The Effects of Bot Fly Parasitism on Aggression in White-footed Mice ( Peromyscus leucopus) Michael J. Cramer and Guy Came...
Sexual Selection <ul><li>Selection to maximize number of matings </li></ul><ul><li>Mechanisms </li></ul><ul><ul><li>Compet...
Mating System in  Peromyscus <ul><li>Ranges from promiscuity to facultative monogamy </li></ul><ul><ul><li>Males home rang...
Aggression in  Peromyscus <ul><li>Aggression limited to breeding season </li></ul><ul><li>Sex differences in home range an...
Parasitism <ul><li>Potential effect on population ecology of both host and parasite species </li></ul><ul><li>Has been stu...
Peromyscus  Bot Fly Life Cycle Females lay eggs in host habitat. Hosts pick up newly hatched larvae . Larvae migrate to in...
Reproductive Cost of Bot Fly Parasitism ? <ul><li>May disrupt pregnancy or lactation </li></ul><ul><li>No evidence of cast...
Objective <ul><li>Determine effects of bot fly parasitism on aggressive behavior </li></ul><ul><li>Test hypothesis that an...
Animal Subjects <ul><li>Trapped on four 6 x 6 grids in beech-maple forest in southwestern Ohio </li></ul><ul><li>Individua...
Intrasexual Aggression Trials <ul><li>Individuals from different grids tested in neutral arena at night in field </li></ul...
Avoid contact with opponent Avoidance/Retreat Up on hind legs, front paws forward; may hit opponent Defense/Retaliation Tu...
<ul><li>Climb-on    Aggressive Groom </li></ul><ul><li>Submissive Posture    Retaliation </li></ul>
Statistical Analysis <ul><li>Analyze sexes separately </li></ul><ul><li>Index of aggression:  factor loadings of principal...
PCA Loadings:  Males Aggressive Submissive
PCA Loadings:  Females Aggressive Submissive
Test of Aggression for Males Aggression higher for uninfected males. Aggressive Submissive
Test of Aggression for Females Aggression similar for uninfected and infected females. Aggressive Submissive
Conclusion <ul><li>Males    uninfected more aggressive </li></ul><ul><li>Females     aggression similar  </li></ul><ul><...
Why Sex Differences <ul><li>Differences between sexes may be explained by mating system </li></ul><ul><li>Male aggression ...
Further Study <ul><li>Increase sample size for males </li></ul><ul><li>Investigate other mechanism of sexual selection:  m...
Acknowledgements <ul><li>Field Work </li></ul><ul><ul><li>Diane McCubbin </li></ul></ul><ul><ul><li>Theresa Pfarr </li></u...
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The effects of bot fly parasitism on aggressive behavior in Peromyscus leucopus

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84th Annual Meeting of the American Society of Mammalogists, Humbolt University, Arcata, California.

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The effects of bot fly parasitism on aggressive behavior in Peromyscus leucopus

  1. 1. The Effects of Bot Fly Parasitism on Aggression in White-footed Mice ( Peromyscus leucopus) Michael J. Cramer and Guy Cameron Department of Biological Sciences University of Cincinnati
  2. 2. Sexual Selection <ul><li>Selection to maximize number of matings </li></ul><ul><li>Mechanisms </li></ul><ul><ul><li>Competition for mates (intrasexual) </li></ul></ul><ul><ul><li>Mate selection (intersexual) </li></ul></ul><ul><li>Strength dependent on mating system </li></ul>
  3. 3. Mating System in Peromyscus <ul><li>Ranges from promiscuity to facultative monogamy </li></ul><ul><ul><li>Males home ranges that overlap with several females </li></ul></ul><ul><ul><li>Dominance hierarchy determines number of matings </li></ul></ul><ul><li>Some evidence of multiply mated females </li></ul>
  4. 4. Aggression in Peromyscus <ul><li>Aggression limited to breeding season </li></ul><ul><li>Sex differences in home range and territory </li></ul><ul><ul><li>Male  home range large, territory used mainly for access to females </li></ul></ul><ul><ul><li>Female  home range small, territory used mainly for nesting and rearing young </li></ul></ul><ul><li>Intrasexual aggression greater for males than females </li></ul><ul><ul><li>Dominance site-specfic </li></ul></ul>
  5. 5. Parasitism <ul><li>Potential effect on population ecology of both host and parasite species </li></ul><ul><li>Has been studied in the context of sexual selection (parasite-mediated sexual selection) </li></ul>
  6. 6. Peromyscus Bot Fly Life Cycle Females lay eggs in host habitat. Hosts pick up newly hatched larvae . Larvae migrate to inguinal region and develop warble. After 3 rd instar, larvae exit host and burrow underground to pupate. Flies emerge and mate at aggregation sites. 5 days 21 days P. Meyer C. N. Shiffer M. J. Cramer
  7. 7. Reproductive Cost of Bot Fly Parasitism ? <ul><li>May disrupt pregnancy or lactation </li></ul><ul><li>No evidence of castration </li></ul><ul><li>No evidence of disruption of gonad function (sperm and egg development) </li></ul><ul><li>Gonad weight lower for infected animals </li></ul><ul><li>May affect reproductively important behaviors </li></ul><ul><ul><li>Competition for mates </li></ul></ul><ul><ul><li>Mate choice </li></ul></ul>
  8. 8. Objective <ul><li>Determine effects of bot fly parasitism on aggressive behavior </li></ul><ul><li>Test hypothesis that animals infected with bot flies are less aggressive than uninfected animals </li></ul><ul><li>If infected animals are less aggressive, then they may not mate as often as uninfected animals </li></ul>
  9. 9. Animal Subjects <ul><li>Trapped on four 6 x 6 grids in beech-maple forest in southwestern Ohio </li></ul><ul><li>Individuals given unique marks </li></ul><ul><li>Animals tested during summer </li></ul><ul><ul><li>Peak density, reproduction and infection </li></ul></ul>
  10. 10. Intrasexual Aggression Trials <ul><li>Individuals from different grids tested in neutral arena at night in field </li></ul><ul><li>10 minute trials (2 minutes acclimation time) videotaped </li></ul><ul><li>Tapes of each trial viewed in lab </li></ul><ul><ul><li>Score behaviors </li></ul></ul><ul><ul><li>Measure locomotion time </li></ul></ul>
  11. 11. Avoid contact with opponent Avoidance/Retreat Up on hind legs, front paws forward; may hit opponent Defense/Retaliation Turn on side, ears flat, eyes half-closed Submissive Posture Quick move towards opponent Lunge Paws on opponent’s back Climb-on Bites, hits, or kicks opponent Attack Groom opponent on face or back Aggressive Groom Description Behavior
  12. 12. <ul><li>Climb-on  Aggressive Groom </li></ul><ul><li>Submissive Posture  Retaliation </li></ul>
  13. 13. Statistical Analysis <ul><li>Analyze sexes separately </li></ul><ul><li>Index of aggression: factor loadings of principal components analysis of behaviors </li></ul><ul><li>Paired t-test: response of one individual dependent on behavior of the other </li></ul><ul><li>H o (null): aggression index similar regardless of infection status </li></ul><ul><li>H A (alternate): infected animal less aggressive relative to uninfected animal </li></ul>
  14. 14. PCA Loadings: Males Aggressive Submissive
  15. 15. PCA Loadings: Females Aggressive Submissive
  16. 16. Test of Aggression for Males Aggression higher for uninfected males. Aggressive Submissive
  17. 17. Test of Aggression for Females Aggression similar for uninfected and infected females. Aggressive Submissive
  18. 18. Conclusion <ul><li>Males  uninfected more aggressive </li></ul><ul><li>Females  aggression similar </li></ul><ul><ul><li>Interpretation of index may be compromised by loading of attack behavior on PC1 </li></ul></ul>
  19. 19. Why Sex Differences <ul><li>Differences between sexes may be explained by mating system </li></ul><ul><li>Male aggression may be subject to stronger sexual selection: competition for matings </li></ul><ul><li>Female aggression may operate in different context: nest defense </li></ul><ul><ul><li>Trials were not conducted on females who were pregnant or lactating </li></ul></ul>
  20. 20. Further Study <ul><li>Increase sample size for males </li></ul><ul><li>Investigate other mechanism of sexual selection: mate choice </li></ul><ul><ul><li>Do females avoid mating with infected males? </li></ul></ul>
  21. 21. Acknowledgements <ul><li>Field Work </li></ul><ul><ul><li>Diane McCubbin </li></ul></ul><ul><ul><li>Theresa Pfarr </li></ul></ul><ul><ul><li>Kelly Roberts </li></ul></ul><ul><ul><li>Ashley Mattingly </li></ul></ul><ul><li>Ohio Department of Natural Resources, Division of Wildlife </li></ul><ul><ul><li>Randy Morgan </li></ul></ul><ul><ul><li>Todd Haynes </li></ul></ul><ul><li>Funding: UC Department of Biological Sciences </li></ul><ul><ul><li>Wieman Summer Research Grant </li></ul></ul><ul><li>Analysis/Discussion </li></ul><ul><ul><li>Craig Wilmhoff </li></ul></ul><ul><ul><li>Andrew Osterberg </li></ul></ul><ul><ul><li>Matt Hopton </li></ul></ul><ul><ul><li>J. Andrew Roberts </li></ul></ul><ul><ul><li>Phil Taylor </li></ul></ul><ul><ul><li>Jerry Hinn </li></ul></ul><ul><li>Research Advisory Committee </li></ul><ul><ul><li>George Uetz </li></ul></ul><ul><ul><li>Ken Petren </li></ul></ul><ul><ul><li>Nancy Solomon </li></ul></ul><ul><ul><li>Michal Polak </li></ul></ul><ul><ul><li>Tom Kane </li></ul></ul>

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