How Are Monarch Colonies Measured?

Imagine the Scientist's Job!
It's a daunting task to estimate the size of the monarch's winter colonies! But it's important to know the size of the monarch population, so scientists have developed a method for estimating it. It is NOT EASY, as you are about to see. In real life, the butterflies, the forest, the weather, and even the scientists are constantly changing!

Try This! Count Butterfly Trees
 The orange in the trees are monarch butterflies! How many butterfly trees do you count? (Click for larger image.)
Before we look at the scientists' methods, walk into a sanctuary, take a look, and try it yourself.
1. Look at the photo to the right. The orange you see in certain trees are monarch butterflies!
2. Draw or imagine a "perimeter" line around what you think is the monarch colony. (This is what scientists do so they can estimate the colony size.)
3. How many butterfly trees do you count within the colony area?
4. As you work, record the challenges you notice, the questions you have, and the decisions you make to reach your final count.
5. When you're done, see how we looked at the problem.
Then Look at the Scientists' Methods

Are you ready now to see how the scientists work? Read the description of the steps they take. Can you name at least one factor (variable) they try to keep the same (control) each time they measure?

Mexican Scientist Eduardo Rendon

Now Try to Identify Variables

Pictures and Descriptions Hold Clues...
Look at the pictures and information at the link below. Keep your tree-counting experience and the scientists' methods in mind. Use the worksheet to record the variables you identify that are hard or impossible to have control over. How might each variable affect the accuracy of the results?

Once you've filled in the worksheet, see our list.

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