Lab 12: Animal Behavior

1. Lab 12: Animal Behavior Pill bugs, roly-polies, potato bugs – what do you call ‘em? (either way they’re crustaceans)

2. The Test Subjects • For our animal behavior lab, we’ll be using the common pill bug (or whatever). • Official name: Woodlouse or Armadillidiumvulgare http://backyardsafari.files.wordpress.com/2010/11/0-pillbugwalking.jpg

3. The Test • In this experiment, you’ll be running a test to determine behavioral preferences of the pillbugs. • You’ll be using a container in which one side provides a certain stimulus and the other side provides a different one. • What exactly those stimuli are is up to you, but you need to decide that now. • You ultimately need three different stimuli, and can use combinations of others.

4. The Stimuli • Some stimuli to consider: • Light/dark • Sweet/sour(acid/base) • Saltiness • Temperature • (cold doesn’t work well for them so that’s obvious, but you can compare heat to ambient temperature) • Spicy • Light color • Make this decision via a written proposal in your lab notebooks and by writing it on a piece of paper (and turning it in). • You always need a control, however – one side of your choice chamber is always going to be a plain ol’ damp cotton ball.

5. The Procedure • Follow the procedure for Lab 12 in your lab manuals. • The lab manual uses fruit flies; we’ll be doing the same experiment but with our pillbugs. • We’ll need to construct a choice chamber, which for us is simply two bottles whose bottoms have been cut off and taped together. • Label each end A and B so you can keep track of stuff. • Be sure the bottles overlap a little so that, when taped, you don’t have any exposed adhesive.

6. The Procedure • Take your 20-30 pillbugs and place them into the chamber. • Place two damp cotton balls (just water) on either side. Make sure your cotton ball is stuck inside the cap and doesn’t fall in. • Let the test subjects mill around for a little bit. • Now’s a good time to make hypotheses for which of your stimuli they’d prefer over others. • You’ll have to “extend” certain things. • For example, if you read that they live under logs and rocks, then they’ll likely prefer darkness to light. • For example: If they eat mostly decaying wood (a carbohydrate), they’ll probably also enjoy things that have sugar.

7. The Choices • Of course, in order to reject the null hypothesis we needchoices. • Trade out one of your cotton balls for a “stimulus.” • Write down how many pillbugs are on each side. Only do this once the entire experiment – you’ll see why later. • Provide another 5 minutes for more pillbug millage.

8. The Choices • After those five minutes, count the pillbugs on each side and record the information. • Move to your next stimulus. • You’re ultimately going to do two trials for each stimulus, but you’ll do it in the order of: • Stimulus 1 (Trial 1) • Stimulus 2 (Trial 1) • Stimulus 3 (Trial 1) • Stimulus 1 (Trial 2) • Stimulus 2 (Trial 2) • Et cetera…

9. Assorted Important Stuff • For chi-squared purposes, ignore the original count of how many are on each side. • Your “expected” values are 50% are on one side and 50% are on the other. • The lab manual says to do otherwise – ignore that too. • RUN MORE THAN ONE TRIAL AT ONCE! • If everyone has enough pillbugs for one run and there are still some left over, get some more. • If not, just be efficient with your time.

10. Overall Sequence • Create choice chamber. • Put around 20 pillbugs in the choice chamber. • Put a damp (with water) cotton ball in each side. • Provide 5 minutes of “milling around” time. • Record how many are on each side. This is your control. • Only do this step once. • Trade one cotton ball out for a dry one. • Provide 5 minutes of “milling around” time. • Count how many are on each side. • Repeat steps 6-7 with a different stimulus. • Repeat step 9 for all your stimuli to complete a second run for each. • While you’re waiting: Complete a chi-squared analysis for the control data. Ensure that there’s no significant preference shown. • Is there a preference shown? Consider that for your lab write-up. It may invalidate your results (but will not cost you points).

11. Formal Lab Report Details • Refer to the file Lab Report Formatting Guidelines and Rubric found in the Labs section of my website. • Besides what’s contained therein, here’s some other stuff to know: • It must be typed. Graphs need to be done in Excel or a similar program. • You will work as a lab table to create a formal lab report. • You may divide the work any way you like, but I suggest each taking a section and rotating duties for each lab.

12. Your lab report must include: • Chi-squared analysis for each stimulus • Chi-squared analysis for the class’s data (for dry cotton – more later) • Table of results • Graph of results (best done as a summed paired bar graph for each “stimulus” – Side A and Side B totals) • Discussion of your hypotheses – does your data support them or not? Importantly, why? • Discussion of relevant questions as found on Page S150 and S151 of your lab manual. • Discussion of limitations of your experiment or corrections that could be made. • This part’s important and will not cost you any points. • In fact, the more critical you are of your own work, the happier I’ll be.

13. Graphing Tips • Here are three nice little graphing tips for the rest of your science lives: • Dependent (measured) variables go on the Y-axis, independent (controlled) variables go on the X-axis. • Use bar graphs if there is no continuous relationship among the different variables. • A good, cheap, consistent graph title is “_____ as a function of _____.” • For example, “Plant growth as a function of light level.”

14. Chi-Squared Details • Since pillbugs either went to Side A or Side B, you only have one degree of freedom (df). • If you somehow counted “middle” separately, that would make for 3 degrees of freedom. • We have to assume that each side of the bottle is originally equal, so your “expected” numbers on each side represent half of the total number of pill bugs. • For each of your stimuli, your chi-squared test will use these variables: • Observed: [what you counted] • Expected: 10 (or whatever is half of your total) • Degrees of freedom: 1.

15. Chi-Squared Details • You’ll also do a chi-squared analysis for your control data. • If you had, for example, 17 on one side and 3 on the other prior to introducing any stimulus, you’ll test to see whether that’s a significant difference. • To put it another way, suppose one of the two bottles is preferred for some other reason. • Tastier saliva residue, maybe? • If our control numbers suggest that there is a significant difference in our bottles themselves, we need to view our other results differently. • Continued…

16. Chi-Squared Details • For another example, suppose after your control run, 17 pillbugs were on Side A and 3 were on Side B. • You trade out Side B’s cotton ball for something acidic. • After 5 minutes, Side A = 19 and Side B = 1. • A chi-squared analysis would say that’s significant compared to the expected 10/10. • However, is that significant if we expected 17 and 3? Not really. • So doing this test of our control data helps us ensure that the control really is a control, and that each side of the bottle really is equal. • Ideally, the control results would be insignificant, but if they’re significant, just be sure you address that in the lab report.

17. Final Note • For the “wet/dry” runs, let’s pool our class data. • Take a moment to sum your runs’ numbers for each category. • I’ll sum the data and include it in the “Assignments” page listing for our lab report. • Maybe your wet/dry run is insignificant, but the class’s data shows significance. We’ll see.