Pillbug Shelter Choice and Humidity Quorum Sensing

ISEF Category: Animal Sciences

Subcategory: Animal Behavior  ·  Difficulty: Beginner  ·  Setup: Home Setup  ·  Time: 1 to 2 Weeks

The Hook

Pillbugs look like tiny armored pebbles, but they make real choices. Put them between two shelters, and the whole group may pile into one side once the conditions feel right. That gives you a simple way to test whether group size changes the final choice. You are studying behavior, moisture, and decision thresholds in one small setup.

What Is It?

Pillbugs, also called roly-polies, lose water easily, so humid spaces matter to them. In this project, you ask whether the bugs only pick the wetter shelter one by one, or whether a group starts to copy itself and settle together after enough animals arrive. That group threshold is the idea behind quorum sensing, which here means a decision shift that happens after a crowd reaches a certain size.

Think of it like students choosing lunch. One person may like both options, but once enough friends sit in one place, the choice gets easier to follow. If pillbugs show the same pattern, their final shelter choice will depend on both humidity and how many peers already gathered.

Why This Is a Good Topic

This project is easy to start, but still real science. You can change humidity, group size, light, or shelter layout and measure whether the bugs split, cluster, or switch sides. That gives you clear data, clean graphs, and a direct link to animal moisture needs, habitat choice, and collective behavior. You can also finish it with school-level materials and basic statistics.

Research Questions

• How does the humidity difference between two shelters affect how many pillbugs choose the wetter shelter?
• What is the effect of group size on the chance that pillbugs reach a clear majority in one shelter?
• Does the time to settle into one shelter change as the humidity gap gets larger?
• To what extent does light level change the humidity-based shelter choice?
• Which group size produces the sharpest switch from split choices to one dominant shelter?
• How does the first pillbug to enter a shelter affect the final group choice?

Basic Materials

• Clear plastic food containers with lids.
• Two identical shelters or hides.
• Pillbugs from a classroom source or outdoor collection site where collection is allowed.
• Spray bottle.
• Distilled water.
• Hygrometer.
• Digital thermometer.
• Paper towels or absorbent bedding.
• Stopwatch or timer.
• Smartphone camera for recording trials.

Advanced Materials

• Humidity-controlled chamber or sealed bins.
• Multiple digital humidity sensors.
• High-resolution camera on a fixed stand.
• Red light source for low-disturbance observation.
• ImageJ for frame-by-frame counting.
• R for statistical analysis.
• Python for scripted graphing and data cleanup.
• Identical arena inserts made from acrylic or 3D-printed plastic.

Software & Tools

• Google Sheets: Organizes trial counts, group sizes, and humidity readings in one table.
• ImageJ: Lets you count pillbugs in each shelter from still frames or video.
• R: Runs basic statistics and plots group choice across humidity levels.
• Python: Automates frame counts or repeated graphing if you want a scripted workflow.
• Jamovi: Gives a point-and-click way to run chi-square tests, t tests, or logistic models.

Experiment Steps

1. Define the outcome you will score first, such as first shelter entered, final shelter choice, or split group size.
2. Design two shelters that differ only in humidity so light, shape, and texture stay matched.
3. Choose a range of group sizes and decide how many repeats each size needs.
4. Build a scoring sheet that captures individual choices at the same time point in every trial.
5. Plan the stats you will use to test for a humidity effect, a group-size effect, and an interaction between them.

Common Pitfalls

• Letting one shelter get darker than the other, which turns the test into a light choice instead of a humidity choice.
• Releasing animals that are too wet or too dry, which changes their behavior before the trial starts.
• Counting every body that touches a shelter edge as a choice, which inflates the final tally.
• Letting the humidity gradient drift during the trial, which makes one session unlike the next.
• Running too few repeats, which makes a lucky pileup look like a real quorum effect.

What Makes This Competitive

A stronger project does more than ask which shelter wins. It looks for a threshold, the point where group size or humidity difference flips a split choice into a clear cluster. If you add blind scoring, repeatable controls, and stats that compare both the size of the group and the speed of the choice, your data will say more about behavior. That kind of design shows you can turn a simple observation into a real model.

Project Variations

• Compare juvenile and adult pillbugs to see whether age changes how strongly the group follows humidity.
• Test a humidity choice against a temperature choice to separate moisture preference from thermal preference.
• Swap the shelter material, such as cardboard, plastic, or leaf litter, to see whether texture changes the group decision.

Learn More

• NIH PubMed: Search review articles on pillbug behavior, isopod aggregation, and moisture preference.
• NCBI Bookshelf: Find open textbook chapters on animal behavior, ecology, and experimental design.
• Animal Behavior Society: Read educational material on choice tests, social behavior, and observation methods.
• NOAA National Weather Service education pages: Review humidity basics so you can describe what your setup is testing.
• University OpenCourseWare: Search introductory ecology or animal behavior lectures for ideas on variables, controls, and sampling.