Lab 8: Mark & Recapture - Detailed Notes

Lab 8: Mark & Recapture - Objectives

  • Sample a lab population randomly
  • Mark live animals
  • Record collected data

Preparation

  • Understand background info from instructor regarding the experiment.
  • Familiarize with the instructions provided.

Introduction

  • The experiment involves a mark-recapture method using lab-raised beetles to estimate the population size.
  • Following the procedure, you will recapture the marked beetles next week for analysis.

Procedure Overview

  • Each group (2-4 students) will work with a designated beetle colony.
Steps for the Experiment

  1. Label Recording

    • Each beetle bin is labeled with a specific number; record this for future identification.
    • Wear masks if sensitive to beetles or bran (available at the lab front).

  2. Creating Sampling Squares

    • Use white string to create 20 ‘sampling squares’ by placing strings across the bin using dots as guides.
    • Secure the string with tape or a knot.

  3. Random Sampling

    • Randomly select 5 out of the 20 squares for sampling. Options include:
      • Mapping and numbering squares, then using random number generator
      • Writing numbers on paper, shuffling, and selecting.

  4. Collecting Samples

    • Use a ‘beetle sampler’ (ladle) to scoop from the first selected square into an aluminum pan.
    • Avoid overfilling and excessive digging to prevent crushing beetles.

  5. Repeat Sampling

    • Continue sampling through all five selected squares.

  6. Identifying Live Beetles

    • Use tweezers to separate live beetles and place them in small plastic cups.
    • Stop sampling if reaching 50 live beetles or capture at least 15 beetles; if not, sample additional squares.

  7. Marking Beetles

    • Mark each beetle with 2 dots of white paint on the back using a toothpick.
    • Ensure dots are visible but not excessive; avoid crushing the beetles.

  8. Drying Time

    • Allow beetles to sit for 30 minutes for paint drying.
    • Monitor to prevent smudging; if necessary, flip beetles with tweezers.

  9. Count & Record

    • Count marked beetles and ensure all group members record this number for future reference in population estimates.

  10. Returning Marked Beetles

    • Release marked beetles back into their habitat evenly.

  11. Cleanup

    • Dispose of excess bran from the sample container back into the original bin and redistribute it to maintain environmental consistency.