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In the North, people know it's time for spring when they see the first robin. In North Carolina, robins are often present all winter long, especially in the mild winters we've had in recent years. We need different heralds for our Carolina springtime. And if we listen, they're out there, calling from nearly every streamside and wetland throughout the Triangle area. They're frogs.
There are at least a dozen species of frog and toad in most areas of the Triangle, and several of them sing in the spring, but the loudest choruses come from two species of tiny tree frogs: the upland chorus frog (Pseudacris feriarum) and the spring peeper (Pseudacris crucifer). The term "tree frog" is a bit misleading, though, because both species live pretty much on the ground, in leaf litter or undergrowth of damp, streamside forests.
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Chorus frogs and spring peepers are roughly 3 cm long--not much more than an inch! Both are brownish or tan, with striping on the back. The stripes on a chorus frog run the length of the body, while those of the spring peeper (shown at right) cross each other. That explains the peeper's scientific name crucifer, cross-bearer. However, you aren't that likely to actually see either frog, because they are so small and so reclusive. Occasionally, one may wander up from a stream in someone's back yard. But if students catch a frog, it's likely to be something bigger: a bullfrog, a green frog, a leopard frog, or a toad. For most of us, chorus frogs and spring peepers are to hear, not to see. |
Spring peepers, on the other hand, have a musical note, a rising, bird-like whistle. It's a very loud note, too: almost painfully loud, if you're close to the frog. Like chorus frogs, they often sing in large numbers, although sometimes you'll hear just one or two whistling away. They may start singing in late February, but you're more likely to hear them in March.
Frogs, like essentially all amphibians, are sensitive both to pollution and to habitat disturbance. As land is developed, many amphibian species disappear. Chorus frogs and spring peepers are more likely to remain than most other species, because they use the wetland the developers can't do much with, and they don't need a large area to survive. In many Triangle area subdivisions, the only amphibians present in any numbers are these two little frogs and Fowler's toads.
Surprisingly little is known about these frogs. Their songs are conspicuous, but the animals aren't; it's hard for scientists even to find them outside the early spring breeding season. And why do they breed so early, when the air is so cold? Because early spring is the season with the most water and the fewest predators, so their tadpoles have the best chance to grow up in the puddle and ditches where the frogs lay their eggs.
Frogs are interesting to students, and many teachers use that interest as a teaching angle. The 'Net references below are some good places to start looking for information and ideas on teaching about frogs and other amphibians. It's also good for students to realize that often we can find evidence of animals without actually seeing those animals, if we use our eyes and our ears. We can't see these tiny frogs every often, but we can hear them by the hundred!
Internet Sources
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Posted February 2, 1998. Link added June 30, 1998. Features remain online as long as they remain current; they may be updated if new information becomes available.
Copyright © 1998, Center for Mathematics and Science Education. Teachers have permission to duplicate this page for use in teaching their own classes. All other rights reserved. You are welcome to link to this page, but do not copy its contents.
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