On the last page you read about a behavioral experiment that showed how leptin affects the mate choice of Plains spadefoot toads, Spea bombifrons. We know that Plains toads will hybridize with New Mexico toads on purpose when they are in shallow ponds of water. We also know that an injection of leptin will cause them to choose to mate with the other species even when they are in deep water.

Unlike Plains toads, female New Mexico toads (Spea multiplicata) almost always choose not to hybridize. Because multiplicata tadpoles would already develop very quickly, having a Plains toad for a father would only hurt them! They would develop more slowly, and they would be less likely to reproduce.

But what would happen if a New Mexico female was given a leptin injection? Would the leptin change her mind? The behavioral experiment that you will perform today will answer this question. The procedure is almost exactly the same as the experiment on the Plains spadefoot toads that you read about earlier. The only difference is that the experiment is performed on the other species of toad and only in deep water.

Why would you only do the experiment in high water?

This was a mistake. There should also be a low-water group
We only want to test one variable.


During this experiment, you will sort toads into control and experimental groups, give them their leptin and saline injections, and then observe the results of six trials each for those two groups.

To move to the next step in the experiment, click the "Next" button at the bottom of each page. Use the "Back" button to return to a previous page. If you need to skip to a specific step, use the drop-down menu labeled "Steps of Experiment" in the navigation bar to move to the correct page.

Many of the animations during the experiment include sound that cannot be paused. If you are using this module in a classroom or public area, you should use headphones.

Before starting the experiment, copy or print the following tables on your own piece of paper. You will record the results of your experiments before drawing a conclusion.

Click here to download printable tables (PDF)

Speaker Chosen by Control Group Speaker Chosen by Experimental Group
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Trial 6

Final Results
Number of toads who chose their own species (Left speaker) Number of toads who chose the other species (Right speaker)
Control Group
Experimental Group