilla, Casey Ott
      • Data collection and analysis: Andrew Evans, David Cleveland
      • Fish dominance hierarchy work: David Cleveland
  • 57. Questions?
  • 58. Methods 4: Weapons
    • Examination of Importance of Weapons (Antennae)
      • Mesocosm Studies at KML, Long Key
        • Free-ranging solitary lobsters vs. 1 fish
          • Intact, missing 1 antenna, missing both
        • Tethered solitary lobster vs. 1 fish
          • Intact, missing 1 antenna, missing both
        • Choice tests for fish: intact lobster vs. 1 missing antenna lobster, both tethered and separated in space
  • 59. Mesocosm Results
    • Results for free-ranging lobsters differ from tethered lobsters
    • Lack of antennae likely to result in less survival
  • 60. Mesocosm Results
    • Fish make more bite attempts, land more bites, and have to circle less with free-ranging antennae-less lobsters
    • Free-ranging antennae-less lobsters lunge more, rear-back more and tailflip more than lobsters with antennae
  • 61. Mesocosm Results
    • Fish make more attacks, bite attempts, and land more bites with tethered antennae-less lobsters
    • Tethered antennae-less lobsters rear-back more than lobsters with antennae
  • 62. Mesocosm Results
    • Fish circle more when lobsters have 2 antenna
  • 63. Mesocosm Results
    • Lobsters with 1 antennae more likely to be injured and less likely to survive than those with both
  • 64. Mesocosm Results
    • Differences between time to land first bite between free-ranging lobsters
    • Difference between time to land first bite between single antenna and no antenna lobsters
  • 65. Triggerfish Trials: Questions
    • What are triggerfish attack strategies on solitary and grouped lobsters?
    • What level of cooperation exists within a social grouping of triggerfish?
    • Is there a social hierarchy within a group of triggerfish and what effect does it have on cooperation?
  • 66. Why Triggerfish?
    • Balistes capriscus and B. carolinensis are found in social groups on reefs
      • May be same species
    • Can feed solitarily or can feed in groups
      • Some evidence from our observations in the field (Barshaw et al. 1996) that they can cooperate in subduing prey
      • Also have evidence that triggerfish can interfere with each other’s attacks
  • 67. Fish Approaches & Passes (Pre-Attack Phase)
  • 68. Triggerfish Hover & Bite Behavior (Attack Phase)
  • 69. Chased and Bitten Triggerfish
  • 70. Fish Involved in the Chases
  • 71. Results
    • Who cooperated with whom?
      •  and  ranked individuals most cooperative during attacks
        •  was able to get some food from lobster while attacking
        •  interfered after lobster’s death
        • fish dealing “death blow” took over kill
          • usually  fish
      •  ranked individual most often did not interact with other fish
        • on few occasions of interactions,  ranked fish chased other fish away
      •  fish never cooperated
    • Attacking fish always displayed light banding
      • non-attacker frequently displayed white coloration with trigger up or AID
  • 72. Discussion
    • Hierarchical ranking seems to predict who is likely to cooperate with whom
    • Cooperation is likely selfish
      • Prior to death of lobster, both striking fish can obtain food (legs, gills, internal organs, muscle tissue)
      • After death, fish who deals final death blow “owns” lobster

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