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LSM3251  ECOLOGY  PROJECT Group 2B: Choo Wan Yee Jordan Michael Senia Yoon Hui Lian
Dung beetles <ul><li>Order Coleoptera (beetles), family Scarabaeidae </li></ul><ul><li>Found in a variety of habitats </li...
Dung beetle morphology
Dung beetle species in Pulau Ubin Horns on head of male Pronotum colouration Distinctive  reddish  pronotum Underside of l...
Catharsius molossus Large -bodied!
Important ecological roles <ul><li>Nutrient recycling </li></ul><ul><li>Seed dispersal </li></ul><ul><li>Controlling of pe...
Foraging & nesting behaviour <ul><li>Some spend more time in the air while others prefer to fly short distances and instea...
Receptors in dung beetles 2. Visual receptors 1. Olfactory receptors Polarized light 3. Infrared receptors ?
Thermoreceptors in organisms <ul><li>Beetle  Melanophila acuminata   </li></ul><ul><li>Blood-sucking bugs  Triatoma infest...
Infrared detection in dung beetles? <ul><li>The ability to detect infrared radiation (IR) produced by a warm dung pile wou...
Experimental Hypothesis <ul><li>Null hypothesis: </li></ul><ul><li>There is no difference between the number of dung beetl...
Sampling Site Pulau Ubin
The Team
<ul><li>Primary forest has been eradicated on the island </li></ul><ul><li>Comprised mainly of dry land and mangrove secon...
Local Environment
Wild Boar Dung Trap Site
Substrate Completed Trap
Experimental Design <ul><li>Hypothesis </li></ul><ul><ul><li>Dung beetles prefer to  forage in warm dung rather than cold ...
Trench-digging
Empty Trap
Bottom Soil Layer
Insulation
Prepared Control
Heat Packs
Prepared Treatment
Treatment in Place Under Topsoil
1 m
Thermal Images  Treatment Control
Obtaining Data
Statistical Analysis <ul><li>Null hypothesis : No difference between numbers of beetles in control and treatment </li></ul...
Statistical Analysis <ul><li>Hypothesis Testing </li></ul><ul><ul><li>Determine if difference between 2 means (effect of h...
One-tailed t-test <ul><li>Shaded region represents values of test stat that may be attributed to real variation rather tha...
Results <ul><li>Qn: Is mean number of beetles found in warm dung greater than that in cold dung?  </li></ul><ul><li>t-valu...
Results <ul><li>What can we infer from the results:  </li></ul><ul><ul><li>Unable to attribute variation between beetle ab...
Limitations  &  Improvements
Spatial <ul><li>Limited sampling at western part of Pulau Ubin; only 3 sites.  </li></ul>
<ul><li>Only allowed small-scale sampling  </li></ul><ul><li>Leads to a very small sample size of 6 </li></ul><ul><li>Only...
Resources <ul><li>Effectiveness of heat packs used </li></ul>
<ul><li>Poor heat conductivity of plastic containers  </li></ul>Resources
Conclusion <ul><li>Failed to reject null hypothesis </li></ul><ul><li>However, cannot reach a definite conclusion that the...
Challenges Rocky terrain Sweat… …  and blood  Exhaustion after the fieldtrip
What we gained Knowledge of dung beetles Knowledge of other organisms  Knowledge of nature
Teamwork Treat
Q & A
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Investigation into the existence of Thermal Sensory Capabilities of Dung Beetles

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Investigation into the existence of Thermal Sensory Capabilities of Dung Beetles

  1. 1. LSM3251 ECOLOGY PROJECT Group 2B: Choo Wan Yee Jordan Michael Senia Yoon Hui Lian
  2. 2. Dung beetles <ul><li>Order Coleoptera (beetles), family Scarabaeidae </li></ul><ul><li>Found in a variety of habitats </li></ul><ul><li>- i.e. deserts, forests, pastures </li></ul><ul><li>Dung as food source and for making brood balls </li></ul><ul><li>Different species prefer different kinds of dung </li></ul><ul><li>- i.e. Onthophagus species prefer swine feces . </li></ul>
  3. 3. Dung beetle morphology
  4. 4. Dung beetle species in Pulau Ubin Horns on head of male Pronotum colouration Distinctive reddish pronotum Underside of legs is yellowish Underside of legs is brownish Onthophagus babirussoides Onthophagus leusermontis Onthophagus semicupreus
  5. 5. Catharsius molossus Large -bodied!
  6. 6. Important ecological roles <ul><li>Nutrient recycling </li></ul><ul><li>Seed dispersal </li></ul><ul><li>Controlling of pest </li></ul><ul><li>populations </li></ul>
  7. 7. Foraging & nesting behaviour <ul><li>Some spend more time in the air while others prefer to fly short distances and instead simply perch atop the leaves of low-lying branches until they catch the scent of nearby dung </li></ul>Dwellers Tunnelers Rollers 1. Detect dung smell 2. Fly towards dung, land on ground a distance away & walk towards it
  8. 8. Receptors in dung beetles 2. Visual receptors 1. Olfactory receptors Polarized light 3. Infrared receptors ?
  9. 9. Thermoreceptors in organisms <ul><li>Beetle Melanophila acuminata </li></ul><ul><li>Blood-sucking bugs Triatoma infestans </li></ul>Melanophila acuminata (De Geer, 1774) Triatoma infestans Klug, 1834
  10. 10. Infrared detection in dung beetles? <ul><li>The ability to detect infrared radiation (IR) produced by a warm dung pile would: </li></ul><ul><li>- allow accurate estimation of distance to the dung </li></ul><ul><li>- reduce the time taken to reach the dung </li></ul><ul><li>Fresh dung is less likely to be inhabited by other organisms, reducing the need for competition for resources </li></ul><ul><li>Presence of thermoreceptors in other organisms to aid in foraging and survival </li></ul><ul><li>To test our assumption that IR thermoreceptors exist, our study sought to demonstrate a preference for warm dung over cold dung among the beetle species. </li></ul>
  11. 11. Experimental Hypothesis <ul><li>Null hypothesis: </li></ul><ul><li>There is no difference between the number of dung beetles in the control and treatment set ups. </li></ul><ul><li>Alternative hypothesis: </li></ul><ul><li>The number of dung beetles in the treatment is more than the number of beetles in the control. </li></ul>
  12. 12. Sampling Site Pulau Ubin
  13. 13. The Team
  14. 14. <ul><li>Primary forest has been eradicated on the island </li></ul><ul><li>Comprised mainly of dry land and mangrove secondary forest </li></ul><ul><li>Traps were placed in a section of dry land secondary forest </li></ul><ul><li>Environmental conditions of sampling sites: </li></ul><ul><ul><li>Relatively dry soil </li></ul></ul><ul><ul><li>Near forest edge </li></ul></ul><ul><ul><li>Wild boar dung found nearby (most likely source of food supply) </li></ul></ul><ul><li>Anthropogenic Activity </li></ul><ul><ul><li>Recreation </li></ul></ul><ul><ul><li>School activities i.e. cadets </li></ul></ul>Habitat
  15. 15. Local Environment
  16. 16. Wild Boar Dung Trap Site
  17. 17. Substrate Completed Trap
  18. 18. Experimental Design <ul><li>Hypothesis </li></ul><ul><ul><li>Dung beetles prefer to forage in warm dung rather than cold dung </li></ul></ul><ul><li>Methods </li></ul><ul><ul><li>3 Sites (n=6) </li></ul></ul><ul><ul><li>Paired Treatment/Control </li></ul></ul><ul><ul><ul><li>Effect of confounding variables standardized, both are affected </li></ul></ul></ul><ul><ul><ul><li>Each site comprised of one 1 control trap, 1 treatment trap </li></ul></ul></ul><ul><ul><ul><li>Treatment= heated dung; Control= ambient temperature dung </li></ul></ul></ul><ul><ul><ul><ul><li>Treatment trap included chemical heat packs to keep dung warm </li></ul></ul></ul></ul><ul><ul><li>Soil layer placed below dung </li></ul></ul>
  19. 19. Trench-digging
  20. 20. Empty Trap
  21. 21. Bottom Soil Layer
  22. 22. Insulation
  23. 23. Prepared Control
  24. 24. Heat Packs
  25. 25. Prepared Treatment
  26. 26. Treatment in Place Under Topsoil
  27. 27. 1 m
  28. 28. Thermal Images Treatment Control
  29. 29. Obtaining Data
  30. 30. Statistical Analysis <ul><li>Null hypothesis : No difference between numbers of beetles in control and treatment </li></ul><ul><li>Alternative hypothesis : More beetles in treatment than control </li></ul><ul><li>t-test= Difference between two means </li></ul><ul><ul><ul><ul><li>Standard Error of Difference </li></ul></ul></ul></ul><ul><ul><li>Compare the means of two groups (treatment and control) and assess if variation is statistically significant </li></ul></ul><ul><ul><li>Paired one-tailed t-test </li></ul></ul>
  31. 31. Statistical Analysis <ul><li>Hypothesis Testing </li></ul><ul><ul><li>Determine if difference between 2 means (effect of heat packs) is large enough to be considered real effect rather than random variation </li></ul></ul><ul><ul><li>t crit = max or min value of test statistic that may be attributed to random variation </li></ul></ul><ul><ul><ul><li>One-tailed t-test focuses on maximum value </li></ul></ul></ul><ul><ul><li>Level of confidence: probability that variation between treatment and control is random (set to 0.05) </li></ul></ul><ul><ul><li>If test statistic is greater than t crit under one-tailed t-test, then variation is not random under given level of confidence </li></ul></ul>
  32. 32. One-tailed t-test <ul><li>Shaded region represents values of test stat that may be attributed to real variation rather than random </li></ul>faculty.uccb.ns.ca/~erudiuk/Intr...k25m.htm
  33. 33. Results <ul><li>Qn: Is mean number of beetles found in warm dung greater than that in cold dung? </li></ul><ul><li>t-value (all beetles) = 0.29 < t crit = 2.92 </li></ul><ul><ul><li>No significant difference between no. of beetles found in treatment and control </li></ul></ul><ul><ul><li>Fail to reject null hypothesis </li></ul></ul>(b) (a)
  34. 34. Results <ul><li>What can we infer from the results: </li></ul><ul><ul><li>Unable to attribute variation between beetle abundance in treatments and controls to real variation </li></ul></ul><ul><ul><li>Observed variation may simply be random </li></ul></ul><ul><ul><li>Existence of thermal sensory capabilities remains unconfirmed </li></ul></ul>
  35. 35. Limitations & Improvements
  36. 36. Spatial <ul><li>Limited sampling at western part of Pulau Ubin; only 3 sites. </li></ul>
  37. 37. <ul><li>Only allowed small-scale sampling </li></ul><ul><li>Leads to a very small sample size of 6 </li></ul><ul><li>Only 30 dung beetle individuals collected in whole experiment </li></ul>Time
  38. 38. Resources <ul><li>Effectiveness of heat packs used </li></ul>
  39. 39. <ul><li>Poor heat conductivity of plastic containers </li></ul>Resources
  40. 40. Conclusion <ul><li>Failed to reject null hypothesis </li></ul><ul><li>However, cannot reach a definite conclusion that thermoreceptors are absent in dung beetles </li></ul><ul><li>Presence of various types of thermoreceptors in many organisms </li></ul><ul><li>Possibility infrared thermoreceptors also present in dung beetles </li></ul><ul><li>Further studies required </li></ul>
  41. 41. Challenges Rocky terrain Sweat… … and blood Exhaustion after the fieldtrip
  42. 42. What we gained Knowledge of dung beetles Knowledge of other organisms Knowledge of nature
  43. 43. Teamwork Treat
  44. 44. Q & A

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