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Social Structure: stability/instability

Social Structure: stability/instability. WFSC 422 Ethology Presentation 6.1. Dr. Jane M. Packard, WFSC TAMU j-packard@tamu.edu. Territories vs. dominance. Territories Intense combat between SEVERAL groups defense of space- group home range group access to resources Dominance

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Social Structure: stability/instability

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  1. Social Structure: stability/instability WFSC 422 Ethology Presentation 6.1 Dr. Jane M. Packard, WFSC TAMU j-packard@tamu.edu

  2. Territories vs. dominance • Territories • Intense combat between SEVERAL groups • defense of space- group home range • group access to resources • Dominance • Minor conflict among individuals in ONE group • defense of personal distance • individual access to resources

  3. Example: trumpeter swans

  4. Swans- “in group” “out group” • In group- stable hierarchy • family- parents & offspring • no turnover in membership • each learns what to expect from others • Out group- contest of strength • family groups gather on lake during migration • contests between families over resources • bigger, stronger families win over singles & smaller families

  5. Social Structure- 3 hypotheses • In stable groups, conflict is predictable • e.g. pecking order in chickens • In unstable groups, conflict depends on friends & rivals • e.g. appeasement & grooming in baboons • In social insects, castes are fixed (nutrition) • no conflict e.g. Leaf cutter ants

  6. Example- chickens

  7. Stable- chicken “peck order” • Alpha- 1 hen pecks all others • beta- “second in command” • pecked by alpha • pecks all others • omega- “bottom of hierarchy” • pecked by all others • does not peck back • stability depends on order of entry into group- younger new ones are pecked

  8. Unstable- baboons (open group)

  9. Example- baboon appeasement

  10. Baboons- age affects stability • Females • youngest daughter supported by mother • older daughters drop in rank • males • leave mother’s group, enter a new group • form alliance with females, appease males • rise in rank as older males weaken or die

  11. Example- fixed instinct

  12. Stable castes- leaf cutter ants

  13. Ant castes- “hard wired roles” • Diploid (fertilized)- females • largest- reproductive queen • large- soldiers • small- workers (brood care, foragers) • dependent on nutrition at a critical stage of development • haploid (unfertilized)- males • produced near the end of queen’s life • mate (3-4 with one queen), then die

  14. SUMMARY • Distinguish between out-group intense combat (e.g. defense of territory) and in-group mild conflict (e.g. hierarchy) • 3 hypotheses of social structure • Stable groups => predictable conflict • Unstable groups=> friends & rivals change • Social insects=> castes fixed by nutrition

  15. Action Items • Do answers for Q6.1, Q6.2 • Search idealibrary for “social structure” • Search Animal Behavior for “dominance”, “hierarchy” • Post examples and sources on WebCT Discussion for Unit 6

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