The frog and toad populations are declining worldwide. Park researchers do not know if the frog and toad populations at Indiana Dunes are in trouble so they are starting to make a baseline study for future comparisons. Please read the background information about this critical issue to the students.
| In 1992, Gary Fellers and Charles Drost surveyed the frogs and toads in the mountains of California's Yosemite National Park. Researchers in 1915 found seven species thriving there, but Fellers and Drost's survey discovered five in serious decline and one had disappeared from large portions of its undisturbed range. Scientists studying rain forests, mountains, and wetlands have noticed an alarming decline throughout the world. Draining wetlands, building dams, cutting forests, and other habitat altering activities can account for a lot of the decline but not for the decline in undisturbed national park areas. Could it be airborne pollutants going through the moist skin of frogs? Maybe increased solar radiation caused by damage to the ozone layer? Maybe the ultraviolet light is affecting the eggs. Indiana Dunes is starting to monitor the frog population in the park. On spring evenings researchers go out to listen to the frogs calling. Each species has a different mating call. Researchers determine the size of a frog population by listening to the frogs calling. When a researcher hears only one frog at a time calling, she records the population as Level One. Level Two is reached when the researcher can hear individual frogs calling but their calls overlap. Level Three indicates so many frogs are calling it sounds like a chorus. |
Fun Activity –This activity will help the students understand the 3 levels used in the monitoring surveys. You need three groups. Each group should choose a different frog or toad call. Choose two or three students to call once every three seconds so their calls do not overlap. They represent Level One. A larger group should voice their calls so there is an overlap that would represent Level Two. The largest group of students can call continuously so they produce a chorus that represents Level Three.
Bullfrog Jug-oh-rum |
Chorus Frog Run fingers over the teeth of a comb |
Cricket Frog Tapping of two stones |
Fowler's Toad Crying baby |
Tree Frog hey-baby |
Green Frog Plucked banjo string |
Follow-up questions:
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What would the night sound like without frogs? |
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Thinking question: What effect would a decline in the frog population have on other animals? Many animals such as herons, fish, and snakes eat frogs. Frogs eat hundreds of bugs including mosquitoes. As the frog populations decline the web of life gets out of balance. |
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Emotional question: How would you feel if the frogs disappeared? |
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Critical thinking question: How can scientists determine the cause of the decline? More research projects need to be designed. Is acid rain in Indiana bringing pollutants into the water? Is there some sort of disease? Is this just a natural decline and frog populations will rebound? |
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This will provide the park with a baseline study for comparison in the
future. If the research indicates a decrease in the singing levels the park will know
there is a problem. No one knows the reason for the worldwide decline. If the frogs and
toads at our park have a problem, there may not be a solution we can use to help them.