Snail Population Growth

Before we dive in, I want to say a bit about mathematical modeling. One of the most amazing things about math is that it can help you make reasonable predictions about the future: you can create models of situations using math to see what the future might hold under certain conditions. When we know how to model with math, we are empowered to make better decisions for ourselves, our families, and our communities.

You and your family aren't going to care as much about our snail population as we do. But there are probably a lot of things that are very important to you and that you wonder about. As you read about our snails, think about how you can use math to make decisions in your own life.

So ... is it unreasonable to expect that our modest (OK, the modesty of our collection is debatable!) collection of snails could rapidly become thousands of snails? We had to gather some information first. We needed to know how many snails we actually have, and we also needed to know a little bit about snail reproduction. After researching snails, we learned that all snails are capable of laying eggs, so if two snails are kept together, each of them can lay eggs after mating. We also learned that when snails lay eggs, they lay anywhere between 30 and 120 eggs.

Any time you model with mathematics, you work with some known information (for example, the number of snails we have) and make assumptions about other pieces of information that are not exact, that vary, or that cannot be known exactly (for example, the approximate number of eggs each snail might lay at a time).

Here's what we know:

• We have about 30 snails as pets.

• Every snail is able to lay eggs.

• Snails lay between 30 and 120 eggs at a time.

Together, my son (a third grader) and I did some calculations mentally, and I recorded them. We started with easier numbers (4 snails laying 40 eggs) and built up from there, using what we had already figured out to calculate the harder combinations. Eventually, we determined that if each of our 30 snails laid 54 eggs, we could quickly have 1,620 baby snails ... for a total of 1,650 snails in all (all of whom are able to lay their own eggs!).

If each snail laid 54 eggs two different times, that gets us quickly into "thousands of snails" territory!

With the information our simple mathematical model provided, we were able to make what feels like a very responsible decision: we will keep each snail in its own jar to limit their reproduction. (Snails can self-fertilize, but they tend not to do that very often.)

Give it a try yourself and tell us about it! Making what seems like an outlandish claim — "Y'all are going to end up spending hundreds of hours in front of screens before the month is over if we don't figure out another way to spend our time!" — and then investigating the veracity of that claim using a mathematical model can be a fun and engaging way to start.